Windows QPA: Fix wrong scaling of fixed size in window creation phase

When a fixed size the window is moved to another screen
by QPlatformWindow::initialGeometry(), the size constraints
would be incorrectly scaled using the initial screen in the handling of
WM_GETMINMAXINFO.
To fix this, pass the resulting screen out of QPlatformWindow::initialGeometry()
and use it during the window creation phase.

Fixes: QTBUG-77307
Change-Id: I149a2a65e816da841a32abc14a495925bf9cc6f6
Reviewed-by: André de la Rocha <andre.rocha@qt.io>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

2 files changed, 11 insertions, 4 deletions

diff --git a/src/gui/kernel/qplatformwindow.cpp b/src/gui/kernel/qplatformwindow.cpp
index 2a0cb1094c..65accc9f68 100644
--- a/src/gui/kernel/qplatformwindow.cpp
+++ b/src/gui/kernel/qplatformwindow.cpp
@@ -694,9 +694,12 @@ static QSize fixInitialSize(QSize size, const QWindow *w,
     However if the given window already has geometry which the application has
     initialized, it takes priority.
 */
-QRect QPlatformWindow::initialGeometry(const QWindow *w,
-    const QRect &initialGeometry, int defaultWidth, int defaultHeight)
+QRect QPlatformWindow::initialGeometry(const QWindow *w, const QRect &initialGeometry,
+                                       int defaultWidth, int defaultHeight,
+                                       const QScreen **resultingScreenReturn)
 {
+    if (resultingScreenReturn)
+        *resultingScreenReturn = w->screen();
     if (!w->isTopLevel()) {
         const qreal factor = QHighDpiScaling::factor(w);
         const QSize size = fixInitialSize(QHighDpi::fromNative(initialGeometry.size(), factor),
@@ -712,6 +715,8 @@ QRect QPlatformWindow::initialGeometry(const QWindow *w,
         : QGuiApplication::screenAt(initialGeometry.center());
     if (!screen)
         return initialGeometry;
+    if (resultingScreenReturn)
+        *resultingScreenReturn = screen;
     // initialGeometry refers to window's screen
     QRect rect(QHighDpi::fromNativePixels(initialGeometry, w));
     if (wp->resizeAutomatic)
diff --git a/src/gui/kernel/qplatformwindow.h b/src/gui/kernel/qplatformwindow.h
index 4d48cc2f13..b6aeb3a86a 100644
--- a/src/gui/kernel/qplatformwindow.h
+++ b/src/gui/kernel/qplatformwindow.h
@@ -63,6 +63,7 @@ QT_BEGIN_NAMESPACE
 
 class QPlatformScreen;
 class QPlatformWindowPrivate;
+class QScreen;
 class QWindow;
 class QIcon;
 class QRegion;
@@ -142,8 +143,9 @@ public:
 
     virtual void invalidateSurface();
 
-    static QRect initialGeometry(const QWindow *w,
-        const QRect &initialGeometry, int defaultWidth, int defaultHeight);
+    static QRect initialGeometry(const QWindow *w, const QRect &initialGeometry,
+                                 int defaultWidth, int defaultHeight,
+                                 const QScreen **resultingScreenReturn = nullptr);
 
     virtual void requestUpdate();
     bool hasPendingUpdateRequest() const;