SDL: Add Emscripten window data to window properties

From cbc26fe2c4b075909d3de5df08ff266010c16a7b Mon Sep 17 00:00:00 2001
From: Temdog007 <[EMAIL REDACTED]>
Date: Tue, 1 Apr 2025 22:01:08 -0700
Subject: [PATCH] Add Emscripten window data to window properties

---
 include/SDL3/SDL_video.h                   | 7 +++++++
 src/video/emscripten/SDL_emscriptenvideo.c | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/include/SDL3/SDL_video.h b/include/SDL3/SDL_video.h
index 4369c9c02f828..d30a5aff3002a 100644
--- a/include/SDL3/SDL_video.h
+++ b/include/SDL3/SDL_video.h
@@ -1542,6 +1542,11 @@ extern SDL_DECLSPEC SDL_Window * SDLCALL SDL_GetWindowParent(SDL_Window *window)
  * - `SDL_PROP_WINDOW_X11_WINDOW_NUMBER`: the X11 Window associated with the
  *   window
  *
+ * On Emscripten:
+ * - `SDL_PROP_WINDOW_EMSCRIPTEN_CANVAS_ID`: the id the canvas element will have
+ * - `SDL_PROP_WINDOW_EMSCRIPTEN_KEYBOARD_ELEMENT`: the keyboard element that associates
+ *   keyboard events to this window
+ *
  * \param window the window to query.
  * \returns a valid property ID on success or 0 on failure; call
  *          SDL_GetError() for more information.
@@ -1587,6 +1592,8 @@ 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"
 
 /**
  * Get the window flags.
diff --git a/src/video/emscripten/SDL_emscriptenvideo.c b/src/video/emscripten/SDL_emscriptenvideo.c
index 52389f1c1d7a4..c8890c5caa852 100644
--- a/src/video/emscripten/SDL_emscriptenvideo.c
+++ b/src/video/emscripten/SDL_emscriptenvideo.c
@@ -525,6 +525,10 @@ 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);
+
     // Window has been successfully created
     return true;
 }