high-dpi: Set screen on QWindow::setGeometry()

Keep (requested) geometry and screen in sync, which
is required for correct high-dpi scaling. The platform
plugin can still override with new geometry (and screen),
as usual.

This has previously been fixed/worked around for QDialog,
see QTBUG-52735. That fix can now be removed in favor
of this change in QWindow.

Change-Id: Ieadb1bfee5fb966c5c2052e9daa5ba124a87f3cd
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 867e658be5..131f55908b 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -529,6 +529,13 @@ void QWindowPrivate::create(bool recursive, WId nativeHandle)
     if (q->parent())
         q->parent()->create();
 
+    // QPlatformWindow will poll geometry() during construction below. Set the
+    // screen here so that high-dpi scaling will use the correct scale factor.
+    if (q->isTopLevel()) {
+        if (QScreen *screen = screenForGeometry(geometry))
+            setTopLevelScreen(screen, false);
+    }
+
     QPlatformIntegration *platformIntegration = QGuiApplicationPrivate::platformIntegration();
     platformWindow = nativeHandle ? platformIntegration->createForeignWindow(q, nativeHandle)
         : platformIntegration->createPlatformWindow(q);
@@ -1726,9 +1733,12 @@ void QWindow::setGeometry(const QRect &rect)
 
     d->positionPolicy = QWindowPrivate::WindowFrameExclusive;
     if (d->platformWindow) {
-        QRect nativeRect;
         QScreen *newScreen = d->screenForGeometry(rect);
         if (newScreen && isTopLevel())
+            d->setTopLevelScreen(newScreen, true);
+
+        QRect nativeRect;
+        if (newScreen && isTopLevel())
             nativeRect = QHighDpi::toNativePixels(rect, newScreen);
         else
             nativeRect = QHighDpi::toNativeLocalPosition(rect, newScreen);