Comment 6 for bug 1333465

How I discovered the cause of the bug:

lp:~inkscapebrony/inkscape/inkscape has a powerstroke width dialog. Zooming in and Shift+clicking the canvas as if it were a powerstroke knot caused the width handler to appear. Also, runs in gdb revealed that at high zoom, sp_knot_handler was being called for every single canvas event when it shouldn't have; calling sp_canvas_item_hide from within gdb made the problem go away.

Why the bug happened:

When an SPCanvasItem is assigned a ridiculous value (such as the ones that would be obtained by a diverging function), it seems to overflow into other values into the struct and/or take up all available space on the canvas (bug!)