How to render text with QOpenGLWidget

Question

In older version of Qt there was QGLWidget, with a nice function called renderText. Now I'm using QOpenGLWidget class and the functionality for rendering text is missing.

Is there a easy way to render text using QOpenGLWidget? I won't like to build the whole text rendering with OpenGL from scratch...

Answer 1

I ended up doing a solution similar to what @jaba wrote. I also noticed some graphical corruption unless I called painter.end() at the end of the method.

void MapCanvas::renderText(double x, double y, double z, const QString &str, const QFont & font = QFont()) {
    // Identify x and y locations to render text within widget
    int height = this->height();
    GLdouble textPosX = 0, textPosY = 0, textPosZ = 0;
    project(x, y, 0f, &textPosX, &textPosY, &textPosZ);
    textPosY = height - textPosY; // y is inverted

    // Retrieve last OpenGL color to use as a font color
    GLdouble glColor[4];
    glGetDoublev(GL_CURRENT_COLOR, glColor);
    QColor fontColor = QColor(glColor[0], glColor[1], glColor[2], glColor[3]);

    // Render text
    QPainter painter(this);
    painter.setPen(fontColor);
    painter.setFont(font);
    painter.drawText(textPosX, textPosY, text);
    painter.end();
}