From ab2cf73440e5fbda9e2a3ba15dc1df7895c49679 Mon Sep 17 00:00:00 2001
From: Alberto Mardegan <mardy@users.sourceforge.net>
Date: Wed, 13 Apr 2016 16:28:57 +0300
Subject: [PATCH] QXcbDrag: forward mouse release event to initiator window
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The mouse release event which ends the drag and drop operation must be
forwarded to the window where the drag started, and not to the
QShapedPixmapWindow, which is not supposed to handle input events.

Task-number: QTBUG-52541
Change-Id: I24a7c7b331a06342ac28b420ff9467aa05fe00dd
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Błażej Szczygieł <spaz16@wp.pl>
Reviewed-by: Dmitry Shachnev <mitya57@gmail.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>
---
 src/plugins/platforms/xcb/qxcbdrag.cpp | 14 ++++++++++++++
 src/plugins/platforms/xcb/qxcbdrag.h   |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/src/plugins/platforms/xcb/qxcbdrag.cpp b/src/plugins/platforms/xcb/qxcbdrag.cpp
index 529f91e1ec0..6fa5dfa4831 100644
--- a/src/plugins/platforms/xcb/qxcbdrag.cpp
+++ b/src/plugins/platforms/xcb/qxcbdrag.cpp
@@ -50,6 +50,7 @@
 
 #include <qpa/qwindowsysteminterface.h>
 
+#include <private/qguiapplication_p.h>
 #include <private/qshapedpixmapdndwindow_p.h>
 #include <private/qsimpledrag_p.h>
 #include <private/qhighdpiscaling_p.h>
@@ -170,6 +171,17 @@ QMimeData *QXcbDrag::platformDropData()
     return dropData;
 }
 
+bool QXcbDrag::eventFilter(QObject *o, QEvent *e)
+{
+    /* We are setting a mouse grab on the QShapedPixmapWindow in order not to
+     * lose the grab when the virtual desktop changes, but
+     * QBasicDrag::eventFilter() expects the events to be coming from the
+     * window where the drag was started. */
+    if (initiatorWindow && o == shapedPixmapWindow())
+        o = initiatorWindow.data();
+    return QBasicDrag::eventFilter(o, e);
+}
+
 void QXcbDrag::startDrag()
 {
     // #fixme enableEventFilter();
@@ -194,6 +206,7 @@ void QXcbDrag::startDrag()
 
     setUseCompositing(current_virtual_desktop->compositingActive());
     setScreen(current_virtual_desktop->screens().constFirst()->screen());
+    initiatorWindow = QGuiApplicationPrivate::currentMouseWindow;
     QBasicDrag::startDrag();
     if (connection()->mouseGrabber() == Q_NULLPTR)
         shapedPixmapWindow()->setMouseGrabEnabled(true);
@@ -202,6 +215,7 @@ void QXcbDrag::startDrag()
 void QXcbDrag::endDrag()
 {
     QBasicDrag::endDrag();
+    initiatorWindow.clear();
 }
 
 static xcb_translate_coordinates_reply_t *
diff --git a/src/plugins/platforms/xcb/qxcbdrag.h b/src/plugins/platforms/xcb/qxcbdrag.h
index c9d257906fa..738da1268d9 100644
--- a/src/plugins/platforms/xcb/qxcbdrag.h
+++ b/src/plugins/platforms/xcb/qxcbdrag.h
@@ -69,6 +69,7 @@ public:
     ~QXcbDrag();
 
     virtual QMimeData *platformDropData() Q_DECL_OVERRIDE;
+    bool eventFilter(QObject *o, QEvent *e) Q_DECL_OVERRIDE;
 
     void startDrag() Q_DECL_OVERRIDE;
     void cancel() Q_DECL_OVERRIDE;
@@ -106,6 +107,7 @@ private:
     Qt::DropAction toDropAction(xcb_atom_t atom) const;
     xcb_atom_t toXdndAction(Qt::DropAction a) const;
 
+    QPointer<QWindow> initiatorWindow;
     QPointer<QWindow> currentWindow;
     QPoint currentPosition;
 
-- 
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