README.txt
author Sam Lantinga <slouken@libsdl.org>
Wed, 30 Nov 2016 22:06:05 -0800
changeset 10668 1889c850fafc
parent 9507 b1e690e9c5b3
child 10890 a2ec89f77e6b
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.

Sylvain

I think this patch fix the issue, but maybe it's worth re-writing "SDL_UpperBlitScaled" using SDL_FRect.
     1 
     2                          Simple DirectMedia Layer
     3 
     4                                   (SDL)
     5 
     6                                 Version 2.0
     7 
     8 ---
     9 http://www.libsdl.org/
    10 
    11 Simple DirectMedia Layer is a cross-platform development library designed
    12 to provide low level access to audio, keyboard, mouse, joystick, and graphics
    13 hardware via OpenGL and Direct3D. It is used by video playback software,
    14 emulators, and popular games including Valve's award winning catalog
    15 and many Humble Bundle games.
    16 
    17 More extensive documentation is available in the docs directory, starting
    18 with README.md
    19 
    20 Enjoy!
    21 	Sam Lantinga				(slouken@libsdl.org)