[Web] Fix Web MouseWheel scrolling

platform/web/display_server_web.cpp

@@ -634,18 +634,18 @@ Point2i DisplayServerWeb::mouse_get_position() const {
 }
 
 // Wheel
-int DisplayServerWeb::mouse_wheel_callback(double p_delta_x, double p_delta_y) {
+int DisplayServerWeb::mouse_wheel_callback(int p_delta_mode, double p_delta_x, double p_delta_y) {
 #ifdef PROXY_TO_PTHREAD_ENABLED
 	if (!Thread::is_main_thread()) {
-		callable_mp_static(DisplayServerWeb::_mouse_wheel_callback).call_deferred(p_delta_x, p_delta_y);
+		callable_mp_static(DisplayServerWeb::_mouse_wheel_callback).call_deferred(p_delta_mode, p_delta_x, p_delta_y);
 		return true;
 	}
 #endif
 
-	return _mouse_wheel_callback(p_delta_x, p_delta_y);
+	return _mouse_wheel_callback(p_delta_mode, p_delta_x, p_delta_y);
 }
 
-int DisplayServerWeb::_mouse_wheel_callback(double p_delta_x, double p_delta_y) {
+int DisplayServerWeb::_mouse_wheel_callback(int p_delta_mode, double p_delta_x, double p_delta_y) {
 	if (!godot_js_display_canvas_is_focused() && !godot_js_is_ime_focused()) {
 		if (get_singleton()->cursor_inside_canvas) {
 			godot_js_display_canvas_focus();
@@ -665,21 +665,44 @@ int DisplayServerWeb::_mouse_wheel_callback(double p_delta_x, double p_delta_y)
 	ev->set_ctrl_pressed(input->is_key_pressed(Key::CTRL));
 	ev->set_meta_pressed(input->is_key_pressed(Key::META));
 
+	enum DeltaMode {
+		DELTA_MODE_PIXEL = 0,
+		DELTA_MODE_LINE = 1,
+		DELTA_MODE_PAGE = 2,
+	};
+	const float MOUSE_WHEEL_PIXEL_FACTOR = 0.03f;
+	const float MOUSE_WHEEL_LINE_FACTOR = 0.3f;
+	const float MOUSE_WHEEL_PAGE_FACTOR = 1.0f;
+	float mouse_wheel_factor;
+
+	switch (p_delta_mode) {
+		case DELTA_MODE_PIXEL: {
+			mouse_wheel_factor = MOUSE_WHEEL_PIXEL_FACTOR;
+		} break;
+		case DELTA_MODE_LINE: {
+			mouse_wheel_factor = MOUSE_WHEEL_LINE_FACTOR;
+		} break;
+		case DELTA_MODE_PAGE: {
+			mouse_wheel_factor = MOUSE_WHEEL_PAGE_FACTOR;
+		} break;
+	}
+
 	if (p_delta_y < 0) {
 		ev->set_button_index(MouseButton::WHEEL_UP);
+		ev->set_factor(-p_delta_y * mouse_wheel_factor);
 	} else if (p_delta_y > 0) {
 		ev->set_button_index(MouseButton::WHEEL_DOWN);
+		ev->set_factor(p_delta_y * mouse_wheel_factor);
 	} else if (p_delta_x > 0) {
 		ev->set_button_index(MouseButton::WHEEL_LEFT);
+		ev->set_factor(p_delta_x * mouse_wheel_factor);
 	} else if (p_delta_x < 0) {
 		ev->set_button_index(MouseButton::WHEEL_RIGHT);
+		ev->set_factor(-p_delta_x * mouse_wheel_factor);
 	} else {
 		return false;
 	}
 
-	// Different browsers give wildly different delta values, and we can't
-	// interpret deltaMode, so use default value for wheel events' factor.
-
 	MouseButtonMask button_flag = mouse_button_to_mask(ev->get_button_index());
 	BitField<MouseButtonMask> button_mask = input->get_mouse_button_mask();
 	button_mask.set_flag(button_flag);

platform/web/display_server_web.h

@@ -122,8 +122,8 @@ private:
 	static int _mouse_button_callback(int p_pressed, int p_button, double p_x, double p_y, int p_modifiers);
 	WASM_EXPORT static void mouse_move_callback(double p_x, double p_y, double p_rel_x, double p_rel_y, int p_modifiers, double p_pressure);
 	static void _mouse_move_callback(double p_x, double p_y, double p_rel_x, double p_rel_y, int p_modifiers, double p_pressure);
-	WASM_EXPORT static int mouse_wheel_callback(double p_delta_x, double p_delta_y);
-	static int _mouse_wheel_callback(double p_delta_x, double p_delta_y);
+	WASM_EXPORT static int mouse_wheel_callback(int p_delta_mode, double p_delta_x, double p_delta_y);
+	static int _mouse_wheel_callback(int p_delta_mode, double p_delta_x, double p_delta_y);
 	WASM_EXPORT static void touch_callback(int p_type, int p_count);
 	static void _touch_callback(int p_type, int p_count);
 	WASM_EXPORT static void key_callback(int p_pressed, int p_repeat, int p_modifiers);

platform/web/godot_js.h

@@ -61,7 +61,7 @@ extern int godot_js_pwa_update();
 // Input
 extern void godot_js_input_mouse_button_cb(int (*p_callback)(int p_pressed, int p_button, double p_x, double p_y, int p_modifiers));
 extern void godot_js_input_mouse_move_cb(void (*p_callback)(double p_x, double p_y, double p_rel_x, double p_rel_y, int p_modifiers, double p_pressure));
-extern void godot_js_input_mouse_wheel_cb(int (*p_callback)(double p_delta_x, double p_delta_y));
+extern void godot_js_input_mouse_wheel_cb(int (*p_callback)(int p_delta_mode, double p_delta_x, double p_delta_y));
 extern void godot_js_input_touch_cb(void (*p_callback)(int p_type, int p_count), uint32_t *r_identifiers, double *r_coords);
 extern void godot_js_input_key_cb(void (*p_callback)(int p_type, int p_repeat, int p_modifiers), char r_code[32], char r_key[32]);
 extern void godot_js_input_vibrate_handheld(int p_duration_ms);

platform/web/js/libs/library_godot_input.js

@@ -526,7 +526,7 @@ const GodotInput = {
 	godot_js_input_mouse_wheel_cb: function (callback) {
 		const func = GodotRuntime.get_func(callback);
 		function wheel_cb(evt) {
-			if (func(evt['deltaX'] || 0, evt['deltaY'] || 0)) {
+			if (func(evt.deltaMode, evt.deltaX ?? 0, evt.deltaY ?? 0)) {
 				evt.preventDefault();
 			}
 		}