How to set dynamic QFont size?

Question

I came across QFontMetrics? http://doc.qt.io/qt-5/qfontmetrics.html
This gives the height and width of the present font.

I need to run my application with full screen mode on on different monitors for which I am using Scale class. http://doc.qt.io/qt-5/qml-qtquick-scale.html

That returns the height and width of the current screen.

Is there a way to use QFontMetrics or anything else to change the font size according to the monitor size?

ApplicationWindow
{
    id: head

    visible: true

    width:  Screen.width
    height: Screen.height

    title: "Novus Pilot"

    property var id: 0;

    Draw_on_qimage
    {
        id: draw_on_qimage
        anchors.fill: parent
        parent: image

        scaleX: head.width / 640
        scaleY: head.height / 480
    }
}

Draw_on_qimage is a cpp class.

Can you show how you are using Scale? your application in QML or C ++? — eyllanesc, Jan 03 '18 at 09:21
There is a `paint` function in the class `Draw_on_qimage`. That uses some some text. I wish to control its size. @eyllanesc — Aquarius_Girl, Jan 03 '18 at 09:39
Draw_on_qimage of what class it inherits, inherits from qquickpainteditem? — eyllanesc, Jan 03 '18 at 09:41
Yes, QQuickPaintedItem. @eyllanesc Anything else you wish to know? — Aquarius_Girl, Jan 03 '18 at 09:42

score 1 · Accepted Answer · answered Jan 03 '18 at 10:20

The easiest way is to set QFont as Q_PROPERTY of your item so you can set it from QML:

#ifndef DRAWITEM_H
#define DRAWITEM_H

#include <QPainter>
#include <QQuickPaintedItem>

class DrawItem : public QQuickPaintedItem
{
    Q_OBJECT
    Q_PROPERTY(QFont font READ font WRITE setFont NOTIFY fontChanged)
public:
    DrawItem(QQuickItem *parent = Q_NULLPTR):QQuickPaintedItem(parent){}
    void paint(QPainter *painter){
        painter->setFont(mFont);
        painter->drawText(boundingRect(), "Hello");
    }
    QFont font() const{
        return mFont;
    }
    void setFont(const QFont &font){
        if(mFont == font)
            return;
        mFont = font;
        emit fontChanged();
        update();
    }

signals:
    void fontChanged();
private:
    QFont mFont;
};

#endif // DRAWITEM_H

To set its size we use the pointSize property of QFont:

DrawItem
{
    id: draw_on_qimage
    anchors.fill: parent
    font.pointSize: some_function(head.width, head.height)
    transform: Scale {
        xScale: head.width / 640
        yScale: head.height / 480
    }
}

Where some_function is the function that establishes the relationship between the font size and the size of the window.

Thanks for the effort. Is the aim of your example to show how to pass screen's height and width to the cpp for font adjustment? — Aquarius_Girl, Jan 03 '18 at 10:57
@Aquarius_Girl no, it is show that you can set the font size from the QML. — eyllanesc, Jan 03 '18 at 10:58
@Aquarius_Girl Look at the following example, if you manually change the size of the window you will see that the size of the font changes https://github.com/eyllanesc/stackoverflow/tree/master/48074369 — eyllanesc, Jan 03 '18 at 11:01

How to set dynamic QFont size?

1 Answers1