macOS: Track screens via Quartz Display Services instead of NSScreen

Using NSScreen as the basis for tracking screens is not recommended, as
the list of screens can be added, removed, or dynamically reconfigured at
any time, and the NSScreen instance, or index in the NSScreen.screens array
may not be stable.

Quartz Display Services on the other hand tracks displays via a unique
display ID, which typically remains constant until the machine is restarted.
The lower level API also gives us earlier callbacks about screen changes
than the corresponding NSApplicationDidChangeScreenParametersNotification
does. By reacting to screen changes _before_ AppKit does, we can remove
workarounds for receiving window move and screen change notifications
before the screen was actually visibly reconfigured.

The new approach also handles changes to the primary screen, which
can happen if the user moves the menu bar in the macOS display
arrangement pane.

The device pixel ratio of the screen has been made into a cached
property, like all the other properties of QCocoaScreen. This is
more consistent, and allows us to qDebug the screen even when it
has been removed and we no longer have access to resolve the
properties from the associated Quarts display.

Change-Id: I2d86c7629ed3bf5fb8c77f174712633752ae4079
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

1 files changed, 21 insertions, 10 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoascreen.h b/src/plugins/platforms/cocoa/qcocoascreen.h
index 9ded98df32..491af2fe9c 100644
--- a/src/plugins/platforms/cocoa/qcocoascreen.h
+++ b/src/plugins/platforms/cocoa/qcocoascreen.h
@@ -48,10 +48,14 @@
 
 QT_BEGIN_NAMESPACE
 
+class QCocoaIntegration;
+
 class QCocoaScreen : public QPlatformScreen
 {
 public:
-    QCocoaScreen(int screenIndex);
+    static void initializeScreens();
+    static void cleanupScreens();
+
     ~QCocoaScreen();
 
     // ----------------------------------------------------
@@ -61,19 +65,18 @@ public:
     QRect availableGeometry() const override { return m_availableGeometry; }
     int depth() const override { return m_depth; }
     QImage::Format format() const override { return m_format; }
-    qreal devicePixelRatio() const override;
+    qreal devicePixelRatio() const override { return m_devicePixelRatio; }
     QSizeF physicalSize() const override { return m_physicalSize; }
     QDpi logicalDpi() const override { return m_logicalDpi; }
     qreal refreshRate() const override { return m_refreshRate; }
     QString name() const override { return m_name; }
     QPlatformCursor *cursor() const override { return m_cursor; }
     QWindow *topLevelAt(const QPoint &point) const override;
-    QList<QPlatformScreen *> virtualSiblings() const override { return m_siblings; }
+    QList<QPlatformScreen *> virtualSiblings() const override;
     QPlatformScreen::SubpixelAntialiasingType subpixelAntialiasingTypeHint() const override;
 
     // ----------------------------------------------------
-    // Additional methods
-    void setVirtualSiblings(const QList<QPlatformScreen *> &siblings) { m_siblings = siblings; }
+
     NSScreen *nativeScreen() const;
     void updateProperties();
 
@@ -82,14 +85,21 @@ public:
     bool isRunningDisplayLink() const;
 
     static QCocoaScreen *primaryScreen();
+    static QCocoaScreen *get(NSScreen *nsScreen);
+    static QCocoaScreen *get(CGDirectDisplayID displayId);
 
     static CGPoint mapToNative(const QPointF &pos, QCocoaScreen *screen = QCocoaScreen::primaryScreen());
     static CGRect mapToNative(const QRectF &rect, QCocoaScreen *screen = QCocoaScreen::primaryScreen());
     static QPointF mapFromNative(CGPoint pos, QCocoaScreen *screen = QCocoaScreen::primaryScreen());
     static QRectF mapFromNative(CGRect rect, QCocoaScreen *screen = QCocoaScreen::primaryScreen());
 
-public:
-    int m_screenIndex;
+private:
+    QCocoaScreen(CGDirectDisplayID displayId);
+    static void add(CGDirectDisplayID displayId);
+    void remove();
+
+    CGDirectDisplayID m_displayId = 0;
+
     QRect m_geometry;
     QRect m_availableGeometry;
     QDpi m_logicalDpi;
@@ -99,11 +109,13 @@ public:
     QImage::Format m_format;
     QSizeF m_physicalSize;
     QCocoaCursor *m_cursor;
-    QList<QPlatformScreen *> m_siblings;
+    qreal m_devicePixelRatio;
 
     CVDisplayLinkRef m_displayLink = nullptr;
     dispatch_source_t m_displayLinkSource = nullptr;
     QAtomicInt m_pendingUpdates;
+
+    friend QDebug operator<<(QDebug debug, const QCocoaScreen *screen);
 };
 
 #ifndef QT_NO_DEBUG_STREAM
@@ -116,5 +128,4 @@ QT_END_NAMESPACE
 @property(readonly) CGDirectDisplayID qt_displayId;
 @end
 
-#endif
-
+#endif // QCOCOASCREEN_H