Fix QWindow::mapToGlobal()/mapFromGlobal() for multi-screen windows

Make these functions handle the case where a window spans multiple
screens, and high-DPI scaling is enabled, and the local position (in the
window) is not on the window primary screen (as returned by
QWindow::screen()).

This is done by detecting the case, and then calculating
the correct position using the native coordinate system.

[ChangeLog][QtGui] QWindow::mapToGlobal()/mapFromGlobal() now handle
windows spanning screens correctly.

Done-with: Friedemann Kleint<Friedemann.Kleint@qt.io>
Task-number: QTBUG-73231
Change-Id: I3c31b741344d9e85e4f5d9e60bae75acce2db741
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 453aa1ed83..bcd8351619 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -1670,9 +1670,9 @@ void QWindow::setGeometry(const QRect &rect)
   chicken and egg problem here: we cannot convert to native coordinates
   before we know which screen we are on.
 */
-QScreen *QWindowPrivate::screenForGeometry(const QRect &newGeometry)
+QScreen *QWindowPrivate::screenForGeometry(const QRect &newGeometry) const
 {
-    Q_Q(QWindow);
+    Q_Q(const QWindow);
     QScreen *currentScreen = q->screen();
     QScreen *fallback = currentScreen;
     QPoint center = newGeometry.center();
@@ -2542,6 +2542,10 @@ QPoint QWindow::mapToGlobal(const QPoint &pos) const
         && (d->platformWindow->isForeignWindow() || d->platformWindow->isEmbedded())) {
         return QHighDpi::fromNativeLocalPosition(d->platformWindow->mapToGlobal(QHighDpi::toNativeLocalPosition(pos, this)), this);
     }
+
+    if (QHighDpiScaling::isActive())
+        return QHighDpiScaling::mapPositionToGlobal(pos, d->globalPosition(), this);
+
     return pos + d->globalPosition();
 }
 
@@ -2562,6 +2566,10 @@ QPoint QWindow::mapFromGlobal(const QPoint &pos) const
         && (d->platformWindow->isForeignWindow() || d->platformWindow->isEmbedded())) {
         return QHighDpi::fromNativeLocalPosition(d->platformWindow->mapFromGlobal(QHighDpi::toNativeLocalPosition(pos, this)), this);
     }
+
+    if (QHighDpiScaling::isActive())
+        return QHighDpiScaling::mapPositionFromGlobal(pos, d->globalPosition(), this);
+
     return pos - d->globalPosition();
 }