xcb: rewrite auto-repeat key detection logic

It's unclear what the original code was doing. It relied on 'm_release'
which could never be 'false' (ref. QTBUG-69679). It was subtracting event
times and comparing with arbitrary '10'. On X11 auto-repeat keys can be
detected by checking time and keycode of the current release event and
the next event in the queue. If an event is an auto-repeat, then next event
in the queue will be a key press with matching time and keycode.

Verified that auto-repeat was unreliable in Qt 4 as well. With this patch
auto-repeat works as expected.

Added support for Xlib's XPeekEvent in our XCB implementation QXcbConnection::checkEvent():

"The XPeekEvent() function returns the first event from the event queue,
but it does not remove the event from the queue."

Sneaking in one variable renaming: "string" -> "text", to match the QKeyEvent::text().

Task-number: QTBUG-57335
Task-number: QTBUG-69679
Change-Id: I0a23f138287f57eaaecf1a009bd939e7e0e23269
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.h b/src/plugins/platforms/xcb/qxcbkeyboard.h
index ab926eab84..95915fb2e6 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.h
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.h
@@ -109,7 +109,8 @@ protected:
 
 private:
     bool m_config = false;
-    xcb_keycode_t m_autorepeat_code = 0;
+    bool m_isAutoRepeat = false;
+    xcb_keycode_t m_autoRepeatCode = 0;
 
     struct _mod_masks {
         uint alt;