Merge lp:~mcfletch/simplegc/suggestions into lp:simplegc

[Mike C. Fletcher]

Your use of eval is unnecessary, the builtin function getattr( obj, attr ) performs the same operation. There is also a 3-argument form getattr( obj, attr, default ) which would allow you to code for cases where a widget does not have an expected method.

[lp:~mcfletch/simplegc/suggestions]

260. By Mike C. Fletcher on 2012-06-18

Alter the helloworld.py example to include a basic event processing operation

261. By Mike C. Fletcher on 2012-06-18

Following tutorial, creating a callback-based version of the clicky demo

262. By Mike C. Fletcher on 2012-06-18

Ignore the egg-info directory and .eric4project directory

263. By Mike C. Fletcher on 2012-06-18

Just a worked example of what a multi-callback slot mechanism might look like...

[Mike C. Fletcher (mcfletch)]

Oh, I also sketched out a sample of a "slot" mechanism that allows multiple callbacks per event, currently just included in the examples directory.

Oh, and there's a couple new samples that follow the tutorial forward from helloworld, as I find it easiest to learn with concrete code. They get a bit too verbose for a tutorial, but maybe you'll find some way to make them useful somehow.

[Sam Bull (dreamsorcerer)]

> Oh, I also sketched out a sample of a "slot" mechanism that allows multiple
> callbacks per event, currently just included in the examples directory.

OK, in your example, it receives the widget as the implicit self argument, because the object is assigned in the class definition. What I'd really like is the option to assign it afterwards, like:

btn = sgc.Button()
btn.on_click = EventSlot("click")

But, when done like this, it no longer receives the implicit self argument. This is the same reason we don't have a reference to the widget when assigning a callback function like this.

Is there an easy way we can get a reference to the object it is being assigned to? The only thing I can think of, is to use __setattr__() in the widget and pass in self when a callback or event slot is being assigned to a widget.

[Mike C. Fletcher (mcfletch)]

On 12-06-20 05:56 PM, Sam Bull wrote:
>> Oh, I also sketched out a sample of a "slot" mechanism that allows multiple
>> callbacks per event, currently just included in the examples directory.
> OK, in your example, it receives the widget as the implicit self argument, because the object is assigned in the class definition. What I'd really like is the option to assign it afterwards, like:
>
> btn = sgc.Button()
> btn.on_click = EventSlot("click")
>
> But, when done like this, it no longer receives the implicit self argument. This is the same reason we don't have a reference to the widget when assigning a callback function like this.
>
> Is there an easy way we can get a reference to the object it is being assigned to? The only thing I can think of, is to use __setattr__() in the widget and pass in self when a callback or event slot is being assigned to a widget.
class EventSlot(object):
     def __set__( self, widget, value ):
         ...

That is, a descriptor (such as EventSlot) can decide what to do when you
go to set the value on the object, so it could simply append, or could
replace, or whatever you feel is appropriate. However, that implies
using an EventSlot (or some *other* descriptor) in the class as your
base definition. Which seems to be what you want to avoid.

HTH,
Mike

--
________________________________________________
   Mike C. Fletcher
   Designer, VR Plumber, Coder
   http://www.vrplumber.com
   http://blog.vrplumber.com

[Sam Bull (dreamsorcerer)]

Yes, so I'm suggesting moving some of that code into the widget. So, something like:

class Simple(object):
  def __setattr__(self, atr, val):
    if atr.startswith("on_"):
      val = lambda: val(self)
    object.__setattr__(self, atr, val)

That should work in making sure callbacks get the widget passed in. Then something slightly more complex might be needed to get the EventSlot thing working in a similar way.

This means in your 'helloworldeventcallback.py' experiment, you would receive the widget as an argument in new() with no code change, solving the issue of not being able to access event properties.

[Sam Bull (dreamsorcerer)]

review: Disapprove

Unmerged revisions

263. By Mike C. Fletcher on 2012-06-18

Just a worked example of what a multi-callback slot mechanism might look like...

262. By Mike C. Fletcher on 2012-06-18

Ignore the egg-info directory and .eric4project directory

261. By Mike C. Fletcher on 2012-06-18

Following tutorial, creating a callback-based version of the clicky demo

260. By Mike C. Fletcher on 2012-06-18

Alter the helloworld.py example to include a basic event processing operation

259. By Mike C. Fletcher on 2012-06-18

Eliminate use of eval for a simple attribute lookup

=== modified file '.bzrignore'
--- .bzrignore	2012-05-27 08:21:03 +0000
+++ .bzrignore	2012-06-18 04:44:18 +0000
@@ -1,1 +1,3 @@
 docs/_build/*
+*.egg-info
+.eric4project

=== added file 'example/helloworldevent.py'
--- example/helloworldevent.py	1970-01-01 00:00:00 +0000
+++ example/helloworldevent.py	2012-06-18 04:44:18 +0000
@@ -0,0 +1,36 @@
+import sgc
+from sgc.locals import *
+
+import pygame
+from pygame.locals import *
+# We'll use the random module to generate colors
+import random
+
+pygame.display.init()
+pygame.font.init()
+
+screen = sgc.surface.Screen((640,480))
+
+clock = pygame.time.Clock()
+
+# The color we'll use for the background
+COLOR = (0,0,0)
+
+btn = sgc.Button(label="Clicky", pos=(100, 100))
+btn.add(0)
+
+while True:
+    time = clock.tick(30)
+
+    for event in pygame.event.get():
+        sgc.event(event)
+        if event.type == QUIT:
+            exit()
+        # now we actually process the event...
+        elif event.type == GUI:
+            if event.widget == btn and event.gui_type == 'click':
+                COLOR = random.randint(0,255),random.randint(0,255),random.randint(0,255)
+
+    screen.fill(COLOR)
+    sgc.update(time)
+    pygame.display.flip()

=== added file 'example/helloworldeventcallback.py'
--- example/helloworldeventcallback.py	1970-01-01 00:00:00 +0000
+++ example/helloworldeventcallback.py	2012-06-18 04:44:18 +0000
@@ -0,0 +1,42 @@
+import sgc
+from sgc.locals import *
+
+import pygame
+from pygame.locals import *
+# We'll use the random module to generate colors
+import random
+
+pygame.display.init()
+pygame.font.init()
+
+screen = sgc.surface.Screen((640,480))
+
+clock = pygame.time.Clock()
+
+class Background( object ):
+    def __init__( self, color, screen ):
+        self.color = color 
+        self.screen = screen
+    def new( self ):
+        # how do I get to the event properties from this callback?
+        # e.g. how do I know which button sent the event?
+        self.color = random.randint(0,255),random.randint(0,255),random.randint(0,255)
+    def draw( self ):
+        self.screen.fill(self.color)
+
+bg = Background( (0,0,0), screen )
+
+btn = sgc.Button(label="Clicky", pos=(100, 100))
+btn.on_click = bg.new
+btn.add(0)
+
+while True:
+    time = clock.tick(30)
+
+    for event in pygame.event.get():
+        sgc.event(event)
+        if event.type == QUIT:
+            exit()
+    bg.draw()
+    sgc.update(time)
+    pygame.display.flip()

=== added file 'example/slots.py'
--- example/slots.py	1970-01-01 00:00:00 +0000
+++ example/slots.py	2012-06-18 04:44:18 +0000
@@ -0,0 +1,131 @@
+import sgc
+from sgc.locals import *
+
+import pygame
+from pygame.locals import *
+# We'll use the random module to generate colors
+import random
+
+import weakref
+import sgc
+import pygame
+import pygame.event
+
+class EventSlot( object ):
+    """Represents an event-generating slot on a Widget"""
+    def __init__( self, gui_type ):
+        self.gui_type = gui_type 
+        self.object_key = '_%s_handlers'%(gui_type,)
+    def __get__( self, widget, typ=None ):
+        if widget is None:
+            return self
+        return BoundSlot( self, widget )
+    def get( self, widget ):
+        return getattr( widget, self.object_key, [] )
+    def set( self, widget, value ):
+        return setattr( widget, self.object_key, value )
+    def create_event( self, widget, **params ):
+        """Create a GUI event from this event-slot"""
+        base = {'widget':widget,'gui_type': self.gui_type}
+        base.update( params )
+        event = pygame.event.Event(GUI, base)
+        return event
+
+def mutates_handlers( func ):
+    """Decorate methods which mutate the handlers"""
+    def with_handlers( self, *args, **named ):
+        handlers = self.slot.get(self.widget)
+        result = func( self, handlers, *args, **named )
+        self.slot.set( self.widget, handlers )
+        return result 
+    with_handlers.__name__ = func.__name__ 
+    with_handlers.__doc__ = func.__doc__
+    with_handlers.__dict__ = func.__dict__
+    return with_handlers
+        
+class BoundSlot( object ):
+    def __init__( self, slot, widget ):
+        self.slot = slot 
+        self.widget = widget 
+    def propagate_event( self, event ):
+        # likely need to do some locking to prevent GUI event loops...
+        for handler in self.slot.get( self.widget )[:]: # copy to prevent alterations to ourselves causing issues...
+            result = handler( event )
+            if result:
+                return result
+        # do bubbling here...
+        pygame.event.post(event)
+    def emit( self, **params ):
+        """Programatically emit the event, triggering all handlers (if registered)"""
+        event = self.slot.create_event( self.widget, **params )
+        self.propagate_event( event ) 
+    @mutates_handlers
+    def append( self, handlers, handler ):
+        if isinstance( handler, (list,tuple)):
+            handlers.extend( handler )
+        else:
+            handlers.append( handler )
+    @mutates_handlers
+    def prepend( self, handlers, handler ):
+        if isinstance( handler, (list,tuple)):
+            handlers[:0] = handler 
+        else:
+            handlers.insert( 0, handler )
+    @mutates_handlers
+    def remove( self, handlers, handler ):
+        while handler in handlers:
+            try:
+                handlers.remove( handler )
+            except ValueError,TypeError:
+                pass # race condition catch...
+    def __call__( self ):
+        self.emit()
+    
+class MyButton( sgc.Button ):
+    on_click = EventSlot( 'click' )
+    def __init__( self, *args, **named ):
+        for key,value in named.items():
+            slot = getattr( self, key, None )
+            if isinstance( slot, BoundSlot ):
+                slot.append( value )
+                named.pop( key )
+        super( MyButton, self ).__init__( *args, **named )
+
+pygame.display.init()
+pygame.font.init()
+
+screen = sgc.surface.Screen((640,480))
+
+clock = pygame.time.Clock()
+
+class Background( object ):
+    def __init__( self, color, screen ):
+        self.color = color 
+        self.screen = screen
+    def new( self, event ):
+        # how do I get to the event properties from this callback?
+        # e.g. how do I know which button sent the event?
+        print 'Clicked on button', event.widget
+        self.color = random.randint(0,255),random.randint(0,255),random.randint(0,255)
+    def draw( self ):
+        self.screen.fill(self.color)
+
+bg = Background( (0,0,0), screen )
+
+btn = MyButton(label="Clicky", pos=(100, 100), on_click=bg.new)
+btn.add(0)
+
+def generic_logger( event ):
+    print 'Event', event
+btn.on_click.append( generic_logger )
+
+while True:
+    time = clock.tick(30)
+
+    for event in pygame.event.get():
+        sgc.event(event)
+        if event.type == QUIT:
+            exit()
+    bg.draw()
+    sgc.update(time)
+    pygame.display.flip()

=== modified file 'sgc/widgets/base_widget.py'
--- sgc/widgets/base_widget.py	2012-06-16 11:01:51 +0000
+++ sgc/widgets/base_widget.py	2012-06-18 04:44:18 +0000
@@ -261,7 +261,9 @@
             if name not in self._images:
                 self._images[name] = create_image(self._extra_images[name])
                 if isinstance(surf, (tuple,list)):
-                    f = eval("self._draw_" + name)
+                    # eval is not necessary, use the built-in getattr
+                    attr = '_draw_%s'%( name, )
+                    f = getattr( self, attr )
                     draw = lambda draw, img=self._images[name]: f(draw, img)
                     self._custom_extra.append(draw)