22 files changed, 252 insertions, 97 deletions

diff --git a/core/hash_map.h b/core/hash_map.h
index 843430d082..10fc931e7a 100644
--- a/core/hash_map.h
+++ b/core/hash_map.h
@@ -280,13 +280,13 @@ public:
 
 	const TData &get(const TKey &p_key) const {
 		const TData *res = getptr(p_key);
-		ERR_FAIL_COND_V(!res, *res);
+		CRASH_COND_MSG(!res, "Map key not found.");
 		return *res;
 	}
 
 	TData &get(const TKey &p_key) {
 		TData *res = getptr(p_key);
-		ERR_FAIL_COND_V(!res, *res);
+		CRASH_COND_MSG(!res, "Map key not found.");
 		return *res;
 	}
 
diff --git a/doc/classes/TextureButton.xml b/doc/classes/TextureButton.xml
index 0e2872755e..a5172586fe 100644
--- a/doc/classes/TextureButton.xml
+++ b/doc/classes/TextureButton.xml
@@ -15,6 +15,12 @@
 		<member name="expand" type="bool" setter="set_expand" getter="get_expand" default="false">
 			If [code]true[/code], the texture stretches to the edges of the node's bounding rectangle using the [member stretch_mode]. If [code]false[/code], the texture will not scale with the node.
 		</member>
+		<member name="flip_h" type="bool" setter="set_flip_h" getter="is_flipped_h" default="false">
+			If [code]true[/code], texture is flipped horizontally.
+		</member>
+		<member name="flip_v" type="bool" setter="set_flip_v" getter="is_flipped_v" default="false">
+			If [code]true[/code], texture is flipped vertically.
+		</member>
 		<member name="stretch_mode" type="int" setter="set_stretch_mode" getter="get_stretch_mode" enum="TextureButton.StretchMode" default="0">
 			Controls the texture's behavior when you resize the node's bounding rectangle, [b]only if[/b] [member expand] is [code]true[/code]. Set it to one of the [enum StretchMode] constants. See the constants to learn more.
 		</member>
diff --git a/editor/filesystem_dock.cpp b/editor/filesystem_dock.cpp
index e1f55bd8a8..133aa39cd3 100644
--- a/editor/filesystem_dock.cpp
+++ b/editor/filesystem_dock.cpp
@@ -2313,7 +2313,7 @@ void FileSystemDock::_tree_rmb_select(const Vector2 &p_pos) {
 		tree_popup->clear();
 		tree_popup->set_size(Size2(1, 1));
 		_file_and_folders_fill_popup(tree_popup, paths);
-		tree_popup->set_position(tree->get_global_position() + p_pos);
+		tree_popup->set_position(tree->get_screen_position() + p_pos);
 		tree_popup->popup();
 	}
 }
diff --git a/editor/scene_tree_dock.cpp b/editor/scene_tree_dock.cpp
index 9831f1bd31..b8ac405f53 100644
--- a/editor/scene_tree_dock.cpp
+++ b/editor/scene_tree_dock.cpp
@@ -2399,7 +2399,7 @@ void SceneTreeDock::_tree_rmb(const Vector2 &p_menu_pos) {
 		}
 
 		menu->set_size(Size2(1, 1));
-		menu->set_position(p_menu_pos);
+		menu->set_position(get_screen_position() + p_menu_pos);
 		menu->popup();
 		return;
 	}
diff --git a/editor/scene_tree_editor.cpp b/editor/scene_tree_editor.cpp
index 1b818036e1..6f29633188 100644
--- a/editor/scene_tree_editor.cpp
+++ b/editor/scene_tree_editor.cpp
@@ -1072,7 +1072,7 @@ void SceneTreeEditor::drop_data_fw(const Point2 &p_point, const Variant &p_data,
 }
 
 void SceneTreeEditor::_rmb_select(const Vector2 &p_pos) {
-	emit_signal("rmb_pressed", tree->get_global_transform().xform(p_pos));
+	emit_signal("rmb_pressed", tree->get_screen_transform().xform(p_pos));
 }
 
 void SceneTreeEditor::_warning_changed(Node *p_for_node) {
diff --git a/platform/javascript/audio_driver_javascript.cpp b/platform/javascript/audio_driver_javascript.cpp
index b8914414e6..9604914b2c 100644
--- a/platform/javascript/audio_driver_javascript.cpp
+++ b/platform/javascript/audio_driver_javascript.cpp
@@ -36,6 +36,15 @@
 
 AudioDriverJavaScript *AudioDriverJavaScript::singleton = nullptr;
 
+bool AudioDriverJavaScript::is_available() {
+	return EM_ASM_INT({
+		if (!(window.AudioContext || window.webkitAudioContext)) {
+			return 0;
+		}
+		return 1;
+	}) != 0;
+}
+
 const char *AudioDriverJavaScript::get_name() const {
 	return "JavaScript";
 }
@@ -207,12 +216,14 @@ void AudioDriverJavaScript::finish_async() {
 
 	/* clang-format off */
 	EM_ASM({
-		var ref = Module.IDHandler.get($0);
+		const id = $0;
+		var ref = Module.IDHandler.get(id);
 		Module.async_finish.push(new Promise(function(accept, reject) {
 			if (!ref) {
-				console.log("Ref not found!", $0, Module.IDHandler);
+				console.log("Ref not found!", id, Module.IDHandler);
 				setTimeout(accept, 0);
 			} else {
+				Module.IDHandler.remove(id);
 				const context = ref['context'];
 				// Disconnect script and input.
 				ref['script'].disconnect();
@@ -226,7 +237,6 @@ void AudioDriverJavaScript::finish_async() {
 				});
 			}
 		}));
-		Module.IDHandler.remove($0);
 	}, id);
 	/* clang-format on */
 }
@@ -293,9 +303,5 @@ Error AudioDriverJavaScript::capture_stop() {
 }
 
 AudioDriverJavaScript::AudioDriverJavaScript() {
-	_driver_id = 0;
-	internal_buffer = nullptr;
-	buffer_length = 0;
-
 	singleton = this;
 }
diff --git a/platform/javascript/audio_driver_javascript.h b/platform/javascript/audio_driver_javascript.h
index 9b26be001e..f029a91db0 100644
--- a/platform/javascript/audio_driver_javascript.h
+++ b/platform/javascript/audio_driver_javascript.h
@@ -34,12 +34,13 @@
 #include "servers/audio_server.h"
 
 class AudioDriverJavaScript : public AudioDriver {
-	float *internal_buffer;
+	float *internal_buffer = nullptr;
 
-	int _driver_id;
-	int buffer_length;
+	int _driver_id = 0;
+	int buffer_length = 0;
 
 public:
+	static bool is_available();
 	void mix_to_js();
 	void process_capture(float sample);
 
diff --git a/platform/javascript/display_server_javascript.cpp b/platform/javascript/display_server_javascript.cpp
index 0312efb377..2f0a2faa83 100644
--- a/platform/javascript/display_server_javascript.cpp
+++ b/platform/javascript/display_server_javascript.cpp
@@ -44,18 +44,15 @@
 #define DOM_BUTTON_XBUTTON1 3
 #define DOM_BUTTON_XBUTTON2 4
 
+char DisplayServerJavaScript::canvas_id[256] = { 0 };
+static bool cursor_inside_canvas = true;
+
 DisplayServerJavaScript *DisplayServerJavaScript::get_singleton() {
 	return static_cast<DisplayServerJavaScript *>(DisplayServer::get_singleton());
 }
 
 // Window (canvas)
-extern "C" EMSCRIPTEN_KEEPALIVE void _set_canvas_id(uint8_t *p_data, int p_data_size) {
-	DisplayServerJavaScript *display = DisplayServerJavaScript::get_singleton();
-	display->canvas_id.parse_utf8((const char *)p_data, p_data_size);
-	display->canvas_id = "#" + display->canvas_id;
-}
-
-static void focus_canvas() {
+void DisplayServerJavaScript::focus_canvas() {
 	/* clang-format off */
 	EM_ASM(
 		Module['canvas'].focus();
@@ -63,7 +60,7 @@ static void focus_canvas() {
 	/* clang-format on */
 }
 
-static bool is_canvas_focused() {
+bool DisplayServerJavaScript::is_canvas_focused() {
 	/* clang-format off */
 	return EM_ASM_INT_V(
 		return document.activeElement == Module['canvas'];
@@ -71,8 +68,21 @@ static bool is_canvas_focused() {
 	/* clang-format on */
 }
 
-static Point2 compute_position_in_canvas(int x, int y) {
-	DisplayServerJavaScript *display = DisplayServerJavaScript::get_singleton();
+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;
 	});
@@ -81,23 +91,22 @@ static Point2 compute_position_in_canvas(int x, int y) {
 	});
 	int canvas_width;
 	int canvas_height;
-	emscripten_get_canvas_element_size(display->canvas_id.utf8().get_data(), &canvas_width, &canvas_height);
+	emscripten_get_canvas_element_size(canvas_id, &canvas_width, &canvas_height);
 
 	double element_width;
 	double element_height;
-	emscripten_get_element_css_size(display->canvas_id.utf8().get_data(), &element_width, &element_height);
+	emscripten_get_element_css_size(canvas_id, &element_width, &element_height);
 
-	return Point2((int)(canvas_width / element_width * (x - canvas_x)),
-			(int)(canvas_height / element_height * (y - canvas_y)));
+	return Point2((int)(canvas_width / element_width * (p_x - canvas_x)),
+			(int)(canvas_height / element_height * (p_y - canvas_y)));
 }
 
-static bool cursor_inside_canvas = true;
-
 EM_BOOL DisplayServerJavaScript::fullscreen_change_callback(int p_event_type, const EmscriptenFullscreenChangeEvent *p_event, void *p_user_data) {
 	DisplayServerJavaScript *display = get_singleton();
 	// Empty ID is canvas.
 	String target_id = String::utf8(p_event->id);
-	if (target_id.empty() || "#" + target_id == display->canvas_id) {
+	String canvas_str_id = String::utf8(canvas_id);
+	if (target_id.empty() || target_id == canvas_str_id) {
 		// This event property is the only reliable data on
 		// browser fullscreen state.
 		if (p_event->isFullscreen) {
@@ -131,14 +140,14 @@ extern "C" EMSCRIPTEN_KEEPALIVE void _drop_files_callback(char *p_filev[], int p
 // Keys
 
 template <typename T>
-static void dom2godot_mod(T *emscripten_event_ptr, Ref<InputEventWithModifiers> godot_event) {
+void DisplayServerJavaScript::dom2godot_mod(T *emscripten_event_ptr, Ref<InputEventWithModifiers> godot_event) {
 	godot_event->set_shift(emscripten_event_ptr->shiftKey);
 	godot_event->set_alt(emscripten_event_ptr->altKey);
 	godot_event->set_control(emscripten_event_ptr->ctrlKey);
 	godot_event->set_metakey(emscripten_event_ptr->metaKey);
 }
 
-static Ref<InputEventKey> setup_key_event(const EmscriptenKeyboardEvent *emscripten_event) {
+Ref<InputEventKey> DisplayServerJavaScript::setup_key_event(const EmscriptenKeyboardEvent *emscripten_event) {
 	Ref<InputEventKey> ev;
 	ev.instance();
 	ev->set_echo(emscripten_event->repeat);
@@ -289,7 +298,7 @@ EM_BOOL DisplayServerJavaScript::mousemove_callback(int p_event_type, const Emsc
 }
 
 // Cursor
-static const char *godot2dom_cursor(DisplayServer::CursorShape p_shape) {
+const char *DisplayServerJavaScript::godot2dom_cursor(DisplayServer::CursorShape p_shape) {
 	switch (p_shape) {
 		case DisplayServer::CURSOR_ARROW:
 			return "auto";
@@ -330,7 +339,7 @@ static const char *godot2dom_cursor(DisplayServer::CursorShape p_shape) {
 	}
 }
 
-static void set_css_cursor(const char *p_cursor) {
+void DisplayServerJavaScript::set_css_cursor(const char *p_cursor) {
 	/* clang-format off */
 	EM_ASM_({
 		Module['canvas'].style.cursor = UTF8ToString($0);
@@ -338,7 +347,7 @@ static void set_css_cursor(const char *p_cursor) {
 	/* clang-format on */
 }
 
-static bool is_css_cursor_hidden() {
+bool DisplayServerJavaScript::is_css_cursor_hidden() const {
 	/* clang-format off */
 	return EM_ASM_INT({
 		return Module['canvas'].style.cursor === 'none';
@@ -820,23 +829,6 @@ DisplayServer *DisplayServerJavaScript::create_func(const String &p_rendering_dr
 }
 
 DisplayServerJavaScript::DisplayServerJavaScript(const String &p_rendering_driver, WindowMode p_mode, uint32_t p_flags, const Vector2i &p_resolution, Error &r_error) {
-	/* clang-format off */
-	EM_ASM({
-		const canvas = Module['canvas'];
-		var enc = new TextEncoder("utf-8");
-		var buffer = new Uint8Array(enc.encode(canvas.id));
-		var len = buffer.byteLength;
-		var out = _malloc(len);
-		HEAPU8.set(buffer, out);
-		ccall("_set_canvas_id",
-			"void",
-			["number", "number"],
-			[out, len]
-		);
-		_free(out);
-	});
-	/* clang-format on */
-
 	RasterizerDummy::make_current(); // TODO GLES2 in Godot 4.0... or webgpu?
 #if 0
 	EmscriptenWebGLContextAttributes attributes;
@@ -859,7 +851,7 @@ DisplayServerJavaScript::DisplayServerJavaScript(const String &p_rendering_drive
 		gl_initialization_error = true;
 	}
 
-	EMSCRIPTEN_WEBGL_CONTEXT_HANDLE ctx = emscripten_webgl_create_context(canvas_id.utf8().get_data(), &attributes);
+	EMSCRIPTEN_WEBGL_CONTEXT_HANDLE ctx = emscripten_webgl_create_context(canvas_id, &attributes);
 	if (emscripten_webgl_make_context_current(ctx) != EMSCRIPTEN_RESULT_SUCCESS) {
 		gl_initialization_error = true;
 	}
@@ -881,7 +873,6 @@ DisplayServerJavaScript::DisplayServerJavaScript(const String &p_rendering_drive
 	}
 
 	EMSCRIPTEN_RESULT result;
-	CharString id = canvas_id.utf8();
 #define EM_CHECK(ev)                         \
 	if (result != EMSCRIPTEN_RESULT_SUCCESS) \
 		ERR_PRINT("Error while setting " #ev " callback: Code " + itos(result));
@@ -895,16 +886,16 @@ DisplayServerJavaScript::DisplayServerJavaScript(const String &p_rendering_drive
 	// JavaScript APIs. For APIs that are not (sufficiently) exposed, EM_ASM
 	// is used below.
 	SET_EM_CALLBACK(EMSCRIPTEN_EVENT_TARGET_WINDOW, mousemove, mousemove_callback)
-	SET_EM_CALLBACK(id.get_data(), mousedown, mouse_button_callback)
+	SET_EM_CALLBACK(canvas_id, mousedown, mouse_button_callback)
 	SET_EM_CALLBACK(EMSCRIPTEN_EVENT_TARGET_WINDOW, mouseup, mouse_button_callback)
-	SET_EM_CALLBACK(id.get_data(), wheel, wheel_callback)
-	SET_EM_CALLBACK(id.get_data(), touchstart, touch_press_callback)
-	SET_EM_CALLBACK(id.get_data(), touchmove, touchmove_callback)
-	SET_EM_CALLBACK(id.get_data(), touchend, touch_press_callback)
-	SET_EM_CALLBACK(id.get_data(), touchcancel, touch_press_callback)
-	SET_EM_CALLBACK(id.get_data(), keydown, keydown_callback)
-	SET_EM_CALLBACK(id.get_data(), keypress, keypress_callback)
-	SET_EM_CALLBACK(id.get_data(), keyup, keyup_callback)
+	SET_EM_CALLBACK(canvas_id, wheel, wheel_callback)
+	SET_EM_CALLBACK(canvas_id, touchstart, touch_press_callback)
+	SET_EM_CALLBACK(canvas_id, touchmove, touchmove_callback)
+	SET_EM_CALLBACK(canvas_id, touchend, touch_press_callback)
+	SET_EM_CALLBACK(canvas_id, touchcancel, touch_press_callback)
+	SET_EM_CALLBACK(canvas_id, keydown, keydown_callback)
+	SET_EM_CALLBACK(canvas_id, keypress, keypress_callback)
+	SET_EM_CALLBACK(canvas_id, keyup, keyup_callback)
 	SET_EM_CALLBACK(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, fullscreenchange, fullscreen_change_callback)
 	SET_EM_CALLBACK_NOTARGET(gamepadconnected, gamepad_change_callback)
 	SET_EM_CALLBACK_NOTARGET(gamepaddisconnected, gamepad_change_callback)
@@ -1012,7 +1003,7 @@ Size2i DisplayServerJavaScript::screen_get_size(int p_screen) const {
 
 Rect2i DisplayServerJavaScript::screen_get_usable_rect(int p_screen) const {
 	int canvas[2];
-	emscripten_get_canvas_element_size(canvas_id.utf8().get_data(), canvas, canvas + 1);
+	emscripten_get_canvas_element_size(canvas_id, canvas, canvas + 1);
 	return Rect2i(0, 0, canvas[0], canvas[1]);
 }
 
@@ -1103,12 +1094,14 @@ Size2i DisplayServerJavaScript::window_get_min_size(WindowID p_window) const {
 }
 
 void DisplayServerJavaScript::window_set_size(const Size2i p_size, WindowID p_window) {
-	emscripten_set_canvas_element_size(canvas_id.utf8().get_data(), p_size.x, p_size.y);
+	last_width = p_size.x;
+	last_height = p_size.y;
+	emscripten_set_canvas_element_size(canvas_id, p_size.x, p_size.y);
 }
 
 Size2i DisplayServerJavaScript::window_get_size(WindowID p_window) const {
 	int canvas[2];
-	emscripten_get_canvas_element_size(canvas_id.utf8().get_data(), canvas, canvas + 1);
+	emscripten_get_canvas_element_size(canvas_id, canvas, canvas + 1);
 	return Size2(canvas[0], canvas[1]);
 }
 
@@ -1134,7 +1127,7 @@ void DisplayServerJavaScript::window_set_mode(WindowMode p_mode, WindowID p_wind
 			strategy.canvasResolutionScaleMode = EMSCRIPTEN_FULLSCREEN_CANVAS_SCALE_STDDEF;
 			strategy.filteringMode = EMSCRIPTEN_FULLSCREEN_FILTERING_DEFAULT;
 			strategy.canvasResizedCallback = nullptr;
-			EMSCRIPTEN_RESULT result = emscripten_request_fullscreen_strategy(canvas_id.utf8().get_data(), false, &strategy);
+			EMSCRIPTEN_RESULT result = emscripten_request_fullscreen_strategy(canvas_id, false, &strategy);
 			ERR_FAIL_COND_MSG(result == EMSCRIPTEN_RESULT_FAILED_NOT_DEFERRED, "Enabling fullscreen is only possible from an input callback for the HTML5 platform.");
 			ERR_FAIL_COND_MSG(result != EMSCRIPTEN_RESULT_SUCCESS, "Enabling fullscreen is only possible from an input callback for the HTML5 platform.");
 		} break;
diff --git a/platform/javascript/display_server_javascript.h b/platform/javascript/display_server_javascript.h
index 9860ecdf98..b149665d67 100644
--- a/platform/javascript/display_server_javascript.h
+++ b/platform/javascript/display_server_javascript.h
@@ -53,6 +53,21 @@ 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();
+	static bool is_canvas_focused();
+	template <typename T>
+	static void dom2godot_mod(T *emscripten_event_ptr, Ref<InputEventWithModifiers> godot_event);
+	static Ref<InputEventKey> setup_key_event(const EmscriptenKeyboardEvent *emscripten_event);
+	static const char *godot2dom_cursor(DisplayServer::CursorShape p_shape);
+	static void set_css_cursor(const char *p_cursor);
+	bool is_css_cursor_hidden() const;
+
+	// events
 	static EM_BOOL fullscreen_change_callback(int p_event_type, const EmscriptenFullscreenChangeEvent *p_event, void *p_user_data);
 
 	static EM_BOOL keydown_callback(int p_event_type, const EmscriptenKeyboardEvent *p_event, void *p_user_data);
@@ -81,17 +96,20 @@ protected:
 public:
 	// Override return type to make writing static callbacks less tedious.
 	static DisplayServerJavaScript *get_singleton();
+	static char canvas_id[256];
 
 	WindowMode window_mode = WINDOW_MODE_WINDOWED;
 
 	String clipboard;
-	String canvas_id;
 
 	Callable window_event_callback;
 	Callable input_event_callback;
 	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;
diff --git a/platform/javascript/javascript_main.cpp b/platform/javascript/javascript_main.cpp
index fd61c46e63..99672745e7 100644
--- a/platform/javascript/javascript_main.cpp
+++ b/platform/javascript/javascript_main.cpp
@@ -30,11 +30,13 @@
 
 #include "core/io/resource_loader.h"
 #include "main/main.h"
-#include "os_javascript.h"
+#include "platform/javascript/display_server_javascript.h"
+#include "platform/javascript/os_javascript.h"
 
 #include <emscripten/emscripten.h>
 
 static OS_JavaScript *os = nullptr;
+static uint64_t target_ticks = 0;
 
 void exit_callback() {
 	emscripten_cancel_main_loop(); // After this, we can exit!
@@ -46,12 +48,32 @@ void exit_callback() {
 }
 
 void main_loop_callback() {
+	uint64_t current_ticks = os->get_ticks_usec();
+
+	bool force_draw = DisplayServerJavaScript::get_singleton()->check_size_force_redraw();
+	if (force_draw) {
+		Main::force_redraw();
+	} else if (current_ticks < target_ticks) {
+		return; // Skip frame.
+	}
+
+	int target_fps = Engine::get_singleton()->get_target_fps();
+	if (target_fps > 0) {
+		target_ticks += (uint64_t)(1000000 / target_fps);
+	}
 	if (os->main_loop_iterate()) {
 		emscripten_cancel_main_loop(); // Cancel current loop and wait for finalize_async.
+		/* clang-format off */
 		EM_ASM({
 			// This will contain the list of operations that need to complete before cleanup.
-			Module.async_finish = [];
+			Module.async_finish = [
+				// Always contains at least one async promise, to avoid firing immediately if nothing is added.
+				new Promise(function(accept, reject) {
+					setTimeout(accept, 0);
+				})
+			];
 		});
+		/* clang-format on */
 		os->get_main_loop()->finish();
 		os->finalize_async(); // Will add all the async finish functions.
 		EM_ASM({
@@ -79,13 +101,35 @@ extern "C" EMSCRIPTEN_KEEPALIVE void main_after_fs_sync(char *p_idbfs_err) {
 	ResourceLoader::set_abort_on_missing_resources(false);
 	Main::start();
 	os->get_main_loop()->init();
-	emscripten_resume_main_loop();
 	// Immediately run the first iteration.
 	// We are inside an animation frame, we want to immediately draw on the newly setup canvas.
 	main_loop_callback();
+	emscripten_resume_main_loop();
 }
 
 int main(int argc, char *argv[]) {
+	// Create and mount userfs immediately.
+	EM_ASM({
+		FS.mkdir('/userfs');
+		FS.mount(IDBFS, {}, '/userfs');
+	});
+
+	// Configure locale.
+	char locale_ptr[16];
+	/* clang-format off */
+	EM_ASM({
+		stringToUTF8(Module['locale'], $0, 16);
+	}, locale_ptr);
+	/* clang-format on */
+	setenv("LANG", locale_ptr, true);
+
+	// Ensure the canvas ID.
+	/* clang-format off */
+	EM_ASM({
+		stringToUTF8("#" + Module['canvas'].id, $0, 255);
+	}, DisplayServerJavaScript::canvas_id);
+	/* clang-format on */
+
 	os = new OS_JavaScript();
 	Main::setup(argv[0], argc - 1, &argv[1], false);
 	emscripten_set_main_loop(main_loop_callback, -1, false);
@@ -95,8 +139,6 @@ int main(int argc, char *argv[]) {
 	// run the 'main_after_fs_sync' function.
 	/* clang-format off */
 	EM_ASM({
-		FS.mkdir('/userfs');
-		FS.mount(IDBFS, {}, '/userfs');
 		FS.syncfs(true, function(err) {
 			requestAnimationFrame(function() {
 				ccall('main_after_fs_sync', null, ['string'], [err ? err.message : ""]);
diff --git a/platform/javascript/os_javascript.cpp b/platform/javascript/os_javascript.cpp
index ad4b5a5afa..1ff4304bcf 100644
--- a/platform/javascript/os_javascript.cpp
+++ b/platform/javascript/os_javascript.cpp
@@ -74,18 +74,12 @@ void OS_JavaScript::initialize() {
 	EngineDebugger::register_uri_handler("ws://", RemoteDebuggerPeerWebSocket::create);
 	EngineDebugger::register_uri_handler("wss://", RemoteDebuggerPeerWebSocket::create);
 #endif
-
-	char locale_ptr[16];
-	/* clang-format off */
-	EM_ASM({
-		stringToUTF8(Module['locale'], $0, 16);
-	}, locale_ptr);
-	/* clang-format on */
-	setenv("LANG", locale_ptr, true);
 }
 
 void OS_JavaScript::resume_audio() {
-	audio_driver_javascript.resume();
+	if (audio_driver_javascript) {
+		audio_driver_javascript->resume();
+	}
 }
 
 void OS_JavaScript::set_main_loop(MainLoop *p_main_loop) {
@@ -133,11 +127,17 @@ void OS_JavaScript::delete_main_loop() {
 
 void OS_JavaScript::finalize_async() {
 	finalizing = true;
-	audio_driver_javascript.finish_async();
+	if (audio_driver_javascript) {
+		audio_driver_javascript->finish_async();
+	}
 }
 
 void OS_JavaScript::finalize() {
 	delete_main_loop();
+	if (audio_driver_javascript) {
+		memdelete(audio_driver_javascript);
+		audio_driver_javascript = nullptr;
+	}
 }
 
 // Miscellaneous
@@ -246,7 +246,10 @@ void OS_JavaScript::initialize_joypads() {
 }
 
 OS_JavaScript::OS_JavaScript() {
-	AudioDriverManager::add_driver(&audio_driver_javascript);
+	if (AudioDriverJavaScript::is_available()) {
+		audio_driver_javascript = memnew(AudioDriverJavaScript);
+		AudioDriverManager::add_driver(audio_driver_javascript);
+	}
 
 	Vector<Logger *> loggers;
 	loggers.push_back(memnew(StdLogger));
diff --git a/platform/javascript/os_javascript.h b/platform/javascript/os_javascript.h
index f0f18b44f8..22234f9355 100644
--- a/platform/javascript/os_javascript.h
+++ b/platform/javascript/os_javascript.h
@@ -40,7 +40,7 @@
 
 class OS_JavaScript : public OS_Unix {
 	MainLoop *main_loop = nullptr;
-	AudioDriverJavaScript audio_driver_javascript;
+	AudioDriverJavaScript *audio_driver_javascript = nullptr;
 
 	bool finalizing = false;
 	bool idb_available = false;
@@ -83,6 +83,9 @@ public:
 	String get_executable_path() const;
 	virtual Error shell_open(String p_uri);
 	virtual String get_name() const;
+	// Override default OS implementation which would block the main thread with delay_usec.
+	// Implemented in javascript_main.cpp loop callback instead.
+	virtual void add_frame_delay(bool p_can_draw) {}
 	virtual bool can_draw() const;
 
 	virtual String get_cache_path() const;
diff --git a/platform/linuxbsd/display_server_x11.cpp b/platform/linuxbsd/display_server_x11.cpp
index cb4b0d745b..827d0361b9 100644
--- a/platform/linuxbsd/display_server_x11.cpp
+++ b/platform/linuxbsd/display_server_x11.cpp
@@ -2349,11 +2349,17 @@ void DisplayServerX11::process_events() {
 		}
 
 		if (!focus_found) {
-			if (OS::get_singleton()->get_main_loop()) {
-				OS::get_singleton()->get_main_loop()->notification(MainLoop::NOTIFICATION_APPLICATION_FOCUS_OUT);
-			}
+			uint64_t delta = OS::get_singleton()->get_ticks_msec() - time_since_no_focus;
 
-			app_focused = false;
+			if (delta > 250) {
+				//X11 can go between windows and have no focus for a while, when creating them or something else. Use this as safety to avoid unnecesary focus in/outs.
+				if (OS::get_singleton()->get_main_loop()) {
+					OS::get_singleton()->get_main_loop()->notification(MainLoop::NOTIFICATION_APPLICATION_FOCUS_OUT);
+				}
+				app_focused = false;
+			}
+		} else {
+			time_since_no_focus = OS::get_singleton()->get_ticks_msec();
 		}
 	}
 
diff --git a/platform/linuxbsd/display_server_x11.h b/platform/linuxbsd/display_server_x11.h
index 3d0b2c7e8a..b5d2ea1c63 100644
--- a/platform/linuxbsd/display_server_x11.h
+++ b/platform/linuxbsd/display_server_x11.h
@@ -167,6 +167,7 @@ class DisplayServerX11 : public DisplayServer {
 	int last_click_button_index;
 	uint32_t last_button_state;
 	bool app_focused = false;
+	uint64_t time_since_no_focus = 0;
 
 	struct {
 		int opcode;
diff --git a/scene/gui/dialogs.cpp b/scene/gui/dialogs.cpp
index bacc65c7bf..faef979090 100644
--- a/scene/gui/dialogs.cpp
+++ b/scene/gui/dialogs.cpp
@@ -298,6 +298,7 @@ AcceptDialog::AcceptDialog() {
 	set_visible(false);
 	set_transient(true);
 	set_exclusive(true);
+	set_clamp_to_embedder(true);
 
 	bg = memnew(Panel);
 	add_child(bg);
diff --git a/scene/gui/line_edit.cpp b/scene/gui/line_edit.cpp
index 251f31ce4e..27c2c70708 100644
--- a/scene/gui/line_edit.cpp
+++ b/scene/gui/line_edit.cpp
@@ -51,7 +51,7 @@ void LineEdit::_gui_input(Ref<InputEvent> p_event) {
 
 	if (b.is_valid()) {
 		if (b->is_pressed() && b->get_button_index() == BUTTON_RIGHT && context_menu_enabled) {
-			menu->set_position(get_global_transform().xform(get_local_mouse_position()));
+			menu->set_position(get_screen_transform().xform(get_local_mouse_position()));
 			menu->set_size(Vector2(1, 1));
 			//menu->set_scale(get_global_transform().get_scale());
 			menu->popup();
diff --git a/scene/gui/texture_button.cpp b/scene/gui/texture_button.cpp
index 6e86f0f299..4187d77083 100644
--- a/scene/gui/texture_button.cpp
+++ b/scene/gui/texture_button.cpp
@@ -166,9 +166,11 @@ void TextureButton::_notification(int p_what) {
 				} break;
 			}
 
+			Point2 ofs;
+			Size2 size;
+
 			if (texdraw.is_valid()) {
-				Point2 ofs;
-				Size2 size = texdraw->get_size();
+				size = texdraw->get_size();
 				_texture_region = Rect2(Point2(), texdraw->get_size());
 				_tile = false;
 				if (expand) {
@@ -218,17 +220,21 @@ void TextureButton::_notification(int p_what) {
 				}
 
 				_position_rect = Rect2(ofs, size);
+
+				size.width *= hflip ? -1.0f : 1.0f;
+				size.height *= vflip ? -1.0f : 1.0f;
+
 				if (_tile) {
-					draw_texture_rect(texdraw, _position_rect, _tile);
+					draw_texture_rect(texdraw, Rect2(ofs, size), _tile);
 				} else {
-					draw_texture_rect_region(texdraw, _position_rect, _texture_region);
+					draw_texture_rect_region(texdraw, Rect2(ofs, size), _texture_region);
 				}
 			} else {
 				_position_rect = Rect2();
 			}
 
 			if (has_focus() && focused.is_valid()) {
-				draw_texture_rect(focused, _position_rect, false);
+				draw_texture_rect(focused, Rect2(ofs, size), false);
 			};
 		} break;
 	}
@@ -243,6 +249,10 @@ void TextureButton::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_click_mask", "mask"), &TextureButton::set_click_mask);
 	ClassDB::bind_method(D_METHOD("set_expand", "p_expand"), &TextureButton::set_expand);
 	ClassDB::bind_method(D_METHOD("set_stretch_mode", "p_mode"), &TextureButton::set_stretch_mode);
+	ClassDB::bind_method(D_METHOD("set_flip_h", "enable"), &TextureButton::set_flip_h);
+	ClassDB::bind_method(D_METHOD("is_flipped_h"), &TextureButton::is_flipped_h);
+	ClassDB::bind_method(D_METHOD("set_flip_v", "enable"), &TextureButton::set_flip_v);
+	ClassDB::bind_method(D_METHOD("is_flipped_v"), &TextureButton::is_flipped_v);
 
 	ClassDB::bind_method(D_METHOD("get_normal_texture"), &TextureButton::get_normal_texture);
 	ClassDB::bind_method(D_METHOD("get_pressed_texture"), &TextureButton::get_pressed_texture);
@@ -262,6 +272,8 @@ void TextureButton::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "texture_click_mask", PROPERTY_HINT_RESOURCE_TYPE, "BitMap"), "set_click_mask", "get_click_mask");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "expand", PROPERTY_HINT_RESOURCE_TYPE, "bool"), "set_expand", "get_expand");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "stretch_mode", PROPERTY_HINT_ENUM, "Scale,Tile,Keep,Keep Centered,Keep Aspect,Keep Aspect Centered,Keep Aspect Covered"), "set_stretch_mode", "get_stretch_mode");
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "flip_h", PROPERTY_HINT_RESOURCE_TYPE, "bool"), "set_flip_h", "is_flipped_h");
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "flip_v", PROPERTY_HINT_RESOURCE_TYPE, "bool"), "set_flip_v", "is_flipped_v");
 
 	BIND_ENUM_CONSTANT(STRETCH_SCALE);
 	BIND_ENUM_CONSTANT(STRETCH_TILE);
@@ -345,9 +357,29 @@ TextureButton::StretchMode TextureButton::get_stretch_mode() const {
 	return stretch_mode;
 }
 
+void TextureButton::set_flip_h(bool p_flip) {
+	hflip = p_flip;
+	update();
+}
+
+bool TextureButton::is_flipped_h() const {
+	return hflip;
+}
+
+void TextureButton::set_flip_v(bool p_flip) {
+	vflip = p_flip;
+	update();
+}
+
+bool TextureButton::is_flipped_v() const {
+	return vflip;
+}
+
 TextureButton::TextureButton() {
 	expand = false;
 	stretch_mode = STRETCH_SCALE;
+	hflip = false;
+	vflip = false;
 
 	_texture_region = Rect2();
 	_position_rect = Rect2();
diff --git a/scene/gui/texture_button.h b/scene/gui/texture_button.h
index a1e66203d3..bfd3d40db6 100644
--- a/scene/gui/texture_button.h
+++ b/scene/gui/texture_button.h
@@ -61,6 +61,9 @@ private:
 	Rect2 _position_rect;
 	bool _tile;
 
+	bool hflip;
+	bool vflip;
+
 protected:
 	virtual Size2 get_minimum_size() const;
 	virtual bool has_point(const Point2 &p_point) const;
@@ -88,6 +91,12 @@ public:
 	void set_stretch_mode(StretchMode p_stretch_mode);
 	StretchMode get_stretch_mode() const;
 
+	void set_flip_h(bool p_flip);
+	bool is_flipped_h() const;
+
+	void set_flip_v(bool p_flip);
+	bool is_flipped_v() const;
+
 	TextureButton();
 };
 
diff --git a/scene/main/viewport.cpp b/scene/main/viewport.cpp
index 6bfad24b65..65a72267b1 100644
--- a/scene/main/viewport.cpp
+++ b/scene/main/viewport.cpp
@@ -2701,6 +2701,27 @@ bool Viewport::_sub_windows_forward_input(const Ref<InputEvent> &p_event) {
 			if (gui.subwindow_drag == SUB_WINDOW_DRAG_MOVE) {
 				Vector2 diff = mm->get_position() - gui.subwindow_drag_from;
 				Rect2i new_rect(gui.subwindow_drag_pos + diff, gui.subwindow_focused->get_size());
+
+				if (gui.subwindow_focused->is_clamped_to_embedder()) {
+					Size2i limit = get_visible_rect().size;
+					if (new_rect.position.x + new_rect.size.x > limit.x) {
+						new_rect.position.x = limit.x - new_rect.size.x;
+					}
+					if (new_rect.position.y + new_rect.size.y > limit.y) {
+						new_rect.position.y = limit.y - new_rect.size.y;
+					}
+
+					if (new_rect.position.x < 0) {
+						new_rect.position.x = 0;
+					}
+
+					int title_height = gui.subwindow_focused->get_flag(Window::FLAG_BORDERLESS) ? 0 : gui.subwindow_focused->get_theme_constant("title_height");
+
+					if (new_rect.position.y < title_height) {
+						new_rect.position.y = title_height;
+					}
+				}
+
 				gui.subwindow_focused->_rect_changed_callback(new_rect);
 			}
 			if (gui.subwindow_drag == SUB_WINDOW_DRAG_CLOSE) {
diff --git a/scene/main/window.cpp b/scene/main/window.cpp
index 8604bb78ac..0463615d4d 100644
--- a/scene/main/window.cpp
+++ b/scene/main/window.cpp
@@ -1251,6 +1251,14 @@ Rect2i Window::get_parent_rect() const {
 	}
 }
 
+void Window::set_clamp_to_embedder(bool p_enable) {
+	clamp_to_embedder = p_enable;
+}
+
+bool Window::is_clamped_to_embedder() const {
+	return clamp_to_embedder;
+}
+
 void Window::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_title", "title"), &Window::set_title);
 	ClassDB::bind_method(D_METHOD("get_title"), &Window::get_title);
diff --git a/scene/main/window.h b/scene/main/window.h
index 4855924660..5fd59e06f5 100644
--- a/scene/main/window.h
+++ b/scene/main/window.h
@@ -92,6 +92,7 @@ private:
 	bool exclusive = false;
 	bool wrap_controls = false;
 	bool updating_child_controls = false;
+	bool clamp_to_embedder = false;
 
 	void _update_child_controls();
 
@@ -195,6 +196,9 @@ public:
 	void set_exclusive(bool p_exclusive);
 	bool is_exclusive() const;
 
+	void set_clamp_to_embedder(bool p_enable);
+	bool is_clamped_to_embedder() const;
+
 	bool can_draw() const;
 
 	void set_ime_active(bool p_active);
diff --git a/servers/audio_server.cpp b/servers/audio_server.cpp
index 09d2914e05..6b70f41e57 100644
--- a/servers/audio_server.cpp
+++ b/servers/audio_server.cpp
@@ -184,6 +184,7 @@ void AudioDriverManager::initialize(int p_driver) {
 	GLOBAL_DEF_RST("audio/enable_audio_input", false);
 	GLOBAL_DEF_RST("audio/mix_rate", DEFAULT_MIX_RATE);
 	GLOBAL_DEF_RST("audio/output_latency", DEFAULT_OUTPUT_LATENCY);
+	GLOBAL_DEF_RST("audio/output_latency.web", 50); // Safer default output_latency for web.
 
 	int failed_driver = -1;