Merge pull request godotengine#87856 from bruvzg/transpbg

Automatically set viewport background to transparent when window flag is set.

doc/classes/Window.xml

@@ -675,7 +675,7 @@
  <member name="transparent" type="bool" setter="set_flag" getter="get_flag" default="false">
  If [code]true[/code], the [Window]'s background can be transparent. This is best used with embedded windows.
  [b]Note:[/b] Transparency support is implemented on Linux, macOS and Windows, but availability might vary depending on GPU driver, display manager, and compositor capabilities.
- [b]Note:[/b] This property has no effect if either [member ProjectSettings.display/window/per_pixel_transparency/allowed], or the window's [member Viewport.transparent_bg] is set to [code]false[/code].
+ [b]Note:[/b] This property has no effect if [member ProjectSettings.display/window/per_pixel_transparency/allowed] is set to [code]false[/code].
  </member>
  <member name="unfocusable" type="bool" setter="set_flag" getter="get_flag" default="false">
  If [code]true[/code], the [Window] can't be focused nor interacted with. It can still be visible.

scene/main/window.cpp

@@ -484,9 +484,12 @@ void Window::set_flag(Flags p_flag, bool p_enabled) {
  ERR_FAIL_INDEX(p_flag, FLAG_MAX);
  flags[p_flag] = p_enabled;
 
+ if (p_flag == FLAG_TRANSPARENT) {
+ set_transparent_background(p_enabled);
+ }
+
  if (embedder) {
  embedder->_sub_window_update(this);
-
  } else if (window_id != DisplayServer::INVALID_WINDOW_ID) {
  if (!is_in_edited_scene_root()) {
  DisplayServer::get_singleton()->window_set_flag(DisplayServer::WindowFlags(p_flag), p_enabled, window_id);
@@ -1285,6 +1288,9 @@ void Window::_notification(int p_what) {
  _update_viewport_size(); // Then feed back to the viewport.
  _update_window_callbacks();
  RS::get_singleton()->viewport_set_update_mode(get_viewport_rid(), RS::VIEWPORT_UPDATE_WHEN_VISIBLE);
+ if (DisplayServer::get_singleton()->window_get_flag(DisplayServer::WindowFlags(FLAG_TRANSPARENT), window_id)) {
+ set_transparent_background(true);
+ }
  } else {
  // Create.
  if (visible) {