How to set dynamic QFont size? - c++

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.

Answer 1

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.