QGLWidget resize problem.

[anderl]

Hi,

i'm using a QGLWidget in my class to establish a OpenGL Context. When i resize the QGLWidget using the resize method, the framebuffer will be resized as expected, but not the actual color target. For example, if i resize the widget to 1280x1024 and clear the scene using a red color, only a part of the scene will be cleared in red (as shown on the the following image)


The class using the QGLWidget:

class OpenGLExample
{
public:
    OpenGLExample()
    {
         widget.resize(1280,1024);
         widget.makeCurrent();
    }
 
    void draw()
    {
        glClearColor(1.0f,0.0f,0.0f,0.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        widget.grabFrameBuffer().save("test.png");
    }
private:
QGLWidget widget;
};

class OpenGLExample
{
public:
    OpenGLExample()
    {
         widget.resize(1280,1024);
         widget.makeCurrent();
    }

    void draw()
    {
        glClearColor(1.0f,0.0f,0.0f,0.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        widget.grabFrameBuffer().save("test.png");
    }
private:
QGLWidget widget;
};

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And the main class:

int main(int argc, char *argv[])
{	
	QApplication app(argc,argv);
        OpenGLExample example;
        example.draw();
        return 0;
}

int main(int argc, char *argv[])
{	
	QApplication app(argc,argv);
        OpenGLExample example;
        example.draw();
        return 0;
}

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glClear should affect the complete framebuffer and not only a part. Whats wrong with my code?

Thanks!

[ConfusedSushi]

try to setup the viewport with glViewPort.

[anderl]

I solved it.
QGLWidget must be visible in order to get the resize working.