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Split SDL_BlitScaled into SDL_UpperBlitScaled and SDL_LowerBlitScaled.

Fixed issue when calling SDL_BlitScaled() directly with src or dst rectangles that were out of bounds.
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KenRogoway committed Mar 14, 2011
1 parent 525e71d commit 8aa92738d04f773eb33b7a5f2cc65cd6e8c5cfc1
Showing with 108 additions and 16 deletions.
  1. +14 −6 include/SDL_surface.h
  2. +94 −10 src/video/SDL_surface.c
@@ -466,15 +466,23 @@ extern DECLSPEC int SDLCALL SDL_SoftStretch(SDL_Surface * src,
SDL_Surface * dst,
const SDL_Rect * dstrect);

#define SDL_BlitScaled SDL_UpperBlitScaled

/**
* \brief Perform a fast, low quality, stretch blit between two surfaces of the
* different pixel formats.
*
* \note This function calls SDL_SoftStretch or SDL_LowerBlit.
* This is the public scaled blit function, SDL_BlitScaled(), and it performs
* rectangle validation and clipping before passing it to SDL_LowerBlitScaled()
*/
extern DECLSPEC int SDLCALL SDL_BlitScaled
extern DECLSPEC int SDLCALL SDL_UpperBlitScaled
(SDL_Surface * src, const SDL_Rect * srcrect,
SDL_Surface * dst, const SDL_Rect * dstrect);
SDL_Surface * dst, SDL_Rect * dstrect);

/**
* This is a semi-private blit function and it performs low-level surface
* scaled blitting only.
*/
extern DECLSPEC int SDLCALL SDL_LowerBlitScaled
(SDL_Surface * src, SDL_Rect * srcrect,
SDL_Surface * dst, SDL_Rect * dstrect);


/* Ends C function definitions when using C++ */
@@ -602,12 +602,101 @@ SDL_UpperBlit(SDL_Surface * src, const SDL_Rect * srcrect,
return 0;
}

/*
* Scale and blit a surface
*/
int
SDL_BlitScaled(SDL_Surface * src, const SDL_Rect * srcrect,
SDL_Surface * dst, const SDL_Rect * dstrect)
SDL_UpperBlitScaled(SDL_Surface * src, const SDL_Rect * srcrect,
SDL_Surface * dst, SDL_Rect * dstrect)
{
SDL_Rect final_src, final_dst, fulldst;

/* Make sure the surfaces aren't locked */
if (!src || !dst) {
SDL_SetError("SDL_UpperBlitScaled: passed a NULL surface");
return (-1);
}
if (src->locked || dst->locked) {
SDL_SetError("Surfaces must not be locked during blit");
return (-1);
}

/* If the destination rectangle is NULL, use the entire dest surface */
if (dstrect == NULL) {
fulldst.x = fulldst.y = 0;
dstrect = &fulldst;
}

/* clip the source rectangle to the source surface */
if (srcrect) {
int maxw, maxh;

final_src.x = srcrect->x;
final_src.w = srcrect->w;
if (final_src.x < 0) {
final_src.w += final_src.x;
final_src.x = 0;
}
maxw = src->w - final_src.x;
if (maxw < final_src.w)
final_src.w = maxw;

final_src.y = srcrect->y;
final_src.h = srcrect->h;
if (final_src.y < 0) {
final_src.h += final_src.y;
final_src.y = 0;
}
maxh = src->h - final_src.y;
if (maxh < final_src.h)
final_src.h = maxh;

} else {
final_src.x = final_src.y = 0;
final_src.w = src->w;
final_src.h = src->h;
}

/* clip the destination rectangle against the clip rectangle */
if (dstrect) {
int maxw, maxh;

final_dst.x = dstrect->x;
final_dst.w = dstrect->w;
if (final_dst.x < 0) {
final_dst.w += final_dst.x;
final_dst.x = 0;
}
maxw = dst->w - final_dst.x;
if (maxw < final_dst.w)
final_dst.w = maxw;

final_dst.y = dstrect->y;
final_dst.h = dstrect->h;
if (final_dst.y < 0) {
final_dst.h += final_dst.y;
final_dst.y = 0;
}
maxh = dst->h - final_dst.y;
if (maxh < final_dst.h)
final_dst.h = maxh;
} else {
final_dst.x = final_dst.y = 0;
final_dst.w = dst->w;
final_dst.h = dst->h;
}

if (final_dst.w > 0 && final_dst.h > 0) {
return SDL_LowerBlitScaled(src, &final_src, dst, &final_dst);
}

return 0;
}

/**
* This is a semi-private blit function and it performs low-level surface
* scaled blitting only.
*/
int
SDL_LowerBlitScaled(SDL_Surface * src, SDL_Rect * srcrect,
SDL_Surface * dst, SDL_Rect * dstrect)
{
/* Save off the original dst width, height */
int dstW = dstrect->w;
@@ -618,11 +707,6 @@ SDL_BlitScaled(SDL_Surface * src, const SDL_Rect * srcrect,
/* Clip the dst surface to the dstrect */
SDL_SetClipRect( dst, &final_dst );

/* If the dest was clipped to a zero sized rect then exit */
if ( dst->clip_rect.w <= 0 || dst->clip_rect.h <= 0 ) {
return -1;
}

/* Did the dst width change? */
if ( dstW != dst->clip_rect.w ) {
/* scale the src width appropriately */

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