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QGuiApplicationPrivate::processTouchEvent: add explanatory comments 

It was very confusing to debug a problem involving detached touchpoints
and not very clear how startPos is stored in activeTouchPoints.

Change-Id: I5c04fb6b5647493a731774e0a1765404cbc8c7d6
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>
bb10
Shawn Rutledge 2016-12-06 14:34:03 +01:00
parent 964d9e8f8a
commit 92672198ed
1 changed files with 8 additions and 2 deletions
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10
src/gui/kernel/qguiapplication.cpp
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@ -2564,6 +2564,9 @@ void QGuiApplicationPrivate::processTouchEvent(QWindowSystemInterfacePrivate::To
Q_ASSERT(w.data() != 0);
// make the *scene* functions return the same as the *screen* functions
// Note: touchPoint is a reference to the one from activeTouchPoints,
// so we can modify it as long as we're careful NOT to call setters and
// otherwise NOT to cause the d-pointer to be detached.
touchPoint.d->scenePos = touchPoint.screenPos();
touchPoint.d->verticalDiameter = touchPoint.screenRect().height();
touchPoint.d->horizontalDiameter = touchPoint.screenRect().width();
@ -2622,8 +2625,8 @@ void QGuiApplicationPrivate::processTouchEvent(QWindowSystemInterfacePrivate::To
QTouchEvent touchEvent(eventType,
e->device,
e->modifiers,
it.value().first,
it.value().second);
it.value().first, // state flags
it.value().second); // list of touchpoints
touchEvent.setTimestamp(e->timestamp);
touchEvent.setWindow(w);
@ -2640,6 +2643,9 @@ void QGuiApplicationPrivate::processTouchEvent(QWindowSystemInterfacePrivate::To
touchPoint.d->verticalDiameter = rect.height();
touchPoint.d->horizontalDiameter = rect.width();
if (touchPoint.state() == Qt::TouchPointPressed) {
// touchPoint is actually a reference to one that is stored in activeTouchPoints,
// and we are now going to store the startPos and lastPos there, for the benefit
// of future moves and releases. It's important that the d-pointer is NOT detached.
touchPoint.d->startPos = w->mapFromGlobal(touchPoint.startScreenPos().toPoint()) + delta;
touchPoint.d->lastPos = w->mapFromGlobal(touchPoint.lastScreenPos().toPoint()) + delta;
}