Clipped sprites in icons

When you create text in an icon that’s too long for the physical bounding box, the text is neatly clipped at the edges. When you create a sprite, the same doesn’t seem to be the case – the too-large sprite overlaps the boundaries, causing redraw glitches.

Is there a reason why this should be the case? Would anything break if the Wimp clipped sprites in sprite-only icons, just as it does text? I can’t really think of any reason why it’s useful to have sprites plotted over icon boundaries. However, I can think of a few applications for clipped sprites, such as natty progress bars and interesting window gadgets.

If changing the default behaviour is problematic, what’s the scope for adding a new flag to indicate that a sprite in the icon will be clipped by its bounding box?

You’re right that it causes redraw glitches, and where it happens it is an error.

However, adding clipping would be new functionality that wouldn’t work on older Wimps, and produces behaviour that isn’t very useful unless you also add an X,Y offset to the validation string. But even then, I’m not sure the result is particularly useful or compelling. And there’s no bits to spare.

I think the reason would have to be more strongly stated than “if I do it wrong, it comes out wrong”.