iOS: Report correct physicalSize and physicalDotsPerInch for iPhone6+

On iPhone 6(s) Plus devices, or when display zoom is enabled in an iPhone 6,
the render buffer is scaled before being output on the physical display.
We have to take this into account when computing the physical size.

Task-number: QTBUG-50941
Change-Id: I318f3a866d039fccf0ba08f381fc9d8bcd676acd
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@theqtcompany.com>

src/plugins/platforms/ios/qiosscreen.h

@@ -73,7 +73,7 @@ private:
     QRect m_geometry;
     QRect m_availableGeometry;
     int m_depth;
-    uint m_pixelDensity;
+    uint m_physicalDpi;
     QSizeF m_physicalSize;
     QIOSOrientationListener *m_orientationListener;
 };

src/plugins/platforms/ios/qiosscreen.mm

@@ -180,18 +180,18 @@ QIOSScreen::QIOSScreen(UIScreen *screen)
 
         if (deviceIdentifier.contains(QRegularExpression("^iPhone(7,1|8,2)$"))) {
             // iPhone 6 Plus or iPhone 6S Plus
-            m_pixelDensity = 401;
+            m_physicalDpi = 401;
         } else if (deviceIdentifier.contains(QRegularExpression("^iPad(1,1|2,[1-4]|3,[1-6]|4,[1-3]|5,[3-4]|6,[7-8])$"))) {
             // All iPads except the iPad Mini series
-            m_pixelDensity = 132 * devicePixelRatio();
+            m_physicalDpi = 132 * devicePixelRatio();
         } else {
             // All non-Plus iPhones, and iPad Minis
-            m_pixelDensity = 163 * devicePixelRatio();
+            m_physicalDpi = 163 * devicePixelRatio();
         }
     } else {
         // External display, hard to say
         m_depth = 24;
-        m_pixelDensity = 96;
+        m_physicalDpi = 96;
     }
 
     for (UIWindow *existingWindow in [[UIApplication sharedApplication] windows]) {
@@ -253,8 +253,23 @@ void QIOSScreen::updateProperties()
     }
 
     if (m_geometry != previousGeometry) {
-        const qreal millimetersPerInch = 25.4;
-        m_physicalSize = QSizeF(m_geometry.size() * devicePixelRatio()) / m_pixelDensity * millimetersPerInch;
+        QRectF physicalGeometry;
+        if (QSysInfo::MacintoshVersion >= QSysInfo::MV_IOS_8_0) {
+             // We can't use the primaryOrientation of screen(), as we haven't reported the new geometry yet
+            Qt::ScreenOrientation primaryOrientation = m_geometry.width() >= m_geometry.height() ?
+                Qt::LandscapeOrientation : Qt::PortraitOrientation;
+
+            // On iPhone 6+ devices, or when display zoom is enabled, the render buffer is scaled
+            // before being output on the physical display. We have to take this into account when
+            // computing the physical size. Note that unlike the native bounds, the physical size
+            // follows the primary orientation of the screen.
+            physicalGeometry = mapBetween(nativeOrientation(), primaryOrientation, fromCGRect(m_uiScreen.nativeBounds).toRect());
+        } else {
+            physicalGeometry = QRectF(0, 0, m_geometry.width() * devicePixelRatio(), m_geometry.height() * devicePixelRatio());
+        }
+
+        static const qreal millimetersPerInch = 25.4;
+        m_physicalSize = physicalGeometry.size() / m_physicalDpi * millimetersPerInch;
     }
 
     // At construction time, we don't yet have an associated QScreen, but we still want