Workaround Qtbug where QAbstractScrollArea::mouseMoveEvent(...)

is called falsely when quickly double tapping on a touchpad of a notebook running Windows (only for specific Qt Versions)

src/frontends/qt4/GuiWorkArea.cpp

@@ -858,6 +858,10 @@ void GuiWorkArea::mouseReleaseEvent(QMouseEvent * e)
 
 	FuncRequest const cmd(LFUN_MOUSE_RELEASE, e->x(), e->y(),
 			q_button_state(e->button()), q_key_state(e->modifiers()));
+#if (QT_VERSION > QT_VERSION_CHECK(5,10,1) && \
+	QT_VERSION < QT_VERSION_CHECK(5,15,1))
+	d->synthetic_mouse_event_.cmd = cmd; // QtBug QAbstractScrollArea::mouseMoveEvent
+#endif
 	d->dispatch(cmd);
 	e->accept();
 }
@@ -865,6 +869,21 @@ void GuiWorkArea::mouseReleaseEvent(QMouseEvent * e)
 
 void GuiWorkArea::mouseMoveEvent(QMouseEvent * e)
 {
+#if (QT_VERSION > QT_VERSION_CHECK(5,10,1) && \
+	QT_VERSION < QT_VERSION_CHECK(5,15,1))
+	// cancel the event if the coordinates didn't change, this is due to QtBug
+	// QAbstractScrollArea::mouseMoveEvent, the event is triggered falsely when quickly
+	// double tapping a touchpad. To test: try to select a word by quickly double tapping
+	// on a touchpad while hovering the cursor over that word in the work area.
+	// This bug does not occur on Qt versions 5.10.1 and below. Only Windows seems to be affected.
+	// ML thread: https://www.mail-archive.com/lyx-devel@lists.lyx.org/msg211699.html
+	// Qt bugtracker: https://bugreports.qt.io/browse/QTBUG-85431
+	// Bug was fixed in Qt 5.15.1
+	if (e->x() == d->synthetic_mouse_event_.cmd.x() && // QtBug QAbstractScrollArea::mouseMoveEvent
+			e->y() == d->synthetic_mouse_event_.cmd.y()) // QtBug QAbstractScrollArea::mouseMoveEvent
+		return; // QtBug QAbstractScrollArea::mouseMoveEvent
+#endif
+
 	// we kill the triple click if we move
 	doubleClickTimeout();
 	FuncRequest cmd(LFUN_MOUSE_MOTION, e->x(), e->y(),

status.23x

@@ -91,6 +91,8 @@ What's new
 
 - Fix display bug when typing in a paragraph where row heights change (bug 11601).
 
+- Fix wrong marking-text-behavior with doubleclick on notebook touchpads (Windows)
+
 - Fix spacing of limits of sum-like operators in display style.
 
 - Fix positioning of super- and subscripts with integral signs.