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/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: http://www.gnu.org/copyleft/fdl.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qtquickcontrols2-differences.html
\title Differences between Qt Quick Controls
Qt Quick Controls were originally developed to support desktop platforms,
with mobile and embedded support coming shortly afterwards. They have a
very broad scope, in that they provide a styling system flexible enough to
allow the development of applications that have either a platform-dependent
or platform-independent style.
On embedded systems, where the hardware has limited resources, this approach
can be inefficient. Qt Quick Controls 2 were designed to solve this problem,
using
\l {https://blog.qt.io/blog/2015/03/31/qt-quick-controls-for-embedded/}{benchmarks}
to guide the development.
\section2 C++ and QML
In many cases, the internal state of a control can be more efficiently
processed in C++. For example, handling input events in C++ makes a
difference for controls that would otherwise need to create internal
MouseAreas and attached Keys objects.
\section2 Styles
Not only does handling events and logic in C++ increase performance, but it
allows the visual QML layer to be a simple, declarative layer on top. This
is reflected in the structure of the controls project: all visual
implementations sit in the \e imports folder, so that users who want to
create their own complete style can copy the folder and start tweaking.
Read more about implementing a style plugin
\l {Creating a Custom Style}{here}.
In Qt Quick Controls 2, styles no longer provide components that are
dynamically instantiated by controls, but controls themselves consist of
item delegates that can be replaced. In effect, this means that delegates
are Qt Quick items that are instantiated on the spot, as properties of the
control, and are simply parented to the control.
\section2 Modularity and Simplicity
When it comes to more complex controls, it is sometimes better to split
them up into separate building blocks. As an example, the complex
ScrollView control:
\qml
ScrollView {
horizontalScrollBarPolicy: Qt.ScrollBarAlwaysOff
Flickable {
// ...
}
}
\endqml
Is replaced with simple ScrollBar/ScrollIndicator controls that can be
attached to any Flickable:
\qml
Flickable {
// ...
ScrollBar.vertical: ScrollBar { }
}
\endqml
The API of Qt Quick Controls 2 aims to be clean and simple. Common
operations are easy, and more advanced ones are liberally documented with
snippets that can be copied into your code.
\section2 Feature Comparison Table
\table
\header
\li
\li Qt Quick Controls
\li Qt Quick Controls 2
\row
\li Stylable delegates
\li Yes
\li Yes
\row
\li Pre-built native styles
\li Yes
\li No
\row
\li Runtime style changes
\li Yes
\li Yes
\row
\li Can be used on Desktop
\li Yes
\li Yes \b *
\row
\li Can be used on Mobile
\li Yes
\li Yes
\row
\li Can be used on Embedded
\li Yes
\li Yes
\row
\li Internal event handling
\li QML
\li C++
\endtable
\b {* No hover support}
\section2 Porting Qt Quick Controls Code
The API of Qt Quick Controls 2 is very similar to Qt Quick Controls, but it
does come with some changes necessary to facilitate the improvements. The
majority of changes are to do with styling; all of a control's delegates
are now accessible in the control itself, instead of in a separate style
object.
For example, to style a button in Qt Quick Controls:
\badcode
Button {
style: ButtonStyle {
label: Label {
// ...
}
}
}
\endcode
To style a button in Qt Quick Controls 2:
\qml
Button {
contentItem: Label {
// ...
}
}
\endqml
\section3 Preparing for Migration
With this in mind, a good way to prepare for a migration to Qt Quick
Controls 2 is to place each control that you have a custom style for in its
own QML file. For example, the Qt Quick Controls button above could be moved to a
file named Button.qml, and used in the following manner:
\badcode
import "controls" as Controls
Controls.Button {
...
}
\endcode
This works with both modules, and will reduce the amount of work needed
when the migration begins.
\section3 Type Changes
\table
\header
\li Qt Quick Controls
\li Qt Quick Controls 2
\row
\li \l [QML QtQuickControls] {Action}
\li No equivalent; see \l [QML QtQuick] {Shortcut} instead.
\row
\li \l [QML QtQuickControls] {ApplicationWindow}
\li \l [QML QtQuickControls2] {ApplicationWindow}
\row
\li \l [QML QtQuickControls] {BusyIndicator}
\li \l [QML QtQuickControls2] {BusyIndicator}
\row
\li \l [QML QtQuickControls] {Button}
\li \l [QML QtQuickControls2] {Button}
\row
\li \l [QML QtQuickControls] {Calendar}
\li No equivalent; see \l [QML] {MonthGrid}, \l [QML] {DayOfWeekRow} and \l [QML] {WeekNumberColumn} instead.
\row
\li \l [QML QtQuickControls] {CheckBox}
\li \l [QML QtQuickControls2] {CheckBox}
\row
\li \l [QML QtQuickControls] {ComboBox}
\li \l [QML QtQuickControls2] {ComboBox}
\row
\li \l [QML QtQuickControls] {ExclusiveGroup}
\li \l [QML QtQuickControls2] {ButtonGroup}
\row
\li \l [QML QtQuickControls] {GroupBox}
\li \l [QtQuickControls2] {GroupBox}, or \l [QML QtQuickControls2] {Frame}
if a title is not required.
\row
\li \l [QML QtQuickControls] {Label}
\li \l [QML QtQuickControls2] {Label}
\row
\li \l [QML QtQuickControls] {Menu}
\li \l [QML QtQuickControls2] {Menu}
\row
\li \l [QML QtQuickControls] {ProgressBar}
\li \l [QML QtQuickControls2] {ProgressBar}
\row
\li \l [QML QtQuickControls] {RadioButton}
\li \l [QML QtQuickControls2] {RadioButton}
\row
\li \l [QML QtQuickControls] {ScrollView}
\li \l [QML QtQuickControls2] {ScrollBar},
\l [QML QtQuickControls2] {ScrollIndicator}
\row
\li \l [QML QtQuickControls] {Slider}
\li \l [QML QtQuickControls2] {Slider}
\row
\li \l [QML QtQuickControls] {SpinBox}
\li \l [QML QtQuickControls2] {SpinBox}
\row
\li \l [QML QtQuickControls] {Stack},
\l [QML QtQuickControls] {StackView},
\l [QML QtQuickControls] {StackViewDelegate}
\li \l [QML QtQuickControls2] {StackView}
\row
\li \l [QML QtQuickControls] {StatusBar}
\li No equivalent
\row
\li \l [QML QtQuickControls] {Switch}
\li \l [QML QtQuickControls2] {Switch}
\row
\li \l [QML QtQuickControls] {Tab},
\l [QML QtQuickControls] {TabView}
\li \l [QML QtQuickControls2] {TabBar} in combination with, for example,
\l [QML QtQuickControls2] {SwipeView}.
\row
\li \l [QML QtQuickControls] {TableView}
\li No equivalent
\row
\li \l [QML QtQuickControls] {TextArea}
\li \l [QML QtQuickControls2] {TextArea}
\row
\li \l [QML QtQuickControls] {TextField}
\li \l [QML QtQuickControls2] {TextField}
\row
\li \l [QML QtQuickControls] {ToolBar}
\li \l [QML QtQuickControls2] {ToolBar}
\row
\li \l [QML QtQuickControls] {ToolButton}
\li \l [QML QtQuickControls2] {ToolButton}
\row
\li \l [QML QtQuickControls] {TreeView}
\li No equivalent
\endtable
\section1 Related Information
\list
\li \l{Qt Quick}
\li \l{Qt Quick Controls}
\li \l{Qt Quick Controls 2 QML Types}
\endlist
*/
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