Fix transparent toplevels on Mac OS X again..

We're using QWindow::format() to decide opacity or not in
a few places, but this used to resolve to
QPlatformFormat::format() which would in turn return a default
format without alpha set. Instead, return the format requested
by the user.

Masked windows were always broken as converting a 32-bit image
to an Indexed8, doesn't give a grayscale image, but rather
a randomly spreadout set of indices based on the colortable
generated by the converToFormat function.

Task-number: QTBUG-28531
Change-Id: I537288f85c70b1e6194785b9ebcb5ea1f9581cee
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>

src/plugins/platforms/cocoa/qcocoawindow.h

@@ -118,6 +118,7 @@ public:
     bool setKeyboardGrabEnabled(bool grab);
     bool setMouseGrabEnabled(bool grab);
     QMargins frameMargins() const;
+    QSurfaceFormat format() const;
 
     void requestActivateWindow();
 

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -253,6 +253,11 @@ QCocoaWindow::~QCocoaWindow()
     [m_nsWindowDelegate release];
 }
 
+QSurfaceFormat QCocoaWindow::format() const
+{
+    return window()->requestedFormat();
+}
+
 void QCocoaWindow::setGeometry(const QRect &rect)
 {
     if (geometry() == rect)

src/plugins/platforms/cocoa/qnsview.mm

@@ -340,15 +340,20 @@ static QTouchDevice *touchDevice = 0;
     }
 
     const QRect &rect = region->boundingRect();
-    QImage maskImage(rect.size(), QImage::Format_RGB888);
-    maskImage.fill(Qt::white);
-    QPainter p(&maskImage);
-    p.setRenderHint(QPainter::Antialiasing);
+    QImage tmp(rect.size(), QImage::Format_RGB32);
+    tmp.fill(Qt::white);
+    QPainter p(&tmp);
     p.setClipRegion(*region);
-    p.fillRect(rect, QBrush(Qt::black));
+    p.fillRect(rect, Qt::black);
     p.end();
-
-    maskImage = maskImage.convertToFormat(QImage::Format_Indexed8);
+    QImage maskImage = QImage(rect.size(), QImage::Format_Indexed8);
+    for (int y=0; y<rect.height(); ++y) {
+        const uint *src = (const uint *) tmp.constScanLine(y);
+        uchar *dst = maskImage.scanLine(y);
+        for (int x=0; x<rect.width(); ++x) {
+            dst[x] = src[x] & 0xff;
+        }
+    }
     m_maskImage = qt_mac_toCGImage(maskImage, true, &m_maskData);
 }