Cocoa: QGLWidget draws wrong within QMainWindow on Mac OS

The resons for this bug is that Qt can share the same backingstore
between several windows (if they exist in the same hierarchy), but
this was just not supported by the Cocoa plugin.

This patch will make sure that we pay attention to which window
the QCocoaBackingStore is told to flush, and forward this information
to the QNSView that backs it up. Inside the views drawRect
function we then take some extra steps to get the correct sub-part
of the possibly shared backingstore image.

This patch also does some effort to ensure that we recreate the
backingstore image as little as possible, as we can often get
several resizes to the backingstore before we actually draw anything.
Moreover, by being a bit careful on how we tell UiKit to update
the view upon a flush, we can minimize the number of drawRect calls
(and then CGImageRef creations) we need to do. This patch actually
ends up improving resize/repaint performance a lot as well.

QT-BUG: 27390
Change-Id: I2c2a26b149fa855411b6bff8b9cc9a61694ae72f
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>

1 files changed, 25 insertions, 71 deletions

diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index 4fb099341e..8e18ca3708 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -55,6 +55,7 @@
 #include <QtGui/QTextFormat>
 #include <QtCore/QDebug>
 #include <private/qguiapplication_p.h>
+#include "qcocoabackingstore.h"
 
 #ifdef QT_COCOA_ENABLE_ACCESSIBILITY_INSPECTOR
 #include <accessibilityinspector.h>
@@ -74,7 +75,7 @@ static QTouchDevice *touchDevice = 0;
 {
     self = [super initWithFrame : NSMakeRect(0,0, 300,300)];
     if (self) {
-        m_cgImage = 0;
+        m_backingStore = 0;
         m_maskImage = 0;
         m_maskData = 0;
         m_window = 0;
@@ -93,8 +94,6 @@ static QTouchDevice *touchDevice = 0;
 
 - (void)dealloc
 {
-    CGImageRelease(m_cgImage);
-    m_cgImage = 0;
     CGImageRelease(m_maskImage);
     m_maskImage = 0;
     delete[] m_maskData;
@@ -211,66 +210,12 @@ static QTouchDevice *touchDevice = 0;
     }
 }
 
-static CGImageRef qt_mac_toCGImage(QImage *qImage, bool isMask, uchar **dataCopy)
+- (void) flushBackingStore:(QCocoaBackingStore *)backingStore region:(const QRegion &)region offset:(QPoint)offset
 {
-    int width = qImage->width();
-    int height = qImage->height();
-
-    if (width <= 0 || height <= 0) {
-        qWarning() << Q_FUNC_INFO <<
-            "setting invalid size" << width << "x" << height << "for qnsview image";
-        return 0;
-    }
-
-    const uchar *imageData = qImage->bits();
-    if (dataCopy) {
-        delete[] *dataCopy;
-        *dataCopy = new uchar[qImage->byteCount()];
-        memcpy(*dataCopy, imageData, qImage->byteCount());
-    }
-    int bitDepth = qImage->depth();
-    int colorBufferSize = 8;
-    int bytesPrLine = qImage->bytesPerLine();
-
-    CGDataProviderRef cgDataProviderRef = CGDataProviderCreateWithData(
-                NULL,
-                dataCopy ? *dataCopy : imageData,
-                qImage->byteCount(),
-                NULL);
-
-    CGImageRef cgImage = 0;
-    if (isMask) {
-        cgImage = CGImageMaskCreate(width,
-                                    height,
-                                    colorBufferSize,
-                                    bitDepth,
-                                    bytesPrLine,
-                                    cgDataProviderRef,
-                                    NULL,
-                                    false);
-    } else {
-        CGColorSpaceRef cgColourSpaceRef = CGColorSpaceCreateDeviceRGB();
-        cgImage = CGImageCreate(width,
-                                height,
-                                colorBufferSize,
-                                bitDepth,
-                                bytesPrLine,
-                                cgColourSpaceRef,
-                                kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipFirst,
-                                cgDataProviderRef,
-                                NULL,
-                                false,
-                                kCGRenderingIntentDefault);
-        CGColorSpaceRelease(cgColourSpaceRef);
-    }
-    CGDataProviderRelease(cgDataProviderRef);
-    return cgImage;
-}
-
-- (void) setImage:(QImage *)image
-{
-    CGImageRelease(m_cgImage);
-    m_cgImage = qt_mac_toCGImage(image, false, 0);
+    m_backingStore = backingStore;
+    m_backingStoreOffset = offset;
+    QRect br = region.boundingRect();
+    [self setNeedsDisplayInRect:NSMakeRect(br.x(), br.y(), br.width(), br.height())];
 }
 
 - (void) setMaskRegion:(const QRegion *)region
@@ -291,36 +236,45 @@ static CGImageRef qt_mac_toCGImage(QImage *qImage, bool isMask, uchar **dataCopy
     p.end();
 
     maskImage = maskImage.convertToFormat(QImage::Format_Indexed8);
-    m_maskImage = qt_mac_toCGImage(&maskImage, true, &m_maskData);
+    m_maskImage = qt_mac_toCGImage(maskImage, true, &m_maskData);
 }
 
 - (void) drawRect:(NSRect)dirtyRect
 {
-    if (!m_cgImage)
+    if (!m_backingStore)
         return;
 
     CGRect dirtyCGRect = NSRectToCGRect(dirtyRect);
-
     NSGraphicsContext *nsGraphicsContext = [NSGraphicsContext currentContext];
     CGContextRef cgContext = (CGContextRef) [nsGraphicsContext graphicsPort];
 
-    CGContextSaveGState( cgContext );
+    // Translate coordiate system from CoreGraphics (bottom-left) to NSView (top-left):
+    CGContextSaveGState(cgContext);
     int dy = dirtyCGRect.origin.y + CGRectGetMaxY(dirtyCGRect);
     CGContextTranslateCTM(cgContext, 0, dy);
     CGContextScaleCTM(cgContext, 1, -1);
 
+    // If a mask is set, modify the sub image accordingly:
     CGImageRef subMask = 0;
     if (m_maskImage) {
         subMask = CGImageCreateWithImageInRect(m_maskImage, dirtyCGRect);
         CGContextClipToMask(cgContext, dirtyCGRect, subMask);
     }
 
-    CGImageRef subImage = CGImageCreateWithImageInRect(m_cgImage, dirtyCGRect);
-    CGContextDrawImage(cgContext,dirtyCGRect,subImage);
-
+    // Clip out and draw the correct sub image from the (shared) backingstore:
+    CGRect backingStoreRect = CGRectMake(
+        dirtyRect.origin.x + m_backingStoreOffset.x(),
+        dirtyRect.origin.y + m_backingStoreOffset.y(),
+        dirtyRect.size.width,
+        dirtyRect.size.height
+    );
+    CGImageRef bsCGImage = m_backingStore->getBackingStoreCGImage();
+    CGImageRef cleanImg = CGImageCreateWithImageInRect(bsCGImage, backingStoreRect);
+    CGContextDrawImage(cgContext, dirtyCGRect, cleanImg);
+
+    // Clean-up:
     CGContextRestoreGState(cgContext);
-
-    CGImageRelease(subImage);
+    CGImageRelease(cleanImg);
     CGImageRelease(subMask);
 }