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, 2 insertions, 89 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index fb3d05d3e4..1d35d9f440 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -207,9 +207,7 @@ QCocoaIntegration::QCocoaIntegration(const QStringList &paramList)
     // which will resolve to an actual value and result in screen invalidation.
     cocoaApplication.presentationOptions = NSApplicationPresentationDefault;
 
-    m_screensObserver = QMacScopedObserver([NSApplication sharedApplication],
-        NSApplicationDidChangeScreenParametersNotification, [&]() { updateScreens(); });
-    updateScreens();
+    QCocoaScreen::initializeScreens();
 
     QMacInternalPasteboardMime::initializeMimeTypes();
     QCocoaMimeTypes::initializeMimeTypes();
@@ -242,10 +240,7 @@ QCocoaIntegration::~QCocoaIntegration()
     QMacInternalPasteboardMime::destroyMimeTypes();
 #endif
 
-    // Delete screens in reverse order to avoid crash in case of multiple screens
-    while (!mScreens.isEmpty()) {
-        QWindowSystemInterface::handleScreenRemoved(mScreens.takeLast());
-    }
+    QCocoaScreen::cleanupScreens();
 
     clearToolbars();
 }
@@ -260,88 +255,6 @@ QCocoaIntegration::Options QCocoaIntegration::options() const
     return mOptions;
 }
 
-/*!
-    \brief Synchronizes the screen list, adds new screens, removes deleted ones
-*/
-void QCocoaIntegration::updateScreens()
-{
-    NSArray<NSScreen *> *scrs = [NSScreen screens];
-    NSMutableArray<NSScreen *> *screens = [NSMutableArray<NSScreen *> arrayWithArray:scrs];
-    if ([screens count] == 0)
-        if ([NSScreen mainScreen])
-           [screens addObject:[NSScreen mainScreen]];
-    if ([screens count] == 0)
-        return;
-    QSet<QCocoaScreen*> remainingScreens = QSet<QCocoaScreen*>::fromList(mScreens);
-    QList<QPlatformScreen *> siblings;
-    uint screenCount = [screens count];
-    for (uint i = 0; i < screenCount; i++) {
-        NSScreen* scr = [screens objectAtIndex:i];
-        CGDirectDisplayID dpy = scr.qt_displayId;
-        // If this screen is a mirror and is not the primary one of the mirror set, ignore it.
-        // Exception: The NSScreen API has been observed to a return a screen list with one
-        // mirrored, non-primary screen when Qt is running as a startup item. Always use the
-        // screen if there's only one screen in the list.
-        if (screenCount > 1 && CGDisplayIsInMirrorSet(dpy)) {
-            CGDirectDisplayID primary = CGDisplayMirrorsDisplay(dpy);
-            if (primary != kCGNullDirectDisplay && primary != dpy)
-                continue;
-        }
-        QCocoaScreen* screen = nullptr;
-        foreach (QCocoaScreen* existingScr, mScreens) {
-            // NSScreen documentation says do not cache the array returned from [NSScreen screens].
-            // However in practice, we can identify a screen by its pointer: if resolution changes,
-            // the NSScreen object will be the same instance, just with different values.
-            if (existingScr->nativeScreen() == scr) {
-                screen = existingScr;
-                break;
-            }
-        }
-        if (screen) {
-            remainingScreens.remove(screen);
-            screen->updateProperties();
-        } else {
-            screen = new QCocoaScreen(i);
-            mScreens.append(screen);
-            qCDebug(lcQpaScreen) << "Adding" << screen;
-            QWindowSystemInterface::handleScreenAdded(screen);
-        }
-        siblings << screen;
-    }
-
-    // Set virtual siblings list. All screens in mScreens are siblings, because we ignored the
-    // mirrors. Note that some of the screens we update the siblings list for here may be deleted
-    // below, but update anyway to keep the to-be-deleted screens out of the siblings list.
-    foreach (QCocoaScreen* screen, mScreens)
-        screen->setVirtualSiblings(siblings);
-
-    // Now the leftovers in remainingScreens are no longer current, so we can delete them.
-    foreach (QCocoaScreen* screen, remainingScreens) {
-        mScreens.removeOne(screen);
-        // Prevent stale references to NSScreen during destroy
-        screen->m_screenIndex = -1;
-        qCDebug(lcQpaScreen) << "Removing" << screen;
-        QWindowSystemInterface::handleScreenRemoved(screen);
-    }
-}
-
-QCocoaScreen *QCocoaIntegration::screenForNSScreen(NSScreen *nsScreen)
-{
-    NSUInteger index = [[NSScreen screens] indexOfObject:nsScreen];
-    if (index == NSNotFound)
-        return nullptr;
-
-    if (index >= unsigned(mScreens.count()))
-        updateScreens();
-
-    for (QCocoaScreen *screen : mScreens) {
-        if (screen->nativeScreen() == nsScreen)
-            return screen;
-    }
-
-    return nullptr;
-}
-
 bool QCocoaIntegration::hasCapability(QPlatformIntegration::Capability cap) const
 {
     switch (cap) {