QGuiApplication: Fix condition for when doubleclick events are triggered

QGuiApplicationPrivate::processMouseEvent() requires the following
conditions to be met in order to trigger a double click event:
1. The same button should be pressed (kept in mousePressButton member)
2. The time between two press events should not exceed doubleClickInterval
3. Movement between presses shouldn't be bigger than doubleClickDistance

Unfortunately, when we are processing *synthesized* mouse events (from
touch), in order to check criterion 2) we cannot rely on
QPointingDevicePrivate::pointById(0)->eventPoint.pressTimestamp();
because this was already updated in QGuiApplication::processTouchEvent(),
so it does not any longer reflect the *previous* press timestamp, but
the current one.
Therefore we could not reliably calculate the time between the previous
press and the current press (in fact, it never exceeded the
doubleClickInterval condition)

I suspect this occurs with all touchscreens, but at least it was
reproduced with e.g. a NVIDIA Terra / Thinkvision touch screen on
Windows 11 and Dell Express SVC touch screen on Windows 11.

=> Since QGuiApplication is a singleton, add a static local variable to
remember the time stamp of the last processed press event.

Autotesting has been modelled in PS7. However, QTest::touchEvent is
unable to synthesize hardware specific detection latency and stray
touch events, which actually reproduce the issue.
=> Not adding an autotest.

Fixes: QTBUG-112479
Fixes: QTBUG-119032
Fixes: QTBUG-100688
Pick-to: 6.6 6.5
Change-Id: Idc97fb9d49ed334f56d702d420451fc062e9b5a9
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index abce792ad3..86715dcf9f 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -2256,12 +2256,14 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
             qAbs(globalPoint.y() - pressPos.y()) > doubleClickDistance)
             mousePressButton = Qt::NoButton;
     } else {
+        static unsigned long lastPressTimestamp = 0;
         mouse_buttons = e->buttons;
         if (mousePress) {
             ulong doubleClickInterval = static_cast<ulong>(QGuiApplication::styleHints()->mouseDoubleClickInterval());
-            doubleClick = e->timestamp - persistentEPD->eventPoint.pressTimestamp()
+            doubleClick = e->timestamp - lastPressTimestamp
                         < doubleClickInterval && button == mousePressButton;
             mousePressButton = button;
+            lastPressTimestamp = e ->timestamp;
         }
     }