Emit QScreen::(availableG|g)eometryChanged() on logical DPI change

When a change in logical DPI occurs due to the user changing the scaling
factor, the screen size in device independent pixels may change
due to High DPI choosing a different scale factor.

Factor out the commonly used code into QScreenPrivate methods
and use them from
QGuiApplicationPrivate::processScreenLogicalDotsPerInchChange().

Pick-to: 5.15
Task-number: QTBUG-76902
Task-number: QTBUG-79248
Change-Id: I241a0f52d8236a65084d501fb4d8f9faeea89c0f
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/gui/kernel/qguiapplication.cpp

@@ -3131,14 +3131,7 @@ void QGuiApplicationPrivate::processScreenGeometryChange(QWindowSystemInterfaceP
             updateFilteredScreenOrientation(s);
     }
 
-    if (availableGeometryChanged)
+    s->d_func()->emitGeometryChangeSignals(geometryChanged, availableGeometryChanged);
-        emit s->availableGeometryChanged(s->availableGeometry());
-
-    if (geometryChanged || availableGeometryChanged) {
-        const auto siblings = s->virtualSiblings();
-        for (QScreen* sibling : siblings)
-            emit sibling->virtualGeometryChanged(sibling->virtualGeometry());
-    }
 
     resetCachedDevicePixelRatio();
 }
@@ -3156,6 +3149,7 @@ void QGuiApplicationPrivate::processScreenLogicalDotsPerInchChange(QWindowSystem
     s->d_func()->logicalDpi = QDpi(e->dpiX, e->dpiY);
 
     emit s->logicalDotsPerInchChanged(s->logicalDotsPerInch());
+    s->d_func()->updateGeometriesWithSignals();
 
     resetCachedDevicePixelRatio();
 }

src/gui/kernel/qscreen.cpp

@@ -77,15 +77,33 @@ QScreen::QScreen(QPlatformScreen *screen)
     d->setPlatformScreen(screen);
 }
 
+void QScreenPrivate::updateGeometriesWithSignals()
+{
+    const QRect oldGeometry = geometry;
+    const QRect oldAvailableGeometry = availableGeometry;
+    updateHighDpi();
+    emitGeometryChangeSignals(oldGeometry != geometry, oldAvailableGeometry != availableGeometry);
+}
+
+void QScreenPrivate::emitGeometryChangeSignals(bool geometryChanged, bool availableGeometryChanged)
+{
+    Q_Q(QScreen);
+    if (availableGeometryChanged)
+        emit q->availableGeometryChanged(availableGeometry);
+
+    if (geometryChanged || availableGeometryChanged) {
+        const auto siblings = q->virtualSiblings();
+        for (QScreen* sibling : siblings)
+            emit sibling->virtualGeometryChanged(sibling->virtualGeometry());
+    }
+}
+
 void QScreenPrivate::setPlatformScreen(QPlatformScreen *screen)
 {
     Q_Q(QScreen);
     platformScreen = screen;
     platformScreen->d_func()->screen = q;
     orientation = platformScreen->orientation();
-    geometry = platformScreen->deviceIndependentGeometry();
-    availableGeometry = QHighDpi::fromNative(platformScreen->availableGeometry(),
-                        QHighDpiScaling::factor(platformScreen), geometry.topLeft());
 
     logicalDpi = QPlatformScreen::overrideDpi(platformScreen->logicalDpi());
 

src/gui/kernel/qscreen_p.h

@@ -72,6 +72,8 @@ public:
     }
 
     void updatePrimaryOrientation();
+    void updateGeometriesWithSignals();
+    void emitGeometryChangeSignals(bool geometryChanged, bool availableGeometryChanged);
 
     QPlatformScreen *platformScreen = nullptr;