emscripten: mouse: proxy canvas access to main thread

Author: jakogut

src/video/emscripten/SDL_emscriptenmouse.c

@@ -26,6 +26,7 @@
 
 #include <emscripten/emscripten.h>
 #include <emscripten/html5.h>
+#include <emscripten/threading.h>
 
 #include "SDL_emscriptenmouse.h"
 
@@ -64,19 +65,9 @@ Emscripten_CreateDefaultCursor()
     return Emscripten_CreateCursorFromString("default", SDL_FALSE);
 }
 
-static SDL_Cursor*
-Emscripten_CreateCursor(SDL_Surface* surface, int hot_x, int hot_y)
+static const char *Emscripten_GetCursorUrl(int w, int h, int hot_x, int hot_y, int pixels)
 {
-    const char *cursor_url = NULL;
-    SDL_Surface *conv_surf;
-
-    conv_surf = SDL_ConvertSurfaceFormat(surface, SDL_PIXELFORMAT_ABGR8888, 0);
-
-    if (!conv_surf) {
-        return NULL;
-    }
-
-    cursor_url = (const char *)EM_ASM_INT({
+    return (const char *)EM_ASM_INT({
         var w = $0;
         var h = $1;
         var hot_x = $2;
@@ -124,7 +115,40 @@ Emscripten_CreateCursor(SDL_Surface* surface, int hot_x, int hot_y)
         stringToUTF8(url, urlBuf, url.length + 1);
 
         return urlBuf;
-    }, surface->w, surface->h, hot_x, hot_y, conv_surf->pixels);
+    }, w, h, hot_x, hot_y, pixels);
+}
+
+static SDL_Cursor*
+Emscripten_CreateCursor(SDL_Surface* surface, int hot_x, int hot_y)
+{
+    const char *cursor_url = NULL;
+    SDL_Surface *conv_surf;
+
+    conv_surf = SDL_ConvertSurfaceFormat(surface, SDL_PIXELFORMAT_ABGR8888, 0);
+
+    if (!conv_surf) {
+        return NULL;
+    }
+
+    if (emscripten_is_main_runtime_thread()) {
+        cursor_url = Emscripten_GetCursorUrl(
+            surface->w,
+            surface->h,
+            hot_x,
+            hot_y,
+            conv_surf->pixels
+        );
+    } else {
+        cursor_url = emscripten_sync_run_in_main_runtime_thread(
+            EM_FUNC_SIG_IIIIIII,
+            Emscripten_GetCursorUrl,
+            surface->w,
+            surface->h,
+            hot_x,
+            hot_y,
+            conv_surf->pixels
+        );
+    }
 
     SDL_FreeSurface(conv_surf);
 
@@ -199,28 +223,43 @@ Emscripten_FreeCursor(SDL_Cursor* cursor)
     }
 }
 
-static int
-Emscripten_ShowCursor(SDL_Cursor* cursor)
+static void
+Emscripten_ShowCursorWorker(SDL_Cursor *cursor)
 {
     Emscripten_CursorData *curdata;
-    if (SDL_GetMouseFocus() != NULL) {
-        if(cursor && cursor->driverdata) {
-            curdata = (Emscripten_CursorData *) cursor->driverdata;
-
-            if(curdata->system_cursor) {
-                EM_ASM_INT({
-                    if (Module['canvas']) {
-                        Module['canvas'].style['cursor'] = UTF8ToString($0);
-                    }
-                    return 0;
-                }, curdata->system_cursor);
-            }
-        }
-        else {
-            EM_ASM(
+    if(cursor && cursor->driverdata) {
+        curdata = (Emscripten_CursorData *) cursor->driverdata;
+
+        if(curdata->system_cursor) {
+            EM_ASM_INT({
                 if (Module['canvas']) {
-                    Module['canvas'].style['cursor'] = 'none';
+                    Module['canvas'].style['cursor'] = UTF8ToString($0);
                 }
+                return 0;
+            }, curdata->system_cursor);
+        }
+    }
+    else {
+        EM_ASM(
+            if (Module['canvas']) {
+                Module['canvas'].style['cursor'] = 'none';
+            }
+        );
+    }
+
+}
+
+static int
+Emscripten_ShowCursor(SDL_Cursor* cursor)
+{
+    if (SDL_GetMouseFocus() != NULL) {
+        if (emscripten_is_main_runtime_thread()) {
+            Emscripten_ShowCursorWorker(cursor);
+        } else {
+            emscripten_sync_run_in_main_runtime_thread(
+                EM_FUNC_SIG_VI,
+                Emscripten_ShowCursorWorker,
+                (uint32_t)cursor
             );
         }
     }