macOS: Simplify helpers for flipping between quadrant I and IV

The different flip-functions have been replaced by a single function,
qt_mac_flip, with overloads for points and rects. This function is
primarily used to implement QCocoaScreen::map(To|From)Native, which
most clients of qt_flip* have been moved to. This makes it clearer
what kind of reference geometry we're flipping in relation to, and
simplifies call-sites.

Change-Id: I8a0862f94bb2c64a83a1c3168f984a195c0af6db
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

1 files changed, 20 insertions, 33 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoahelpers.mm b/src/plugins/platforms/cocoa/qcocoahelpers.mm
index 67d42a2544..85d12040de 100644
--- a/src/plugins/platforms/cocoa/qcocoahelpers.mm
+++ b/src/plugins/platforms/cocoa/qcocoahelpers.mm
@@ -232,50 +232,37 @@ QString qt_mac_applicationName()
     return appName;
 }
 
-int qt_mac_primaryScreenHeight()
-{
-    QMacAutoReleasePool pool;
-    NSArray *screens = [NSScreen screens];
-    if ([screens count] > 0) {
-        // The first screen in the screens array is documented to
-        // have the (0,0) origin and is designated the primary screen.
-        NSRect screenFrame = [[screens objectAtIndex: 0] frame];
-        return screenFrame.size.height;
-    }
-    return 0;
-}
+// -------------------------------------------------------------------------
 
-int qt_mac_flipYCoordinate(int y)
-{
-    return qt_mac_primaryScreenHeight() - y;
-}
+/*!
+    \fn QPointF qt_mac_flip(const QPointF &pos, const QRectF &reference)
+    \fn QRectF qt_mac_flip(const QRectF &rect, const QRectF &reference)
 
-qreal qt_mac_flipYCoordinate(qreal y)
-{
-    return qt_mac_primaryScreenHeight() - y;
-}
+    Flips the Y coordinate of the point/rect between quadrant I and IV.
 
-QPointF qt_mac_flipPoint(const NSPoint &p)
-{
-    return QPointF(p.x, qt_mac_flipYCoordinate(p.y));
-}
+    The native coordinate system on macOS uses quadrant I, with origin
+    in bottom left, and Qt uses quadrant IV, with origin in top left.
 
-NSPoint qt_mac_flipPoint(const QPoint &p)
-{
-    return NSMakePoint(p.x(), qt_mac_flipYCoordinate(p.y()));
-}
+    By flipping the Y coordinate, we can map the point/rect between
+    the two coordinate systems.
 
-NSPoint qt_mac_flipPoint(const QPointF &p)
+    The flip is always in relation to a reference rectangle, e.g.
+    the frame of the parent view, or the screen geometry. In the
+    latter case the specialized QCocoaScreen::mapFrom/To functions
+    should be used instead.
+*/
+QPointF qt_mac_flip(const QPointF &pos, const QRectF &reference)
 {
-    return NSMakePoint(p.x(), qt_mac_flipYCoordinate(p.y()));
+    return QPointF(pos.x(), reference.height() - pos.y());
 }
 
-NSRect qt_mac_flipRect(const QRect &rect)
+QRectF qt_mac_flip(const QRectF &rect, const QRectF &reference)
 {
-    int flippedY = qt_mac_flipYCoordinate(rect.y() + rect.height());
-    return NSMakeRect(rect.x(), flippedY, rect.width(), rect.height());
+    return QRectF(qt_mac_flip(rect.bottomLeft(), reference), rect.size());
 }
 
+// -------------------------------------------------------------------------
+
 Qt::MouseButton cocoaButton2QtButton(NSInteger buttonNum)
 {
     if (buttonNum >= 0 && buttonNum <= 31)