Qml Styling: Difference between revisions

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m (add fix for qmldir listing after trying to use it in my project as is)
(the mentioned bug is already resolved, the import is not necessary now (tested in 5.15))
 
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QML provides several mechanisms for styling a UI. Below are three common approaches.
QML provides several mechanisms for styling a UI. Below are three common approaches.


== Approach 1: Custom Component ==
==Approach 1: Custom Component==


QML supports defining your own [http://doc.qt.io/qt-5/qtqml-referenceexamples-properties-example.html custom components]. Below, we create a custom component '''TitleText''' that we can use whenever our UI requires a title. If we want to change the appearance of all the titles in our UI, we can then just edit ''TitleText.qml'', and the changes will apply wherever it is used.
QML supports defining your own [http://doc.qt.io/qt-5/qtqml-referenceexamples-properties-example.html custom components]. Below, we create a custom component '''TitleText''' that we can use whenever our UI requires a title. If we want to change the appearance of all the titles in our UI, we can then just edit ''TitleText.qml'', and the changes will apply wherever it is used.<syntaxhighlight lang="qml">
 
// TitleText.qml
<code>// TitleText.qml
Text {
Text {
horizontalAlignment: Text.AlignHCenter
    horizontalAlignment: Text.AlignHCenter
font.pixelSize: 50
    font.pixelSize: 50
color: "green"
    color: "green"
}
}
 
</syntaxhighlight><syntaxhighlight lang="qml">
// in use
// In use
TitleText {
TitleText {
text: "Title 1"
    text: "Title 1"
}</code>
}
 
</syntaxhighlight>
== Approach 2: Style Singleton ==


In this approach we define a '''Style''' QML singleton object that contains a collection of properties defining the style. As a QML singleton, a common instance can be access from anywhere which imports this directory. Note that QML singletons require a qmldir file with the '''singleton''' keyword preceding the Style type declaration; they cannot be picked up implicitly like other types. When using Qrc resources both the Style.qml and the qmldir file must be included in the .qrc resource file.
==Approach 2: Style Singleton==


<code>// Style.qml
In this approach we define a '''Style''' QML singleton object that contains a collection of properties defining the style. As a QML singleton, a common instance can be access from anywhere which imports this directory. Note that QML singletons require a qmldir file with the '''singleton''' keyword preceding the Style type declaration; they cannot be picked up implicitly like other types. When using Qrc resources both the Style.qml and the qmldir file must be included in the .qrc resource file.<syntaxhighlight lang="qml">
// Style.qml
pragma Singleton
pragma Singleton
import QtQuick 2.0
import QtQuick 2.0
QtObject {
QtObject {
property int textSize: 20
    property int textSize: 20
property color textColor: "green"
    property color textColor: "green"
}
}
 
</syntaxhighlight><syntaxhighlight lang="qml">
// qmldir
// In use
singleton Style 1.0 Style.qml
 
// in use
import QtQuick 2.0
import QtQuick 2.0
import "." // QTBUG-34418, singletons require explicit import to load qmldir file


Text {
Text {
font.pixelSize: Style.textSize
    font.pixelSize: Style.textSize
color: Style.textColor
    color: Style.textColor
text: "Hello World"
    text: "Hello World"
}</code>
}
</syntaxhighlight>


== Approach 3: Hybrid (Style Singleton + Custom Component) ==
==Approach 3: Hybrid (Style Singleton + Custom Component)==


In this approach, we have a '''Style''' singleton that is used by our custom component.
In this approach, we have a '''Style''' singleton that is used by our custom component.<syntaxhighlight lang="qml">
 
// Style.qml
<code>// Style.qml
pragma Singleton
import QtQuick 2.0
import QtQuick 2.0
pragma Singleton


QtObject {
QtObject {
property int titleAlignment: Text.AlignHCenter
    property int titleAlignment: Text.AlignHCenter
property int titleFontSize: 50
    property int titleFontSize: 50
property color titleColor: "green"
    property color titleColor: "green"
}
}
 
</syntaxhighlight><syntaxhighlight lang="qml">
// TitleText.qml
// TitleText.qml
import QtQuick 2.0
import QtQuick 2.0
import "." // QTBUG-34418, singletons require explicit import to load qmldir file


Text {
Text {
horizontalAlignment: Style.titleAlignment
    horizontalAlignment: Style.titleAlignment
font.pixelSize: Style.titleFontSize
    font.pixelSize: Style.titleFontSize
color: Style.titleColor
    color: Style.titleColor
}
}
 
</syntaxhighlight><syntaxhighlight lang="qml">
// in use
// In use
TitleText {
TitleText {
text: "Title 1"
    text: "Title 1"
}</code>
}  
</syntaxhighlight>


== Nesting QtObjects ==
==Nesting QtObjects==


If you need to nest QtObject to access more defined properties (i.e. border.width.normal) you can do the following:
If you need to nest QtObject to access more defined properties (i.e. border.width.normal) you can do the following:<syntaxhighlight lang="qml">
 
// Style.qml
<code>// Style.qml
pragma Singleton
.pragma Singleton


QtObject {
QtObject {
 
    property QtObject window: QtObject {
property QtObject window: QtObject{
        property color background: "white"
property color background: "white";
    }
}
    property QtObject border: QtObject {
 
        property QtObject width: QtObject {
property QtObject border: QtObject{
            property int normal: 1
property QtObject width: QtObject{
            property int big: 3
property int normal: 1;
        }
property int big: 3;
        property QtObject color: QtObject {
}
            property color normal: "gray"
 
            property color focus: "blue"
property QtObject color: QtObject{
            property color disabled: "red"
property color normal: "gray";
        }
property color focus: "blue";
    }
property color disabled: "red";
}  
}
</syntaxhighlight>
}
}</code>

Latest revision as of 17:28, 5 October 2021

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QML provides several mechanisms for styling a UI. Below are three common approaches.

Approach 1: Custom Component

QML supports defining your own custom components. Below, we create a custom component TitleText that we can use whenever our UI requires a title. If we want to change the appearance of all the titles in our UI, we can then just edit TitleText.qml, and the changes will apply wherever it is used.

// TitleText.qml
Text {
    horizontalAlignment: Text.AlignHCenter
    font.pixelSize: 50
    color: "green"
}
// In use
TitleText {
    text: "Title 1"
}

Approach 2: Style Singleton

In this approach we define a Style QML singleton object that contains a collection of properties defining the style. As a QML singleton, a common instance can be access from anywhere which imports this directory. Note that QML singletons require a qmldir file with the singleton keyword preceding the Style type declaration; they cannot be picked up implicitly like other types. When using Qrc resources both the Style.qml and the qmldir file must be included in the .qrc resource file.

// Style.qml
pragma Singleton
import QtQuick 2.0

QtObject {
    property int textSize: 20
    property color textColor: "green"
}
// In use
import QtQuick 2.0

Text {
    font.pixelSize: Style.textSize
    color: Style.textColor
    text: "Hello World"
}

Approach 3: Hybrid (Style Singleton + Custom Component)

In this approach, we have a Style singleton that is used by our custom component.

// Style.qml
pragma Singleton
import QtQuick 2.0

QtObject {
    property int titleAlignment: Text.AlignHCenter
    property int titleFontSize: 50
    property color titleColor: "green"
}
// TitleText.qml
import QtQuick 2.0

Text {
    horizontalAlignment: Style.titleAlignment
    font.pixelSize: Style.titleFontSize
    color: Style.titleColor
}
// In use
TitleText {
    text: "Title 1"
}

Nesting QtObjects

If you need to nest QtObject to access more defined properties (i.e. border.width.normal) you can do the following:

// Style.qml
pragma Singleton

QtObject {
    property QtObject window: QtObject {
        property color background: "white"
    }
    property QtObject border: QtObject {
        property QtObject width: QtObject {
            property int normal: 1
            property int big: 3
        }
        property QtObject color: QtObject {
            property color normal: "gray"
            property color focus: "blue"
            property color disabled: "red"
        }
    }
}