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[SDL] Bad math in SDL_RenderCopy

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Mason Wheeler to sdl

When I tried to render an image using something other than NULL for srcrect, it got horribly distorted.  I traced it down to the fact that the math in the rectangle adjustments performed just before the call to renderer->RenderCopy is written inside out.  It should look like this:

       if (dstrect->w != real_dstrect.w) {
           int deltax = (dstrect->x - real_dstrect.x);
           int deltaw = (dstrect->w - real_dstrect.w);
           real_srcrect.x += (deltax * real_srcrect.w) / dstrect->w;
           real_srcrect.w += (deltaw * real_srcrect.w) / dstrect->w;
       }
       if (dstrect->h != real_dstrect.h) {
           int deltay = (dstrect->y - real_dstrect.y);
           int deltah = (dstrect->h - real_dstrect.h);
           real_srcrect.y += (deltay * real_srcrect.h) / dstrect->h;
           real_srcrect.h += (deltah * real_srcrect.h) / dstrect->h;
This commit is contained in:
Sam Lantinga 2009-10-03 16:23:16 +00:00
parent 8fa2d005ca
commit 63382d1cee
1 changed files with 4 additions and 4 deletions
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8
src/video/SDL_video.c
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@ -2463,14 +2463,14 @@ SDL_RenderCopy(SDL_TextureID textureID, const SDL_Rect * srcrect,
if (dstrect->w != real_dstrect.w) {
int deltax = (real_dstrect.x - dstrect->x);
int deltaw = (real_dstrect.w - dstrect->w);
real_srcrect.x += (deltax * dstrect->w) / real_srcrect.w;
real_srcrect.w += (deltaw * dstrect->w) / real_srcrect.w;
real_srcrect.x += (deltax * real_srcrect.w) / dstrect->w;
real_srcrect.w += (deltaw * real_srcrect.w) / dstrect->w;
}
if (dstrect->h != real_dstrect.h) {
int deltay = (real_dstrect.y - dstrect->y);
int deltah = (real_dstrect.h - dstrect->h);
real_srcrect.y += (deltay * dstrect->h) / real_srcrect.h;
real_srcrect.h += (deltah * dstrect->h) / real_srcrect.h;
real_srcrect.y += (deltay * real_srcrect.h) / dstrect->h;
real_srcrect.h += (deltah * real_srcrect.h) / dstrect->h;
}
}