iOS: Compute screen available geometry based on safe area insets

In addition to the (deprecated) applicationFrame property, we
base the available geometry on the root view's safe area, which
also takes into account system-reserved areas on iPhone X, and
the screen's bezel in the case of tvOS.

Change-Id: I252d960a0e486dd0c7e30843f88c0bf5684feb24
Reviewed-by: Jake Petroules <jake.petroules@qt.io>

src/plugins/platforms/ios/qiosscreen.mm

@@ -175,6 +175,21 @@ static QIOSScreen* qtPlatformScreenFor(UIScreen *uiScreen)
 
 @end
 
+@interface UIScreen (Compatibility)
+@property (nonatomic, readonly) CGRect qt_applicationFrame;
+@end
+
+@implementation UIScreen (Compatibility)
+- (CGRect)qt_applicationFrame
+{
+#ifdef Q_OS_IOS
+    return self.applicationFrame;
+#else
+    return self.bounds;
+#endif
+}
+@end
+
 // -------------------------------------------------------------------------
 
 QT_BEGIN_NAMESPACE
@@ -271,11 +286,15 @@ void QIOSScreen::updateProperties()
     QRect previousAvailableGeometry = m_availableGeometry;
 
     m_geometry = QRectF::fromCGRect(m_uiScreen.bounds).toRect();
-#ifdef Q_OS_TVOS
-    m_availableGeometry = m_geometry;
-#else
-    m_availableGeometry = QRectF::fromCGRect(m_uiScreen.applicationFrame).toRect();
-#endif
+
+    // The application frame doesn't take safe area insets into account, and
+    // the safe area insets are not available before the UIWindow is shown,
+    // and do not take split-view constraints into account, so we have to
+    // combine the two to get the correct available geometry.
+    QRect applicationFrame = QRectF::fromCGRect(m_uiScreen.qt_applicationFrame).toRect();
+    UIEdgeInsets safeAreaInsets = m_uiWindow.qt_safeAreaInsets;
+    m_availableGeometry = m_geometry.adjusted(safeAreaInsets.left, safeAreaInsets.top,
+        -safeAreaInsets.right, -safeAreaInsets.bottom).intersected(applicationFrame);
 
 #ifndef Q_OS_TVOS
     if (m_uiScreen == [UIScreen mainScreen]) {

src/plugins/platforms/ios/quiview.h

@@ -77,5 +77,6 @@ QT_END_NAMESPACE
 - (QWindow *)qwindow;
 - (UIViewController *)viewController;
 - (QIOSViewController*)qtViewController;
+@property (nonatomic, readonly) UIEdgeInsets qt_safeAreaInsets;
 @end
 

src/plugins/platforms/ios/quiview.mm

@@ -545,6 +545,22 @@
     return nil;
 }
 
+- (UIEdgeInsets)qt_safeAreaInsets
+{
+#if QT_DARWIN_PLATFORM_SDK_EQUAL_OR_ABOVE(__MAC_NA, 110000, 110000, __WATCHOS_NA)
+    if (__builtin_available(iOS 11, tvOS 11, *))
+        return self.safeAreaInsets;
+#endif
+
+    // Fallback for iOS < 11
+    UIEdgeInsets safeAreaInsets = UIEdgeInsetsZero;
+    CGPoint topInset = [self convertPoint:CGPointMake(0, self.viewController.topLayoutGuide.length) fromView:nil];
+    CGPoint bottomInset = [self convertPoint:CGPointMake(0, self.viewController.bottomLayoutGuide.length) fromView:nil];
+    safeAreaInsets.top = topInset.y;
+    safeAreaInsets.bottom = bottomInset.y;
+    return safeAreaInsets;
+}
+
 @end
 
 #ifndef QT_NO_ACCESSIBILITY