From 542ba35f2f0dfd265435f32ee79e498226989e6c Mon Sep 17 00:00:00 2001
From: Laszlo Agocs <laszlo.p.agocs@nokia.com>
Date: Thu, 12 May 2011 16:20:03 +0200
Subject: [PATCH] Fix deadlocks in wayland clipboard that can occur in special
 scenarios.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

setMimeData() emits the changed signal always so to prevent duplicated
signals keyboardFocus() must only emit when the change came from
another wayland client. However direct connection may cause issues
when invoking the slot from a wayland callback, so use a metacall
to make sure we return from the callback. Unnecessary data transfer
and potential deadlock is now also avoided when a client is requesting
the mime data from itself.

Reviewed-by: Jørgen Lind
---
 .../platforms/wayland/qwaylandclipboard.cpp   | 25 ++++++++++++-------
 .../platforms/wayland/qwaylandclipboard.h     |  9 ++++++-
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/plugins/platforms/wayland/qwaylandclipboard.cpp b/src/plugins/platforms/wayland/qwaylandclipboard.cpp
index 47ca22865b1..cf9c5a75916 100644
--- a/src/plugins/platforms/wayland/qwaylandclipboard.cpp
+++ b/src/plugins/platforms/wayland/qwaylandclipboard.cpp
@@ -96,7 +96,6 @@ public:
     QWaylandSelection(QWaylandDisplay *display, QMimeData *data);
     ~QWaylandSelection();
 
-private:
     static uint32_t getTime();
     static void send(void *data, struct wl_selection *selection, const char *mime_type, int fd);
     static void cancelled(void *data, struct wl_selection *selection);
@@ -164,7 +163,7 @@ void QWaylandSelection::cancelled(void *data, struct wl_selection *selection)
 }
 
 QWaylandClipboard::QWaylandClipboard(QWaylandDisplay *display)
-    : mDisplay(display), mSelection(0), mMimeDataIn(0), mOffer(0)
+    : mDisplay(display), mMimeDataIn(0), mOffer(0)
 {
     clipboard = this;
 }
@@ -222,6 +221,8 @@ QVariant QWaylandClipboard::retrieveData(const QString &mimeType, QVariant::Type
 QMimeData *QWaylandClipboard::mimeData(QClipboard::Mode mode)
 {
     Q_ASSERT(mode == QClipboard::Clipboard);
+    if (!mSelections.isEmpty())
+        return mSelections.last()->mMimeData;
     if (!mMimeDataIn)
         mMimeDataIn = new QWaylandMimeData;
     mMimeDataIn->clearAll();
@@ -236,7 +237,7 @@ void QWaylandClipboard::setMimeData(QMimeData *data, QClipboard::Mode mode)
     if (!mDisplay->inputDevices().isEmpty()) {
         if (!data)
             data = new QMimeData;
-        mSelection = new QWaylandSelection(mDisplay, data);
+        mSelections.append(new QWaylandSelection(mDisplay, data));
     } else {
         qWarning("QWaylandClipboard::setMimeData: No input devices");
     }
@@ -266,21 +267,27 @@ void QWaylandClipboard::offer(void *data,
                               struct wl_selection_offer *selection_offer,
                               const char *type)
 {
+    Q_UNUSED(data);
     Q_UNUSED(selection_offer);
-    QWaylandClipboard *self = static_cast<QWaylandClipboard *>(data);
-    self->mOfferedMimeTypes.append(QString::fromLatin1(type));
+    clipboard->mOfferedMimeTypes.append(QString::fromLatin1(type));
 }
 
 void QWaylandClipboard::keyboardFocus(void *data,
                                       struct wl_selection_offer *selection_offer,
                                       wl_input_device *input_device)
 {
-    QWaylandClipboard *self = static_cast<QWaylandClipboard *>(data);
+    Q_UNUSED(data);
     if (!input_device) {
         wl_selection_offer_destroy(selection_offer);
-        self->mOffer = 0;
+        clipboard->mOffer = 0;
         return;
     }
-    self->mOffer = selection_offer;
-    self->emitChanged(QClipboard::Clipboard);
+    clipboard->mOffer = selection_offer;
+    if (clipboard->mSelections.isEmpty())
+        QMetaObject::invokeMethod(&clipboard->mEmitter, "emitChanged", Qt::QueuedConnection);
+}
+
+void QWaylandClipboardSignalEmitter::emitChanged()
+{
+    clipboard->emitChanged(QClipboard::Clipboard);
 }
diff --git a/src/plugins/platforms/wayland/qwaylandclipboard.h b/src/plugins/platforms/wayland/qwaylandclipboard.h
index 6a02254cae9..db436b890a3 100644
--- a/src/plugins/platforms/wayland/qwaylandclipboard.h
+++ b/src/plugins/platforms/wayland/qwaylandclipboard.h
@@ -51,6 +51,13 @@ class QWaylandSelection;
 class QWaylandMimeData;
 struct wl_selection_offer;
 
+class QWaylandClipboardSignalEmitter : public QObject
+{
+    Q_OBJECT
+public slots:
+    void emitChanged();
+};
+
 class QWaylandClipboard : public QPlatformClipboard
 {
 public:
@@ -80,11 +87,11 @@ private:
     static void forceRoundtrip(struct wl_display *display);
 
     QWaylandDisplay *mDisplay;
-    QWaylandSelection *mSelection;
     QWaylandMimeData *mMimeDataIn;
     QList<QWaylandSelection *> mSelections;
     QStringList mOfferedMimeTypes;
     struct wl_selection_offer *mOffer;
+    QWaylandClipboardSignalEmitter mEmitter;
 };
 
 #endif // QWAYLANDCLIPBOARD_H