author Sam Lantinga <>
Wed, 30 Nov 2016 22:06:05 -0800
changeset 10668 1889c850fafc
parent 7856 cb37776926ad
permissions -rw-r--r--
Fixed bug 3340 - SDL_BlitScaled causes access violation in some cases.

Simon Hug

The SDL_BlitScaled function runs into an access violation for specific blit coordinates and surface sizes. The attached testcase blits a 800x600 surface to a 1280x720 surface at the coordinates -640,-345 scaled to 1280x720. The blit function that moves the data then runs over and reads after the pixel data from the src surface causing an access violation.

I can't say where exactly it goes wrong, but I think it could have something to do with the rounding in SDL_UpperBlitScaled. final_src.y is 288 and final_src.h is 313. Together that's 601, which I believe is one too much, but I just don't know the code enough to make sure that's the problem.


I think this patch fix the issue, but maybe it's worth re-writing "SDL_UpperBlitScaled" using SDL_FRect.
     1 Future work roadmap:
     2  *
     4  * Check 1.2 revisions:
     5 	3554 - Need to resolve semantics for locking keys on different platforms
     6 	4874 - Do we want screen rotation?  At what level?
     7 	4974 - Windows file code needs to convert UTF-8 to Unicode, but we don't need to tap dance for Windows 95/98
     8 	4865 - See if this is still needed (mouse coordinate clamping)
     9 	4866 - See if this is still needed (blocking window repositioning)