xcb: add a timeout control when reading INCR property

For the first call of QXcbClipboard::clipboardReadProperty()
inside of clipboardReadIncrementalProperty() in getSelection(),
it will get a XCB_NONE reply before the contents arrived via
property change. Then we give a chance to read more.

Manually tested with following setups:
* examples/widgets/mainwindows/application with gvim(gtk3)
* examples/widgets/widgets/imageviewer with GIMP 2.10.18(based on
gtk2) and GIMP 2.99.6(based on gtk3 via flatpak)

Fixes: QTBUG-56595
Done-With: JiDe Zhang <zhangjide@uniontech.com>
Change-Id: Ib45f08464d39ad79137b1da99808c89b7dca2d08
Reviewed-by: JiDe Zhang <zhangjide@uniontech.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
(cherry picked from commit 02248eea5562c1df39ee23f195011afacc6759b0)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/plugins/platforms/xcb/qxcbclipboard.cpp b/src/plugins/platforms/xcb/qxcbclipboard.cpp
index 725c0e4d51..a4940f1c49 100644
--- a/src/plugins/platforms/xcb/qxcbclipboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbclipboard.cpp
@@ -841,6 +841,8 @@ QByteArray QXcbClipboard::clipboardReadIncrementalProperty(xcb_window_t win, xcb
         alloc_error = buf.size() != nbytes+1;
     }
 
+    QElapsedTimer timer;
+    timer.start();
     for (;;) {
         connection()->flush();
         xcb_generic_event_t *ge = waitForClipboardEvent(win, XCB_PROPERTY_NOTIFY);
@@ -876,9 +878,11 @@ QByteArray QXcbClipboard::clipboardReadIncrementalProperty(xcb_window_t win, xcb
                 tmp_buf.resize(0);
                 offset += length;
             }
-        } else {
-            break;
         }
+
+        const auto elapsed = timer.elapsed();
+        if (elapsed > clipboard_timeout)
+            break;
     }
 
     // timed out ... create a new requestor window, otherwise the requestor