Apple IIgs #62
No Non-Solid Window Background Patterns

Written by Dave Lyons (July 1989)

This Technical Note discusses why window background patterns should always be solid; non-solid patterns are not always drawn with the expected alignment.

When the Window Manager erases part of a window's content area to its port's background pattern, it is not always aligned with already-drawn parts of the window. With a solid background pattern, this has no visible effect; however, if you try to use a grid, for example, the effect is obvious.

To simulate a non-solid background pattern, just erase the desired area to the pattern you want in your update routine. For best results, use a solid background pattern of the color most common in the pattern you really want.

For example, if you want a white grid on a black background, give the window a solid black background pattern, and use FillRect during the update routine to draw the grid. If you keep the default white background pattern, the end result will be the same, but your window content will briefly be solid white before your update routine fills it with your pattern.

Further Reference

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