From f646439624766ec994d341102dc73b2b16d7fca2 Mon Sep 17 00:00:00 2001
From: John Preston <johnprestonmail@gmail.com>
Date: Mon, 21 Jun 2021 11:28:53 +0400
Subject: [PATCH] Fix full screen OpenGL native child window.

---
 ui/gl/gl_window.cpp               | 14 +++++++++++++-
 ui/platform/win/ui_window_win.cpp | 14 ++++++++++----
 ui/platform/win/ui_window_win.h   |  3 ++-
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/ui/gl/gl_window.cpp b/ui/gl/gl_window.cpp
index 497aba1..ed06f93 100644
--- a/ui/gl/gl_window.cpp
+++ b/ui/gl/gl_window.cpp
@@ -11,6 +11,8 @@
 #include "base/platform/base_platform_info.h"
 #include "base/debug_log.h"
 
+#include <QtGui/QScreen>
+
 namespace Ui::GL {
 namespace {
 
@@ -95,9 +97,19 @@ std::unique_ptr<Ui::RpWidget> Window::createNativeBodyWrap() {
 	raw->setParent(nativeParent);
 	raw->show();
 	raw->update();
+
 	_window->sizeValue(
 	) | rpl::start_with_next([=](QSize size) {
-		raw->setGeometry(QRect(QPoint(), size));
+		auto geometry = QRect(QPoint(), size);
+		if constexpr (::Platform::IsWindows()) {
+			if (const auto screen = _window->screen()) {
+				if (screen->size() == size) {
+					// Fix flicker in FullScreen OpenGL window on Windows.
+					geometry = geometry.marginsAdded({ 0, 0, 0, 1 });
+				}
+			}
+		}
+		raw->setGeometry(geometry);
 	}, raw->lifetime());
 
 	return result;
diff --git a/ui/platform/win/ui_window_win.cpp b/ui/platform/win/ui_window_win.cpp
index 70b8399..bde97e8 100644
--- a/ui/platform/win/ui_window_win.cpp
+++ b/ui/platform/win/ui_window_win.cpp
@@ -585,12 +585,18 @@ not_null<WindowHelper::NativeFilter*> WindowHelper::GetNativeFilter() {
 	return GlobalFilter;
 }
 
-HWND GetWindowHandle(not_null<RpWidget*> widget) {
-	widget->window()->createWinId();
+HWND GetWindowHandle(not_null<QWidget*> widget) {
+	const auto toplevel = widget->window();
+	toplevel->createWinId();
+	return GetWindowHandle(toplevel->windowHandle());
+}
+
+HWND GetWindowHandle(not_null<QWindow*> window) {
+	if (!window->winId()) {
+		window->create();
+	}
 
-	const auto window = widget->window()->windowHandle();
 	const auto native = QGuiApplication::platformNativeInterface();
-	Assert(window != nullptr);
 	Assert(native != nullptr);
 
 	return static_cast<HWND>(native->nativeResourceForWindow(
diff --git a/ui/platform/win/ui_window_win.h b/ui/platform/win/ui_window_win.h
index c74eb0b..23bcc49 100644
--- a/ui/platform/win/ui_window_win.h
+++ b/ui/platform/win/ui_window_win.h
@@ -58,7 +58,8 @@ private:
 
 };
 
-[[nodiscard]] HWND GetWindowHandle(not_null<RpWidget*> widget);
+[[nodiscard]] HWND GetWindowHandle(not_null<QWidget*> widget);
+[[nodiscard]] HWND GetWindowHandle(not_null<QWindow*> window);
 
 } // namespace Platform
 } // namespace Ui