problem on QGLWidget and QGLFramebufferObject

[xylosper]

I wrote a simple code using QGLWidget and QGLFramebufferObject like this:

#include <QApplication>
#include <QTextDocument>
#include <QPainter>
#include <QGLFramebufferObject>
#include <QGLWidget>
 
class GLWidget : public QGLWidget {
public:
	GLWidget(QWidget *parent = 0): QGLWidget(parent), fbo(0) {}
	~GLWidget() {if (fbo) delete fbo;}
protected:
	void initializeGL() {
		fbo = new QGLFramebufferObject(200, 200);
		glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
		QTextDocument doc;
		doc.setHtml("<font color=red>Test text</font>");
		QPainter p(fbo);
		doc.drawContents(&p, QRect(QPoint(0, 0), fbo->size()));
		p.end();
	}
	void resizeGL(int w, int h) {
		if(h == 0) h = 1;
		glViewport(0, 0, w, h);
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		gluOrtho2D(0.0f, (GLfloat) w, (GLfloat) h, 0.0f);
		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
	}
	void paintEvent(QPaintEvent *event) {
		QPainter painter(this);
		QRect r = rect();
		painter.fillRect(r, Qt::white);
		r.moveTo(100, 0); // line1
		painter.fillRect(r, Qt::black); // line2
		drawTexture(QPoint(10, 10), fbo->texture());
	}
private:
	QGLFramebufferObject *fbo;
};
 
int main(int argc, char **argv) {
	QApplication app(argc, argv);
	GLWidget w;
	w.resize(200, 100);
	w.show();
	return app.exec();
}

#include <QApplication>
#include <QTextDocument>
#include <QPainter>
#include <QGLFramebufferObject>
#include <QGLWidget>

class GLWidget : public QGLWidget {
public:
	GLWidget(QWidget *parent = 0): QGLWidget(parent), fbo(0) {}
	~GLWidget() {if (fbo) delete fbo;}
protected:
	void initializeGL() {
		fbo = new QGLFramebufferObject(200, 200);
		glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
		QTextDocument doc;
		doc.setHtml("<font color=red>Test text</font>");
		QPainter p(fbo);
		doc.drawContents(&p, QRect(QPoint(0, 0), fbo->size()));
		p.end();
	}
	void resizeGL(int w, int h) {
		if(h == 0) h = 1;
		glViewport(0, 0, w, h);
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		gluOrtho2D(0.0f, (GLfloat) w, (GLfloat) h, 0.0f);
		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
	}
	void paintEvent(QPaintEvent *event) {
		QPainter painter(this);
		QRect r = rect();
		painter.fillRect(r, Qt::white);
		r.moveTo(100, 0); // line1
		painter.fillRect(r, Qt::black); // line2
		drawTexture(QPoint(10, 10), fbo->texture());
	}
private:
	QGLFramebufferObject *fbo;
};

int main(int argc, char **argv) {
	QApplication app(argc, argv);
	GLWidget w;
	w.resize(200, 100);
	w.show();
	return app.exec();
}

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I expected red texts, but the result is black texts like the attached file "tow-color.png"


I found out that the commenting out the line1 and line2 of the paintEvent() in the class changes the result like the attached file "one-color.png".


What's going on?
And, how can I get red texts with the original code?

[kwisp]

I think, when you fillRect(...,Qt::black), you setBrush to black color.

May be -

painter.fillRect(r, Qt::black); // line2
painter.setBrush(Qt::red);// ???
drawTexture(QPoint(10, 10), fbo->texture());

painter.fillRect(r, Qt::black); // line2
painter.setBrush(Qt::red);// ???
drawTexture(QPoint(10, 10), fbo->texture());

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[xylosper]

Thanks for answering.

The color of brush doesn't matter, because the texts are already rendered by QTextDocument and all informations are in fbo's texture.
In addition to that, I tried your code actually, but nothing is changed.