Making stable kernels more stable

Losing the graphics context is not like unmapping a window. When a window is unmapped you still have all the resources (e.g. pixmaps) which were previously registered with the server. For that matter the window itself still exists and things like OpenGL contexts which were generated from it remain intact; all you need to do when the window is uniconified is redraw.

Losing the graphics context is more like losing the connection to the X server. Most applications aren't prepared to deal with that gracefully. There is also the extra complication that the context includes *hardware* resources which are no longer available, and which may have been mapped directly into the application's address space. The backing for XShm mappings doesn't suddenly cease to exist even if you do lose your connection to the server.