diff --git a/scene/main/viewport.cpp b/scene/main/viewport.cpp
index 0cdb23618f8..02d037ea360 100644
--- a/scene/main/viewport.cpp
+++ b/scene/main/viewport.cpp
@@ -127,7 +127,7 @@ int ViewportTexture::get_width() const {
 		_err_print_viewport_not_set();
 		return 0;
 	}
-	return vp->size.width;
+	return get_size().width;
 }
 
 int ViewportTexture::get_height() const {
@@ -135,7 +135,7 @@ int ViewportTexture::get_height() const {
 		_err_print_viewport_not_set();
 		return 0;
 	}
-	return vp->size.height;
+	return get_size().height;
 }
 
 Size2 ViewportTexture::get_size() const {
@@ -143,7 +143,7 @@ Size2 ViewportTexture::get_size() const {
 		_err_print_viewport_not_set();
 		return Size2();
 	}
-	return vp->size;
+	return Size2(vp->size * vp->get_screen_transform().get_scale()).ceil();
 }
 
 RID ViewportTexture::get_rid() const {
@@ -313,10 +313,8 @@ void Viewport::_sub_window_update(Window *p_window) {
 	SubWindow &sw = gui.sub_windows.write[index];
 	sw.pending_window_update = false;
 
-	Transform2D pos;
-	pos.set_origin(p_window->get_position());
 	RS::get_singleton()->canvas_item_clear(sw.canvas_item);
-	Rect2i r = Rect2i(p_window->get_position(), sw.window->get_size());
+	Rect2i r = Rect2i(p_window->get_position(), p_window->get_size());
 
 	if (!p_window->get_flag(Window::FLAG_BORDERLESS)) {
 		Ref<StyleBox> panel = gui.subwindow_focused == p_window ? p_window->theme_cache.embedded_border : p_window->theme_cache.embedded_unfocused_border;
@@ -980,6 +978,7 @@ void Viewport::update_canvas_items() {
 		for (Viewport::SubWindow w : gui.sub_windows) {
 			if (w.window && !w.pending_window_update) {
 				w.pending_window_update = true;
+				w.window->_update_viewport_size();
 				callable_mp(this, &Viewport::_sub_window_update).call_deferred(w.window);
 			}
 		}
diff --git a/scene/main/window.cpp b/scene/main/window.cpp
index 045c3ae02d8..0e6cdc8b1df 100644
--- a/scene/main/window.cpp
+++ b/scene/main/window.cpp
@@ -1231,6 +1231,10 @@ void Window::_update_viewport_size() {
 	notification(NOTIFICATION_WM_SIZE_CHANGED);
 
 	if (embedder) {
+		float scale = MIN(embedder->stretch_transform.get_scale().width, embedder->stretch_transform.get_scale().height);
+		Size2 s = Size2(final_size.width * scale, final_size.height * scale).ceil();
+		RS::get_singleton()->viewport_set_global_canvas_transform(get_viewport_rid(), global_canvas_transform * scale * content_scale_factor);
+		RS::get_singleton()->viewport_set_size(get_viewport_rid(), s.width, s.height);
 		embedder->_sub_window_update(this);
 	}
 }