How to draw text surrounding circle? - c++

Question

Using QT, how would I go about taking user-supplied input (text) and drawing the font in such a way that it "follows" a circular path?

Answer 1

I really know nothing at all about QT but if I understood your question right, I found the solution with a simple google search. Code is below and here is the source link:
http://developer.qt.nokia.com/faq/answer/how_do_i_make_text_follow_the_line_curve_and_angle_of_the_qpainterpath
#include <QtGui>
#include <cmath>
class Widget : public QWidget
{
public:
Widget ()
: QWidget() { }
private:
void paintEvent ( QPaintEvent *)
{
QString hw("hello world");
int drawWidth = width() / 100;
QPainter painter(this);
QPen pen = painter.pen();
pen.setWidth(drawWidth);
pen.setColor(Qt::darkGreen);
painter.setPen(pen);
QPainterPath path(QPointF(0.0, 0.0));
QPointF c1(width()*0.2,height()*0.8);
QPointF c2(width()*0.8,height()*0.2);
path.cubicTo(c1,c2,QPointF(width(),height()));
//draw the bezier curve
painter.drawPath(path);
//Make the painter ready to draw chars
QFont font = painter.font();
font.setPixelSize(drawWidth*2);
painter.setFont(font);
pen.setColor(Qt::red);
painter.setPen(pen);
qreal percentIncrease = (qreal) 1/(hw.size()+1);
qreal percent = 0;
for ( int i = 0; i < hw.size(); i++ ) {
percent += percentIncrease;
QPointF point = path.pointAtPercent(percent);
qreal angle = path.angleAtPercent(percent);
qreal rad =qreal(0.017453292519943295769)*angle; // PI/180
// From the documentation:
/**
QTransform transforms a point in the plane to another point using the following formulas:
x' = m11*x + m21*y + dx
y' = m22*y + m12*x + dy
**/
// So the idea is to find the "new position of the character
// After we apply the world rotation.
// Then translate the painter back to the original position.
qreal sina = std::sin(rad);
qreal cosa = std::cos(rad);
// Finding the delta for the penwidth
// Don't divide by 2 because some space would be nice
qreal deltaPenX = cosa * pen.width();
qreal deltaPenY = sina * pen.width();
// Finding new posision after rotation
qreal newX = (cosa * point.x()) - (sina * point.y());
qreal newY = (cosa * point.y()) + (sina * point.x());
// Getting the delta distance
qreal deltaX = newX - point.x();
qreal deltaY = newY - point.y();
// Applying the rotation with the translation.
QTransform tran(cosa,sina,-sina,cosa,-deltaX + deltaPenX,-deltaY - deltaPenY);
painter.setWorldTransform(tran);
painter.drawText(point,QString(hw[i]));
}
}
};
int main(int argc, char **argv)
{
QApplication app(argc, argv);
Widget widget;
widget.show();
return app.exec();
}