Windows: Refactor QWindowsDragCursorWindow().

QWindowsDragCursorWindow is a helper window used to display the drag
cursor when doing DnD by touch, in which case Windows hides the mouse
cursor. Base it on QRasterWindow and fix the size calculation for
device pixel ratio scaling.

Task-number: QTBUG-38858
Task-number: QTBUG-38993
Change-Id: I462ece3e5c8fe8be914e039ba391a28a77e0d771
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

1 files changed, 13 insertions, 29 deletions

diff --git a/src/plugins/platforms/windows/qwindowsdrag.cpp b/src/plugins/platforms/windows/qwindowsdrag.cpp
index 861ddbe5b6..716d892472 100644
--- a/src/plugins/platforms/windows/qwindowsdrag.cpp
+++ b/src/plugins/platforms/windows/qwindowsdrag.cpp
@@ -54,9 +54,7 @@
 #include <QtGui/QMouseEvent>
 #include <QtGui/QPixmap>
 #include <QtGui/QPainter>
-#include <QtGui/QPaintDevice>
-#include <QtGui/QBackingStore>
-#include <QtGui/QWindow>
+#include <QtGui/QRasterWindow>
 #include <QtGui/QGuiApplication>
 #include <qpa/qwindowsysteminterface_p.h>
 #include <QtGui/private/qguiapplication_p.h>
@@ -78,7 +76,7 @@ QT_BEGIN_NAMESPACE
     \ingroup qt-lighthouse-win
 */
 
-class QWindowsDragCursorWindow : public QWindow
+class QWindowsDragCursorWindow : public QRasterWindow
 {
 public:
     explicit QWindowsDragCursorWindow(QWindow *parent = 0);
@@ -86,18 +84,18 @@ public:
     void setPixmap(const QPixmap &p);
 
 protected:
-    void exposeEvent(QExposeEvent *);
+    void paintEvent(QPaintEvent *)
+    {
+        QPainter painter(this);
+        painter.drawPixmap(0, 0, m_pixmap);
+    }
 
 private:
-    void render();
-
-    QBackingStore m_backingStore;
     QPixmap m_pixmap;
 };
 
 QWindowsDragCursorWindow::QWindowsDragCursorWindow(QWindow *parent)
-    : QWindow(parent)
-    , m_backingStore(this)
+    : QRasterWindow(parent)
 {
     QSurfaceFormat windowFormat = format();
     windowFormat.setAlphaBufferSize(8);
@@ -113,31 +111,17 @@ void QWindowsDragCursorWindow::setPixmap(const QPixmap &p)
     if (p.cacheKey() == m_pixmap.cacheKey())
         return;
     const QSize oldSize = m_pixmap.size();
-    const QSize newSize = p.size();
+    QSize newSize = p.size();
     qCDebug(lcQpaMime) << __FUNCTION__ << p.cacheKey() << newSize;
     m_pixmap = p;
     if (oldSize != newSize) {
+        const qreal pixDevicePixelRatio = p.devicePixelRatio();
+        if (pixDevicePixelRatio > 1.0 && qFuzzyCompare(pixDevicePixelRatio, devicePixelRatio()))
+            newSize /= qRound(pixDevicePixelRatio);
         resize(newSize);
-        m_backingStore.resize(newSize);
     }
     if (isVisible())
-        render();
-}
-
-void QWindowsDragCursorWindow::exposeEvent(QExposeEvent *)
-{
-    Q_ASSERT(!m_pixmap.isNull());
-    render();
-}
-
-void QWindowsDragCursorWindow::render()
-{
-    const QRect rect(QPoint(0, 0), m_pixmap.size());
-    m_backingStore.beginPaint(rect);
-    QPainter painter(m_backingStore.paintDevice());
-    painter.drawPixmap(0, 0, m_pixmap);
-    m_backingStore.endPaint();
-    m_backingStore.flush(rect);
+        update();
 }
 
 /*!