[AD] [WIN] bitmap/sub-bitmap locking bug

["Eric Botcazou" <ebotcazou@xxxxxxxxxx>]

Henrik has just found a bug in the Windows port, which causes the computer
to freeze when sub-bitmaps of the screen bitmap are used and the mouse
pointer simultaneously displayed on the screen.

The bug is rather serious and already exists in the 3.9.33 release; it is
related to the bitmap/sub-bitmap locking mechanism and can potentially
freeze every multi-threaded program written with Allegro (including Allegro
itself) which locks a bitmap/sub-bitmap couple in two different threads.

Has such a problem ever been reported in the past ? Has the Windows bitmap
locking code undergone changes before the 3.9.33 release ?

After investigating a little, I found a fix but it works only for the accel
driver (!): the software driver keeps freezing and the windowed driver
doesn't behave correctly; very strange indeed...
I've attached Henrik's code (warning: freeze !!!) and my preliminary fix.

--
Eric Botcazou (ebotcazou@xxxxxxxxxx)
Web Site: http://www.multimania.com/ebotcazou

Attachment: lock_bug.zip
Description: Zip compressed data