First go at the sketch pad thing

sugar/chat/sketchpad/Sketch.py

@@ -0,0 +1,16 @@
+class Sketch:
+	def __init__(self):
+		self._points = []
+	
+	def add_point(self, x, y):
+		self._points.append([x, y])
+		
+	def draw(self, ctx):
+		start = True
+		for [x, y] in self._points:
+			if start:
+				ctx.move_to(x, y)
+				start = False
+			else:
+				ctx.line_to(x, y)
+		ctx.stroke()

sugar/chat/sketchpad/SketchPad.py

@@ -0,0 +1,57 @@
+import pygtk
+pygtk.require('2.0')
+import gtk
+import cairo
+
+from Sketch import Sketch
+
+class SketchPad(gtk.DrawingArea):
+	def __init__(self):
+		gtk.DrawingArea.__init__(self)
+
+		self._active_sketch = None
+		self._sketches = []
+
+		self.add_events(gtk.gdk.BUTTON_PRESS_MASK |
+						gtk.gdk.BUTTON1_MOTION_MASK)
+		self.connect("button-press-event", self.__button_press_cb)
+		self.connect("button-release-event", self.__button_release_cb)
+		self.connect("motion-notify-event", self.__motion_notify_cb)
+		self.connect('expose_event', self.expose)
+
+	def expose(self, widget, event):
+		rect = self.get_allocation()
+		ctx = widget.window.cairo_create()
+		
+		for sketch in self._sketches:
+			sketch.draw(ctx)
+		
+		return False
+
+	def add_sketch(self, sketch):
+		self._sketches.append(sketch)
+	
+	def __button_press_cb(self, widget, event):
+		self._active_sketch = Sketch()
+		self.add_sketch(self._active_sketch)
+	
+	def __button_release_cb(self, widget, event):
+		self._active_sketch = None
+	
+	def __motion_notify_cb(self, widget, event):
+		if self._active_sketch:
+			self._active_sketch.add_point(event.x, event.y)
+		self.window.invalidate_rect(None, False)
+		
+if __name__ == "__main__":
+	window = gtk.Window()
+	window.set_default_size(400, 300)
+	window.connect("destroy", lambda w: gtk.main_quit())
+        
+	sketchpad = SketchPad()
+	window.add(sketchpad)
+	sketchpad.show()
+	
+	window.show()
+	
+	gtk.main()