xcb: Use functors in QXcbConnection::checkEvent()

... to check for buffered events. This makes the code less verbose and
easier to read. Changed the filter signature to pass an event type in addition
to the actual event, for the convenience of API user. And do not pass worthless
nullptr-s to the filter.

The only reason why KeyChecker from qxcbkeyboard.cpp was not converted
to lambda expression is that the code looks suspicious - KeyChecker::m_release
default value is 'true' and I don't see where it would ever be assigned
'false' (ref. QTBUG-69679) and the code is known to be buggy (ref. QTBUG-57335).
Those issues are out-of-scope for this patch.

Change-Id: If2fdd60fbb93eb983f3c9ad616aaf04834fede9f
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Mikhail Svetkin <mikhail.svetkin@qt.io>

1 files changed, 12 insertions, 31 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index c14f3f3703..1a5d9d1667 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -1484,54 +1484,35 @@ void QXcbConnection::sendConnectionEvent(QXcbAtom::Atom a, uint id)
     xcb_flush(xcb_connection());
 }
 
-namespace
-{
-    class PropertyNotifyEvent {
-    public:
-        PropertyNotifyEvent(xcb_window_t win, xcb_atom_t property)
-            : window(win), type(XCB_PROPERTY_NOTIFY), atom(property) {}
-        xcb_window_t window;
-        int type;
-        xcb_atom_t atom;
-        bool checkEvent(xcb_generic_event_t *event) const {
-            if (!event)
-                return false;
-            if ((event->response_type & ~0x80) != type) {
-                return false;
-            } else {
-                xcb_property_notify_event_t *pn = reinterpret_cast<xcb_property_notify_event_t *>(event);
-                if ((pn->window == window) && (pn->atom == atom))
-                    return true;
-            }
-            return false;
-        }
-    };
-}
-
 xcb_timestamp_t QXcbConnection::getTimestamp()
 {
     // send a dummy event to myself to get the timestamp from X server.
-    xcb_window_t root_win = rootWindow();
-    xcb_change_property(xcb_connection(), XCB_PROP_MODE_APPEND, root_win, atom(QXcbAtom::CLIP_TEMPORARY),
-                        XCB_ATOM_INTEGER, 32, 0, NULL);
+    xcb_window_t window = rootWindow();
+    xcb_atom_t dummyAtom = atom(QXcbAtom::CLIP_TEMPORARY);
+    xcb_change_property(xcb_connection(), XCB_PROP_MODE_APPEND, window, dummyAtom,
+                        XCB_ATOM_INTEGER, 32, 0, nullptr);
 
     connection()->flush();
-    PropertyNotifyEvent checker(root_win, atom(QXcbAtom::CLIP_TEMPORARY));
 
-    xcb_generic_event_t *event = 0;
+    xcb_generic_event_t *event = nullptr;
     // lets keep this inside a loop to avoid a possible race condition, where
     // reader thread has not yet had the time to acquire the mutex in order
     // to add the new set of events to its event queue
     while (!event) {
         connection()->sync();
-        event = checkEvent(checker);
+        event = checkEvent([window, dummyAtom](xcb_generic_event_t *event, int type) {
+            if (type != XCB_PROPERTY_NOTIFY)
+                return false;
+            auto propertyNotify = reinterpret_cast<xcb_property_notify_event_t *>(event);
+            return propertyNotify->window == window && propertyNotify->atom == dummyAtom;
+        });
     }
 
     xcb_property_notify_event_t *pn = reinterpret_cast<xcb_property_notify_event_t *>(event);
     xcb_timestamp_t timestamp = pn->time;
     free(event);
 
-    xcb_delete_property(xcb_connection(), root_win, atom(QXcbAtom::CLIP_TEMPORARY));
+    xcb_delete_property(xcb_connection(), window, dummyAtom);
 
     return timestamp;
 }