Fix stretch transform when resizing SubViewports

Move calculation of stretch transform from outside to inside
of `Viewport::_set_size` function.

scene/main/viewport.cpp

@@ -791,15 +791,21 @@ void Viewport::update_canvas_items() {
 	_update_canvas_items(this);
 }
 
-void Viewport::_set_size(const Size2i &p_size, const Size2i &p_size_2d_override, const Rect2i &p_to_screen_rect, const Transform2D &p_stretch_transform, bool p_allocated) {
-	if (size == p_size && size_allocated == p_allocated && stretch_transform == p_stretch_transform && p_size_2d_override == size_2d_override && to_screen_rect == p_to_screen_rect) {
+void Viewport::_set_size(const Size2i &p_size, const Size2i &p_size_2d_override, const Rect2i &p_to_screen_rect, bool p_allocated) {
+	Transform2D stretch_transform_new = Transform2D();
+	if (is_size_2d_override_stretch_enabled() && p_size_2d_override.width > 0 && p_size_2d_override.height > 0) {
+		Size2 scale = Size2(p_size) / Size2(p_size_2d_override);
+		stretch_transform_new.scale(scale);
+	}
+
+	if (size == p_size && size_allocated == p_allocated && stretch_transform == stretch_transform_new && p_size_2d_override == size_2d_override && to_screen_rect == p_to_screen_rect) {
 		return;
 	}
 
 	size = p_size;
 	size_allocated = p_allocated;
 	size_2d_override = p_size_2d_override;
-	stretch_transform = p_stretch_transform;
+	stretch_transform = stretch_transform_new;
 	to_screen_rect = p_to_screen_rect;
 
 #ifndef _3D_DISABLED
@@ -4132,7 +4138,7 @@ void SubViewport::_internal_set_size(const Size2i &p_size, bool p_force) {
 		return;
 	}
 
-	_set_size(p_size, _get_size_2d_override(), Rect2i(), _stretch_transform(), true);
+	_set_size(p_size, _get_size_2d_override(), Rect2i(), true);
 
 	if (c) {
 		c->update_minimum_size();
@@ -4144,7 +4150,7 @@ Size2i SubViewport::get_size() const {
 }
 
 void SubViewport::set_size_2d_override(const Size2i &p_size) {
-	_set_size(_get_size(), p_size, Rect2i(), _stretch_transform(), true);
+	_set_size(_get_size(), p_size, Rect2i(), true);
 }
 
 Size2i SubViewport::get_size_2d_override() const {
@@ -4157,7 +4163,7 @@ void SubViewport::set_size_2d_override_stretch(bool p_enable) {
 	}
 
 	size_2d_override_stretch = p_enable;
-	_set_size(_get_size(), _get_size_2d_override(), Rect2i(), _stretch_transform(), true);
+	_set_size(_get_size(), _get_size_2d_override(), Rect2i(), true);
 }
 
 bool SubViewport::is_size_2d_override_stretch_enabled() const {
@@ -4186,17 +4192,6 @@ DisplayServer::WindowID SubViewport::get_window_id() const {
 	return DisplayServer::INVALID_WINDOW_ID;
 }
 
-Transform2D SubViewport::_stretch_transform() {
-	Transform2D transform;
-	Size2i view_size_2d_override = _get_size_2d_override();
-	if (size_2d_override_stretch && view_size_2d_override.width > 0 && view_size_2d_override.height > 0) {
-		Size2 scale = Size2(_get_size()) / Size2(view_size_2d_override);
-		transform.scale(scale);
-	}
-
-	return transform;
-}
-
 Transform2D SubViewport::get_screen_transform() const {
 	Transform2D container_transform;
 	SubViewportContainer *c = Object::cast_to<SubViewportContainer>(get_parent());

scene/main/viewport.h

@@ -471,7 +471,7 @@ private:
 	uint64_t event_count = 0;
 
 protected:
-	void _set_size(const Size2i &p_size, const Size2i &p_size_2d_override, const Rect2i &p_to_screen_rect, const Transform2D &p_stretch_transform, bool p_allocated);
+	void _set_size(const Size2i &p_size, const Size2i &p_size_2d_override, const Rect2i &p_to_screen_rect, bool p_allocated);
 
 	Size2i _get_size() const;
 	Size2i _get_size_2d_override() const;
@@ -649,6 +649,8 @@ public:
 	void set_canvas_cull_mask_bit(uint32_t p_layer, bool p_enable);
 	bool get_canvas_cull_mask_bit(uint32_t p_layer) const;
 
+	virtual bool is_size_2d_override_stretch_enabled() const { return true; }
+
 	virtual Transform2D get_screen_transform() const;
 	virtual Transform2D get_popup_base_transform() const { return Transform2D(); }
 
@@ -759,7 +761,6 @@ private:
 protected:
 	static void _bind_methods();
 	virtual DisplayServer::WindowID get_window_id() const override;
-	Transform2D _stretch_transform();
 	void _notification(int p_what);
 
 public:
@@ -771,7 +772,7 @@ public:
 	Size2i get_size_2d_override() const;
 
 	void set_size_2d_override_stretch(bool p_enable);
-	bool is_size_2d_override_stretch_enabled() const;
+	bool is_size_2d_override_stretch_enabled() const override;
 
 	void set_update_mode(UpdateMode p_mode);
 	UpdateMode get_update_mode() const;

scene/main/window.cpp

@@ -905,7 +905,6 @@ void Window::_update_viewport_size() {
 	Size2i final_size;
 	Size2i final_size_override;
 	Rect2i attach_to_screen_rect(Point2i(), size);
-	Transform2D stretch_transform_new;
 	float font_oversampling = 1.0;
 	window_transform = Transform2D();
 
@@ -913,9 +912,6 @@ void Window::_update_viewport_size() {
 		font_oversampling = content_scale_factor;
 		final_size = size;
 		final_size_override = Size2(size) / content_scale_factor;
-
-		stretch_transform_new = Transform2D();
-		stretch_transform_new.scale(Size2(content_scale_factor, content_scale_factor));
 	} else {
 		//actual screen video mode
 		Size2 video_mode = size;
@@ -991,9 +987,6 @@ void Window::_update_viewport_size() {
 				attach_to_screen_rect = Rect2(margin, screen_size);
 				font_oversampling = (screen_size.x / viewport_size.x) * content_scale_factor;
 
-				Size2 scale = Vector2(screen_size) / Vector2(final_size_override);
-				stretch_transform_new.scale(scale);
-
 				window_transform.translate_local(margin);
 			} break;
 			case CONTENT_SCALE_MODE_VIEWPORT: {
@@ -1011,7 +1004,7 @@ void Window::_update_viewport_size() {
 	}
 
 	bool allocate = is_inside_tree() && visible && (window_id != DisplayServer::INVALID_WINDOW_ID || embedder != nullptr);
-	_set_size(final_size, final_size_override, attach_to_screen_rect, stretch_transform_new, allocate);
+	_set_size(final_size, final_size_override, attach_to_screen_rect, allocate);
 
 	if (window_id != DisplayServer::INVALID_WINDOW_ID) {
 		RenderingServer::get_singleton()->viewport_attach_to_screen(get_viewport_rid(), attach_to_screen_rect, window_id);