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/*!
    \page qtquicklayouts-overview.html
    \title Qt Quick Layouts Overview
    \brief A set of APIs for arranging QML items in a user interface.

    Qt Quick Layouts are items that are used to arrange items in a user interface. Since Qt Quick
    Layouts also resize their items, they are well suited for resizable user interfaces.

    \section1 Getting Started

    The QML types can be imported into your application using the following import statement in your \c {.qml} file.

    \code
     import QtQuick.Layouts 1.2
    \endcode

    \section1 Key Features


    Some of the key features are:

    \list
        \li \l{Layout::alignment}{Alignment} of items can be specified with the
            \l{Layout::alignment}{Layout.alignment} property
        \li \l{Layout::fillWidth}{Resizable items} can be specified with the
            \l{Layout::fillWidth}{Layout.fillWidth} and \l{Layout::fillHeight}{Layout.fillHeight}
            properties.
        \li \l{Size constraints} can be specified with
            \l{Layout::minimumWidth}{Layout.minimumWidth},
            \l{Layout::preferredWidth}{Layout.preferredWidth}, and
            \l{Layout::maximumWidth}{Layout.maximumWidth}  properties ("Width" can be replaced
            with "Height" for specifying similar constraints to the height).
        \li \l{RowLayout::spacing}{Spacings} can be specified with \l{RowLayout::spacing}{spacing},
            \l{GridLayout::rowSpacing}{rowSpacing} or \l{GridLayout::columnSpacing}{columnSpacing}
    \endlist

    In addition to the above features, GridLayout adds these features:
    \list
        \li \l{Layout::row}{Grid coordinates} can be specified with the \l{Layout::row}{Layout.row} and
            \l{Layout::column}{Layout.column} properties.
        \li \l{GridLayout::flow}{Automatic grid coordinates} used together with the
            \l{GridLayout::flow}{flow}, \l{GridLayout::rows}{rows}, and
            \l{GridLayout::columns}{columns} properties.
        \li \l{Layout::columnSpan}{Spans} across rows or columns can be specified with the
            \l{Layout::rowSpan}{Layout.rowSpan} and \l{Layout::columnSpan}{Layout.columnSpan}
            properties.
    \endlist


    \section1 A Simple Layout

    \snippet qml/layout-simple.qml 1

    As the intention of using a layout is to rearrange its children whenever the layout changes
    size, the application should make sure that the layout gets resized. In the above snippet the
    RowLayout ensures that by specifying \c{anchors.fill: parent}. However, it can also be by other
    means, such as directly specifying \l{Item::width}{width} and \l{Item::height}{height}
    properties. In the same snippet, the \c azure Rectangle has a fixed size of \c{(100, 150)}
    pixels, and the \c plum Rectangle will expand to occupy all the space it gets allocated.

    \note A layout is responsible for its children's geometry. You should
    therefore not specify \l{Item::width}{width}, \l{Item::height}{height}, \l{Item::x}{x},
    \l{Item::y}{y} or any other properties that might influence those properties (such as
    \l{Item::anchors}{anchors}) on those items. Otherwise there would be a conflict of interest,
    and the result is undefined. This is also the case if the child item is a layout. Therefore,
    only layouts with no parent layout can have \c{anchors.fill: parent}.

    All items in the layout will have 6 pixels of spacing between them:

    \snippet qml/layout-simple.qml spacing


    \section2 Size Constraints

    Since an item can be resized by its layout, the layout needs to know the
    \l{Layout::minimumWidth}{minimum}, \l{Layout::preferredWidth}{preferred},
    and \l{Layout::maximumWidth}{maximum} sizes of all items where \l{Layout::fillWidth}{Layout.fillWidth} or
    \l{Layout::fillHeight}{Layout.fillHeight} is set to \c true.
    For instance, the following will produce a layout with two rectangles lying side-by-side that
    stretches horizontally. The azure rectangle can be resized from 50x150 to 300x150, and the plum
    rectangle can be resized from 100x100 to ∞x100.

    \snippet qml/windowconstraints.qml rowlayout

    \image rowlayout-minimum.png "RowLayout at its minimum"

    Combining each item's constraints will give these implicit constraints to the layout element:

    \table
    \header
        \li
        \li minimum
        \li preferred
        \li maximum
    \row
        \li implicit constraints (width)
        \li 156
        \li 306
        \li ∞ (\c Number.POSITIVE_INFINITY)
    \row
        \li implicit constraints (heights)
        \li 150
        \li 150
        \li 150
    \endtable

    Thus, the layout cannot be narrower than 156 or be taller or shorter than 150 without breaking
    any of the constraints of its child items.

    \section2 Specifying Preferred Size
    For each item, the effective preferred size may come from one of several candidate properties.
    For determining the effective preferred size, it will query these candidate properties in the
    following order, and use the first candidate with a valid width or height.

    \table
    \header
        \li Candidate properties
        \li Description
    \row
        \li \l{Layout::preferredWidth}{Layout.preferredWidth} or
            \l{Layout::preferredHeight}{Layout.preferredHeight}
        \li These properties are supposed to be modified by the application if the default implicit
            size does not give the optimal arrangement.
    \row
        \li \l{Item::implicitWidth}{implicitWidth} or \l{Item::implicitHeight}{implicitHeight}
        \li These properties are supposed to be supplied by each item to give a meaningful ideal size,
            for example the size needed to display all the contents of a \l Text type.
            An implicit width or height of \c 0 is interpreted as invalid.
    \row
        \li \l{Item::width}{width} and \l{Item::height}{height}
        \li If none of the above properties are valid, the layout will resort to the
            \l{Item::width}{width} and \l{Item::height}{height} properties.
    \endtable

    An item can specify \l{Layout::preferredWidth}{Layout.preferredWidth} without having to specify
    \l{Layout::preferredHeight}{Layout.preferredHeight}. In this case, the effective preferred
    height will be determined from the \l{Item::implicitHeight}{implicitHeight} (or ultimately
    \l{Item::height}{height}).

    \note Resorting to \l{Item::width}{width} or \l{Item::height}{height} properties is only
    provided as a final fallback. If you want to override the preferred size, it is recommended to
    use \l{Layout::preferredWidth}{Layout.preferredWidth} or
    \l{Layout::preferredHeight}{Layout.preferredHeight}. Relying on the \l{Item::width}{width} or
    \l{Item::height}{height} properties for specifying the preferred size might give some
    unexpected behavior. For instance, changing the \l{Item::width}{width} or
    \l{Item::height}{height} properties won't trigger a layout rearrangement. Also, when the layout
    is forced to do a full rebuild it might use the actual width and height, and not the width and
    height specified in the QML file.


    \section1 Connecting Windows and Layouts
    You can just use normal anchoring concepts to ensure that the layout will follow the window
    resizing.

    \snippet qml/windowconstraints.qml anchoring

    The size constraints of layouts can be used to ensure that the window cannot be resized beyond
    the layout constraints. You can take the size constraints from the layout and set these
    constraints on the minimumWidth, minimumHeight, maximumWidth, and maximumHeight of the Window
    element. The following code ensures that the window cannot be resized beyond the constraints of
    the layout:

    \snippet qml/windowconstraints.qml bindconstraints

    \note Since layout.Layout.maximumWidth is infinite in this case, we cannot bind that to the
    maximumWidth property of Window, since that is an integer number. We therefore set a fixed
    maximum width to 1000.

    Finally, you usually want the initial size of the window to be the layout's implicit size:

    \snippet qml/windowconstraints.qml binddefaultsize
*/
