macOS: Implement QCocoaBackingStore in terms of QRasterBackingStore

The previous detection of device pixel ratio changes in paintDevice()
is not needed, as QBackingStore::beginPaint() already does this check
and calls resize().

Change-Id: I9ee8410fa3a5404c5ec19d2cba4543a9e3359fe9
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

3 files changed, 18 insertions, 79 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.h b/src/plugins/platforms/cocoa/qcocoabackingstore.h
index 52a3e756b9..562be2be8f 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.h
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.h
@@ -40,33 +40,20 @@
 #ifndef QBACKINGSTORE_COCOA_H
 #define QBACKINGSTORE_COCOA_H
 
-#include <AppKit/AppKit.h>
-
-#include "qcocoawindow.h"
-#include "qnsview.h"
-
-#include <qpa/qplatformbackingstore.h>
+#include <QtPlatformSupport/private/qrasterbackingstore_p.h>
 
 QT_BEGIN_NAMESPACE
 
-class QCocoaBackingStore : public QPlatformBackingStore
+class QCocoaBackingStore : public QRasterBackingStore
 {
 public:
     QCocoaBackingStore(QWindow *window);
     ~QCocoaBackingStore();
 
-    QPaintDevice *paintDevice() Q_DECL_OVERRIDE;
-    void flush(QWindow *widget, const QRegion &region, const QPoint &offset) Q_DECL_OVERRIDE;
-    QImage toImage() const Q_DECL_OVERRIDE;
-
-    void resize (const QSize &size, const QRegion &) Q_DECL_OVERRIDE;
-    bool scroll(const QRegion &area, int dx, int dy) Q_DECL_OVERRIDE;
-    void beginPaint(const QRegion &region) Q_DECL_OVERRIDE;
-    qreal getBackingStoreDevicePixelRatio();
+    void flush(QWindow *, const QRegion &, const QPoint &) Q_DECL_OVERRIDE;
 
 private:
-    QImage m_qImage;
-    QSize m_requestedSize;
+    QImage::Format format() const Q_DECL_OVERRIDE;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.mm b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
index 20233518b3..af5418315c 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.mm
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
@@ -38,13 +38,13 @@
 ****************************************************************************/
 
 #include "qcocoabackingstore.h"
-#include <QtGui/QPainter>
-#include "qcocoahelpers.h"
+
+#include "qcocoawindow.h"
 
 QT_BEGIN_NAMESPACE
 
 QCocoaBackingStore::QCocoaBackingStore(QWindow *window)
-    : QPlatformBackingStore(window)
+    : QRasterBackingStore(window)
 {
 }
 
@@ -54,69 +54,21 @@ QCocoaBackingStore::~QCocoaBackingStore()
         [cocoaWindow->m_qtView clearBackingStore:this];
 }
 
-QPaintDevice *QCocoaBackingStore::paintDevice()
-{
-    QCocoaWindow *cocoaWindow = static_cast<QCocoaWindow *>(window()->handle());
-    int windowDevicePixelRatio = int(cocoaWindow->devicePixelRatio());
-
-    // Receate the backing store buffer if the effective buffer size has changed,
-    // either due to a window resize or devicePixelRatio change.
-    QSize effectiveBufferSize = m_requestedSize * windowDevicePixelRatio;
-    if (m_qImage.size() != effectiveBufferSize) {
-        QImage::Format format = (window()->format().hasAlpha() || cocoaWindow->m_drawContentBorderGradient)
-                ? QImage::Format_ARGB32_Premultiplied : QImage::Format_RGB32;
-        m_qImage = QImage(effectiveBufferSize, format);
-        m_qImage.setDevicePixelRatio(windowDevicePixelRatio);
-        if (format == QImage::Format_ARGB32_Premultiplied)
-            m_qImage.fill(Qt::transparent);
-    }
-    return &m_qImage;
-}
-
-void QCocoaBackingStore::flush(QWindow *win, const QRegion &region, const QPoint &offset)
+QImage::Format QCocoaBackingStore::format() const
 {
-    if (!m_qImage.isNull()) {
-        if (QCocoaWindow *cocoaWindow = static_cast<QCocoaWindow *>(win->handle()))
-            [cocoaWindow->m_qtView flushBackingStore:this region:region offset:offset];
-    }
-}
+    if (static_cast<QCocoaWindow *>(window()->handle())->m_drawContentBorderGradient)
+        return QImage::Format_ARGB32_Premultiplied;
 
-QImage QCocoaBackingStore::toImage() const
-{
-    return m_qImage;
+    return QRasterBackingStore::format();
 }
 
-void QCocoaBackingStore::resize(const QSize &size, const QRegion &)
+void QCocoaBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
 {
-    m_requestedSize = size;
-}
+    if (m_image.isNull())
+        return;
 
-bool QCocoaBackingStore::scroll(const QRegion &area, int dx, int dy)
-{
-    extern void qt_scrollRectInImage(QImage &img, const QRect &rect, const QPoint &offset);
-    const qreal devicePixelRatio = m_qImage.devicePixelRatio();
-    QPoint qpoint(dx * devicePixelRatio, dy * devicePixelRatio);
-    for (const QRect &rect : area) {
-        const QRect qrect(rect.topLeft() * devicePixelRatio, rect.size() * devicePixelRatio);
-        qt_scrollRectInImage(m_qImage, qrect, qpoint);
-    }
-    return true;
-}
-
-void QCocoaBackingStore::beginPaint(const QRegion &region)
-{
-    if (m_qImage.hasAlphaChannel()) {
-        QPainter p(&m_qImage);
-        p.setCompositionMode(QPainter::CompositionMode_Source);
-        const QColor blank = Qt::transparent;
-        for (const QRect &rect : region)
-            p.fillRect(rect, blank);
-    }
-}
-
-qreal QCocoaBackingStore::getBackingStoreDevicePixelRatio()
-{
-    return m_qImage.devicePixelRatio();
+    if (QCocoaWindow *cocoaWindow = static_cast<QCocoaWindow *>(window->handle()))
+        [cocoaWindow->m_qtView flushBackingStore:this region:region offset:offset];
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index 3d30aca7e7..22a32c7ceb 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -495,7 +495,7 @@ static bool _q_dontOverrideCtrlLMB = false;
     qCDebug(lcQpaCocoaWindow) << "[QNSView flushBackingStore:]" << m_window << region.rectCount() << region.boundingRect() << offset;
 
     m_backingStore = backingStore;
-    m_backingStoreOffset = offset * m_backingStore->getBackingStoreDevicePixelRatio();
+    m_backingStoreOffset = offset * m_backingStore->paintDevice()->devicePixelRatio();
     for (const QRect &rect : region)
         [self setNeedsDisplayInRect:NSMakeRect(rect.x(), rect.y(), rect.width(), rect.height())];
 }
@@ -577,7 +577,7 @@ static bool _q_dontOverrideCtrlLMB = false;
 
     // The backing store source rect will be larger on retina displays.
     // Scale dirtyRect by the device pixel ratio:
-    const qreal devicePixelRatio = m_backingStore->getBackingStoreDevicePixelRatio();
+    const qreal devicePixelRatio = m_backingStore->paintDevice()->devicePixelRatio();
     CGRect dirtyBackingRect = CGRectMake(dirtyRect.origin.x * devicePixelRatio,
                                          dirtyRect.origin.y * devicePixelRatio,
                                          dirtyRect.size.width * devicePixelRatio,