OcempGUI Manual

The following applications and libraries are needed before OcempGUI can be installed:

Please refer to the documentation of the respective package about how to install it.

OcempGUI is not provided as binary package by the author. However, it might be that someone else set up such a package for your wanted operating system or distribution. Those packages are usually not supported by the author, what means that installation problems or similar issues, which do not target the library directly, should be escalated to the respective supplier of that package.

The unpacked package contains two possibilities of building and installing it. Both ways are mostly identical but the one or other user might tend to prefer a specific way. The first is the python way of installing software, the second follows the tradition of the unix environment and uses a Makefile (which actually simply starts the python way). While being in the top source directory, it is possible to type either

make install

for the traditional unix way or

python setup.py install

for the python way.

The package might have some special options, which are described in the README file shipped with it.

Using the latest development sources is possible via CVS. More information about how to use the SourceForge repository can be found on SourceForge.

The following OcempGUI modules are currently available:

The ocempgui.draw.Draw submodule contains several functions for geometric objects. Although most of them are only wrappers around the respective pygame functions, some of them can be used to create more complex geometric objects. The following list gives an overview about the functions defined within this submodule.

The ocempgui.draw.Image submodule contains image related functions, such as loading or saving image data.

The ocempgui.draw.String submodule contains functions, which allow the creation and manipulation of fonts and string surfaces. It includes a simple font caching system, which provides a fast availability of fonts, which were created earlier. Besides this feature, the string surface related functions are mostly wrappers around the respective pygame functions.

The event management system of OcempGUI uses a simple approach using signal slots. This means, that objects will register themselves only for specific event types, of which they want to be notified. Any other event will not be sent to them.This reduces the overhead of events the objects have to deal with (either by dropping or processing them) and improves the performance and scalability of the event management system (especially with many objects).

Figure 1. Event management

An object, which shall be event aware, has to implement a notify() method, which will receive events distributed by the EventManager. The signature of the method looks like the following:

class OwnObject:
    ...
    def notify (self, event):
        ...

The event argument of the method will be an Event object, which can be used to perform certain actions within the method body then:

class OwnObject:
    ...
    def move (self, coords):
       # Moves the object to the desired coordinates (x, y).
       self.x = coords[0]
       self.y = coords[1]
       print "Moved to %d,%d" % (self.x, self.y)

    def notify (self, event):
        # Check the event signal and run a certain action with its data.
        if event.signal == "clicked":
           print "Something was clicked!"
        elif event.signal == "move":
           # Assuming that the event.data contains a coordinate tuple.
           self.move (event.data)
        

Setting up the main event management is nearly as easy as enhancing the objects. To add objects to the EventManager, the add_object() method has to be invoked. It receives the object to add and a list of signal ids as arguments. The signal ids will cause the object to be registered in specific queues, to which events with matching signal ids then will be sent.

Objects can be removed from the EventManager using the remove_object() method. The method allows you to either remove the object from specific slots or from all slots, it is registered for, at once.

# Create an EventManager and OwnObject instance.
manager = EventManager ()
myobj = OwnObject ()

# Add the object to the EventManager.
manager.add_object (myobj, "move", "clicked")

# Remove the object from the 'clicked' slot.
manager.remove_object (myobj, "clicked")

# Remove the object from _all_ slots it still listens on.
manager.remove_object (myobj)
        

Now let us proceed to the most important: sending events. To send events to the objects of the EventManager, you can use the emit() method. It receives two arguments, which will become the signal and data of a Event object. The Event will be created by the EventManager and then sent to the matching objects. So all you have to do is to pass the emit() method the correct information for the event.

Both arguments the emit() receives, have no limitations of type, length or whatsoever. It is up to you to to send correct information through the event management system and to check for correct information on the object side.

# Send events to the registered objects via the emit() method.
manager.emit ("clicked", None)
manager.emit ("move", (10, 10))
        

The following example is a complete example based on the excerpts from above. You can find it as python script under examples/eventmanager.py

# EventManager usage example.
from ocempgui.events import EventManager

# Create a new event capable object. This can be acquired by adding a
# 'notify ()' method to the object, which receives a single argument.
class OwnObject:
    def __init__ (self):
        self.x = 0
        self.y = 0
    
    def move (self, coords):
       # Moves the object to the desired coordinates (x, y).
       self.x = coords[0]
       self.y = coords[1]
       print "Moved to %d,%d" % (self.x, self.y)

    def notify (self, event):
        # Check the event signal and run a certain action with its data.
        if event.signal == "clicked":
           print "Something was clicked!"
        elif event.signal == "move":
           # Assuming that the event.data contains a coordinate tuple.
           self.move (event.data)

# Create an EventManager and OwnObject instance.
manager = EventManager ()
myobj = OwnObject ()

# Add the object to the EventManager.
manager.add_object (myobj, "move", "clicked")

# Send events to the registered objects via the emit() method.
manager.emit ("clicked", None)
manager.emit ("move", (10, 10))

# Remove the object from the 'clicked' slot.
manager.remove_object (myobj, "clicked")

# Send the 'clicked' event once more.
manager.emit ("clicked", None)

# Remove the object from _all_ slots it still listens on.
manager.remove_object (myobj)

# Send the 'move' event again.
manager.emit ("move", (40, 40))

The BaseObject is event driven, which means, that it acts and reacts upon events it receives and that it can raise events. Hereby you have to distinguish between Signals and Events. Signals are certain identifiers, a BaseObject can listen to, while Events are a combination of a Signal and additional data.

What does that mean in practice? As you already know from the section called “Building event driven systems”, objects will register themselves at an event manager with a specific signal, they listen to. Events in turn carry a specific signal id and additional data. A BaseObject will register itself at an event manager with its signals. If events are passed to the event manager, it will distribute them to the object, if needed. The object in turn will react according to its programming instructions.

To allow your object to react according to the application needs on certain events easily, the BaseObject supports the connection of callbacks to signals you can define for it. A callback is a method or function, which should be invoked, when the object receives a certain event.

Figure 2.  Signal handling of the BaseObject class

The first thing you should do is to let your existing object or the newly created one inherit from the BaseObject class. Afterwards you can unleash its full power by adding just a minimal set of code.

from ocempgui.object import BaseObject

class OwnObject (BaseObject):
    def __init__ (self):
        BaseObject.__init__ (self)
    
    ...
        

That is not all of course. You also have to set up the signals the object has to listen to and create callbacks. Let us create a small ping-pong example, where two objects react upon a 'ping' and 'pong' signal.

The BaseObject has a _signals attribute, which basically is a dictionary with the signal ids it listens to as keys and list for the callbacks as values. To allow your object to listen to the 'ping' or 'pong' signal, you have to add those to this dictionary.

from ocempgui.object import BaseObject

class OwnObject (BaseObject):
    def __init__ (self):
        BaseObject.__init__ (self)
        self._signals["ping"] = []
        self._signals["pong"] = []
    ...
        

Now we just need to make the notify() aware of those signal types and let it invoke the appropriate callbacks, which will be connected to those signals.

class OwnObject (BaseObject):
    ...
    def notify (self, event):
        if event.signal == "ping":
            self.run_signal_handlers ("ping")
        elif event.signal == "pong":
            self.run_signal_handlers ("pong")
        

As you see, the run_signal_handlers() takes care of invoking the connected callbacks. Now you have anything set up to allow the object to listen to specific events, to connect callbacks to it and let it invoke them, when it receives the specific signal.

To connect methods or functions as callbacks to a specific signal, the connect_signal() method of the BaseObject can be used. It allows additional data to be passed to the callback by specifiying the data right after the signal and callback. If the callbacks is not needed anymore, it can be disconnected using the disconnect_signal() method.

class OwnObject (BaseObject):
    ...

my_obj = OwnObject ()
ev_callback1 = my_obj.connect_signal ("ping", ping_callback, data)
ev_callback2 = my_obj.connect_signal ("pong", pong_callback, data1, data2)
...

my_obj.disconnect_signal (ev_callback1)
my_obj.disconnect_signal (ev_callback2)
        

Now it just needs to be connected to an event manager. In contrast to the earlier section, you do not need to register any signal of your BaseObject inheritor manually. When you connect it to an event manager, it will automatically do that for you.

class OwnObject (BaseObject):
    ...


manager = EventManager
my_obj = OwnObject ()

# Any signal of the object will be registered automatically.
my_obj.manager = manager
        

The last important thing to know about the BaseObject is its ability to emit events. If the object is connected to an event manager, you can let it send events through the manager with the object its emit() method. The syntax is the same as if you would emit events on the EventManager directly.

Now let us look at the example we just went through (the following oone is slightly modified only). You can find the example as python script under examples/baseobject.py

# BaseObject usage example.
from ocempgui.object import BaseObject
from ocempgui.events import EventManager

# Callbacks, which should be invoked for the object.
def ping_callback (obj, additional_data):
    print "The object is: %s" % obj.name
    print "Passed data is: %s" % additional_data

def pong_callback ():
    print "Another callback with no arguments."

# Object implementation, which can listen to specific events.
class OwnObject (BaseObject):
    def __init__ (self, name):
        BaseObject.__init__ (self)
        self.name = name
        # The object should be able to listen to 'ping' and 'pong'
        # events.
        self._signals["ping"] = []
        self._signals["pong"] = []

    def notify (self, event):
        # This simple notify method will not be used in this
        # example. Instead, the signals are invoked directly.
        if event.signal == "ping":
            self.run_signal_handlers ("ping")
        elif event.signal == "pong":
            self.run_signal_handlers ("pong")

manager = EventManager ()

# Create an object and connect callbacks to its both events.
my_obj = OwnObject ("First object")
ev1 = my_obj.connect_signal ("ping", ping_callback, my_obj, "data")
ev2 = my_obj.connect_signal ("pong", pong_callback)

# Connect it to the event manager
my_obj.manager = manager

# Invoke the connected signals handlers for a specific event.
manager.emit ("ping", None)
manager.emit ("pong", None)

# After disconnecting a callback, it will not be invoked anymore.
my_obj.disconnect_signal (ev1)
my_obj.disconnect_signal (ev2)
manager.emit ("ping", None)
manager.emit ("pong", None)

The ocempgui.object module includes another event capable object class, the ActionListener, which inherits from the BaseObject class, but allows you to create and delete signals and listening queues as you need them without the necessity to subclass.

The ActionListener creates the signal id and a callback queue, when you connect a callback to it and registers itself for this signal automatically at its event manager. This can be extremeley useful, if a more flexible event capable object type is needed, which does not need to do any sanity checks on the event data. Instead it will send the event data to the callback as well, which then can work with it.

Once more let us create a ping-ping example using the ActionListener class instead of a BaseObject now.

You can find the example as python script under examples/actionlistener.py

# ActionListener usage example.
import sys
from ocempgui.events import EventManager
from ocempgui.object import ActionListener

count = 0

def emit_pong (event, manager):
    print "emit_pong received: [%s] - emitting pong..." % event
    manager.emit ("pong", "pong_event")

def emit_ping (event, manager):
    global count
    if count > 10:
        sys.exit ()
    count += 1
    print "emit_ping received: [%s] - emitting ping..." % event
    manager.emit ("ping", "ping_event")

# Create an event manager and two ping-pong listeners.
manager = EventManager ()

listener1 = ActionListener ()
listener1.connect_signal ("ping", emit_pong, manager)
listener1.manager = manager

listener2 = ActionListener ()
listener2.connect_signal ("pong", emit_ping, manager)
listener2.manager = manager

# start ping-pong actions
print "Starting Ping-Pong"
manager.emit ("ping", "ping_event")

Looking at the first interesting line, line eight,

def emit_pong (event, manager):
    print "emit_pong received: [%s] - emitting pong..." % event
    manager.emit ("pong", "pong_event")
        

Line twelve and following does the same, but breaks, if it was invoked more than ten times.

The next lines of interest are line twenty-three to twenty-nine,

listener1 = ActionListener ()
listener1.connect_signal ("ping", emit_pong, manager)
listener1.manager = manager
        

The first thing an application using OcempGUI should do is to initialize the renderering system. The Renderer class from the ocempgui.widgets package contains all necessary parts to take care of this. It includes

The Renderer can be set up with only three lines of code.

from ocempgui.widgets import *
re = Renderer ()
re.create_screen (200, 200) # Creates the pygame window
        

Now that the Renderer is set up, you can start to place widgets on the pygame window by adding them using the Renderer.add_widget() method. Let us do this by building a simple (and well-known) application with a Button widget on it, that displays 'Hello World'.

You can find the example as python script under examples/hello_world.py

# Hello World example.
from ocempgui.widgets import *

# Initialize the drawing window.
re = Renderer ()
re.create_screen (100, 50)
re.title = "Hello World"
re.color = (250, 250, 250)

button = Button ("Hello World")
button.position = (10, 10)
re.add_widget (button)

# Start the main rendering loop.
re.start ()

The second line

from ocempgui.widgets import*
        

The fifth and sixth lines

re = Renderer ()
re.create_screen (100, 50)
        

The seventh and eight line

re.title = "Hello World"
re.color = (250, 250, 250)
        

In line ten

button = Button ("Hello World")

The next line will place the Button at a specific position.

button.position = (10, 10)

Line twelve

re.add_widget (button)

The last line will start the main processing loop of the Renderer.

re.start ()

Every widget of OcempGUI inherits from the ocempgui.object.BaseObject class and its event handling makes heavy usage of the BaseObject features.

To cause a Button to print a message upon a mouse click, you would connect a message printing function to the click signal of the Button. In turn, if this callback is not needed anymore in the later program flow, you would disconnect the function from the Button's signal.

This theoretical model is used in many different toolkits and OcempGUI stays with it. We will enhance our 'Hello world' example application from the previous chapter with a callback now, wich prints a message each time the Button is clicked.

You can find the example as python script under examples/hello_world_signals.py

# Hello World example.
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def print_message  ():
    print "The button was clicked!"

# Initialize the drawing window.
re = Renderer ()
re.create_screen (100, 50)
re.title = "Hello World"
re.color = (250, 250, 250)

button = Button ("Hello World")
button.position = (10, 10)
button.connect_signal (SIG_CLICKED, print_message)
re.add_widget (button)

# Start the main rendering loop.
re.start ()

The first change you note is the new import directive in line three.

from ocempgui.widgets.Constants import *
        

Line five and six contain the function, which will be used as the callback for the button. It is indifferent, if the callback is a class or object method or a function. Both cases will work in the same way.

The next notably change was done in line 16

button.connect_signal (SIG_CLICKED, print_message)
        

The ocempgui.widgets module contains some globally accessed settings, that influence its complete behaviour. Those can be found in the ocempgui.widgets.base part and contain the Style, which is currently in use, the timer rate for double-clicks and a debugging flag. You can adjust those settings easily by simply binding them to new values.

Before you go ahead and change base.GlobalStyle, you should read the section called “Changing the widget appearance”.

The base.debug setting is for additional debugging output and should not be set to True usually (unless you are using a development version).

The last one, base.DoubleClickRate should be set using the base.set_doubleclick_rate() method only and denotes the maximum time to elaps between two click operations to identify them as a double-click.

A widget can be set to a specific position on the main screen using the position attribute.

widget.position = 10, 15
        

If you read the current position value of a widget, keep in mind, that it will return a tuple containing the both, x and y, coordinates.

Every widget supports a minimum size, that will be respected by the default drawing methods.

widget.size = 80, 20
        

The currently used width and height, which can differ from its size can be retrieved using the width and height attributes.

if (widget.width == widget.size[0]) and (widget.height == widget.size[1]):
    print "Widget does not exceed its minimum size."
        

To allow an easy and logical keyboard navigation, widgets have an index attribute, which influences the navigation order using the keyboard.

widget.index = 3
        

The input focus mentioned above denotes a state of the widget, in which the user can interact with it using the keyboard only. A Button widget will react upon pressing the space bar with a click while an Entry widget will let the user type text. You can set the input focus of a widget manually with the focus attribute.

widget.focus = True
        

frame = VFrame ()
focusok = frame.set_focus (True)
if not focusok:
    print "Focus could not be set."
        

Widgets can be disabled from user interaction and receiving events, if you set their sensitive attribute to False.

widget.sensitive = False
        

The renderering system of the ocempgui.widgets module can use different layers, on which widgets are drawn. This is especially useful and often necessary to place widgets above others (e.g. to place a Window widget above another one).

widget.depth = 3
        

You already learned about the Button widget in an earlier section, so let us look at some interesting details of it now.

The Button widget is a interactive widget, which reacts upon mouse input such as clicks. Basically it is a container (which will be explained detailled later on), which holds a Label widget to display its text.

To create a Button, you usually will type

button = Button (text)
        

The usage of mnemonics for the Button is easy to achieve by simply supplying a mnemonic text as described in the section called “Labels”. You can set the text directly through the text attribute or set_text() method.

button.text = "#Mnemonic"
button.set_text ("#Mnemonic")
        

As one of only few widgets the Button supports different border styles to adjust its look and feel without the need to override its drawing methods.

button.border = BORDER_NONE
button.set_border (BORDER_NONE)
        

The Button widget has some default signals, it listens to. Those are

Below you will find an example to illustrate most of the abilities of the Button widget class. You do not need to care about other widgets like the Frame class for now as those are explained later on.

You can find the following example as a python script under examples/button.py.

# Button examples.
import os
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _create_vframe (text):
    frame = VFrame (Label (text))
    frame.spacing = 5
    frame.align = ALIGN_LEFT
    return frame

def create_button_view ():
    states = ("STATE_NORMAL", "STATE_ENTERED", "STATE_ACTIVE",
              "STATE_INSENSITIVE")

    table = Table (2, 3)
    table.spacing = 5

    # Frame with the states.
    frm_states = _create_vframe ("States")
    for i in xrange (len (states)):
        btn = Button (states[i])
        if STATE_TYPES[i] == STATE_INSENSITIVE:
            btn.sensitive = False
        else:
            btn.state = STATE_TYPES[i]
        frm_states.add_child (btn)
    table.add_child (0, 0, frm_states)
    table.set_align (0, 0, ALIGN_TOP)

    # Frame with different padding.
    frm_padding = _create_vframe ("Padding")
    for i in xrange (5):
        btn = Button ("Padding: %dpx" % (i * 2))
        btn.padding = i * 2
        frm_padding.add_child (btn)
    table.add_child (0, 1, frm_padding)
    table.set_align (0, 1, ALIGN_TOP)

    # Mnemonics.
    frm_mnemonic = _create_vframe ("Mnemonics")
    btn = Button ("#Simple Mnemonic")
    btn2 = Button ("#Activate using <ALT><Underlined Key>")
    frm_mnemonic.add_child (btn, btn2)
    table.add_child (0, 2, frm_mnemonic)
    table.set_align (0, 2, ALIGN_TOP)

    # Borders.
    frm_borders = _create_vframe ("Borders")
    btn_raised = Button ("Raised border")
    btn_sunken = Button ("Sunken border")
    btn_sunken.border = BORDER_SUNKEN
    btn_flat = Button ("Flat border")
    btn_flat.border = BORDER_FLAT
    btn_none = Button ("No border")
    btn_none.border = BORDER_NONE
    btn_etchedin = Button ("Etched in")
    btn_etchedin.border = BORDER_ETCHED_IN
    btn_etchedout = Button ("Etched out")
    btn_etchedout.border = BORDER_ETCHED_OUT
    frm_borders.add_child (btn_raised, btn_sunken, btn_flat, btn_none,
                           btn_etchedin, btn_etchedout)
    table.add_child (1, 0, frm_borders)
    table.set_align (1, 0, ALIGN_TOP)

    # Multiline labeled buttons
    frm_multiline = _create_vframe ("Multiline labels")
    strings = ("Single lined Button", "Two lines on" + os.linesep + "a Button",
               "Two lines with a" + os.linesep + "#mnemonic")
    for i in xrange (len (strings)):
        button = Button (strings[i])
        button.child.multiline = True
        frm_multiline.add_child (button)
    table.add_child (1, 1, frm_multiline)
    table.set_align (1, 1, ALIGN_TOP)
    
    return table
    
if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (550, 470)
    re.title = "Button examples"
    re.color = (234, 228, 223)
    re.add_widget (create_button_view ())
    # Start the main rendering loop.
    re.start ()

The ImageButton is basically a subclass of the Button, but enhances it by the ability to load and display image data. It supports any image data format, that can be handled by the underlying pygame library. Due to its inheritance, everything said about the Button widget applies to the ImageButton as well.

The creation of an ImageButton is slightly different to the Button. Instead of passing the text to display, you can pass either the name of a file to load (including the full path to it) or a pygame.Surface object to display.

button = ImageButton ("path/to/an/image.png")
button = ImageButton (pygame_surface)
        

button.text = "Additional text"
        

Below you will find an example to illustrate most of the abilities of the ImageButton widget class. You do not need to care about other widgets like the Frame class for now as those are explained later on.

You can find the following example as a python script under examples/imagebutton.py.

# ImageButton examples.
import pygame, os
from ocempgui.draw import Image
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _create_vframe (text):
    frame = VFrame (Label (text))
    frame.spacing = 5
    frame.align = ALIGN_LEFT
    return frame

def create_button_view ():
    states = ("STATE_NORMAL", "STATE_ENTERED", "STATE_ACTIVE",
              "STATE_INSENSITIVE")

    image = Image.load_image ("./image.png")
    table = Table (2, 2)
    table.spacing = 5

    # Frame with the states.
    frm_states = _create_vframe ("States")
    for i in xrange (len (states)):
        btn = ImageButton (image)
        if STATE_TYPES[i] == STATE_INSENSITIVE:
            btn.sensitive = False
        else:
            btn.state = STATE_TYPES[i]
        btn.text = states[i]
        frm_states.add_child (btn)
    table.add_child (0, 0, frm_states)
    table.set_align (0, 0, ALIGN_TOP)

    # Frame with different padding.
    frm_padding = _create_vframe ("Padding")
    for i in xrange (4):
        btn = ImageButton (image)
        btn.padding = i * 2
        frm_padding.add_child (btn)
    table.add_child (0, 1, frm_padding)
    table.set_align (0, 0, ALIGN_TOP)

    # Mnemonics.
    frm_mnemonic = _create_vframe ("Mnemonics")
    btn = ImageButton (image)
    btn.text = "#Simple Mnemonic"
    btn2 = ImageButton (image)
    btn2.text = "#Activate using <ALT><Underlined Key>"
    frm_mnemonic.add_child (btn, btn2)
    table.add_child (1, 0, frm_mnemonic)
    table.set_align (1, 0, ALIGN_TOP)

    # Multiline labeled ImageButton
    frm_multiline = _create_vframe ("Multiline label")
    button = ImageButton (image)
    button.text = "Multiple lines" + os.linesep + "with a #mnemonic"
    button.child.multiline = True
    frm_multiline.add_child (button)
    table.add_child (1, 1, frm_multiline)
    table.set_align (1, 1, ALIGN_TOP)

    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (570, 400)
    re.title = "ImageButton examples"
    re.color = (234, 228, 223)
    re.add_widget (create_button_view ())
    # Start the main rendering loop.
    re.start ()

Inherited from the Button the ToggleButton widget does not differ from it except that it is always in one state, either active or inactive, which are alternated by a click. By default it is displayed in a depressed state on a click and pops up after clicking it again.

To create a ToggleButton, you can do the same as with the Button class.

button = ToggleButton (text)
        

You can retrieve the current state as boolean value of the ToggleButton through its active attribute and set its state programmatically via this attribute or the set_active() method.

if button.active:
    print "The ToggleButton is currently active!"
button.set_active (False)
        

To track changes of this state, the ToggleButton supplies a SIG_TOGGLED signal, which will be raised, if the state is changed via a mouse input or the accelerator action of a Label.

def state_changed (togglebutton):
    state = "active"
    if not togglebutton.active:
       state = "inactive"
    out = "The state of the ToggleButton has been set to %s" % state

button = ToggleButton ("A ToggleButton")
button.connect_signal (SIG_TOGGLED, state_changed, button)
        

Below you will find an example to illustrate most of the abilities of the ToggleButton widget class. You do not need to care about other widgets like the Frame class for now as those are explained later on.

You can find the following example as a python script under examples/togglebutton.py.

# ToggleButton examples.
import os
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _create_vframe (text):
    frame = VFrame (Label (text))
    frame.spacing = 5
    frame.align = ALIGN_LEFT
    return frame

def create_button_view ():
    states = ("STATE_NORMAL", "STATE_ENTERED", "STATE_ACTIVE",
              "STATE_INSENSITIVE")

    table = Table (2, 3)
    table.spacing = 5

    # Frame with the states.
    frm_states = _create_vframe ("States")
    for i in xrange (len (states)):
        btn = ToggleButton (states[i])
        if STATE_TYPES[i] == STATE_INSENSITIVE:
            btn.sensitive = False
        else:
            btn.state = STATE_TYPES[i]
        frm_states.add_child (btn)
    table.add_child (0, 0, frm_states)
    table.set_align (0, 0, ALIGN_TOP)

    # Frame with different padding.
    frm_padding = _create_vframe ("Padding")
    for i in xrange (5):
        btn = ToggleButton ("Padding: %dpx" % (i * 2))
        btn.padding = i * 2
        frm_padding.add_child (btn)
    table.add_child (0, 1, frm_padding)
    table.set_align (0, 0, ALIGN_TOP)

    # Mnemonics.
    frm_mnemonic = _create_vframe ("Mnemonics")
    btn = ToggleButton ("#Simple Mnemonic")
    btn2 = ToggleButton ("#Activate using <ALT><Underlined Key>")
    frm_mnemonic.add_child (btn, btn2)
    table.add_child (0, 2, frm_mnemonic)
    table.set_align (0, 2, ALIGN_TOP)


    # Multiline labeled buttons
    frm_multiline = _create_vframe ("Multiline labels")
    strings = ("Single lined ToggleButton",
               "Two lines on" + os.linesep + "a ToggleButton",
               "Two lines with a" + os.linesep + "#mnemonic")
    for i in xrange (len (strings)):
        button = ToggleButton (strings[i])
        button.child.multiline = True
        frm_multiline.add_child (button)
    table.add_child (1, 0, frm_multiline)
    table.set_align (1, 0, ALIGN_TOP)

    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (530, 400)
    re.title = "ToggleButton examples"
    re.color = (234, 228, 223)
    re.add_widget (create_button_view ())
    # Start the main rendering loop.
    re.start ()

The CheckButton, which inherits from the ToggleButton, does not bring in any new features. Instead it just uses a different look to display its set state. The state of the CheckButton is indicated by a small (usually 10x10 px) square, which is either checked or unchecked.

To create a CheckButton widget, you usually will do the same as with the ToggleButton.

button = CheckButton (text)
        

Below you will find an example to illustrate most of the abilities of the CheckButton widget class. You do not need to care about other widgets like the Frame class for now as those are explained later on.

You can find the following example as a python script under examples/checkbutton.py.

# CheckButton examples.
import os
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _create_vframe (text):
    frame = VFrame (Label (text))
    frame.spacing = 5
    frame.align = ALIGN_LEFT
    return frame

def create_button_view ():
    states = ("STATE_NORMAL", "STATE_ENTERED", "STATE_ACTIVE",
              "STATE_INSENSITIVE")

    table = Table (2, 3)
    table.spacing = 5

    # Frame with the states.
    frm_states = _create_vframe ("States")
    for i in xrange (len (states)):
        btn = CheckButton (states[i])
        if STATE_TYPES[i] == STATE_INSENSITIVE:
            btn.sensitive = False
        else:
            btn.state = STATE_TYPES[i]
        frm_states.add_child (btn)
    table.add_child (0, 0, frm_states)
    table.set_align (0, 0, ALIGN_TOP)

    # Frame with different padding.
    frm_padding = _create_vframe ("Padding")
    frm_padding.spacing = 5
    frm_padding.align = ALIGN_LEFT
    for i in xrange (5):
        btn = CheckButton ("Padding: %dpx" % (i * 2))
        btn.padding = i * 2
        frm_padding.add_child (btn)
    table.add_child (0, 1, frm_padding)
    table.set_align (0, 0, ALIGN_TOP)

    # Mnemonics.
    frm_mnemonic = _create_vframe ("Mnemonics")
    btn = CheckButton ("#Simple Mnemonic")
    btn2 = CheckButton ("#Activate using <ALT><Underlined Key>")
    frm_mnemonic.add_child (btn, btn2)
    table.add_child (0, 2, frm_mnemonic)
    table.set_align (0, 2, ALIGN_TOP)

    # Multiline labeled buttons
    frm_multiline = _create_vframe ("Multiline labels")
    strings = ("Single lined CheckButton",
               "Two lines on" + os.linesep + "a CheckButton",
               "Two lines with a" + os.linesep + "#mnemonic")
    for i in xrange (len (strings)):
        button = CheckButton (strings[i])
        button.child.multiline = True
        frm_multiline.add_child (button)
    table.add_child (1, 0, frm_multiline)
    table.set_align (1, 0, ALIGN_TOP)

    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (550, 350)
    re.title = "CheckButton examples"
    re.color = (234, 228, 223)
    re.add_widget (create_button_view ())
    # Start the main rendering loop.
    re.start ()

RadioButton widgets are similar to the CheckButton widgets, except that they can grouped, so that only one button of a group can be activated at a time. This is especially helpful, if you need to have the user to choose between a small amount of options.

The creation of a RadioButton is done using

button = RadioButton (text, group)
        

Alternatively to the group argument of the constructor, a RadioButton can be assigned to a group after its creation with the group attribute or set_group() method.

button.group = other_radio_button
button.set_goup (other_radio_button)
        

Given those possibilities a group of four choices can be created like the following example.

group = RadioButton ("Choice 1")
button1 = RadioButton ("Choice 2", group)

button2 = RadioButton ("Choice 3")
button2.group = group

button3 = RadioButton ("Choice 4")
group.add_button (button3)
        

In contrast to its parent classes, activating a RadioButton causes the other buttons in its group to loose their active state.

Below you will find an example to illustrate most of the abilities of the RadioButton widget class. You do not need to care about other widgets like the Frame class for now as those are explained later on.

You can find the following example as a python script under examples/radiobutton.py.

# RadioButton examples.
import os
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _create_vframe (text):
    frame = VFrame (Label (text))
    frame.spacing = 5
    frame.align = ALIGN_LEFT
    return frame

def create_button_view ():
    states = ("STATE_NORMAL", "STATE_ENTERED", "STATE_ACTIVE",
              "STATE_INSENSITIVE")

    table = Table (2, 3)
    table.spacing = 5

    # Frame with the states.
    frm_states = _create_vframe ("States")
    group = None
    for i in xrange (len (states)):
        btn = RadioButton (states[i], group)
        if i == 0:
            group = btn
        if STATE_TYPES[i] == STATE_INSENSITIVE:
            btn.sensitive = False
        else:
            btn.state = STATE_TYPES[i]
        frm_states.add_child (btn)
    table.add_child (0, 0, frm_states)
    table.set_align (0, 0, ALIGN_TOP)

    # Frame with different padding.
    frm_padding = _create_vframe ("Padding")
    group = None
    for i in xrange (5):
        btn = RadioButton ("Padding: %dpx" % (i * 2), group)
        if i == 0:
            group = btn
        btn.padding = i * 2
        frm_padding.add_child (btn)
    table.add_child (0, 1, frm_padding)
    table.set_align (0, 0, ALIGN_TOP)

    # Mnemonics.
    frm_mnemonic = _create_vframe ("Mnemonics")
    btn = RadioButton ("#Simple Mnemonic")
    btn2 = RadioButton ("#Activate using <ALT><Underlined Key>", btn)
    frm_mnemonic.add_child (btn, btn2)
    table.add_child (0, 2, frm_mnemonic)
    table.set_align (0, 2, ALIGN_TOP)

    # Multiline labeled buttons
    frm_multiline = _create_vframe ("Multiline labels")
    strings = ("Single lined RadioButton",
               "Two lines on" + os.linesep + "a RadioButton",
               "Two lines with a" + os.linesep + "#mnemonic")
    group = None
    for i in xrange (len (strings)):
        btn = RadioButton (strings[i], group)
        if i == 0:
            group = btn
        btn.child.multiline = True
        frm_multiline.add_child (btn)
    table.add_child (1, 0, frm_multiline)
    table.set_align (1, 0, ALIGN_TOP)

    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (550, 330)
    re.title = "RadioButton examples"
    re.color = (234, 228, 223)
    re.add_widget (create_button_view ())
    # Start the main rendering loop.
    re.start ()

The Editable class is an abstract base class, which takes care of dealing with keyboard events and text caret positioning. It is used as backend for the Entry widget class, which will be explained in the next section.

You usually will not create an Editable object directly, but rather use it as parent for your own classes.

It can store and operate on (unicode) text through its text attribute. The text usually will be set via this attribute or the set_text() method.

editable.text = "Text"
editable.set_text ("Text")
        

It also supports a virtual text caret position, which will be used by its internals to determine the position for editing operations. The caret attribute and set_caret() allow you to adjust the caret position.

editable.caret = 7
editable.set_caret (7)
        

Given both the text and caret attribute, the internals of the Editable will modify the text of it upon receiving keyboard events, if it has the input focus. Given an Editable, which contains the text "This is a Test." and its caret is set to 4, the processing of a pressed key ("D") causes:

The previous list mentioned a check, whether the text of an Editable can be modified. To allow or disallow editing the hold text, you can adjust the value of the editable attribute.

editable.editable = True
editable.set_editable (True)
        

The Editable listens by default to the following signals:

The Entry widget is a single line text input box, that inherits from the Editable class. It fully supports the Editable features and enhances it by mouse event sensitivity.

To create a Entry widget, you usually will type

entry = Entry (text)
        

Entry widgets support a password-like mode, in which any typed character will be displayed as an asterisk ('*').

entry.password = True
        

To allow a better look for some special fonts, the Entry can place an additional amount of pixels between its border and the text input area via the padding attribute or set_padding() method.

entry.padding = 5
entry.set_padding (10)
        

The Entry supports the SIG_MOUSEDOWN signal to get the input focus upon a left mouse button press.

Below you will find an example to illustrate most of the abilities of the Entry widget class. You do not need to care about other widgets like the Frame class for now as those are explained later on.

You can find the following example as a python script under examples/entry.py.

# Entry examples.
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def create_entry_view ():
    states = ("STATE_NORMAL", "STATE_ENTERED", "STATE_ACTIVE",
              "STATE_INSENSITIVE")

    table = Table (10, 10)
    table.spacing = 5

    # Frame with the states.
    frm_states = VFrame (Label ("States"))
    frm_states.spacing = 5
    frm_states.align = ALIGN_LEFT
    for i in xrange (len (states)):
        entry = Entry (states[i])
        if STATE_TYPES[i] == STATE_INSENSITIVE:
            entry.sensitive = False
        else:
            entry.state = STATE_TYPES[i]
        frm_states.add_child (entry)
    table.add_child (0, 0, frm_states)
    table.set_align (0, 0, ALIGN_TOP)

    # Frame with different padding.
    frm_padding = VFrame (Label ("Padding"))
    frm_padding.spacing = 5
    frm_padding.align = ALIGN_LEFT
    for i in xrange (5):
        entry = Entry ("Padding: %dpx" % (i * 2))
        entry.padding = i * 2
        frm_padding.add_child (entry)
    table.add_child (0, 1, frm_padding)
    table.set_align (0, 0, ALIGN_TOP)

    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (400, 400)
    re.title = "Entry examples"
    re.color = (234, 228, 223)
    re.add_widget (create_entry_view ())
    # Start the main rendering loop.
    re.start ()

The Range widget class is an abstract class, which enables inheriting classes to set and use value ranges. It can make use of float values, thus providing a high and for most cases exact resolution of values and it supports setting minimum and maximum values as well as stepwise increments.

You usually will not create a Range object directly, but inherit from it in your own widget classes. The constructor of a Range

range = Range (minimum, maximum, step)
        

The minimum attribute defines the lower limit of the value range it serves, while the maximum attribute defines the upper limit of it. Both can be set either via the attribute or the set_minimum() or set_maximum() methods.

if range.minimum < 0:
    range.set_minimum (0)
if range.maximum > 100:
    range.set_maximum (100)
        

The step attribute of the Range is useful to increment or decrement the value of it in a constant manner. By default it is set to 1.0.

range.step = 10.0
range.set_step (-3.2)
        

The value of the Range can be read and set via the value attribute and set_value() method. It can not grow beyond the upper or lower limit of the Range. Assigning a value not within those limitations will let it raise an exception.

range.value = 4.59
range.set_value (4.59)
        

For an efficient usage of the Range within loops, etc. the increase() and decrease() are supplied by it.

range.increase ()
range.decrease ()
        

The Range raises a SIG_VALCHANGED event, whenever its value changed. This means a real value change, reassignments of the same value are ignored. The following example code shows this behaviour.

def val_changed (range):
   print "The value changed to: %d" % range.value

range.connect_signal (SIG_VALCHANGED, val_changed, range)
if range.value != 10.0:
    range.value = 10.0 # Signal handler is invoked.
range.value = 10.0     # Nothing happens.
        

Scale widgets separate in an abstract Scale base class, which mainly contains internal code needed by its both subclasses, the VScale and HScale widget. A Scale, inherited from the Range, is a widget that lets you pick a value from a range using a vertical (VScale) or horizontal (HScale) slider. Those both widgets only differ in their appearance.

To create a HScale or VScale widget, you typically will use the same constructor syntax as for the Range widget.

hscale = HScale (minimum, maximum, step)
vscale = VScale (minimum, maximum, step)
        

The most important attributes and methods are already explained in the section called “Range”, so they will not be explained here again.

The Scale widgets listen to the three available mouse events,

Similar to the Scale widget, the ScrollBar lets you pick a value from a range, but additionally contains two buttons at its ends, which allow the user to increment or decrement the value stepwise. The ScrollBar is usually not used as standalone widget, but instead serves as control in more complex widgets, which need scrolling abilities.

In contrast to the Scale, the ScrollBar uses a slider with a variable size, which depends on the length of the ScrollBar and the maximum value of it. The slider however has a defined minimum size, so that it will not shrink to an unusable size by default.

The procedure to create a ScrollBar is similar to the Scale and Range.

hscrollbar = HScrollBar (minimum, maximum, step)
vscrollbar = VScrollBar (minimum, maximum, step)
        

The most important attributes and methods are already explained in the section called “Scale” and the section called “Range”, so they will not be explained here again.

The Scrollbar widgets listen to the three available mouse events,

The abstract Bin class is a container, that is able to hold exactly one child. It allows to bind und unbind a child widget and supports setting an additional padding between its surface borders and the child surface.

You usually will not create a Bin object directly, but inherit from it in your own widget classes.

The child of a Bin can be set with the child attribute or set_child() method. It is not necessary to register the child at an event manager after binding it to the Bin as this will set the event manager of the child to its own one.

label = Label ("Label for a bin")
bin.set_child (label)
# No need to set an event manager explicitly for the label.
bin.manager = eventmanager
        

For layout purposes the Bin can make use of additional pixels to place between its outer surface edges and the child surface. This pixel amount can be modified and used using the padding attribute of the Bin. Various inheritors within the widgets module of OcempGUI make heavy use of this attribute to adjust the look of themselves. The following example demonstrates this.

from ocempgui.widgets import Button, Renderer
renderer = Renderer ()
renderer.create_screen (200, 120)
button_5px = Button ("Button with 5px padding")
button_5px.position = 5, 5
button_5px.padding = 5

button_10px = Button ("Button with 10px padding")
button_10px.position = 5, 60
button_10px.padding = 10

renderer.add_widget (button_5px, button_10px)
renderer.start ()
        

TODO: provide implementation examples

The abstract Container widget class is similar to the Bin class, except that it can hold more than one widget.

As well as with the Bin, you usually will not create a Container object directly, but inherit from it in your own class.

The children can be added and removed using the add_child() and remove_child() methods of the Container. In contrast to the Bin you cannot add those to the children attribute directly, which also should be modified by no means except, that you know, what you are doing. Doing otherwise can result in an unwanted misbehaviour of the Container and GUI.

Adding multiple children at once is possible, while the removal of them can be done with one widget at a time only.

container.add_child (label1, button1, label2, entry1)

# Only one child can be removed at a time.
container.remove_child (button1)
        

Besides the padding attribute, which was already explained in the section called “Bin” the Container has a spacing attribute, which indicates the pixel amount to place between its children.

container.spacing = 10
        

TODO: provide implementation examples

Frame widgets are Containers, that support drawing a decorative border and title widget around their children. The basic Frame class is an abstract class, which defines the common attributes and methods for its inheritors, while the HFrame and VFrame widgets are concrete implementations, that place their children horizontally or vertically. Both subclasses only differ in the placing behaviour of their widgets and the basic aligning possibilities, so that, if not stated otherwise, the following examples always apply to both widget types, although the HFrame is used.

The creation of a HFrame is done using

frame = HFrame ()
frame = HFrame (widget)
        

frame = HFrame (Label ("A title label"))
frame.widget = Button ("Button as frame title")
frame.set_widget (VFrame (Label ("Frame in a frame")))
        

To adjust the look of the Frame, it is possible to change its border style using the border attribute

frame.border = BORDER_NONE
frame.set_border (BORDER_SUNKEN)
        

frame.align = ALIGN_TOP
frame.align = ALIGN_LEFT
        

hframe.align = ALIGN_TOP
hframe.set_align (ALIGN_BOTTOM)
        

vframe.align = ALIGN_LEFT
vframe.set_align (ALIGN_RIGHT)
        

Below you will find an example to illustrate most of the abilities of the Frame widget classes. You do not need to care about other widgets like the Table class for now as those are explained later on.

You can find the following example as a python script under examples/frame.py.

# Frame examples.
import os
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def create_frame_view ():
    table = Table (2, 3)
    table.position = 5, 5
    table.spacing = 5
    
    # Create and display two 'standard' frames.
    hframe = HFrame (Label ("Horizontal Frame"))
    table.add_child (0, 0, hframe)

    lbl = Label ("Vertical Frame" + os.linesep + "with 5 px spacing")
    lbl.multiline = True
    vframe = VFrame (lbl)
    vframe.spacing = 5
    table.add_child (0, 1, vframe)
    
    for i in xrange(3):
        btn = Button ("Button %d" % i)
        hframe.add_child (btn)
        btn2 = Button ("Button %d" % i)
        vframe.add_child (btn2)

    # Create framed frames.
    framed1 = VFrame (Label ("VFrame"))
    framed2 = HFrame ()
    framed3 = VFrame (Label ("VFrame as HFrame.widget"))
    framed3.add_child (Label ("Child of a VFrame"))
    framed2.widget = framed3
    framed2.add_child (Button ("Button 1"), Button ("Button 2"))
    button = Button ("Simple Button")
    framed1.add_child (framed2, button)
    table.add_child (1, 0, framed1)

    # Create a Frame with alignment.
    frame_align = VFrame (Label ("VFrame with right alignment"))
    frame_align.align = ALIGN_RIGHT
    label1 = Label ("Label")
    label2 = Label ("Even longer label")
    button = CheckButton ("A CheckButton")
    frame_align.add_child (label1, label2, button)
    table.add_child (1, 1, frame_align)

    # Add insensitive frames.
    hframe = HFrame (Label ("Insensitive HFrame"))
    hframe.sensitive = False
    table.add_child (0, 2, hframe)
    
    vframe = VFrame (Label ("Insensitive VFrame"))
    vframe.sensitive = False
    table.add_child (1, 2, vframe)
    
    for i in xrange(3):
        btn = Button ("Button %d" % i)
        hframe.add_child (btn)
        btn2 = Button ("Button %d" % i)
        vframe.add_child (btn2)
   
    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (600, 300)
    re.title = "Frame examples"
    re.color = (234, 228, 223)
    re.add_widget (create_frame_view ())

    # Start the main rendering loop.
    re.start ()

Table widgets, which inherit from the Container class, allow a table-like placement of their children in rows and columns. The children can be placed in the table cells and each cell supports an individual alignment.

The Table constructor expects the row and column dimensions to set up for the table, so that

table = Table (2, 2)
table2 = Table (3, 5)
        

Adding children is different from the usual Container methods. The Table needs the additional information, in which cell to place the child. Thus instead of using

table.add_child (child_widget1, child_widget2) # This does not work!
        

table.add_child (row, column, child_widget1)
table.add_child (row1, column1, child_widget2)
        

As said above, each cell of the Table supports using an own alignment, which can be set with the set_align() method.

table.set_align (0, 1, ALIGN_TOP)
table.set_align (1, 1, ALIGN_LEFT)
        

# Aligning the child at the topleft.
table.set_align (0, 1, ALIGN_TOP | ALIGN_LEFT)

# Conflicting alignments, thus using the higher priority of ALIGN_BOTTOM.
table.set_align (0, 1, ALIGN_TOP | ALIGN_BOTTOM)

# Again a conflict. ALIGN_NONE has the lowest priority, thus it will be
# left aligned.
table.set_align (0, 1, ALIGN_LEFT | ALIGN_NONE)
        

table.set_row_align (row, alignment)
table.set_column_align (column, alignment)
        

Below you will find an example to illustrate most of the abilities of the Table widget class.

You can find the following example as a python script under examples/table.py.

# Table examples.
from ocempgui.widgets import Renderer, Table, Label, Button
from ocempgui.widgets.Constants import *

def create_table_view ():
    # Crate and display a Table.
    table = Table (9, 2)
    table.spacing = 5
    table.position = 5, 5

    label = Label ("Nonaligned wide Label")
    table.add_child (0, 0, label)
    table.add_child (0, 1, Button ("Simple Button"))

    label = Label ("Top align")
    table.add_child (1, 0, label)
    table.set_align (1, 0, ALIGN_TOP)
    table.add_child (1, 1, Button ("Simple Button"))

    label = Label ("Bottom align")
    table.add_child (2, 0, label)
    table.set_align (2, 0, ALIGN_BOTTOM)
    table.add_child (2, 1, Button ("Simple Button"))
    
    label = Label ("Left align")
    table.add_child (3, 0, label)
    table.set_align (3, 0, ALIGN_LEFT)
    table.add_child (3, 1, Button ("Simple Button"))
    
    label = Label ("Right align")
    table.add_child (4, 0, label)
    table.set_align (4, 0, ALIGN_RIGHT)
    table.add_child (4, 1, Button ("Simple Button"))

    label = Label ("Topleft align")
    table.add_child (5, 0, label)
    table.set_align (5, 0, ALIGN_TOP | ALIGN_LEFT)
    table.add_child (5, 1, Button ("Simple Button"))

    label = Label ("Topright align")
    table.add_child (6, 0, label)
    table.set_align (6, 0, ALIGN_TOP | ALIGN_RIGHT)
    table.add_child (6, 1, Button ("Simple Button"))

    label = Label ("Bottomleft align")
    table.add_child (7, 0, label)
    table.set_align (7, 0, ALIGN_BOTTOM |ALIGN_LEFT)
    table.add_child (7, 1, Button ("Simple Button"))

    label = Label ("Bottomright align")
    table.add_child (8, 0, label)
    table.set_align (8, 0, ALIGN_BOTTOM |ALIGN_RIGHT)
    table.add_child (8, 1, Button ("Simple Button"))

    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (250, 350)
    re.title = "Table examples"
    re.color = (234, 228, 223)
    re.add_widget (create_table_view ())
    # Start the main rendering loop.
    re.start ()

ScrolledWindow widgets are Bin widgets that add scrolling abilities to their attached child. This is extremely useful for situations, in which the widget to scroll should not exceed a specific size, but has to display all of its data. Putting such a widget in a ScrolledWindow allows you to respect this specific size, while the widget can grow as it wants.

You create a ScrolledWindow using

window = ScrolledWindow (width, height)
        

The widget, which needs to be scrolled is packed into the ScrolledWindow the usual Bin way.

window.child = widget_to_scroll
        

To allow a flexibly scrolling behaviour, you can adjust the scrolling attribute to make the ScrolledWindow automatic scrolling, always scrolling or never scrolling.

window.scrolling = SCROLL_ALWAYS
window.scrolling = SCROLL_NEVER
window.scrolling = SCROLL_AUTO
        

You also can influence the scrollbars of the ScrolledWindow programmatically.

window.vscrollbar.value = 0
window.hscrollbar.value = window.vscrollbar.maximum
       

The ScrolledWindow widget natively listens to two signals to support better navigation possibilities. Those are

The ScrolledList widget class can be used to display and manage collections in a list-style look and feel. Technically it is a ScrolledWindow, which holdes a ListViewPort that takes care of displaying the list contents.

As the ScrolledWindow the ScrolledList supports different scrolling types and anything else, while the keyboard and mouse behaviour differ slightly to match the needs of list browsing.

To create a ScrolledList you have to supply the sizing dimensions and an optional collection, which makes up the contents.

scrolledlist = ScrolledList (width, height, collection=None)
        

Items can be added and removed dynamically to the list using the items property.

for no in xrange (10):
    scrolledlist.items.append (TextListItem ("Item no. %d" % no))

# Last one was too much.
scrolledlist.items.remove (scrolledlist.items[-1])
        

The FileList widget is useful to display filesystem contents in a list-style manner. It supports the distinction between different filetypes through the FileListItem item type and allows you to browse filesystem contents.

As the ScrolledList, from which the FileList inherits, you need to pass the size dimensions it should occupy and optionally the initial starting directory to list the contents of.

filelist = FileList (200, 400, "/usr/home")
        

It allows to list directories programmatically through the directory attribute and set_directory() method.

filelist.directory = "C:\"
filelist.set_directory ("/tmp")
        

The FileList additionally supports the SIG_DOUBLECLICKED signal to allow changing directories interactively. Of course own methods can be bound to it.

The base for all the different window types is the Window class. It is a Bin container with the additional ability to collapse itself to its caption bar.

To create a Window you can simply call its constructor and provide an optional title text, that will be used as caption.

window = Window ("My new window")
        

The title can be retrieved or set at any later time with the title attribute.

window.title = "A new title!"
        

As already mentioned above, the Window allows the user to minimize it (and of course restore it), which is also possible in your own code.

if not window.minimized:
    window.minimize (True)
        

You can align the child of the window using the align attribute. Different alignments can be combined, although not any case makes sense and some alignment combinations conflict with each other.

# Align the child at the top.
window.align = ALIGN_TOP

# Align the child at the bottom left.
window.align = ALIGN_BOTTOM | ALIGN_LEFT

# Invalid alignment, ALIGN_BOTTOM has a higher priority, thus
# the child will be aligned at the bottom.
window.align = ALIGN_TOP | ALIGN_BOTTOM
        

The Window widget by default listens to the following signals:

Below you will find an example of the Window widget class. You do not need to care about the DialogWindow class for now as this is explained in the next section.

You can find the following example as a python script under examples/window.py.

# Window examples.
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _destroy_dialog (window):
    window.child.text = "#Close"
    
def create_window_view ():
    # Create and display a simple window.
    window = Window ("Simple window")
    window.child = Button ("#Not clickable")
    window.child.connect_signal (SIG_CLICKED, window.destroy)
    window.position = 5, 5
    window.depth = 1
    
    # Create dialog window.
    dialog = DialogWindow ("Modal dialog window")
    dialog.child = Button ("#Close first to use other widgets")
    dialog.child.connect_signal (SIG_CLICKED, _destroy_dialog, window)
    dialog.child.connect_signal (SIG_CLICKED, dialog.destroy)
    dialog.position = 100, 5
    dialog.depth = 2
    
    return window, dialog

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (400, 200)
    re.title = "Window examples"
    re.color = (234, 228, 223)
    re.add_widget (*create_window_view ())
    # Start the main rendering loop.
    re.start ()

The DialogWindow is a modal Window widget, that grabs all events that are sent through the event manager it is attached to. The user will not be able to interact with other event capable elements until the DialogWindow is destroyed. Widgets, that are attached to it of course will still be notified.

The DialogWindow does not offer any new features besides those it incorporates from its parent class(es). To create a new DialogWindow you use the same constructor syntax as for the Window.

window = DialogWindow ("A new DialogWindow")
        

You can find an example of the DialogWindow in Example 33, “Window example”.

It is often needed to know about how the user interacted with a certain dialog. Creating various Buttons with different callbacks or one callback, in which the buttons are distinguished is of course possible, but finding a safe distinction mode is a more complex task. You might argue, that you could check the text of the Button, but that only will work, if you do not want to offer localized version of you program.

To circumvent this and other issues the GenericDialog widget class was created. It allows you to associate different states with the buttons you want to place on it.

To create a GenericDialog you have to pass two lists to its constructor, one containing the Button widgets you want to display and one with the result states to associate with.

list1 = [Button ("OK"), Button("Cancel")]
list2 = [DLGRESULT_OK, DLGRESULT_CANCEL]
dialog = GenericDialog ("Title", list1, list2)
        

This means, that the first Button in the list will be displayed at the leftmost of all other Buttons, while it will be associated with the first item of the result list.

To allow a more flexible button and result behaviour (as needed in wizard dialogs for example), you can place new buttons and results at runtime on the dialog.

newlist1 = [Button ("Close"), Button ("Help")]
newlist2 = [DLGRESULT_CLOSE, DLGRESULT_USER]
dialog.set_buttons (newlist1, newlist2)
        

Now all you have to do is to connect your GenericDialog with a callback for the SIG_DIALOGRESPONSE signal, it listens to.

def my_callback (result, dlg):
    if result == DLGRESULT_CLOSE:
        dlg.destroy ()
    elif result == DLGRESULT_USER:
        ...

dialog,connect_signal (SIG_DIALOGRESPONSE, my_callback, dialog)
        

To place your own widgets and contents in the dialog, you can use the content attribute, which is a VFrame.

label1 = Label ("Label 1")
entry = Entry ("Hello world")
dialog.content.add_child (label1, entry)
...
        

Below you will find an example of the GenericDialog widget class.

You can find the following example as a python script under examples/genericdialog.py.

# GenericDialog examples.
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _close (result, dialog, label):
    if result == DLGRESULT_OK:
        label.text = "You pressed OK!"
    elif result == DLGRESULT_CANCEL:
        label.text = "You pressed Cancel!"
    elif result == DLGRESULT_CLOSE:
        dialog.destroy ()

def create_dialog_view ():
    buttons = [Button ("#OK"), Button ("#Cancel"), Button ("Clo#se")]
    results = [DLGRESULT_OK, DLGRESULT_CANCEL, DLGRESULT_CLOSE]
    dialog = GenericDialog ("Generic dialog", buttons, results)
    lbl = Label ("Press the buttons to see the action.")
    dialog.content.add_child (lbl)
    dialog.connect_signal (SIG_DIALOGRESPONSE, _close, dialog, lbl)
    dialog.position = 30, 30
    dialog.depth = 1
    return dialog

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (300, 300)
    re.title = "GenericDialog examples"
    re.color = (234, 228, 223)
    re.add_widget (create_dialog_view ())
    # Start the main rendering loop.
    re.start ()

The FileDialog widget allows the user to choose files and directories from a FileList and can return those easily by a corresponding method. It also includes an Entry widget at the top, which keeps track of the current location and lets the user change the directory path quickly.

To create a FileDialog you have would type something like

dialog = FileDialog ("Select a file...", [Button ("OK")], [DLGRESULT_OK])
        

The selected file and directory entries can be received easily using the get_filenames() method.

selection = dialog.get_filenames()
        

Below you will find an example of the FileDialog widget class.

You can find the following example as a python script under examples/filedialog.py.

# FileDialog examples.
import os
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _set_files (result, dialog, entry):
    string = ""
    if result == DLGRESULT_OK:
        string = "".join(["\"%s\" " % f for f in dialog.get_filenames ()])
    else:
        string = "Nothing selected"
    dialog.destroy ()
    entry.text = string
    
def _open_filedialog (renderer, entry):
    buttons = [Button ("#OK"), Button ("#Cancel")]
    buttons[0].size = 80, buttons[0].size[1]
    buttons[1].size = 80, buttons[1].size[1]
    results = [DLGRESULT_OK, DLGRESULT_CANCEL]

    dialog = FileDialog ("Select your file(s)", buttons, results)
    dialog.depth = 1 # Make it the top window.
    dialog.position = 100, 20
    dialog.filelist.selectionmode = SELECTION_MULTIPLE
    dialog.connect_signal (SIG_DIALOGRESPONSE, _set_files, dialog, entry)
    renderer.add_widget (dialog)

def create_file_view (renderer):
    table = Table (1, 2)
    
    hframe = HFrame (Label ("FileList"))
    hframe.add_child (FileList (200, 200))
    table.add_child (0, 0, hframe)
    
    hframe2 = HFrame (Label ("FileDialog"))
    label = Label ("Selection:")
    entry = Entry ()
    entry.size = 200, entry.size[1]
    button = Button ("#Browse")
    button.connect_signal (SIG_CLICKED, _open_filedialog, renderer, entry)
    hframe2.add_child (label, entry, button)
    table.add_child (0, 1, hframe2)
    
    table.set_row_align (0, ALIGN_TOP)
    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (550, 300)
    re.title = "FileDialog examples"
    re.color = (234, 228, 223)
    re.add_widget (create_file_view (re))
    # Start the main rendering loop.
    re.start ()

The ImageMap is a widget, that can display any type of image, pygame can handle, and supports different mouse events.

In contrast to the ImageButton it does not react visually upon those events, but can store the last event, that occured as well as providing the relative position coordinates of the event.

To create an ImageMap, you have to provide an image surface or filename similar to the ImageButton constructor.

imagemap = ImageMap ("path/to/an/image.png")
imagemap = ImageMap (pygame_surface)
        

Below you will find an example of the ImageMap widget class.

You can find the following example as a python script under examples/imagemap.py.

# ImageMap examples.
import os
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _get_type (eventtype):
    if eventtype == SIG_MOUSEDOWN:
        return "SIG_MOUSEDOWN"
    elif eventtype == SIG_MOUSEUP:
        return "SIG_MOUSEUP"
    elif eventtype == SIG_MOUSEMOVE:
        return "SIG_MOUSEMOVE"
    else:
        return "Unknown signal"

def _got_mouseevent (event, imagemap, labels):
    labels[0].text = "Signal: %s" % _get_type (imagemap.last_event.signal)
    if imagemap.last_event.signal != SIG_MOUSEMOVE:
        labels[1].text = "Button: %d" % imagemap.last_event.data.button
    else:
        labels[1].text = "Button: None"
    labels[2].text = "Event pos: %s" % str (imagemap.last_event.data.pos)
    labels[3].text = "Rel. pos: %s" % str (imagemap.relative_position)

def _create_vframe (text):
    frame = VFrame (Label (text))
    frame.spacing = 5
    frame.align = ALIGN_LEFT
    return frame

def create_imagemap_view ():
    frm_map = _create_vframe ("ImageMap")

    imagemap = ImageMap ("image.png")
    
    lbl_desc = Label ("Move the mouse over the ImageMap and" + os.linesep +
                      "press the mouse buttons to interact with it.")
    lbl_desc.multiline = True
    
    lbl_results = [Label ("Signal:"), Label ("Button:"), Label ("Event pos:"),
                   Label ("Rel. pos:")]
    for label in lbl_results:
        label.get_style()["fgcolor"][STATE_NORMAL] = (255, 0, 0)
    imagemap.connect_signal (SIG_MOUSEDOWN, _got_mouseevent, imagemap,
                             lbl_results)
    imagemap.connect_signal (SIG_MOUSEMOVE, _got_mouseevent, imagemap,
                             lbl_results)
    imagemap.connect_signal (SIG_MOUSEUP, _got_mouseevent, imagemap,
                             lbl_results)

    frm_map.add_child (imagemap, lbl_desc, *lbl_results)
    return frm_map

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (550, 470)
    re.title = "ImageMap examples"
    re.color = (234, 228, 223)
    re.add_widget (create_imagemap_view ())
    # Start the main rendering loop.
    re.start ()

The ProgressBar is a non-interactive widget class, that uses a horizontal bar to display operation efforts. Its value range reaches from 0.0 to 100.0.

To create a ProgressBar widget, you simply will invoke its constructor with no arguments.

bar = ProgressBar ()
        

Similar to the Range widget class, the ProgressBar supports the step and set_step() methods to set the step range for continouos increments/decrements

bar.step = 1.4
bar.set_step (10)

# Increment/decrement the bar value by the currently set step range.
while process_runs:
    bar.increment ()           # or bar.decrement ()
    ...
        

bar.value = 50.0
        

You can optionally display a short amount of text centered on it, which can be set with the text attribute or set_text() method.

bar.text = "Processing data..."
bar.set_text ("Please wait...")
        

Below you will find an example of the ProgressBar widget class.

You can find the following example as a python script under examples/progressbar.py.

# ProgressBar examples.
from ocempgui.widgets import *
from ocempgui.widgets.Constants import *

def _update_bar (bar, button):
    if bar.value == 0:
        while bar.value < 100:
            bar.increase ()
            bar.manager.force_update ()
        button.text = "Clean the progressbar"
    else:
        while bar.value > 0:
            bar.decrease ()
            bar.manager.force_update ()
        button.text = "Fill the progressbar"

def _update_text (bar):
    bar.text = "%.2f" % bar.value + "%"

def _create_vframe (text):
    frame = VFrame (Label (text))
    frame.spacing = 5
    frame.align = ALIGN_LEFT
    return frame

def create_progressbar_view ():
    table = Table (1, 3)
    table.spacing = 5
    
    # Create and display a simple ProgressBar.
    frame = _create_vframe ("ProgressBar")
    progress = ProgressBar ()
    progress.step = 0.5

    # Create a button to start filling.
    btn = Button ("#Fill the ProgressBar")
    btn.connect_signal ("clicked", _update_bar, progress, btn)
    frame.add_child (progress, btn)
    table.add_child (0, 0, frame)

    # ProgressBar with text.
    frame = _create_vframe ("Progressbar with text")
    progress = ProgressBar ()
    progress.text = "0.00%"
    progress.step = 0.5
    progress.connect_signal (SIG_VALCHANGED, _update_text, progress)
                             
    # Create a button to start filling.
    btn = Button ("Fill the ProgressBar")
    btn.connect_signal ("clicked", _update_bar, progress, btn)
    frame.add_child (progress, btn)
    table.add_child (0, 1, frame)

    # Insensitive progressbar.
    frame = _create_vframe ("Insensitive Progressbar")
    progress = ProgressBar ()
    progress.value = 50.0
    progress.text = "50.00%"
    progress.sensitive = False
    frame.add_child (progress)
    table.add_child (0, 2, frame)
    
    return table

if __name__ == "__main__":
    # Initialize the drawing window.
    re = Renderer ()
    re.create_screen (450, 150)
    re.title = "ProgressBar examples"
    re.color = (234, 228, 223)
    re.add_widget (create_progressbar_view ())
    # Start the main rendering loop.
    re.start ()

The ListItem component is an abstract base class for creating own item implementations, which are suitable for the usage in list or tree widgets. It contains a set of attributes and methods, which make it ready to be used in the ListItemCollection collection class.

You usually will not create ListItem objects directly, but instead subclass them, whenever you need a more advanced or specialized item type, than the TextListItem and FileListItem offer.

Similar to the widgets inheriting from the BaseWidget class, the ListItem offers a style attribute, that lets you set up an instance specific look and feel for it.

# Create the instance specific style information.
listitem.get_style()
listitem.style['font']['size'] = 16 
        

The collection, the item should be or is bound to, can be read and set by accessing its collection attribute.

if listitem.collection != my_collection:
    listitem.set_collection (my_collection)
        

To make the ListItem suitable for tree or list widgets, it contains a selected attribute that, as the name says, can be used by the according widget implementation to set or determine the selection state of the item.

if not listitem.selected:
    listitem.selected = True
        

For optimization purposes in drawing the ListItem contains, similar to the BaseWidget, a dirty attribute and set_dirty() method.

listitem.dirty = True
        

For concrete implementations and examples, the author recommends to look at the source code of the TextListItem and FileListItem implementations, which will be explained hereafter.

The TextListItem - as its name suggests - is a ListItem, that is able to store and show text. Besides this it does not offer anything oustanding so that its only improvements are to set and get text.

A TextListItem is created by passing the text it should store to its constructor.

listitem = TextListItem ("This is a TextListItem")
        

listitem.text = "I contain changed text."
        

The FileListItem is an advanced TextListItem, which contains additional attributes to make it suitable for storing different file related information.

The FileListItem requires besides a text the file mode information (those are explained in detail in the stat documentation).

# Retrieve the stats for a file.
st = os.stat ("myfile")

# Create the item with the file modes.
listitem = ("myfile", st.st_mode)
        

Dependant on the passed file mode, which will be stored in the filetype attribute,

if stat.S_ISDIR (listitem.filetype):
    print "Item %s is a directory, hooray!" % listitem.text
        

The ListItemCollection is a wrapper around the python builtin type list. It supports a set of most important list operations, such as iterators, slicing and sorting. Several methods, especially the arithmetic overloads (addition, mulitplication, etc.) are not available. For a complete list of supported operations, browse the documentation strings of the ListItemCollection.

The ListItemCollection is created by simply invoking its constructor.

collection = ListItemCollection ()
        

collection.append (item1)
collection.insert (9, item2)
        

The specialities of the ListItemCollection are, that it only accepts ListItem objects as valid items on the one hand and supports two notification slots on the other. Those notification slots are implemented as attributes, item_changed and list_changed. Any method or function can be bound to those to get informed about item changes in the list (e.g. an item has changed its contents) and list changes in general (items were added, removed, etc.). The item_changed attribute additionally passes the affected item to the notification handler, while list_changed() will pass the ListItemCollection.

You can find the following example as a python script under examples/label.py.

# ListItemCollection example.
from ocempgui.widgets.components import ListItemCollection, TextListItem

# Item change handler.
def item_has_changed (item):
    print "Item '%s' has changed" % item.text

# List change handler.
def list_has_changed (l):
    print "List now contains %d item(s)" % l.length

collection = ListItemCollection ()

# Set up a notification handler for item changes.
collection.item_changed = item_has_changed

# Set up a notification handler for list changes
collection.list_changed = list_has_changed

for i in xrange (5):
    collection.append (TextListItem ("Item no. %d" % i))

collection[2].text = "New text in item 3"

First of all you should make yourself a picture about how the widget should look like and what it should be able to do. In our case, this would be an area consisting of 9x9 squares, of which each is clickable exactly one time and should fill - dependant on whose turn it is - the square with either a cross or a circle. When the game is ended, the widget should note that by sending a corresponding event, so that other widgets can update themselves according to that.

After you know about how it should look like and what it should be able to do, its time to collect the things you need. Whenever it is possible, you should use existing code or classes, so that you do not need to reinvent anything.

Luckily our example can be completed by using a Table widget with 3 rows and 3 columns and nine ImageButton widgets, that can display the circle or cross. The only things, that do not exist are the signal and graphics for a circle and cross.

We start by creating a custom class, that inherits directly from the Table.

from ocempgui.draw import Image
from ocempgui.widgets import Table
from ocempgui.widgets.Constants import *

class TicTacToe (Table):
    """The famous game as widget.
    """
    def __init__ (self):
        Table.__init__ (self, 3, 3)
        

class TicTacToe (Table):
    ...
    def __init__ (self):
        Table.__init__ (self, 3, 3)
        for i in xrange (3):
            for j in xrange (3):
                button = ImageButton ()
                button.size = 60, 60
                self.add_child (i, j, button)
        

class TicTacToe (Table):
    ...
    def __init__ (self):
        Table.__init__ (self, 3, 3)
        self._curplayer = "Player 1"

        for i in xrange (3):
            for j in xrange (3):
                ...
                button.connect_signal (SIG_CLICKED, self._clicked, button,
                                       i, j)
        

class TicTacToe (Table):
    ...
    def __init__ (self):
        ...

    def _clicked (self, button, i, j):
        """Sets the image of the button, if not already done.
        """
        button = self.grid[(i, j)]
        # Check, if it is not already set.
        if button.picture == None:
            if self._curplayer == "Player 1":
                # Use the cross. As the ImageButton does not make use of
                # transparency or colorkeys, we will load our images
                # manually and set the image surface then.
                button.picture = Image.load_image ("cross.png", True)
                self._curplayer = "Player 2"
            else:
                button.picture = Image.load_image ("circle.png", True)
                self._curplayer = "Player 1"
        

The widget is fairly usable now, but still lacks the event mechanism, which will be explained in the next section.

To allow a better interactivity with the TicTacToe widget, it will invoke its event handlers, whenever a player clicked on a square. Dependant on what happens, the event mechanism should indicate this. Thus it will have to pass additional data to the event handlers. We want it to send the following data:

Implementing the first and second event is easy and we only have to add four lines of code to our existing class. The first line will define the SIG_TICTACTOE signal.

from ocempgui.widgets import Table
from ocempgui.widgets.Constants import *

SIG_TICTACTOE = "tictactoe"

class TicTacToe (Table):
    """The famous game as widget.
    """
    ...
        

class TicTacToe (Table):
    """The famous game as widget.
    """
    def __init__ (self):
        ...
        self._signals[SIG_TICTACTOE] = []
        

class TicTacToe (Table):
    ...
    def _clicked (self, button, i, j):
        """Sets the image of the button, if not already done.
        """
        button = self.grid[(i, j)]
        # Check, if it is not already set.
        if button.picture == None:
            if self._curplayer == "Player 1":
                button.picture = "cross.png"
                self._curplayer = "Player 2"
            else:
                button.picture = "circle.png"
                self._curplayer = "Player 1"
            self.run_signal_handlers (SIG_TICTACTOE, "valid square")
        else:
            self.run_signal_handlers (SIG_TICTACTOE, "invalid square")
        

The third event handler requires a bit more work as we have to check, if there are three buttons displaying the same picture in a row. The simplest (and unoptimized) algorithm for that would be:

class TicTacToe (Table):
    ...
    def _check_input (self):
        """Checks for three in a row.
        """
        three = False
        image = None

        # Check the columns
        for i in xrange (3):
            if three:
                break
            image = self.grid[(i, 0)].path
            if image:
                three = (self.grid[(i, 1)].path == image) and \
                        (self.grid[(i, 2)].path == image)

        if not three:
            # Check the rows.
            for i in xrange (3):
                if three:
                    break
                image = self.grid[(0, i)].path
                if image:
                    three = (self.grid[(1, i)].path == image) and \
                            (self.grid[(2, i)].path == image)

        if not three:
            # Diagonal left to right
            image = self.grid[(0, 0)].path
            if image:
                three = (self.grid[(1, 1)].path == image) and \
                        (self.grid[(2, 2)].path == image)
            if not three:
                # Diagonal right to left
                image = self.grid[(2, 0)].path
                if image:
                    three = (self.grid[(1, 1)].path == image) and \
                            (self.grid[(0, 2)].path == image)

        if three:
            self._finished = True
            self.run_signal_handlers (SIG_TICTACTOE, ("win", self._curplayer))
        

class TicTacToe (Table):
    """The famous game as widget.
    """
    def __init__ (self):
        ...
        self._finished = False
        

    def _clicked (self, button, i, j):
        """Sets the image of the button, if not already done.
        """
        if self._finished:
            return
        
        button = self.grid[(i, j)]
        # Check, if it is not already set.
        if button.picture == None:
            if self._curplayer == "Player 1":
                # Use the cross.
                button.picture = "cross.png"
            else:
                button.picture = "circle.png"
            self.run_signal_handlers (SIG_TICTACTOE, "valid square")
            self._check_input ()

            # Set it after the check, so we can get the correct player name.
            if self._curplayer == "Player 1":
                self._curplayer = "Player 2"
            else:
                self._curplayer = "Player 1"
        else:
            self.run_signal_handlers (SIG_TICTACTOE, "invalid square")
        

The rendering engine contains several methods to draw each widget and some generalized methods for some commonly used parts such as the basic widget surface. The widget to draw is passed to its matching drawing method, which will look up its style settings and then draw it.

Figure 3. Widget drawing process

The Style supports cascading the widget style settings. This means, that it will, when it retrieves the widget style and does not find the style setting it needs, walk through the inherited classes (the __mro__ attribute) of the widget until it finds the setting. The last instance it looks the setting up in is the "default" entry of its styles attribute.

Theme files for OcempGUI define the most basic settings for the widgets, such as the background color or the font to use. They however do not cause the widget to look completely different. The basic widget layout will stay the same.

The theme files are read by the currently active Style class (see the section called “Using own drawing routines” for details about the currently active class) and their information will be stored in its styles dictionary.

The currently active theme information for a specific widget class are stored in the styles attribute by using its lowercase classname. This means that the specific theme for a Button widget is stored in Style.styles["button"]. For a Label widget it would be Style.styles["label"] and so on.

Such an theme entry is a dictionary, that contains various information such as the background and foreground color for the different supported widget states, the font settings for that widget and more. The complete list of possible settings can be found in the documentation of the Style, so it will not be covered in detail here.

Setting up individual styles should be done using an own file for them, so you can easily change them without touching your program code. Let us create a separate theme file, that will cause the buttons to use a blue background color and the labels a different font and foreground color.

After creating the file for that (the author recommends using the suffix ".rc" for theme files), we use the python syntax for the contents. First we have to let the file and its content know about the supported widget states, thus we will import the Constants of the ocempgui.widgets module.

from ocempgui.widgets import Constants
        

Now we will set up our theme dictionary for the Button widget.

from ocempgui.widgets import Constants

button = { "bgcolor" : { Constants.STATE_NORMAL : (18, 12, 135),
                         Constants.STATE_ENTERED : (32, 25, 164),
                         Constants.STATE_ACTIVE : (18, 12, 135),
                         Constants.STATE_INSENSITIVE : (54, 51, 106) }
           }
        

You can easily see this by placing a Button and a CheckButton side by side.

Let us now set the styles for the Label widget. The first part sets up the font, its size and if antialiasing should be used, the second one sets up different colors to use for the text according to the widget its state.

from ocempgui.widgets import Constants

...
label = { "font" : { "name" : "Helvetica", "size" : 16, "alias" : True },
          "fgcolor" : { Constants.STATE_NORMAL : (250, 250, 250),
                        Constants.STATE_ENTERED : (150, 150, 150),
                        Constants.STATE_ACTIVE : (0, 0, 0),
                        Constants.STATE_INSENSITIVE : (235, 235, 235) }
          }
        

As you see, setting up own themes for widgets is not a complex task. Let us now examine the complete code and a small example, that will make use of the just created theme.

from ocempgui.widgets import Constants

button = { "bgcolor" : { Constants.STATE_NORMAL : (18, 12, 135),
                         Constants.STATE_ENTERED : (32, 25, 164),
                         Constants.STATE_ACTIVE : (18, 12, 135),
                         Constants.STATE_INSENSITIVE : (54, 51, 106) }
           }
label = { "font" : { "name" : "Helvetica", "size" : 16, "alias" : True },
          "fgcolor" : { Constants.STATE_NORMAL : (250, 250, 250),
                        Constants.STATE_ENTERED : (150, 150, 150),
                        Constants.STATE_ACTIVE : (0, 0, 0),
                        Constants.STATE_INSENSITIVE : (235, 235, 235) }
          }

# Theme usage example.
from ocempgui.widgets import *

# Load the theme.
base.GlobalStyle.load ("theme_example.rc")

# Create screen.
re = Renderer ()
re.create_screen (200, 100)
re.title = "Theme example"

# Create widgets.
button = Button ("Button")
button.position = 5, 5
label = Label ("Label")
label.position = 100, 5
re.add_widget (button, label)
re.start ()

Whenever you need an completely different layout, the creation of own theme files will not be enough. This section explains how to modify and/or override the drawing methods for the widgets.

First you should make yourself clear about if you need to provide and own layout only for specific instances of a widget or if those widgets always should be drawn that way. Dependant on your needs, you have several possibilites.

While the first both entries should not need any explanation, the last one includes a bit more work, so let us take a closer look at it.

We will create an own Style subclass and use an own drawing method for Label widgets, which adds a dropshadow to them by default. After creating this subclass we will use an instance of it for our own small test application.

The first we have to do is to inherit from the Style subclass.

from ocempgui.widgets import Style

class OwnStyle (Style):
    def __init__ (self):
        Style.__init__ (self)
        

As you can see from its signature, it receives one argument, the Label object, for which the surface should be created.

We will use the existing draw_label() method as template for our own one and modify it, so it matches our needs.

    def draw_label (self, label):
        """Overrides the label drawing method and adds a dropshadow."""
        # We do not care about multiline labels. Thus pass those to the
        # parent.
        if label.multiline:
            return Style.draw_label (self, label)
        

Now we shorten some attributes, which we will need in our method more often.

    def draw_label (self, label):
        ...
        cls = label.__class__
        state = label.state
        
        # Peek the style of the label so we can get the colors later.
        st = label.style or self.get_style (cls)
        

Now will get the foreground color to use for the text and store it temporarily as we will modify it in the st variable later.

    def draw_label (self, label):
        ...
        # Save the label color temporarily as we will change it for the
        # dropshadow. Because we are using references, not plain style
        # copies, we have to do this.
        fgcolor = self.get_style_entry (cls, st, "fgcolor", state)

        # The 2px added here are used for the dropshadow.
        width = 2 * label.padding + 2
        height = 2 * label.padding + 2
        

The basics are set up, so that we can proceed with drawing the surfaces for our widget.

    def draw_label (self. label):
        ...
        # Draw the text.
        front = None
        drop = None
        if label.mnemonic[0] != -1:
            front = self.draw_string_with_mnemonic (label.text, state,
                                                    label.mnemonic[0], cls,
                                                    label.style)
            # Swap colors.
            st["fgcolor"] = { state : self.get_style_entry (cls, st,
                                                            "lightcolor",
                                                            state) }
            drop = self.draw_string_with_mnemonic (label.text, state,
                                                   label.mnemonic[0], cls, st)
        else:
            front = self.draw_string (label.text, state, cls, label.style)
            # Swap colors.
            st["fgcolor"] = { state : self.get_style_entry (cls, st,
                                                            "lightcolor",
                                                            state) }
            drop = self.draw_string (label.text, state, cls, st)
        

You might wonder, why we use the get_style_entry() method here, as we could simply assign their both variables. If you remember correctly, what was stated in the section called “Changing the widget appearance”, the style information are cascaded, thus it is not guaranteed, that the lightcolor values are set. Therefore we will use this (more or less) failsafe method to retrieve a valid style entry for the lightcolor.

So we have our both surfaces now and are nearly done. But we have to respect some definitions of the BaseWidget and we have to reset the swapped colors.

    def draw_label (self, label):
        ...
        # Surface creation done. Restore the colors.
        st["fgcolor"][state] = fgcolor

        # Get the size of the surface(s) and add it to the complete
        # width and height, the label will occupy.
        rect = front.get_rect ()
        width += rect.width
        height += rect.height
        
        # Guarantee size.
        if width < label.size[0]:
            width = label.size[0]
        if height < label.size[1]:
            height = label.size[1]
        

    def draw_label (self, label):
        ...
        # Blit all and return the label surface to the caller.
        surface = self.draw_rect (width, height, label.state, cls, label.style)
        surface.blit (drop, (label.padding + 2, label.padding + 2))
        surface.blit (front, (label.padding, label.padding))
        return surface
        

So far so good. We now have our Style subclass, that will draw Label widgets with a dropshadow by default. The very last thing to do is to make the omcepgui.widgets module use our own class instead of the default. This is done by assigning the base.GlobalStyle variable an instance of our own class in the code, it should make use of it.

base.GlobalStyle = OwnStyle ()
        

The complete code of the previous example follows. It includes some test code, so you can easily evaluate the results.

# Style usage example.
from ocempgui.widgets import *

class OwnStyle (Style):
    def __init__ (self):
        Style.__init__ (self)

    def draw_label (self, label):
        """Overrides the label drawing method and adds a dropshadow."""
        # We do not care about multiline labels. Thus pass those to the
        # parent.
        if label.multiline:
            return Style.draw_label (self, label)

        cls = label.__class__
        state = label.state
        
        # Peek the style of the label so we can get the colors later.
        st = label.style or self.get_style (cls)

        # Save the label color temporarily as we will change it for the
        # dropshadow. Because we are using references, not plain style
        # copies, we have to do this.
        fgcolor = self.get_style_entry (cls, st, "fgcolor", state)

        # The 2px added here are used for the dropshadow.
        width = 2 * label.padding + 2
        height = 2 * label.padding + 2

        # Draw the text.
        front = None
        drop = None
        if label.mnemonic[0] != -1:
            front = self.draw_string_with_mnemonic (label.text, state,
                                                    label.mnemonic[0], cls,
                                                    label.style)
            # Swap colors.
            st["fgcolor"] = { state : self.get_style_entry (cls, st,
                                                            "lightcolor",
                                                            state) }
            drop = self.draw_string_with_mnemonic (label.text, state,
                                                   label.mnemonic[0], cls, st)
        else:
            front = self.draw_string (label.text, state, cls, label.style)
            # Swap colors.
            st["fgcolor"] = { state : self.get_style_entry (cls, st,
                                                            "lightcolor",
                                                            state) }
            drop = self.draw_string (label.text, state, cls, st)

        # Surface creation done. Restore the colors.
        st["fgcolor"][state] = fgcolor

        # Get the size of the surface(s) and add it to the complete
        # width and height, the label will occupy.
        rect = front.get_rect ()
        width += rect.width
        height += rect.height
        
        # Guarantee size.
        if width < label.size[0]:
            width = label.size[0]
        if height < label.size[1]:
            height = label.size[1]

        # Blit all and return the label surface to the caller.
        surface = self.draw_rect (width, height, label.state, cls, label.style)
        surface.blit (drop, (label.padding + 2, label.padding + 2))
        surface.blit (front, (label.padding, label.padding))
        return surface

if __name__ == "__main__":
    base.GlobalStyle = OwnStyle ()

    re = Renderer ()
    re.create_screen (200, 200)
    re.title = "Style example."
    re.color = (234, 228, 223)

    label = Label ("Example label")
    label.get_style ()["font"]["size"] = 30
    label.position = 10, 10

    label2 = Label ("#Mnemonic")
    label2.get_style ()["font"]["size"] = 30
    label2.position = 10, 60

    button = CheckButton ("Dropshadow")
    button.position = 10, 100
    re.add_widget (label, label2, button)
    re.start ()