Standardized property names for internal SDL properties

include/SDL3/SDL_properties.h

@@ -95,6 +95,8 @@ extern DECLSPEC void SDLCALL SDL_UnlockProperties(SDL_PropertiesID props);
 /**
  * Set a property on a set of properties
  *
+ * By convention, the names of properties that SDL exposes on objects will start with "SDL.", and properties that SDL uses internally will start with "SDL.internal.". These should be considered read-only and should not be modified by applications.
+ *
  * \param props the properties to modify
  * \param name the name of the property to modify
  * \param value the new value of the property, or NULL to delete the property

src/render/SDL_render.c

@@ -43,7 +43,7 @@ this should probably be removed at some point in the future.  --ryan. */
 #define DONT_DRAW_WHILE_HIDDEN 0
 #endif
 
-#define SDL_WINDOWRENDERDATA "_SDL_WindowRenderData"
+#define SDL_WINDOWRENDERDATA "SDL.internal.window.renderer"
 
 #define CHECK_RENDERER_MAGIC(renderer, retval)                  \
     if (!(renderer) || (renderer)->magic != &renderer_magic) {  \

src/video/SDL_video.c

@@ -183,7 +183,7 @@ static SDL_bool DisableUnsetFullscreenOnMinimize(SDL_VideoDevice *_this)
 
 /* Support for framebuffer emulation using an accelerated renderer */
 
-#define SDL_WINDOWTEXTUREDATA "_SDL_WindowTextureData"
+#define SDL_WINDOWTEXTUREDATA "SDL.internal.window.texturedata"
 
 typedef struct
 {

src/video/dummy/SDL_nullframebuffer.c

@@ -25,7 +25,7 @@
 #include "../SDL_sysvideo.h"
 #include "SDL_nullframebuffer_c.h"
 
-#define DUMMY_SURFACE "_SDL_DummySurface"
+#define DUMMY_SURFACE "SDL.internal.window.surface"
 
 static void CleanupSurface(void *userdata, void *value)
 {

src/video/n3ds/SDL_n3dsframebuffer.c

@@ -26,7 +26,7 @@
 #include "SDL_n3dsframebuffer_c.h"
 #include "SDL_n3dsvideo.h"
 
-#define N3DS_SURFACE "_SDL_N3DSSurface"
+#define N3DS_SURFACE "SDL.internal.window.surface"
 
 typedef struct
 {

src/video/offscreen/SDL_offscreenframebuffer.c

@@ -25,7 +25,7 @@
 #include "../SDL_sysvideo.h"
 #include "SDL_offscreenframebuffer_c.h"
 
-#define OFFSCREEN_SURFACE "_SDL_DummySurface"
+#define OFFSCREEN_SURFACE "SDL.internal.window.surface"
 
 static void CleanupSurface(void *userdata, void *value)
 {