From da473f3a80798d84d0f1bd9175158024a548ec68 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timoth=C3=A9e=20Keller?= <timothee.keller@qt.io>
Date: Mon, 14 Aug 2023 16:11:35 +0200
Subject: [PATCH] Windows QPA: don't take dpi rounding policy into account when
 fullscreen

With some HighDpiScaleFactorRoundingPolicy, going fullscreen can end up
not filling the whole screen. In this case, ignore the rounding (only for
the window size, not its content).

Fixes: QTBUG-115954
Pick-to: 6.7 6.6
Change-Id: Ie87196358ef28dbe2fcbc180b1740ed9f784b4a0
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
---
 .../platforms/windows/qwindowswindow.cpp      | 20 +++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index c76595e970..3b3f15610c 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -2579,26 +2579,26 @@ void QWindowsWindow::setWindowState_sys(Qt::WindowStates newState)
             if (testFlag(HasBorderInFullScreen))
                 newStyle |= WS_BORDER;
             setStyle(newStyle);
-            // Use geometry of QWindow::screen() within creation or the virtual screen the
-            // window is in (QTBUG-31166, QTBUG-30724).
-            const QScreen *screen = window()->screen();
-            if (!screen)
-                screen = QGuiApplication::primaryScreen();
-            const QRect r = screen ? QHighDpi::toNativePixels(screen->geometry(), window()) : m_savedFrameGeometry;
-
+            const HMONITOR monitor = MonitorFromWindow(m_data.hwnd, MONITOR_DEFAULTTONEAREST);
+            MONITORINFO monitorInfo = {};
+            monitorInfo.cbSize = sizeof(MONITORINFO);
+            GetMonitorInfoW(monitor, &monitorInfo);
+            const QRect screenGeometry(monitorInfo.rcMonitor.left, monitorInfo.rcMonitor.top,
+                                       monitorInfo.rcMonitor.right - monitorInfo.rcMonitor.left,
+                                       monitorInfo.rcMonitor.bottom - monitorInfo.rcMonitor.top);
             if (newState & Qt::WindowMinimized) {
-                setMinimizedGeometry(m_data.hwnd, r);
+                setMinimizedGeometry(m_data.hwnd, screenGeometry);
                 if (stateChange & Qt::WindowMaximized)
                     setRestoreMaximizedFlag(m_data.hwnd, newState & Qt::WindowMaximized);
             } else {
                 const UINT swpf = SWP_FRAMECHANGED | SWP_NOACTIVATE;
                 const bool wasSync = testFlag(SynchronousGeometryChangeEvent);
                 setFlag(SynchronousGeometryChangeEvent);
-                SetWindowPos(m_data.hwnd, HWND_TOP, r.left(), r.top(), r.width(), r.height(), swpf);
+                SetWindowPos(m_data.hwnd, HWND_TOP, screenGeometry.left(), screenGeometry.top(), screenGeometry.width(), screenGeometry.height(), swpf);
                 if (!wasSync)
                     clearFlag(SynchronousGeometryChangeEvent);
                 clearFlag(MaximizeToFullScreen);
-                QWindowSystemInterface::handleGeometryChange(window(), r);
+                QWindowSystemInterface::handleGeometryChange(window(), screenGeometry);
                 QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents);
             }
         } else {