[Bug]: Full Screen Transparent Windows are White on Windows 10

[carterbs]

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Electron Version

14.0.0

What operating system are you using?

Windows

Operating System Version

Windows 10 Pro version 20H2, OS build 19042.1110

What arch are you using?

x64

Last Known Working Electron version

No response

Expected Behavior

A transparent window should be transparent, no matter its height or width.

Actual Behavior

BROKEN

GIVEN your window is transparent, frameless, and you are running on windows
AND your window's width === monitor width and the window's height === monitor height
AND its top left corner is the top left corner of your monitor
THEN your transparent window will be white and render nothing

GIVEN prereqs above
AND your window's width === monitor width - 1 and the window's height === monitor height
AND its top left corner is the top left corner of your monitor
THEN your transparent window will be white and render nothing

GIVEN prereqs above
AND your window's width === monitor width and the window's height === monitor height
AND its top left corner is the top left corner of your monitor
THEN your transparent window will be white and render nothing

WORKS
GIVEN prereqs above
AND your window's width === monitor width and the window's height === monitor height
AND its top left corner is the top left corner of your monitor + 1 px in the X or Y direction
THEN your transparent window will be transparent and perfect

GIVEN prereqs above
AND your window's width === monitor width - 1 and the window's height === monitor height - 1
AND its top left corner is the top left corner of your monitor
THEN your transparent window will be transparent and perfect

Testcase Gist URL

https://gist.github.com/d52ceca16461bfe12b2bf936bc462412

Additional Information

If you shift the top left corner of the window by 1 pixel, the bug goes away. I assume there's a falsey check somewhere and 0 is triggering it. I didn't test this on a secondary monitor.

[samuelmaddock]

Confirmed that I can reproduce this issue on Windows 10 21H1 build 19043.1165

I forked your gist to automatically get the primary display's width/height: https://gist.github.com/817c57f1aaffece3cae795bba640f829

[carterbs]

Confirmed that I can reproduce this issue on Windows 10 21H1 build 19043.1165

I forked your gist to automatically get the primary display's width/height: https://gist.github.com/817c57f1aaffece3cae795bba640f829

Gracias. Didn't take the time to do that - appreciate it.

[samuelmaddock]

This happens only when the BrowserWindow is shown within the first tick after its creation when the size matches the primary display's size.

Calling Show() attempts to get the window's restore state in GetRestoredState().

electron/shell/browser/native_window_views.cc

Lines 459 to 464 in 49e62f1

	void NativeWindowViews::Show() {
	if (is_modal() && NativeWindow::parent() &&
	!widget()->native_widget_private()->IsVisible())
	static_cast<NativeWindowViews*>(parent())->IncrementChildModals();
	widget()->native_widget_private()->Show(GetRestoredState(), gfx::Rect());

electron/shell/browser/native_window_views.cc

Lines 1631 to 1638 in 49e62f1

	ui::WindowShowState NativeWindowViews::GetRestoredState() {
	if (IsMaximized())
	return ui::SHOW_STATE_MAXIMIZED;
	if (IsFullscreen())
	return ui::SHOW_STATE_FULLSCREEN;
	return ui::SHOW_STATE_NORMAL;
	}

It ends up using the ui::SHOW_STATE_MAXIMIZED restore state since it's a transparent window and its bounds match that of the display.

electron/shell/browser/native_window_views.cc

Lines 597 to 610 in 49e62f1

	bool NativeWindowViews::IsMaximized() {
	if (widget()->IsMaximized()) {
	return true;
	} else {
	#if defined(OS_WIN)
	if (transparent()) {
	// Compare the size of the window with the size of the display
	auto display = display::Screen::GetScreen()->GetDisplayNearestWindow(
	GetNativeWindow());
	// Maximized if the window is the same dimensions and placement as the
	// display
	return GetBounds() == display.work_area();
	}
	#endif

Restoring the maximized state causes problems in Chromium code: https://source.chromium.org/chromium/chromium/src/+/main:ui/views/widget/desktop_aura/desktop_window_tree_host_platform.cc;l=342-351;drc=11aaa9f9150091c805928724c83d8a807cb65faf

A temporary workaround is to delay showing the BrowserWindow until either the ready-to-show event or delaying by one tick.

[carterbs]

I gave both of those a try with hardware acc disabled, and the window just never rendered. Even if it did render eventually, (and I'm just doing something wrong), I worry that it'd butt up against this bug (#27265). The +1 trick is very dirty but it won't prevent me from deploying my feature, so I'm going to roll with it.