Interaction with X Drawing Operations

Drawables that have been rendered to with non-opaque alpha have additional pixel storage associated with them, called the alpha channel. X Window system operations do not affect the alpha channel, with the following exceptions:

• When windows with alpha channel are exposed, if the window has an X background defined (background != None), when the background is painted, the alpha component of the exposed pixels is painted with alpha = 1.

• When a window is resized, the alpha channel storage is resized.