Document that the pitch value may be zero for surfaces that will be filled in by the application later.

Also verify that the pitch isn't zero for surfaces with valid pixels

Fixes https://github.com/libsdl-org/SDL/issues/7143

include/SDL3/SDL_surface.h

@@ -137,6 +137,9 @@ extern DECLSPEC SDL_Surface *SDLCALL SDL_CreateSurface
  * No copy is made of the pixel data. Pixel data is not managed automatically;
  * you must free the surface before you free the pixel data.
  *
+ * You may pass NULL for pixels and 0 for pitch to create a surface that you
+ * will fill in with valid values later.
+ *
  * \param pixels a pointer to existing pixel data
  * \param width the width of the surface
  * \param height the height of the surface

src/video/SDL_surface.c

@@ -203,7 +203,6 @@ SDL_CreateSurfaceFrom(void *pixels,
                       Uint32 format)
 {
     SDL_Surface *surface;
-    size_t minimalPitch;
 
     if (width < 0) {
         SDL_InvalidParamError("width");
@@ -215,20 +214,26 @@ SDL_CreateSurfaceFrom(void *pixels,
         return NULL;
     }
 
-    if (SDL_ISPIXELFORMAT_FOURCC(format)) {
-        int p;
-        if (SDL_CalculateYUVSize(format, width, height, NULL, &p) < 0) {
+    if (pitch == 0 && pixels == NULL) {
+        /* The application will fill these in later with valid values */
+    } else {
+        size_t minimalPitch;
+
+        if (SDL_ISPIXELFORMAT_FOURCC(format)) {
+            int p;
+            if (SDL_CalculateYUVSize(format, width, height, NULL, &p) < 0) {
+                SDL_InvalidParamError("pitch");
+                return NULL;
+            }
+            minimalPitch = p;
+        } else {
+            minimalPitch = SDL_CalculatePitch(format, width, SDL_TRUE);
+        }
+
+        if (pitch < 0 || (size_t)pitch < minimalPitch) {
             SDL_InvalidParamError("pitch");
             return NULL;
         }
-        minimalPitch = p;
-    } else {
-        minimalPitch = SDL_CalculatePitch(format, width, SDL_TRUE);
-    }
-
-    if (pitch < 0 || (pitch > 0 && ((size_t)pitch) < minimalPitch)) {
-        SDL_InvalidParamError("pitch");
-        return NULL;
     }
 
     surface = SDL_CreateSurface(0, 0, format);

test/testautomation_surface.c

@@ -621,6 +621,14 @@ int surface_testOverflow(void *arg)
     SDLTest_AssertCheck(surface == NULL, "Should detect negative pitch");
     SDLTest_AssertCheck(SDL_strcmp(SDL_GetError(), expectedError) == 0,
                         "Expected \"%s\", got \"%s\"", expectedError, SDL_GetError());
+    surface = SDL_CreateSurfaceFrom(buf, 1, 1, 0, SDL_PIXELFORMAT_RGBA8888);
+    SDLTest_AssertCheck(surface == NULL, "Should detect zero pitch");
+    SDLTest_AssertCheck(SDL_strcmp(SDL_GetError(), expectedError) == 0,
+                        "Expected \"%s\", got \"%s\"", expectedError, SDL_GetError());
+    surface = SDL_CreateSurfaceFrom(NULL, 1, 1, 0, SDL_PIXELFORMAT_RGBA8888);
+    SDLTest_AssertCheck(surface != NULL, "Allow zero pitch for partially set up surfaces: %s",
+                        surface != NULL ? "(success)" : SDL_GetError());
+    SDL_DestroySurface(surface);
 
     /* Less than 1 byte per pixel: the pitch can legitimately be less than
      * the width, but it must be enough to hold the appropriate number of