QML: How to retrieve a default font object? - c++

Question

I have a QML Item with some Text fields in it, which should have all the same font. Do achieve this i introduce a new property myFont of type font. Do initialize this property I use the Qt.font function, which creates a font object. But I have to specify at least one property (either family or pointSize).
My Question is now: How can I retrieve the default font for the myFont property?
If I create only a Text{} item, it has already a default font attached, how can I get the same font for the myFont property? (Meanwhile I use a hidden Text field and create an alias to it's font property, but I want a better solution).
Item {
property font myFont: Qt.font({pointSize: 10})
Text {
id: header
font: myFont
text: "My Header"
}
Text {
id: subject
font: myFont
text: "My Subject"
}
Text {
id: message
font: myFont
text: "Some meassage!"
}
}

Answer 1

I think the right way to solve this is to create your own object type with the font you need to use.
In the following example, the new object would be MyText.qml. I don't know your whole code, but I suppose you have a ListView with the delegate you posted in your question.
MyText.qml
import QtQuick 2.0
Text {
font: Qt.font({pointSize: 10})
}
main.qml
import QtQuick 2.5
import QtQuick.Window 2.2
Window {
visible: true
ListModel {
id: myModel
ListElement {
header: "header xxx"
subject: "subject xxx"
message: "message xxx"
}
ListElement {
header: "header yyy"
subject: "subject yyy"
message: "message yyy"
}
ListElement {
header: "header zzz"
subject: "subject zzz"
message: "message zzz"
}
}
ListView {
anchors.fill: parent
model: myModel
delegate: Item {
width: 300; height: 80
Column {
MyText {
id: myheader
text: header + " - family: " + font.family + " size: " + font.pointSize
}
MyText {
id: mysubject
text: subject + " - family: " + font.family + " size: " + font.pointSize
}
MyText {
id: mymessage
text: message + " - family: " + font.family + " size: " + font.pointSize
}
}
}
}
}

Answer 2

Now, I've digged into Qt source code.
And it turns out that Qt uses a registered private TextSingleton which is defined (Qt 5.6) as:
pragma Singleton
import QtQuick 2.2
Text {
}
The font property of various qml controls is initialized:
font: TextSingleton.font
Digging further into C++ code reveals that for the Text item, the font property is a default initialized QFont, which gives the QFont object retrieved from QGuiApplication::font().

Answer 3

As I mentioned here, FontMetrics is the way to go since it's configurable and without using Qt.font(). You can declare it in your parent item or in a SIngleton type and the you can bind the property to it.
Here there's an example
Item {
id: root
FontMetrics {
id: fontMetrics
font.family: "Arial"
font.pixelSize: 24
}
property alias font: fontMetrics.font
Text { font: root.font }
Text { font: root.font }
}

Answer 4

You can access the default font in QML with Qt.application.font.
You can get and set this font in C++ using
QFont font = QApplication::font();
font.setPointSize(12); //make various other changes or get a completely new QFont
QApplication::setFont(font);