invalidate-window-on-resize

Arguments: window

This generic function is called when a window is created. If it returns true, a flag associated with a window is set telling the Operating System to invalidate the entire window whenever it is resized. If this generic function returns nil, the flag is not set. The flag cannot subsequently be changed.

Note that this generic function is called only when a window is created (as its purpose is to set a flag at window-creation time). This means that any custom methods should exist and return the appropriate value at window creation time and, of course, programmers should not expect the methods to be run when the window is subsequently resized.

The default method returns nil, but programmers can define methods on their own window classes that return true.

For example, if a window's redisplay-window method draws a picture in the window such that it is stretched to fill the window interior, then resizing the window should require the entire picture to be redrawn. Adding an invalidate-window-on-resize method that returns true for that window's class (before any instances are created) will ensure that redisplay-window is called whenever the window is resized so that the needed redrawing is done.

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This page was not revised from the 10.0 page.
Created 2019.8.20.