Fix transparency background issue on Android

[m4gr3d]

Updates the logic to detect when transparency is required on Android using display/window/per_pixel_transparency/allowed, display/window/size/transparent, and rendering/viewport/transparent_background, which updates the render view configuration and the app's theme.

The requirement to update the app's theme means the feature is only available to gradle build exports.

Fixes #106703

Before

Screen_Recording_20250522_001406_GLTF.Viewer.mp4

After

Screen_Recording_20250522_001458_GLTF.Viewer.mp4

[m4gr3d]

Switching to draft until #106724 is merged.

[Alex2782]

Test project: godot-demo-projects/.../window_management

DisplayServer.has_feature(DisplayServer.FEATURE_WINDOW_TRANSPARENCY)

godot/platform/android/display_server_android.cpp

Line 79 in de37627

//case FEATURE_WINDOW_TRANSPARENCY:

Can we activate that now too? Or evaluate android:windowIsTranslucent there?

[Alex2782]

Test project: godot-demo-projects/.../window_management

display/window/size/transparent = true and disabled DisplayServer.has_feature check:

func _on_transparent_check_button_toggled(button_pressed: bool) -> void:
	#if not DisplayServer.has_feature(DisplayServer.FEATURE_WINDOW_TRANSPARENCY):
	#	OS.alert("Window transparency is not supported by the current display server (%s)." % DisplayServer.get_name())
	#	return
	get_viewport().transparent_bg = button_pressed
	DisplayServer.window_set_flag(DisplayServer.WINDOW_FLAG_TRANSPARENT, button_pressed)

On Android 13, Samsung Tab S7 (Adreno 650).

OpenGL

glsl_Screen_recording_20250529_015017.mp4

Vulkan (Mobile)

mobile_Screen_recording_20250529_015358.mp4

on MacOS, Metal (Mobile) for comparison

Screen-2025-05-29-020905.mp4

---

At first glance OpenGL Renderer works correctly / as it should.
But after switching back and forth for the second time, the 3D scene is no longer rendered.
But these are other issues that have nothing to do with this PR. (i think)

[Alex2782]

Test project: godot-demo-projects/.../window_management

In the test project, display/window/size/transparent isn't enabled, so I tried without it and didn't encounter any problems. Or is there anything wrong with that?

---

removed size/transparent from export_plugin.cpp

bool EditorExportPlatformAndroid::_should_be_transparent(const Ref<EditorExportPreset> &p_preset) const {
	return (bool)get_project_setting(p_preset, "display/window/per_pixel_transparency/allowed");
}

and Godot.kt

// Check whether the render view should be made transparent
val shouldBeTransparent = java.lang.Boolean.parseBoolean(GodotLib.getGlobal("display/window/per_pixel_transparency/allowed"))

[m4gr3d]

In the test project, display/window/size/transparent isn't enabled, so I tried without it and didn't encounter any problems. Or is there anything wrong with that?

@Alex2782 That's because DisplayServer.window_set_flag(DisplayServer.WINDOW_FLAG_TRANSPARENT, button_pressed) plays a similar role on desktop.
That method is not implemented on Android so instead we rely on the display/window/size/transparent property.

[m4gr3d]

"display/window/per_pixel_transparency/allowed"

I've updated the logic to only check "display/window/per_pixel_transparency/allowed" in order to match the demo project.

[Alex2782]

Test project: godot-demo-projects/.../window_management

Tried again on the Samsung Tab S7 and the Pixel 4a. It looks fine during startup/initialization.

The Pixel 4a OpenGLES has other rendering issues; the 2D scene (UI) fades out after switching back and forth several times.

[m4gr3d]

The Pixel 4a OpenGLES has other rendering issues; the 2D scene (UI) fades out after switching back and forth several times.

@Alex2782 I'm seeing the same issue on a Samsung Tab S8 when using the OpenGL renderer. I'll create a bug for the rendering team.

[m4gr3d]

The Pixel 4a OpenGLES has other rendering issues; the 2D scene (UI) fades out after switching back and forth several times.

@Alex2782 I'm seeing the same issue on a Samsung Tab S8 when using the OpenGL renderer. I'll create a bug for the rendering team.

The issue is also reproducible on 4.4.1-stable after disabling the feature check, so it should not be a blocker for this PR:

func _on_transparent_check_button_toggled(button_pressed: bool) -> void:
	#if not DisplayServer.has_feature(DisplayServer.FEATURE_WINDOW_TRANSPARENCY):
	#	OS.alert("Window transparency is not supported by the current display server (%s)." % DisplayServer.get_name())
	#	return
	get_viewport().transparent_bg = button_pressed
	DisplayServer.window_set_flag(DisplayServer.WINDOW_FLAG_TRANSPARENT, button_pressed)

Screen_Recording_20250529_090905_Window.Management.mp4

[syntaxerror247]

I am running the demo directly from Android Editor and having the same issue in opengl renderer but also having issues in vulkan renderer. Notice that after toggled off transparent button, window is translucent instead of opaque But I think it's expected due to windowIsTranslucent attribute?

Screenrecorder-2025-05-29-23-00-53-465.mp4

[syntaxerror247]

This should be set at runtime, if window transparent flag changes in Godot.

[akien-mga]

Thanks!

[Alex2782]

Can these 2 issue reports for Godot 3.x also be closed?

#52725
#36860

... or cherrypick necessary?

[syntaxerror247]

Can these 2 issue reports for Godot 3.x also be closed?

#52725 #36860

... or cherrypick necessary?

Cherry picking is not possible because it uses a new method for adding custom theme attributes during export. So, that would need to be implemented in 3.x first.