How to get the pixmap's position?

[=?big5?q?anukeey?= <anukeey yahoo com tw>]

Hi all:
   I had designed a GtkPixmap widget, and set eventbox
for the pixmap widget, now I captured the button ress
event when user clicked the pixmap to load another
pixmap. As we know, the pixmap widget is rectangle
shape, but the pixmap that we loaded may be polygon
shape, so how to make sure the mouse pointer is only
on the top of pixmap not the else part of pixmap
widget?

Thanks~~~
anukeey

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