cpython/Demo/tkinter/matt/canvas-mult-item-sel.py

from tkinter import *

# allows moving dots with multiple selection.

SELECTED_COLOR = "red"
UNSELECTED_COLOR = "blue"

class Test(Frame):
    ###################################################################
    ###### Event callbacks for THE CANVAS (not the stuff drawn on it)
    ###################################################################
    def mouseDown(self, event):
        # see if we're inside a dot. If we are, it
        # gets tagged as CURRENT for free by tk.

        if not event.widget.find_withtag(CURRENT):
            # we clicked outside of all dots on the canvas. unselect all.

            # re-color everything back to an unselected color
            self.draw.itemconfig("selected", fill=UNSELECTED_COLOR)
            # unselect everything
            self.draw.dtag("selected")
        else:
            # mark as "selected" the thing the cursor is under
            self.draw.addtag("selected", "withtag", CURRENT)
            # color it as selected
            self.draw.itemconfig("selected", fill=SELECTED_COLOR)

        self.lastx = event.x
        self.lasty = event.y


    def mouseMove(self, event):
        self.draw.move("selected", event.x - self.lastx, event.y - self.lasty)
        self.lastx = event.x
        self.lasty = event.y

    def makeNewDot(self):
        # create a dot, and mark it as current
        fred = self.draw.create_oval(0, 0, 20, 20,
                                     fill=SELECTED_COLOR, tags=CURRENT)
        # and make it selected
        self.draw.addtag("selected", "withtag", CURRENT)

    def createWidgets(self):
        self.QUIT = Button(self, text='QUIT', foreground='red',
                           command=self.quit)

        ################
        # make the canvas and bind some behavior to it
        ################
        self.draw = Canvas(self, width="5i", height="5i")
        Widget.bind(self.draw, "<1>", self.mouseDown)
        Widget.bind(self.draw, "<B1-Motion>", self.mouseMove)

        # and other things.....
        self.button = Button(self, text="make a new dot", foreground="blue",
                             command=self.makeNewDot)

        message = ("%s dots are selected and can be dragged.\n"
                   "%s are not selected.\n"
                   "Click in a dot to select it.\n"
                   "Click on empty space to deselect all dots."
                   ) % (SELECTED_COLOR, UNSELECTED_COLOR)
        self.label = Message(self, width="5i", text=message)

        self.QUIT.pack(side=BOTTOM, fill=BOTH)
        self.label.pack(side=BOTTOM, fill=X, expand=1)
        self.button.pack(side=BOTTOM, fill=X)
        self.draw.pack(side=LEFT)

    def __init__(self, master=None):
        Frame.__init__(self, master)
        Pack.config(self)
        self.createWidgets()

test = Test()
test.mainloop()