Tkinter event question

Russell E. Owen no at spam.invalid
Tue Nov 4 02:04:26 CET 2003


I've found a quirk in Tkinter and am wondering if anyone knows a 
workaround. I've got some widgets that generate events. Sometimes the 
widgets are not displayed, but they may still want to generate these 
events.

The problem is, if a widget has never been displayed, event_generate 
appears to be ignored. If I display the widget and then hide it again, 
event_generate works fine. But...I've got many widgets that are normally 
hidden and don't really want the screen flashing with stuff being 
displayed and hidden again right away as the application starts up.

Here is a minimal and unrealistic script that shows the problem. Push 
the button to generate a <<Foo>> event. The event is actually only 
generated if the label that generates it is shown (you can then hide it 
again and the events are still generated). Note that the label *is* 
initially gridded, but it's taken hidden again before the window manager 
ever actually gets to display it.

Suggestions? This is driving me mad, as such events could be quite 
useful for communication if I could only generate them reliably.

-- Russell

#!/usr/local/bin/python
from Tkinter import *
root = Tk()

class myLabel(Label):
    def sendFoo(self):
        self.event_generate("<<Foo>>")

def gotFoo(evt):
    print "Got <<Foo>>"
root.bind("<<Foo>>", gotFoo)

c = myLabel(text="I Am A Label")
b = Button(root, text="Send <<Foo>>", command=c.sendFoo)
c.grid(row=0, column=0)
c.grid_remove()
b.grid(row=1, column=0)

showVar = IntVar()
def showFoo():
    if showVar.get():
        c.grid()
    else:
        c.grid_remove()
showC = Checkbutton(root, text="Show Label",
    variable=showVar, command=showFoo)
showC.grid(row=2, column=0)

root.mainloop()




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