Make it clear that you can't mix 2D rendering and the window surface API

Also added functions to query and destroy the window surface so you can switch between modes if you want.

See https://github.com/pygame-community/pygame-ce/issues/2190 for more details.

WhatsNew.txt

@@ -6,6 +6,7 @@ This is a list of major changes in SDL's version history.
 ---------------------------------------------------------------------------
 
 General:
+* Added SDL_HasWindowSurface() and SDL_DestroyWindowSurface() to switch between the window surface and rendering APIs
 * Added a display event SDL_DISPLAYEVENT_MOVED which is sent when the primary monitor changes or displays change position relative to each other
 * Added the hint SDL_HINT_ENABLE_SCREEN_KEYBOARD to control whether the on-screen keyboard should be shown when text input is active
 

include/SDL_video.h

@@ -1275,6 +1275,17 @@ extern DECLSPEC void SDLCALL SDL_RestoreWindow(SDL_Window * window);
 extern DECLSPEC int SDLCALL SDL_SetWindowFullscreen(SDL_Window * window,
                                                     Uint32 flags);
 
+/**
+ * Return whether the window has a surface associated with it.
+ *
+ * \returns SDL_TRUE if there is a surface associated with the window, or SDL_FALSE otherwise.
+ *
+ * \since This function is available since SDL 2.28.0.
+ *
+ * \sa SDL_GetWindowSurface
+ */
+extern DECLSPEC SDL_bool SDLCALL SDL_HasWindowSurface(SDL_Window *window);
+
 /**
  * Get the SDL surface associated with the window.
  *
@@ -1295,6 +1306,8 @@ extern DECLSPEC int SDLCALL SDL_SetWindowFullscreen(SDL_Window * window,
  *
  * \since This function is available since SDL 2.0.0.
  *
+ * \sa SDL_DestroyWindowSurface
+ * \sa SDL_HasWindowSurface
  * \sa SDL_UpdateWindowSurface
  * \sa SDL_UpdateWindowSurfaceRects
  */
@@ -1343,6 +1356,20 @@ extern DECLSPEC int SDLCALL SDL_UpdateWindowSurfaceRects(SDL_Window * window,
                                                          const SDL_Rect * rects,
                                                          int numrects);
 
+/**
+ * Destroy the surface associated with the window.
+ *
+ * \param window the window to update
+ * \returns 0 on success or a negative error code on failure; call
+ *          SDL_GetError() for more information.
+ *
+ * \since This function is available since SDL 2.28.0.
+ *
+ * \sa SDL_GetWindowSurface
+ * \sa SDL_HasWindowSurface
+ */
+extern DECLSPEC int SDLCALL SDL_DestroyWindowSurface(SDL_Window *window);
+
 /**
  * Set a window's input grab mode.
  *

src/dynapi/SDL2.exports

@@ -868,3 +868,5 @@
 ++'_SDL_ResetHints'.'SDL2.dll'.'SDL_ResetHints'
 ++'_SDL_strcasestr'.'SDL2.dll'.'SDL_strcasestr'
 # ++'_SDL_GDKSuspendComplete'.'SDL2.dll'.'SDL_GDKSuspendComplete'
+++'_SDL_HasWindowSurface'.'SDL2.dll'.'SDL_HasWindowSurface'
+++'_SDL_DestroyWindowSurface'.'SDL2.dll'.'SDL_DestroyWindowSurface'

src/dynapi/SDL_dynapi_overrides.h

@@ -894,3 +894,5 @@
 #define SDL_ResetHints SDL_ResetHints_REAL
 #define SDL_strcasestr SDL_strcasestr_REAL
 #define SDL_GDKSuspendComplete SDL_GDKSuspendComplete_REAL
+#define SDL_HasWindowSurface SDL_HasWindowSurface_REAL
+#define SDL_DestroyWindowSurface SDL_DestroyWindowSurface_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -979,3 +979,5 @@ SDL_DYNAPI_PROC(char*,SDL_strcasestr,(const char *a, const char *b),(a,b),return
 #if defined(__GDK__)
 SDL_DYNAPI_PROC(void,SDL_GDKSuspendComplete,(void),(),)
 #endif
+SDL_DYNAPI_PROC(SDL_bool,SDL_HasWindowSurface,(SDL_Window *a),(a),return)
+SDL_DYNAPI_PROC(int,SDL_DestroyWindowSurface,(SDL_Window *a),(a),return)

src/render/SDL_render.c

@@ -950,6 +950,11 @@ SDL_Renderer *SDL_CreateRenderer(SDL_Window *window, int index, Uint32 flags)
         goto error;
     }
 
+    if (SDL_HasWindowSurface(window)) {
+        SDL_SetError("Surface already associated with window");
+        goto error;
+    }
+
     if (SDL_GetRenderer(window)) {
         SDL_SetError("Renderer already associated with window");
         goto error;

src/video/SDL_video.c

@@ -1884,12 +1884,7 @@ int SDL_RecreateWindow(SDL_Window *window, Uint32 flags)
     }
 
     /* Tear down the old native window */
-    if (window->surface) {
-        window->surface->flags &= ~SDL_DONTFREE;
-        SDL_FreeSurface(window->surface);
-        window->surface = NULL;
-        window->surface_valid = SDL_FALSE;
-    }
+    SDL_DestroyWindowSurface(window);
 
     if (_this->checked_texture_framebuffer) { /* never checked? No framebuffer to destroy. Don't risk calling the wrong implementation. */
         if (_this->DestroyWindowFramebuffer) {
@@ -2670,16 +2665,19 @@ static SDL_Surface *SDL_CreateWindowFramebuffer(SDL_Window *window)
     return SDL_CreateRGBSurfaceFrom(pixels, window->w, window->h, bpp, pitch, Rmask, Gmask, Bmask, Amask);
 }
 
+SDL_bool SDL_HasWindowSurface(SDL_Window *window)
+{
+    CHECK_WINDOW_MAGIC(window, SDL_FALSE);
+
+    return window->surface ? SDL_TRUE : SDL_FALSE;
+}
+
 SDL_Surface *SDL_GetWindowSurface(SDL_Window *window)
 {
     CHECK_WINDOW_MAGIC(window, NULL);
 
     if (!window->surface_valid) {
-        if (window->surface) {
-            window->surface->flags &= ~SDL_DONTFREE;
-            SDL_FreeSurface(window->surface);
-            window->surface = NULL;
-        }
+        SDL_DestroyWindowSurface(window);
         window->surface = SDL_CreateWindowFramebuffer(window);
         if (window->surface) {
             window->surface_valid = SDL_TRUE;
@@ -2761,6 +2759,19 @@ int SDL_SetWindowOpacity(SDL_Window * window, float opacity)
     return retval;
 }
 
+int SDL_DestroyWindowSurface(SDL_Window *window)
+{
+    CHECK_WINDOW_MAGIC(window, -1);
+
+    if (window->surface) {
+        window->surface->flags &= ~SDL_DONTFREE;
+        SDL_DestroySurface(window->surface);
+        window->surface = NULL;
+        window->surface_valid = SDL_FALSE;
+    }
+    return 0;
+}
+
 int SDL_GetWindowOpacity(SDL_Window *window, float *out_opacity)
 {
     CHECK_WINDOW_MAGIC(window, -1);
@@ -3206,12 +3217,7 @@ void SDL_DestroyWindow(SDL_Window *window)
         }
     }
 
-    if (window->surface) {
-        window->surface->flags &= ~SDL_DONTFREE;
-        SDL_FreeSurface(window->surface);
-        window->surface = NULL;
-        window->surface_valid = SDL_FALSE;
-    }
+    SDL_DestroyWindowSurface(window);
     if (_this->checked_texture_framebuffer) { /* never checked? No framebuffer to destroy. Don't risk calling the wrong implementation. */
         if (_this->DestroyWindowFramebuffer) {
             _this->DestroyWindowFramebuffer(_this, window);