xcb: Use XShape for DnD when a compositing manager is not running

Otherwise transparent areas of the drag'n'drop pixmap are painted
with the black color.

Task-number: QTBUG-45193
Change-Id: I55b7c7caababe13584fa1c7a52835f112e20f920
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

4 files changed, 19 insertions, 3 deletions

diff --git a/src/gui/kernel/qshapedpixmapdndwindow.cpp b/src/gui/kernel/qshapedpixmapdndwindow.cpp
index 5736c41e25..d77b6dc262 100644
--- a/src/gui/kernel/qshapedpixmapdndwindow.cpp
+++ b/src/gui/kernel/qshapedpixmapdndwindow.cpp
@@ -35,12 +35,16 @@
 
 #include <QtGui/QPainter>
 #include <QtGui/QCursor>
+#include <QtGui/QGuiApplication>
+#include <QtGui/QPalette>
+#include <QtGui/QBitmap>
 
 QT_BEGIN_NAMESPACE
 
 QShapedPixmapWindow::QShapedPixmapWindow(QScreen *screen)
     : QWindow(screen),
-      m_backingStore(0)
+      m_backingStore(0),
+      m_useCompositing(true)
 {
     QSurfaceFormat format;
     format.setAlphaBufferSize(8);
@@ -68,7 +72,10 @@ void QShapedPixmapWindow::render()
 
     {
         QPainter p(device);
-        p.setCompositionMode(QPainter::CompositionMode_Source);
+        if (m_useCompositing)
+            p.setCompositionMode(QPainter::CompositionMode_Source);
+        else
+            p.fillRect(rect, QGuiApplication::palette().base());
         p.drawPixmap(0, 0, m_pixmap);
     }
 
@@ -79,6 +86,8 @@ void QShapedPixmapWindow::render()
 void QShapedPixmapWindow::setPixmap(const QPixmap &pixmap)
 {
     m_pixmap = pixmap;
+    if (!m_useCompositing)
+        setMask(m_pixmap.mask());
 }
 
 void QShapedPixmapWindow::setHotspot(const QPoint &hotspot)
diff --git a/src/gui/kernel/qshapedpixmapdndwindow_p.h b/src/gui/kernel/qshapedpixmapdndwindow_p.h
index 7536c09165..3d7974fa82 100644
--- a/src/gui/kernel/qshapedpixmapdndwindow_p.h
+++ b/src/gui/kernel/qshapedpixmapdndwindow_p.h
@@ -60,6 +60,7 @@ public:
 
     void render();
 
+    void setUseCompositing(bool on) { m_useCompositing = on; }
     void setPixmap(const QPixmap &pixmap);
     void setHotspot(const QPoint &hotspot);
 
@@ -72,6 +73,7 @@ private:
     QBackingStore *m_backingStore;
     QPixmap m_pixmap;
     QPoint m_hotSpot;
+    bool m_useCompositing;
 };
 
 QT_END_NAMESPACE
diff --git a/src/gui/kernel/qsimpledrag.cpp b/src/gui/kernel/qsimpledrag.cpp
index 6acac4cade..9f38c9b78a 100644
--- a/src/gui/kernel/qsimpledrag.cpp
+++ b/src/gui/kernel/qsimpledrag.cpp
@@ -88,7 +88,7 @@ static QWindow* topLevelAt(const QPoint &pos)
 QBasicDrag::QBasicDrag() :
     m_restoreCursor(false), m_eventLoop(0),
     m_executed_drop_action(Qt::IgnoreAction), m_can_drop(false),
-    m_drag(0), m_drag_icon_window(0)
+    m_drag(0), m_drag_icon_window(0), m_useCompositing(true)
 {
 }
 
@@ -226,6 +226,7 @@ void QBasicDrag::recreateShapedPixmapWindow(QScreen *screen, const QPoint &pos)
     // when QDrag is used without a pixmap - QDrag::setPixmap()
     m_drag_icon_window = new QShapedPixmapWindow(screen);
 
+    m_drag_icon_window->setUseCompositing(m_useCompositing);
     m_drag_icon_window->setPixmap(m_drag->pixmap());
     m_drag_icon_window->setHotspot(m_drag->hotSpot());
     m_drag_icon_window->updateGeometry(pos);
diff --git a/src/gui/kernel/qsimpledrag_p.h b/src/gui/kernel/qsimpledrag_p.h
index 4c9edbae05..055136c436 100644
--- a/src/gui/kernel/qsimpledrag_p.h
+++ b/src/gui/kernel/qsimpledrag_p.h
@@ -87,6 +87,9 @@ protected:
     bool canDrop() const { return m_can_drop; }
     void setCanDrop(bool c) { m_can_drop = c; }
 
+    bool useCompositing() const { return m_useCompositing; }
+    void setUseCompositing(bool on) { m_useCompositing = on; }
+
     Qt::DropAction executedDropAction() const { return m_executed_drop_action; }
     void  setExecutedDropAction(Qt::DropAction da) { m_executed_drop_action = da; }
 
@@ -104,6 +107,7 @@ private:
     bool m_can_drop;
     QDrag *m_drag;
     QShapedPixmapWindow *m_drag_icon_window;
+    bool m_useCompositing;
 };
 
 class Q_GUI_EXPORT QSimpleDrag : public QBasicDrag