Checked in some new Tk demos that I wrote a while ago.
diff --git a/Demo/tkinter/guido/canvasevents.py b/Demo/tkinter/guido/canvasevents.py
new file mode 100644
index 0000000..60f4096
--- /dev/null
+++ b/Demo/tkinter/guido/canvasevents.py
@@ -0,0 +1,244 @@
+#! /usr/bin/env python
+
+from Tkinter import *
+from Canvas import Oval, Group, CanvasText
+
+
+# Fix a bug in Canvas.Group as distributed in Python 1.4. The
+# distributed bind() method is broken. This is what should be used:
+
+class Group(Group):
+ def bind(self, sequence=None, command=None):
+ return self.canvas.tag_bind(self.id, sequence, command)
+
+class Object:
+
+ """Base class for composite graphical objects.
+
+ Objects belong to a canvas, and can be moved around on the canvas.
+ They also belong to at most one ``pile'' of objects, and can be
+ transferred between piles (or removed from their pile).
+
+ Objects have a canonical ``x, y'' position which is moved when the
+ object is moved. Where the object is relative to this position
+ depends on the object; for simple objects, it may be their center.
+
+ Objects have mouse sensitivity. They can be clicked, dragged and
+ double-clicked. The behavior may actually determined by the pile
+ they are in.
+
+ All instance attributes are public since the derived class may
+ need them.
+
+ """
+
+ def __init__(self, canvas, x=0, y=0, fill='red', text='object'):
+ self.canvas = canvas
+ self.x = x
+ self.y = y
+ self.pile = None
+ self.group = Group(self.canvas)
+ self.createitems(fill, text)
+
+ def __str__(self):
+ return str(self.group)
+
+ def createitems(self, fill, text):
+ self.__oval = Oval(self.canvas,
+ self.x-20, self.y-10, self.x+20, self.y+10,
+ fill=fill, width=3)
+ self.group.addtag_withtag(self.__oval)
+ self.__text = CanvasText(self.canvas,
+ self.x, self.y, text=text)
+ self.group.addtag_withtag(self.__text)
+
+ def moveby(self, dx, dy):
+ if dx == dy == 0:
+ return
+ self.group.move(dx, dy)
+ self.x = self.x + dx
+ self.y = self.y + dy
+
+ def moveto(self, x, y):
+ self.moveby(x - self.x, y - self.y)
+
+ def transfer(self, pile):
+ if self.pile:
+ self.pile.delete(self)
+ self.pile = None
+ self.pile = pile
+ if self.pile:
+ self.pile.add(self)
+
+ def tkraise(self):
+ self.group.tkraise()
+
+
+class Bottom(Object):
+
+ """An object to serve as the bottom of a pile."""
+
+ def createitems(self, *args):
+ self.__oval = Oval(self.canvas,
+ self.x-20, self.y-10, self.x+20, self.y+10,
+ fill='gray', outline='')
+ self.group.addtag_withtag(self.__oval)
+
+
+class Pile:
+
+ """A group of graphical objects."""
+
+ def __init__(self, canvas, x, y, tag=None):
+ self.canvas = canvas
+ self.x = x
+ self.y = y
+ self.objects = []
+ self.bottom = Bottom(self.canvas, self.x, self.y)
+ self.group = Group(self.canvas, tag=tag)
+ self.group.addtag_withtag(self.bottom.group)
+ self.bindhandlers()
+
+ def bindhandlers(self):
+ self.group.bind('<1>', self.clickhandler)
+ self.group.bind('<Double-1>', self.doubleclickhandler)
+
+ def add(self, object):
+ self.objects.append(object)
+ self.group.addtag_withtag(object.group)
+ self.position(object)
+
+ def delete(self, object):
+ object.group.dtag(self.group)
+ self.objects.remove(object)
+
+ def position(self, object):
+ object.tkraise()
+ i = self.objects.index(object)
+ object.moveto(self.x + i*4, self.y + i*8)
+
+ def clickhandler(self, event):
+ pass
+
+ def doubleclickhandler(self, event):
+ pass
+
+
+class MovingPile(Pile):
+
+ def bindhandlers(self):
+ Pile.bindhandlers(self)
+ self.group.bind('<B1-Motion>', self.motionhandler)
+ self.group.bind('<ButtonRelease-1>', self.releasehandler)
+
+ movethis = None
+
+ def clickhandler(self, event):
+ tags = self.canvas.gettags('current')
+ for i in range(len(self.objects)):
+ o = self.objects[i]
+ if o.group.tag in tags:
+ break
+ else:
+ self.movethis = None
+ return
+ self.movethis = self.objects[i:]
+ for o in self.movethis:
+ o.tkraise()
+ self.lastx = event.x
+ self.lasty = event.y
+
+ doubleclickhandler = clickhandler
+
+ def motionhandler(self, event):
+ if not self.movethis:
+ return
+ dx = event.x - self.lastx
+ dy = event.y - self.lasty
+ self.lastx = event.x
+ self.lasty = event.y
+ for o in self.movethis:
+ o.moveby(dx, dy)
+
+ def releasehandler(self, event):
+ objects = self.movethis
+ if not objects:
+ return
+ self.movethis = None
+ self.finishmove(objects)
+
+ def finishmove(self, objects):
+ for o in objects:
+ self.position(o)
+
+
+class Pile1(MovingPile):
+
+ x = 50
+ y = 50
+ tag = 'p1'
+
+ def __init__(self, demo):
+ self.demo = demo
+ MovingPile.__init__(self, self.demo.canvas, self.x, self.y, self.tag)
+
+ def doubleclickhandler(self, event):
+ try:
+ o = self.objects[-1]
+ except IndexError:
+ return
+ o.transfer(self.other())
+ MovingPile.doubleclickhandler(self, event)
+
+ def other(self):
+ return self.demo.p2
+
+ def finishmove(self, objects):
+ o = objects[0]
+ p = self.other()
+ x, y = o.x, o.y
+ if (x-p.x)**2 + (y-p.y)**2 < (x-self.x)**2 + (y-self.y)**2:
+ for o in objects:
+ o.transfer(p)
+ else:
+ MovingPile.finishmove(self, objects)
+
+class Pile2(Pile1):
+
+ x = 150
+ y = 50
+ tag = 'p2'
+
+ def other(self):
+ return self.demo.p1
+
+
+class Demo:
+
+ def __init__(self, master):
+ self.master = master
+ self.canvas = Canvas(master,
+ width=200, height=200,
+ background='yellow',
+ relief=SUNKEN, borderwidth=2)
+ self.canvas.pack(expand=1, fill=BOTH)
+ self.p1 = Pile1(self)
+ self.p2 = Pile2(self)
+ o1 = Object(self.canvas, fill='red', text='o1')
+ o2 = Object(self.canvas, fill='green', text='o2')
+ o3 = Object(self.canvas, fill='light blue', text='o3')
+ o1.transfer(self.p1)
+ o2.transfer(self.p1)
+ o3.transfer(self.p2)
+
+
+# Main function, run when invoked as a stand-alone Python program.
+
+def main():
+ root = Tk()
+ demo = Demo(root)
+ root.protocol('WM_DELETE_WINDOW', root.quit)
+ root.mainloop()
+
+if __name__ == '__main__':
+ main()