macOS: Report correct available geometry for non-primary screens

The assumption that the primary screen is the only one whose available
geometry differs from its full geometry no longer holds, so we need to
compute the available geometry for all screens.

Helpers methods for flipping between coordinates have been introduced
in QCocoaScreen, to make flipping possible relative to a specific
screen, and for exposing similar functionality in the future for
QScreen. The corresponding functions in qcocoahelpers.mm should
possibly be deprecated in favor of being explicit about which
screen is doing the mapping.

Change-Id: Iede658fabb4c3e4ef1f1b715db84fb927a661fa9
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

2 files changed, 50 insertions, 22 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.h b/src/plugins/platforms/cocoa/qcocoaintegration.h
index 892ff6e00f..d0d88994d5 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.h
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.h
@@ -87,6 +87,15 @@ public:
     NSScreen *nsScreen() const;
     void updateGeometry();
 
+    QPointF mapToNative(const QPointF &pos) const { return flipCoordinate(pos); }
+    QRectF mapToNative(const QRectF &rect) const { return flipCoordinate(rect); }
+    QPointF mapFromNative(const QPointF &pos) const { return flipCoordinate(pos); }
+    QRectF mapFromNative(const QRectF &rect) const { return flipCoordinate(rect); }
+
+private:
+    QPointF flipCoordinate(const QPointF &pos) const;
+    QRectF flipCoordinate(const QRectF &rect) const;
+
 public:
     NSScreen *m_nsScreen;
     QRect m_geometry;
diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index 5a77d8e367..d48722b82f 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -86,34 +86,53 @@ NSScreen *QCocoaScreen::nsScreen() const
     return m_nsScreen;
 }
 
+/*!
+    Flips the Y coordinate of the point between quadrant I and IV.
+
+    The native coordinate system on macOS uses quadrant I, with origin
+    in bottom left, and Qt uses quadrant IV, with origin in top left.
+
+    By flippig the Y coordinate, we can map the position between the
+    two coordinate systems.
+*/
+QPointF QCocoaScreen::flipCoordinate(const QPointF &pos) const
+{
+    return QPointF(pos.x(), m_geometry.height() - pos.y());
+}
+
+/*!
+    Flips the Y coordinate of the rectangle between quadrant I and IV.
+
+    The native coordinate system on macOS uses quadrant I, with origin
+    in bottom left, and Qt uses quadrant IV, with origin in top left.
+
+    By flippig the Y coordinate, we can map the rectangle between the
+    two coordinate systems.
+*/
+QRectF QCocoaScreen::flipCoordinate(const QRectF &rect) const
+{
+    return QRectF(flipCoordinate(rect.topLeft() + QPoint(0, rect.height())), rect.size());
+}
+
 void QCocoaScreen::updateGeometry()
 {
     if (!m_nsScreen)
         return;
 
-    NSRect frameRect = [m_nsScreen frame];
+    // At this point the geometry is in native coordinates, but the size
+    // is correct, which we take advantage of next when we map the native
+    // coordinates to the Qt coordinate system.
+    m_geometry = QRectF::fromCGRect(m_nsScreen.frame).toRect();
+    m_availableGeometry = QRectF::fromCGRect(m_nsScreen.visibleFrame).toRect();
 
-    if (m_nsScreen == [[NSScreen screens] firstObject]) {
-        m_geometry = QRect(frameRect.origin.x, frameRect.origin.y, frameRect.size.width, frameRect.size.height);
-        // This is the primary screen, the one that contains the menubar. Its origin should be
-        // (0, 0), and it's the only one whose available geometry differs from its full geometry.
-        NSRect visibleRect = [m_nsScreen visibleFrame];
-        m_availableGeometry = QRect(visibleRect.origin.x,
-                                    frameRect.size.height - (visibleRect.origin.y + visibleRect.size.height), // invert y
-                                    visibleRect.size.width, visibleRect.size.height);
-    } else {
-        // NSScreen origin is at the bottom-left corner, QScreen is at the top-left corner.
-        // When we get the NSScreen frame rect, we need to re-align its origin y coordinate
-        // w.r.t. the primary screen, whose origin is (0, 0).
-        NSRect r = [[[NSScreen screens] objectAtIndex:0] frame];
-        QRect referenceScreenGeometry = QRect(r.origin.x, r.origin.y, r.size.width, r.size.height);
-        m_geometry = QRect(frameRect.origin.x,
-                           referenceScreenGeometry.height() - (frameRect.origin.y + frameRect.size.height),
-                           frameRect.size.width, frameRect.size.height);
-
-        // Not primary screen. See above.
-        m_availableGeometry = m_geometry;
-    }
+    // The reference screen for the geometry is always the primary screen, but since
+    // we may be in the process of creating and registering the primary screen, we
+    // must special-case that and assign it direcly.
+    QCocoaScreen *primaryScreen = (m_nsScreen == [[NSScreen screens] firstObject]) ?
+        this : static_cast<QCocoaScreen*>(QGuiApplication::primaryScreen()->handle());
+
+    m_geometry = primaryScreen->mapFromNative(m_geometry).toRect();
+    m_availableGeometry = primaryScreen->mapFromNative(m_availableGeometry).toRect();
 
     m_format = QImage::Format_RGB32;
     m_depth = NSBitsPerPixelFromDepth([m_nsScreen depth]);