The rectangles passed to SDL_BlitSurfaceUnchecked() and SDL_BlitSurfaceUncheckedScaled() are const.

The destination rectangle passed to SDL_BlitSurface() and SDL_BlitSurfaceScaled() is non-const and filled in with the final destination rectangle after clipping, and now documented as such.

Fixes https://github.com/libsdl-org/SDL/issues/7911

include/SDL3/SDL_surface.h

@@ -99,8 +99,8 @@ typedef struct SDL_Surface
 /**
  * \brief The type of function used for surface blitting functions.
  */
-typedef int (SDLCALL *SDL_blit) (struct SDL_Surface *src, SDL_Rect *srcrect,
-                                 struct SDL_Surface *dst, SDL_Rect *dstrect);
+typedef int (SDLCALL *SDL_blit) (struct SDL_Surface *src, const SDL_Rect *srcrect,
+                                 struct SDL_Surface *dst, const SDL_Rect *dstrect);
 
 /**
  * \brief The formula used for converting between YUV and RGB
@@ -773,8 +773,9 @@ extern DECLSPEC int SDLCALL SDL_FillSurfaceRects
  * \param srcrect the SDL_Rect structure representing the rectangle to be
  *                copied, or NULL to copy the entire surface
  * \param dst the SDL_Surface structure that is the blit target
- * \param dstrect the SDL_Rect structure representing the rectangle that is
- *                copied into
+ * \param dstrect the SDL_Rect structure representing the target rectangle
+ *                in the destination surface, filled with the actual rectangle
+ *                used after clipping
  * \returns 0 on success or a negative error code on failure; call
  *          SDL_GetError() for more information.
  *
@@ -796,8 +797,8 @@ extern DECLSPEC int SDLCALL SDL_BlitSurface
  * \param srcrect the SDL_Rect structure representing the rectangle to be
  *                copied, or NULL to copy the entire surface
  * \param dst the SDL_Surface structure that is the blit target
- * \param dstrect the SDL_Rect structure representing the rectangle that is
- *                copied into
+ * \param dstrect the SDL_Rect structure representing the target rectangle
+ *                in the destination surface
  * \returns 0 on success or a negative error code on failure; call
  *          SDL_GetError() for more information.
  *
@@ -806,8 +807,8 @@ extern DECLSPEC int SDLCALL SDL_BlitSurface
  * \sa SDL_BlitSurface
  */
 extern DECLSPEC int SDLCALL SDL_BlitSurfaceUnchecked
-    (SDL_Surface *src, SDL_Rect *srcrect,
-     SDL_Surface *dst, SDL_Rect *dstrect);
+    (SDL_Surface *src, const SDL_Rect *srcrect,
+     SDL_Surface *dst, const SDL_Rect *dstrect);
 
 
 /**
@@ -820,8 +821,8 @@ extern DECLSPEC int SDLCALL SDL_BlitSurfaceUnchecked
  * \param srcrect the SDL_Rect structure representing the rectangle to be
  *                copied
  * \param dst the SDL_Surface structure that is the blit target
- * \param dstrect the SDL_Rect structure representing the rectangle that is
- *                copied into
+ * \param dstrect the SDL_Rect structure representing the target rectangle
+ *                in the destination surface
  * \returns 0 on success or a negative error code on failure; call
  *          SDL_GetError() for more information.
  *
@@ -839,8 +840,8 @@ extern DECLSPEC int SDLCALL SDL_SoftStretch(SDL_Surface *src,
  * \param srcrect the SDL_Rect structure representing the rectangle to be
  *                copied
  * \param dst the SDL_Surface structure that is the blit target
- * \param dstrect the SDL_Rect structure representing the rectangle that is
- *                copied into
+ * \param dstrect the SDL_Rect structure representing the target rectangle
+ *                in the destination surface
  * \returns 0 on success or a negative error code on failure; call
  *          SDL_GetError() for more information.
  *
@@ -859,8 +860,9 @@ extern DECLSPEC int SDLCALL SDL_SoftStretchLinear(SDL_Surface *src,
  * \param srcrect the SDL_Rect structure representing the rectangle to be
  *                copied
  * \param dst the SDL_Surface structure that is the blit target
- * \param dstrect the SDL_Rect structure representing the rectangle that is
- *                copied into
+ * \param dstrect the SDL_Rect structure representing the target rectangle
+ *                in the destination surface, filled with the actual rectangle
+ *                used after clipping
  * \returns 0 on success or a negative error code on failure; call
  *          SDL_GetError() for more information.
  *
@@ -868,7 +870,7 @@ extern DECLSPEC int SDLCALL SDL_SoftStretchLinear(SDL_Surface *src,
  */
 extern DECLSPEC int SDLCALL SDL_BlitSurfaceScaled
     (SDL_Surface *src, const SDL_Rect *srcrect,
-    SDL_Surface *dst, SDL_Rect *dstrect);
+     SDL_Surface *dst, SDL_Rect *dstrect);
 
 /**
  * Perform low-level surface scaled blitting only.
@@ -880,8 +882,8 @@ extern DECLSPEC int SDLCALL SDL_BlitSurfaceScaled
  * \param srcrect the SDL_Rect structure representing the rectangle to be
  *                copied
  * \param dst the SDL_Surface structure that is the blit target
- * \param dstrect the SDL_Rect structure representing the rectangle that is
- *                copied into
+ * \param dstrect the SDL_Rect structure representing the target rectangle
+ *                in the destination surface
  * \returns 0 on success or a negative error code on failure; call
  *          SDL_GetError() for more information.
  *
@@ -890,8 +892,8 @@ extern DECLSPEC int SDLCALL SDL_BlitSurfaceScaled
  * \sa SDL_BlitSurfaceScaled
  */
 extern DECLSPEC int SDLCALL SDL_BlitSurfaceUncheckedScaled
-    (SDL_Surface *src, SDL_Rect *srcrect,
-    SDL_Surface *dst, SDL_Rect *dstrect);
+    (SDL_Surface *src, const SDL_Rect *srcrect,
+     SDL_Surface *dst, const SDL_Rect *dstrect);
 
 /**
  * Set the YUV conversion mode

src/dynapi/SDL_dynapi_procs.h

@@ -136,8 +136,8 @@ SDL_DYNAPI_PROC(SDL_JoystickID,SDL_AttachVirtualJoystick,(SDL_JoystickType a, in
 SDL_DYNAPI_PROC(SDL_JoystickID,SDL_AttachVirtualJoystickEx,(const SDL_VirtualJoystickDesc *a),(a),return)
 SDL_DYNAPI_PROC(int,SDL_BlitSurface,(SDL_Surface *a, const SDL_Rect *b, SDL_Surface *c, SDL_Rect *d),(a,b,c,d),return)
 SDL_DYNAPI_PROC(int,SDL_BlitSurfaceScaled,(SDL_Surface *a, const SDL_Rect *b, SDL_Surface *c, SDL_Rect *d),(a,b,c,d),return)
-SDL_DYNAPI_PROC(int,SDL_BlitSurfaceUnchecked,(SDL_Surface *a, SDL_Rect *b, SDL_Surface *c, SDL_Rect *d),(a,b,c,d),return)
-SDL_DYNAPI_PROC(int,SDL_BlitSurfaceUncheckedScaled,(SDL_Surface *a, SDL_Rect *b, SDL_Surface *c, SDL_Rect *d),(a,b,c,d),return)
+SDL_DYNAPI_PROC(int,SDL_BlitSurfaceUnchecked,(SDL_Surface *a, const SDL_Rect *b, SDL_Surface *c, const SDL_Rect *d),(a,b,c,d),return)
+SDL_DYNAPI_PROC(int,SDL_BlitSurfaceUncheckedScaled,(SDL_Surface *a, const SDL_Rect *b, SDL_Surface *c, const SDL_Rect *d),(a,b,c,d),return)
 SDL_DYNAPI_PROC(int,SDL_BroadcastCondition,(SDL_Condition *a),(a),return)
 SDL_DYNAPI_PROC(int,SDL_CaptureMouse,(SDL_bool a),(a),return)
 SDL_DYNAPI_PROC(void,SDL_CleanupTLS,(void),(),)

src/render/SDL_sysrender.h

@@ -307,7 +307,7 @@ extern SDL_BlendOperation SDL_GetBlendModeAlphaOperation(SDL_BlendMode blendMode
    the next call, because it might be in an array that gets realloc()'d. */
 extern void *SDL_AllocateRenderVertices(SDL_Renderer *renderer, const size_t numbytes, const size_t alignment, size_t *offset);
 
-extern int SDL_PrivateBlitSurfaceUncheckedScaled(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect, SDL_ScaleMode scaleMode);
+extern int SDL_PrivateBlitSurfaceUncheckedScaled(SDL_Surface *src, const SDL_Rect *srcrect, SDL_Surface *dst, const SDL_Rect *dstrect, SDL_ScaleMode scaleMode);
 extern int SDL_PrivateBlitSurfaceScaled(SDL_Surface *src, const SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect, SDL_ScaleMode scaleMode);
 
 /* Ends C function definitions when using C++ */

src/video/SDL_RLEaccel.c

@@ -432,7 +432,7 @@
     } while (0)
 
 static void RLEClipBlit(int w, Uint8 *srcbuf, SDL_Surface *surf_dst,
-                        Uint8 *dstbuf, SDL_Rect *srcrect, unsigned alpha)
+                        Uint8 *dstbuf, const SDL_Rect *srcrect, unsigned alpha)
 {
     SDL_PixelFormat *fmt = surf_dst->format;
 
@@ -442,8 +442,8 @@ static void RLEClipBlit(int w, Uint8 *srcbuf, SDL_Surface *surf_dst,
 #undef RLECLIPBLIT
 
 /* blit a colorkeyed RLE surface */
-static int SDLCALL SDL_RLEBlit(SDL_Surface *surf_src, SDL_Rect *srcrect,
-                               SDL_Surface *surf_dst, SDL_Rect *dstrect)
+static int SDLCALL SDL_RLEBlit(SDL_Surface *surf_src, const SDL_Rect *srcrect,
+                               SDL_Surface *surf_dst, const SDL_Rect *dstrect)
 {
     Uint8 *dstbuf;
     Uint8 *srcbuf;
@@ -626,7 +626,7 @@ typedef struct
 
 /* blit a pixel-alpha RLE surface clipped at the right and/or left edges */
 static void RLEAlphaClipBlit(int w, Uint8 *srcbuf, SDL_Surface *surf_dst,
-                             Uint8 *dstbuf, SDL_Rect *srcrect)
+                             Uint8 *dstbuf, const SDL_Rect *srcrect)
 {
     SDL_PixelFormat *df = surf_dst->format;
     /*
@@ -717,8 +717,8 @@ static void RLEAlphaClipBlit(int w, Uint8 *srcbuf, SDL_Surface *surf_dst,
 }
 
 /* blit a pixel-alpha RLE surface */
-static int SDLCALL SDL_RLEAlphaBlit(SDL_Surface *surf_src, SDL_Rect *srcrect,
-                                    SDL_Surface *surf_dst, SDL_Rect *dstrect)
+static int SDLCALL SDL_RLEAlphaBlit(SDL_Surface *surf_src, const SDL_Rect *srcrect,
+                                    SDL_Surface *surf_dst, const SDL_Rect *dstrect)
 {
     int x, y;
     int w = surf_src->w;

src/video/SDL_blit.c

@@ -29,8 +29,8 @@
 #include "SDL_pixels_c.h"
 
 /* The general purpose software blit routine */
-static int SDLCALL SDL_SoftBlit(SDL_Surface *src, SDL_Rect *srcrect,
-                                SDL_Surface *dst, SDL_Rect *dstrect)
+static int SDLCALL SDL_SoftBlit(SDL_Surface *src, const SDL_Rect *srcrect,
+                                SDL_Surface *dst, const SDL_Rect *dstrect)
 {
     int okay;
     int src_locked;

src/video/SDL_surface.c

@@ -636,8 +636,8 @@ int SDL_GetSurfaceClipRect(SDL_Surface *surface, SDL_Rect *rect)
  * you know exactly what you are doing, you can optimize your code
  * by calling the one(s) you need.
  */
-int SDL_BlitSurfaceUnchecked(SDL_Surface *src, SDL_Rect *srcrect,
-                  SDL_Surface *dst, SDL_Rect *dstrect)
+int SDL_BlitSurfaceUnchecked(SDL_Surface *src, const SDL_Rect *srcrect,
+                             SDL_Surface *dst, const SDL_Rect *dstrect)
 {
     /* Check to make sure the blit mapping is valid */
     if ((src->map->dst != dst) ||
@@ -927,14 +927,14 @@ int SDL_PrivateBlitSurfaceScaled(SDL_Surface *src, const SDL_Rect *srcrect,
  *  This is a semi-private blit function and it performs low-level surface
  *  scaled blitting only.
  */
-int SDL_BlitSurfaceUncheckedScaled(SDL_Surface *src, SDL_Rect *srcrect,
-                        SDL_Surface *dst, SDL_Rect *dstrect)
+int SDL_BlitSurfaceUncheckedScaled(SDL_Surface *src, const SDL_Rect *srcrect,
+                                   SDL_Surface *dst, const SDL_Rect *dstrect)
 {
     return SDL_PrivateBlitSurfaceUncheckedScaled(src, srcrect, dst, dstrect, SDL_SCALEMODE_NEAREST);
 }
 
-int SDL_PrivateBlitSurfaceUncheckedScaled(SDL_Surface *src, SDL_Rect *srcrect,
-                               SDL_Surface *dst, SDL_Rect *dstrect, SDL_ScaleMode scaleMode)
+int SDL_PrivateBlitSurfaceUncheckedScaled(SDL_Surface *src, const SDL_Rect *srcrect,
+                                          SDL_Surface *dst, const SDL_Rect *dstrect, SDL_ScaleMode scaleMode)
 {
     static const Uint32 complex_copy_flags = (SDL_COPY_MODULATE_COLOR | SDL_COPY_MODULATE_ALPHA |
                                               SDL_COPY_BLEND | SDL_COPY_ADD | SDL_COPY_MOD | SDL_COPY_MUL |