[JS] Check canvas size each loop, force redraw.

Fix compatibility issues, achieve smoother resizing.

platform/javascript/display_server_javascript.cpp

@@ -68,6 +68,20 @@ bool DisplayServerJavaScript::is_canvas_focused() {
 	/* clang-format on */
 }
 
+bool DisplayServerJavaScript::check_size_force_redraw() {
+	int canvas_width;
+	int canvas_height;
+	emscripten_get_canvas_element_size(DisplayServerJavaScript::canvas_id, &canvas_width, &canvas_height);
+	if (last_width != canvas_width || last_height != canvas_height) {
+		last_width = canvas_width;
+		last_height = canvas_height;
+		// Update the framebuffer size and for redraw.
+		emscripten_set_canvas_element_size(DisplayServerJavaScript::canvas_id, canvas_width, canvas_height);
+		return true;
+	}
+	return false;
+}
+
 Point2 DisplayServerJavaScript::compute_position_in_canvas(int p_x, int p_y) {
 	int canvas_x = EM_ASM_INT({
 		return Module['canvas'].getBoundingClientRect().x;
@@ -1080,6 +1094,8 @@ Size2i DisplayServerJavaScript::window_get_min_size(WindowID p_window) const {
 }
 
 void DisplayServerJavaScript::window_set_size(const Size2i p_size, WindowID p_window) {
+	last_width = p_size.x;
+	last_height = p_size.y;
 	emscripten_set_canvas_element_size(canvas_id, p_size.x, p_size.y);
 }
 

platform/javascript/display_server_javascript.h

@@ -53,6 +53,9 @@ class DisplayServerJavaScript : public DisplayServer {
 	double last_click_ms = 0;
 	int last_click_button_index = -1;
 
+	int last_width = 0;
+	int last_height = 0;
+
 	// utilities
 	static Point2 compute_position_in_canvas(int p_x, int p_y);
 	static void focus_canvas();
@@ -104,6 +107,9 @@ public:
 	Callable input_text_callback;
 	Callable drop_files_callback;
 
+	// utilities
+	bool check_size_force_redraw();
+
 	// from DisplayServer
 	virtual void alert(const String &p_alert, const String &p_title = "ALERT!");
 	virtual bool has_feature(Feature p_feature) const;

platform/javascript/javascript_main.cpp

@@ -47,6 +47,10 @@ void exit_callback() {
 }
 
 void main_loop_callback() {
+	bool force_draw = DisplayServerJavaScript::get_singleton()->check_size_force_redraw();
+	if (force_draw) {
+		Main::force_redraw();
+	}
 	if (os->main_loop_iterate()) {
 		emscripten_cancel_main_loop(); // Cancel current loop and wait for finalize_async.
 		EM_ASM({