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Bug 1346

Summary: SDL_DisplayFormatAlpha uses incorrect format in windowed mode
Product: SDL Reporter: alarantalara
Component: videoAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: alarantalara
Version: HG 1.2   
Hardware: x86   
OS: Mac OS X (All)   
Attachments: patch correcting problem

Description alarantalara 2011-12-19 20:43:13 UTC 
Created attachment 738 [details]
patch correcting problem

On little endian systems using the Quartz code, an unusual set of RBGA masks is used when using the windowed video mode.
This set is not taken into account in SDL_DisplayFormatAlpha and so it converts the supplied surface to a format that does not match the video surface, preventing fast blitting.

This was observed in recent builds of Battle for Wesnoth when SDL was updated to cover the problem when switching to full screen in Lion (https://gna.org/bugs/?18319).

You can observe the performance issue if you download Wesnoth 1.9.13 for OS X at
http://sourceforge.net/projects/wesnoth/files/wesnoth/wesnoth-1.9.13/Wesnoth_1.9.13.dmg/download
and replace the included SDL library with any build of SDL 1.2.14 or later. (I have already patched the included version, so the problem is not observable without replacement.)

A patch resolving the issue is attached.
Comment 1 Sam Lantinga 2011-12-29 01:58:09 UTC 
Fixed, thanks!
http://hg.libsdl.org/SDL/rev/2280c0954104