Add preliminary support for Qt for visionOS

Qt already runs on Vision Pro as "Designed for iPad", using Qt
for iOS. This change enables building Qt for visionOS directly,
which opens the door to visionOS specific APIs and use-cases
such as volumes and immersive spaces.

The platform removes some APIs we depend on, notably UIScreen,
so some code paths have been disabled or mocked to get something
up and running.

As our current window management approach on UIKit platforms
depends on UIWindow and UIScreen there is currently no way to
bring up QWindows. This will improve once we refactor our
window management to use window scenes.

To configure for visionOS, pass -platform macx-visionos-clang,
and optionally add -sdk xrsimulator to build for the simulator.

Change-Id: I4eda55fc3fd06e12d30a188928487cf68940ee07
Reviewed-by:  Alexey Edelev <alexey.edelev@qt.io>

1 files changed, 17 insertions, 12 deletions

diff --git a/src/plugins/platforms/ios/qiostheme.mm b/src/plugins/platforms/ios/qiostheme.mm
index 3d6d60f971..251d0434cb 100644
--- a/src/plugins/platforms/ios/qiostheme.mm
+++ b/src/plugins/platforms/ios/qiostheme.mm
@@ -18,12 +18,15 @@
 #include <UIKit/UIFont.h>
 #include <UIKit/UIInterface.h>
 
-#ifndef Q_OS_TVOS
+#if !defined(Q_OS_TVOS) && !defined(Q_OS_VISIONOS)
 #include "qiosmenu.h"
+#endif
+
+#if !defined(Q_OS_TVOS)
 #include "qiosfiledialog.h"
-#include "qiosmessagedialog.h"
 #include "qioscolordialog.h"
 #include "qiosfontdialog.h"
+#include "qiosmessagedialog.h"
 #include "qiosscreen.h"
 #endif
 
@@ -82,23 +85,17 @@ const QPalette *QIOSTheme::palette(QPlatformTheme::Palette type) const
     return 0;
 }
 
+#if !defined(Q_OS_TVOS) && !defined(Q_OS_VISIONOS)
 QPlatformMenuItem* QIOSTheme::createPlatformMenuItem() const
 {
-#ifdef Q_OS_TVOS
-    return 0;
-#else
-    return new QIOSMenuItem();
-#endif
+    return new QIOSMenuItem;
 }
 
 QPlatformMenu* QIOSTheme::createPlatformMenu() const
 {
-#ifdef Q_OS_TVOS
-    return 0;
-#else
-    return new QIOSMenu();
-#endif
+    return new QIOSMenu;
 }
+#endif
 
 bool QIOSTheme::usePlatformNativeDialog(QPlatformTheme::DialogType type) const
 {
@@ -149,6 +146,13 @@ QVariant QIOSTheme::themeHint(ThemeHint hint) const
 
 Qt::ColorScheme QIOSTheme::colorScheme() const
 {
+#if defined(Q_OS_VISIONOS)
+    // On visionOS the concept of light or dark mode does not
+    // apply, as the UI is constantly changing based on what
+    // the lighting conditions are outside the headset, but
+    // the OS reports itself as always being in dark mode.
+    return Qt::ColorScheme::Dark;
+#else
     // Set the appearance based on the QUIWindow
     // Fallback to the UIScreen if no window is created yet
     UIUserInterfaceStyle appearance = UIScreen.mainScreen.traitCollection.userInterfaceStyle;
@@ -163,6 +167,7 @@ Qt::ColorScheme QIOSTheme::colorScheme() const
     return appearance == UIUserInterfaceStyleDark
                        ? Qt::ColorScheme::Dark
                        : Qt::ColorScheme::Light;
+#endif
 }
 
 const QFont *QIOSTheme::font(Font type) const