Editing: canvasevents.py
#! /usr/bin/python2.7 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 be 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()
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