Revert "Drop call to setPlatformScreen in QHighDpiScaling::setScreenFactor"

This reverts commit 7b2ae3faab.

Reason for revert: this breaks multi-monitor XCB with HighDPI.

Fixes: QTBUG-105079
Pick-to: 6.4
Change-Id: I386c9480c33d1f67b3478332c8e03fe3eeeeee39
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Fushan Wen <qydwhotmail@gmail.com>

src/gui/kernel/qhighdpiscaling.cpp

@@ -555,8 +555,9 @@ void QHighDpiScaling::setScreenFactor(QScreen *screen, qreal factor)
     else
         QHighDpiScaling::m_namedScreenScaleFactors.insert(name, factor);
 
+    // hack to force re-evaluation of screen geometry
     if (screen->handle())
-        screen->d_func()->updateLogicalDpi();
+        screen->d_func()->setPlatformScreen(screen->handle()); // updates geometries based on scale factor
 }
 
 QPoint QHighDpiScaling::mapPositionToNative(const QPoint &pos, const QPlatformScreen *platformScreen)

src/gui/kernel/qplatformscreen.h

@@ -135,7 +135,7 @@ protected:
     QScopedPointer<QPlatformScreenPrivate> d_ptr;
 
 private:
-    friend QScreen;
+    friend class QScreenPrivate;
 };
 
 // Qt doesn't currently support running with no platform screen

src/gui/kernel/qscreen.cpp

@@ -41,26 +41,7 @@ QScreen::QScreen(QPlatformScreen *screen)
     : QObject(*new QScreenPrivate(), nullptr)
 {
     Q_D(QScreen);
-    d->platformScreen = screen;
-    d->platformScreen->d_func()->screen = this;
-    d->orientation = d->platformScreen->orientation();
-
-    d->logicalDpi = QPlatformScreen::overrideDpi(d->platformScreen->logicalDpi());
-
-    d->refreshRate = d->platformScreen->refreshRate();
-    // safeguard ourselves against buggy platform behavior...
-    if (d->refreshRate < 1.0)
-        d->refreshRate = 60.0;
-
-    d->updateHighDpi();
-    d->updatePrimaryOrientation(); // derived from the geometry
-}
-
-void QScreenPrivate::updateLogicalDpi()
-{
-    Q_Q(QScreen);
-    logicalDpi = QPlatformScreen::overrideDpi(q->handle()->logicalDpi());
-    updateGeometriesWithSignals(); // updates geometries based on scale factor
+    d->setPlatformScreen(screen);
 }
 
 void QScreenPrivate::updateGeometriesWithSignals()
@@ -90,6 +71,25 @@ void QScreenPrivate::emitGeometryChangeSignals(bool geometryChanged, bool availa
         emit q->physicalDotsPerInchChanged(q->physicalDotsPerInch());
 }
 
+void QScreenPrivate::setPlatformScreen(QPlatformScreen *screen)
+{
+    Q_Q(QScreen);
+    platformScreen = screen;
+    platformScreen->d_func()->screen = q;
+    orientation = platformScreen->orientation();
+
+    logicalDpi = QPlatformScreen::overrideDpi(platformScreen->logicalDpi());
+
+    refreshRate = platformScreen->refreshRate();
+    // safeguard ourselves against buggy platform behavior...
+    if (refreshRate < 1.0)
+        refreshRate = 60.0;
+
+    updateHighDpi();
+    updatePrimaryOrientation(); // derived from the geometry
+}
+
+
 /*!
     Destroys the screen.
  */

src/gui/kernel/qscreen_p.h

@@ -28,12 +28,12 @@ class QScreenPrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QScreen)
 public:
+    void setPlatformScreen(QPlatformScreen *screen);
     void updateHighDpi()
     {
         geometry = platformScreen->deviceIndependentGeometry();
         availableGeometry = QHighDpi::fromNative(platformScreen->availableGeometry(), QHighDpiScaling::factor(platformScreen), geometry.topLeft());
     }
-    void updateLogicalDpi();
 
     void updatePrimaryOrientation();
     void updateGeometriesWithSignals();