Qt Quick Layouts Overview

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.

Getting started

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

import QtQuick.Layouts 1.2

Key Features

Some of the key features are:

In addition to the above features, GridLayout adds these features:

Size Constraints

Since an item can be resized by its layout, the layout needs to know the minimum, preferred, and maximum sizes of all items where Layout.fillWidth or Layout.fillHeight is set to 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.

"RowLayout at its minimum"

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

minimumpreferredmaximum
implicit constraints (width)156306∞ (Number.POSITIVE_INFINITY)
implicit constraints (heights)150150150

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.

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.

Candidate propertiesDescription
Layout.preferredWidth or Layout.preferredHeightThese properties are supposed to be modified by the application if the default implicit size does not give the optimal arrangement.
implicitWidth or implicitHeightThese 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 Text type. An implicit width or height of 0 is interpreted as invalid.
width and heightIf none of the above properties are valid, the layout will resort to the width and height properties.

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

Note: Resorting to width or height properties is only provided as a final fallback. If you want to override the preferred size, it is recommended to use Layout.preferredWidth or Layout.preferredHeight. Relying on the width or height properties for specifying the preferred size might give some unexpected behavior. For instance, changing the width or 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.

Connecting windows and layouts

You can just use normal anchoring concepts to ensure that the layout will follow the window resizing.

RowLayout {
    id: layout
    anchors.fill: parent

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:

minimumWidth: layout.Layout.minimumWidth
minimumHeight: layout.Layout.minimumHeight
maximumWidth: 1000
maximumHeight: layout.Layout.maximumHeight

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:

width: layout.implicitWidth
height: layout.implicitHeight

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