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, 28 insertions, 70 deletions

diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index e313e2f648..9c589771d0 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -1809,53 +1809,6 @@ bool QXcbWindow::requestSystemTrayWindowDock()
     return true;
 }
 
-class ExposeCompressor
-{
-public:
-    ExposeCompressor(xcb_window_t window, QRegion *region)
-        : m_window(window)
-        , m_region(region)
-        , m_pending(true)
-    {
-    }
-
-    bool checkEvent(xcb_generic_event_t *event)
-    {
-        if (!event)
-            return false;
-        if ((event->response_type & ~0x80) != XCB_EXPOSE)
-            return false;
-        xcb_expose_event_t *expose = (xcb_expose_event_t *)event;
-        if (expose->window != m_window)
-            return false;
-        if (expose->count == 0)
-            m_pending = false;
-        *m_region |= QRect(expose->x, expose->y, expose->width, expose->height);
-        return true;
-    }
-
-    bool pending() const
-    {
-        return m_pending;
-    }
-
-private:
-    xcb_window_t m_window;
-    QRegion *m_region;
-    bool m_pending;
-};
-
-bool QXcbWindow::compressExposeEvent(QRegion &exposeRegion)
-{
-    ExposeCompressor compressor(m_window, &exposeRegion);
-    xcb_generic_event_t *filter = 0;
-    do {
-        filter = connection()->checkEvent(compressor);
-        free(filter);
-    } while (filter);
-    return compressor.pending();
-}
-
 bool QXcbWindow::handleGenericEvent(xcb_generic_event_t *event, long *result)
 {
     return QWindowSystemInterface::handleNativeEvent(window(),
@@ -1867,9 +1820,24 @@ bool QXcbWindow::handleGenericEvent(xcb_generic_event_t *event, long *result)
 void QXcbWindow::handleExposeEvent(const xcb_expose_event_t *event)
 {
     QRect rect(event->x, event->y, event->width, event->height);
-
     m_exposeRegion |= rect;
-    bool pending = compressExposeEvent(m_exposeRegion);
+
+    bool pending = true;
+    xcb_generic_event_t *e = nullptr;
+    do { // compress expose events
+        e = connection()->checkEvent([this, &pending](xcb_generic_event_t *event, int type) {
+            if (type != XCB_EXPOSE)
+                return false;
+            auto expose = reinterpret_cast<xcb_expose_event_t *>(event);
+            if (expose->window != m_window)
+                return false;
+            if (expose->count == 0)
+                pending = false;
+            m_exposeRegion |= QRect(expose->x, expose->y, expose->width, expose->height);
+            return true;
+        });
+        free(e);
+    } while (e);
 
     // if count is non-zero there are more expose events pending
     if (event->count == 0 || !pending) {
@@ -2162,24 +2130,6 @@ static bool ignoreEnterEvent(quint8 mode, quint8 detail, QXcbConnection *conn =
             || detail == XCB_NOTIFY_DETAIL_NONLINEAR_VIRTUAL);
 }
 
-class EnterEventChecker
-{
-public:
-    bool checkEvent(xcb_generic_event_t *event)
-    {
-        if (!event)
-            return false;
-        if ((event->response_type & ~0x80) != XCB_ENTER_NOTIFY)
-            return false;
-
-        xcb_enter_notify_event_t *enter = (xcb_enter_notify_event_t *)event;
-        if (ignoreEnterEvent(enter->mode, enter->detail))
-            return false;
-
-        return true;
-    }
-};
-
 void QXcbWindow::handleEnterNotifyEvent(int event_x, int event_y, int root_x, int root_y,
                                         quint8 mode, quint8 detail, xcb_timestamp_t timestamp)
 {
@@ -2206,9 +2156,17 @@ void QXcbWindow::handleLeaveNotifyEvent(int root_x, int root_y,
     if (ignoreLeaveEvent(mode, detail, connection()) || connection()->mousePressWindow())
         return;
 
-    EnterEventChecker checker;
-    xcb_enter_notify_event_t *enter = (xcb_enter_notify_event_t *)connection()->checkEvent(checker);
-    QXcbWindow *enterWindow = enter ? connection()->platformWindowFromId(enter->event) : 0;
+    // check if enter event is buffered
+    auto event = connection()->checkEvent([](xcb_generic_event_t *event, int type) {
+        if (type != XCB_ENTER_NOTIFY)
+            return false;
+        auto enter = reinterpret_cast<xcb_enter_notify_event_t *>(event);
+        if (ignoreEnterEvent(enter->mode, enter->detail))
+            return false;
+        return true;
+    });
+    auto enter = reinterpret_cast<xcb_enter_notify_event_t *>(event);
+    QXcbWindow *enterWindow = enter ? connection()->platformWindowFromId(enter->event) : nullptr;
 
     if (enterWindow) {
         QPoint local(enter->event_x, enter->event_y);