Bug #69705 for Tk: WinPhoto vs window partly off-screen

With recent debian perl-tk 804.029 and perl 5.12.4 if a window is partly off-screen then taking a Tk::WinPhoto of it gives an xlib error and the program exits. Eg. foo.pl below if it's positioned to be partly off-screen when clicked. X Error of failed request: BadMatch (invalid parameter attributes) Major opcode of failed request: 73 (X_GetImage) Serial number of failed request: 704 Current serial number in output stream: 704 This is the usual behaviour of XGetImage() when asked to get something partly or wholly outside the whole screen. It's happy to give back garbage for overlapped windows, or bits outside the bounds of a parent, but not outside the whole screen. I struck this in a Tk::Canvas with a window item that through it's anchor direction etc ended up partly off screen, depending where on the screen the main window was positioned. It'd be good if Tk::WinPhoto caught this so it doesn't kill the whole program. Throwing a perl level error would allow it to be caught and continue. Or maybe the winphoto code could try to see what part of the requested window is within the screen and photograph only that. Ideally it'd still want an X error catch though, since of course any window can move at any time. I suppose XSetErrorHandler() is the place to watch/catch, just set temporarily across the XGetImage() call maybe. I think if the handler returns 0 or 1 or something then XGetImage() returns NULL, but I haven't actually tried it, or tried letting other non-image errors handle as normal etc :-).

#!/usr/bin/perl -w use strict; use Tk; use Tk::WinPhoto; my $mw = MainWindow->new; my $button; $button = $mw->Button (-text => 'click me when partly off-screen', -command => sub { print "update() ...\n"; $button->update; print "Photo() ...\n"; my $photo = $button->Photo (-format => 'window', -data => oct($button->id)); print "ok\n"; exit 0; }); $button->pack; MainLoop; exit 0;