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From e203a185cfab199a89a33b903096d6d0023a8a88 Mon Sep 17 00:00:00 2001
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From: Shawn Rutledge <shawn.rutledge@qt.io>
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Date: Wed, 30 Sep 2020 13:51:59 +0200
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Subject: [PATCH 24/28] doc: explain QQItem event delivery, handlers,
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setAcceptTouchEvents()
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We quietly recommended calling setAcceptTouchEvents() in the Qt 5.10
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release notes in any Item subclass that wants to receive touch events,
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and in the docs for setAcceptTouchEvents() itself; but the message about
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the impending behavior change might not have been obvious enough.
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In Qt 6 it becomes mandatory, so clearer docs will hopefully help to
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stave off bogus bug reports.
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We also never had a great overview of event handling from an Item's
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perspective; now it's a little better.
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Followup to ab91e7fa02a562d80fd0747f28a60e00c3b45a01 and
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a97759a336c597327cb82eebc9f45c793aec32c9
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[ChangeLog][QtQuick][QQuickItem] When subclassing QQuickItem, you
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should call setAcceptTouchEvents(true) if you need the item to receive
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touch events. It will be required in Qt 6.
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Task-number: QTBUG-87018
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Task-number: QTBUG-87082
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Change-Id: I1c7a43979e3665778d61949c9d37c1d085ed594b
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Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
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(cherry picked from commit 7c648280bb53c4276ba4ae2abf26d070fedde71a)
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Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
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---
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src/quick/items/qquickitem.cpp | 34 +++++++++++++++++++++++++++++-----
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1 file changed, 29 insertions(+), 5 deletions(-)
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diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
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index ddd67522b9..e02df00595 100644
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--- a/src/quick/items/qquickitem.cpp
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+++ b/src/quick/items/qquickitem.cpp
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@@ -1,9 +1,9 @@
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/****************************************************************************
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**
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-** Copyright (C) 2016 The Qt Company Ltd.
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+** Copyright (C) 2021 The Qt Company Ltd.
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** Contact: https://www.qt.io/licensing/
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**
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-** This file is part of the QtQuick module of the Qt Toolkit.
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+** This file is part of the QtQuick module of the Qt Toolkit.fset
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**
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** $QT_BEGIN_LICENSE:LGPL$
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** Commercial License Usage
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@@ -1883,7 +1883,23 @@ void QQuickItemPrivate::updateSubFocusItem(QQuickItem *scope, bool focus)
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\endqml
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- \section2 Key Handling
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+ \section2 Event Handling
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+
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+ All Item-based visual types can use \l {Qt Quick Input Handlers}{Input Handlers}
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+ to handle incoming input events (subclasses of QInputEvent), such as mouse,
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+ touch and key events. This is the preferred declarative way to handle events.
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+
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+ An alternative way to handle touch events is to subclass QQuickItem, call
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+ setAcceptTouchEvents() in the constructor, and override touchEvent().
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+ \l {QEvent::setAccepted()}{Accept} the entire event to stop delivery to
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+ items underneath, and to exclusively grab all the event's touch points.
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+
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+ Likewise, a QQuickItem subclass can call setAcceptedMouseButtons()
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+ to register to receive mouse button events, setAcceptHoverEvents()
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+ to receive hover events (mouse movements while no button is pressed),
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+ and override the virtual functions mousePressEvent(), mouseMoveEvent(), and
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+ mouseReleaseEvent(). Those can also accept the event to prevent further
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+ delivery and get an implicit grab at the same time.
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Key handling is available to all Item-based visual types via the \l Keys
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attached property. The \e Keys attached property provides basic signals
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@@ -7301,7 +7317,9 @@ bool QQuickItem::isAncestorOf(const QQuickItem *child) const
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If an item does not accept the mouse button for a particular mouse event,
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the mouse event will not be delivered to the item and will be delivered
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to the next item in the item hierarchy instead.
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- */
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+
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+ \sa acceptTouchEvents()
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+*/
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Qt::MouseButtons QQuickItem::acceptedMouseButtons() const
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{
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Q_D(const QQuickItem);
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@@ -7310,7 +7328,13 @@ Qt::MouseButtons QQuickItem::acceptedMouseButtons() const
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/*!
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Sets the mouse buttons accepted by this item to \a buttons.
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- */
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+
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+ \note In Qt 5, calling setAcceptedMouseButtons() implicitly caused
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+ an item to receive touch events as well as mouse events; but it was
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+ recommended to call setAcceptTouchEvents() to subscribe for them.
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+ In Qt 6, it is necessary to call setAcceptTouchEvents() to continue
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+ to receive them.
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+*/
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void QQuickItem::setAcceptedMouseButtons(Qt::MouseButtons buttons)
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{
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Q_D(QQuickItem);
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--
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2.31.1
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