how to use mirrored text in Qt - c++

Question

code sample
type here
void MainWindow::paintEvent(QPaintEvent *event){
QPainter chartPainter;
QPointF qChart;
QFont font;
chartPainter.begin(this);
qChart = QPointF(100, 100); // x postion, y position
chartPainter.drawText(qChart, "A", 0, 0);
}
How can I display the letter "A" in Qt as mirrored text?
How to apply mirrored text to all text, not just "A"?
QImage has a function called mirrored that can be applied. However, the method using QPainter is not found even after searching.
Is there a way that can be implemented with QPainter or some other way?

Answer 1

Yes you can create a QImage and draw on it. You draw over the image in the Painter.
.h
............
protected:
void paintEvent(QPaintEvent *);
private:
void drawText(const QString &text);
private:
Ui::Widget *ui;
QImage image;
bool drawing;
...........
.cpp
Widget::Widget(QWidget *parent)
: QWidget(parent)
, ui(new Ui::Widget)
{
ui->setupUi(this);
image = QImage(size(), QImage::Format_ARGB32_Premultiplied);
drawing = true; // for updating once
}
void Widget::paintEvent(QPaintEvent *)
{
image = image.mirrored(true, false);
QPainter painter(this);
painter.fillRect(rect(), QGradient(QGradient::SaintPetersburg));
painter.drawImage(rect(), image);
if(drawing)
drawText("Mirrored");
}
void Widget::drawText(const QString &text)
{
QPainter painter(&image);
// set a font
QFont font = painter.font();
font.setFamily("Helvetica");
font.setPixelSize(20);
painter.setFont(font);
// metrics for centerPos and size
QFontMetrics metrics(painter.fontMetrics());
painter.setPen(Qt::black);
// keep it in the middle if possible (is only for the optics. you don't have to do it like that)
painter.drawText((width()/2) -(metrics.horizontalAdvance(text))-10,
(height()/2) - (metrics.height()),
metrics.horizontalAdvance(text),
metrics.height(),
0,
text);
update();
drawing = false;
}
Just a small note: if you draw directly in the painter, the picture will flicker. you can work around it by calling the image directly in the constructor.
Widget::Widget(QWidget *parent)
: QWidget(parent)
, ui(new Ui::Widget)
{
ui->setupUi(this);
image = QImage(size(), QImage::Format_ARGB32_Premultiplied);
//image.fill(Qt::white);
//drawing = true; // update once
drawText("Mirrored");
image = image.mirrored(true, false);
}
.........
void Widget::paintEvent(QPaintEvent *)
{
QPainter painter(this);
painter.fillRect(rect(), QGradient(QGradient::SaintPetersburg));
painter.drawImage(rect(), image);
}
........

Answer 2

you need to set the Qt::TextDirection property of a QPainter object.
Add these to your code:
painter.setLayoutDirection(Qt::RightToLeft);
painter.drawText(rect, Qt::AlignRight, tr("Text goes here"));