Note that the Emscripten window properties are strings

include/SDL3/SDL_video.h

@@ -1544,9 +1544,9 @@ extern SDL_DECLSPEC SDL_Window * SDLCALL SDL_GetWindowParent(SDL_Window *window)
  *
  * On Emscripten:
  *
- * - `SDL_PROP_WINDOW_EMSCRIPTEN_CANVAS_ID`: the id the canvas element will
+ * - `SDL_PROP_WINDOW_EMSCRIPTEN_CANVAS_ID_STRING`: the id the canvas element will
  *   have
- * - `SDL_PROP_WINDOW_EMSCRIPTEN_KEYBOARD_ELEMENT`: the keyboard element that
+ * - `SDL_PROP_WINDOW_EMSCRIPTEN_KEYBOARD_ELEMENT_STRING`: the keyboard element that
  *   associates keyboard events to this window
  *
  * \param window the window to query.
@@ -1594,8 +1594,8 @@ extern SDL_DECLSPEC SDL_PropertiesID SDLCALL SDL_GetWindowProperties(SDL_Window
 #define SDL_PROP_WINDOW_X11_DISPLAY_POINTER                         "SDL.window.x11.display"
 #define SDL_PROP_WINDOW_X11_SCREEN_NUMBER                           "SDL.window.x11.screen"
 #define SDL_PROP_WINDOW_X11_WINDOW_NUMBER                           "SDL.window.x11.window"
-#define SDL_PROP_WINDOW_EMSCRIPTEN_CANVAS_ID                        "SDL.window.emscripten.canvas_id"
-#define SDL_PROP_WINDOW_EMSCRIPTEN_KEYBOARD_ELEMENT                 "SDL.window.emscripten.keyboard_element"
+#define SDL_PROP_WINDOW_EMSCRIPTEN_CANVAS_ID_STRING                 "SDL.window.emscripten.canvas_id"
+#define SDL_PROP_WINDOW_EMSCRIPTEN_KEYBOARD_ELEMENT_STRING          "SDL.window.emscripten.keyboard_element"
 
 /**
  * Get the window flags.

src/video/emscripten/SDL_emscriptenvideo.c

@@ -526,8 +526,8 @@ static bool Emscripten_CreateWindow(SDL_VideoDevice *_this, SDL_Window *window,
     }, window);
 
     // Ensure canvas_id and keyboard_element are added to the window's properties
-    SDL_SetStringProperty(window->props, SDL_PROP_WINDOW_EMSCRIPTEN_CANVAS_ID, wdata->canvas_id);
-    SDL_SetStringProperty(window->props, SDL_PROP_WINDOW_EMSCRIPTEN_KEYBOARD_ELEMENT, wdata->keyboard_element);
+    SDL_SetStringProperty(window->props, SDL_PROP_WINDOW_EMSCRIPTEN_CANVAS_ID_STRING, wdata->canvas_id);
+    SDL_SetStringProperty(window->props, SDL_PROP_WINDOW_EMSCRIPTEN_KEYBOARD_ELEMENT_STRING, wdata->keyboard_element);
 
     // Window has been successfully created
     return true;