Check for the clipboard manager when looping due to app quiting

One can be extremely unlucky and on session logout get this:
 * All apps are going down
 * A Qt app checks if the clipboard manager is there to yield its clipboard contents
 * The clipboard manager is still there
 * Then just after that check, the clipboard manager finishes because of the session end
 * This means the Qt app will loop for 5 seconds trying to yield its clipboard contents
   to a clipboard manager that is not there anymore
This is a backport of 689c4009fb9be348f9137a9092b068e056a3d8b3 in the qtbase (Qt 5.0) repo

Change-Id: I8ab1f460aa5936c03f1afc1b6ff18824f1d6cbc1
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

2 files changed, 9 insertions, 3 deletions

diff --git a/src/gui/kernel/qclipboard_x11.cpp b/src/gui/kernel/qclipboard_x11.cpp
index 7990f5d..803b1ba 100644
--- a/src/gui/kernel/qclipboard_x11.cpp
+++ b/src/gui/kernel/qclipboard_x11.cpp
@@ -515,7 +515,7 @@ static Bool checkForClipboardEvents(Display *, XEvent *e, XPointer)
                                               || e->xselectionclear.selection == ATOM(CLIPBOARD))));
 }
 
-bool QX11Data::clipboardWaitForEvent(Window win, int type, XEvent *event, int timeout)
+bool QX11Data::clipboardWaitForEvent(Window win, int type, XEvent *event, int timeout, bool checkManager)
 {
     QElapsedTimer started;
     started.start();
@@ -544,6 +544,9 @@ bool QX11Data::clipboardWaitForEvent(Window win, int type, XEvent *event, int ti
                 return true;
             }
 
+            if (checkManager && XGetSelectionOwner(X11->display, ATOM(CLIPBOARD_MANAGER)) == XNone)
+                return false;
+
             XSync(X11->display, false);
             usleep(50000);
 
@@ -571,6 +574,9 @@ bool QX11Data::clipboardWaitForEvent(Window win, int type, XEvent *event, int ti
             if (XCheckTypedWindowEvent(X11->display,win,type,event))
                 return true;
 
+            if (checkManager && XGetSelectionOwner(X11->display, ATOM(CLIPBOARD_MANAGER)) == XNone)
+                return false;
+
             // process other clipboard events, since someone is probably requesting data from us
             XEvent e;
             if (XCheckIfEvent(X11->display, &e, checkForClipboardEvents, 0))
@@ -933,7 +939,7 @@ bool QClipboard::event(QEvent *e)
 
         XEvent event;
         // waiting until the clipboard manager fetches the content.
-        if (!X11->clipboardWaitForEvent(ownerId, SelectionNotify, &event, 10000)) {
+        if (!X11->clipboardWaitForEvent(ownerId, SelectionNotify, &event, 10000, true)) {
             qWarning("QClipboard: Unable to receive an event from the "
                      "clipboard manager in a reasonable time");
         }
diff --git a/src/gui/kernel/qt_x11_p.h b/src/gui/kernel/qt_x11_p.h
index bdca019..ed7c146 100644
--- a/src/gui/kernel/qt_x11_p.h
+++ b/src/gui/kernel/qt_x11_p.h
@@ -350,7 +350,7 @@ struct QX11Data
     Window findClientWindow(Window, Atom, bool);
 
     // from qclipboard_x11.cpp
-    bool clipboardWaitForEvent(Window win, int type, XEvent *event, int timeout);
+    bool clipboardWaitForEvent(Window win, int type, XEvent *event, int timeout, bool checkManager = false);
     bool clipboardReadProperty(Window win, Atom property, bool deleteProperty,
                             QByteArray *buffer, int *size, Atom *type, int *format);
     QByteArray clipboardReadIncrementalProperty(Window win, Atom property, int nbytes, bool nullterm);