OpenGL extension doesn't work

[pbartosz]

I'm trying to uses GL_NV_Path_rendering OpenGL extension in my Qt 4.8.4 application. To render OpenGL i'm using QGLWidget class.
My graphics card is recognised correctly:
@OpenGL Versions Supported: QFlags(0x1|0x2|0x4|0x8|0x10|0x20|0x40|0x1000|0x2000|0x4000|0x8000|0x10000)
Driver Version String: "4.2.0"
Current Context: QGLFormat(options QFlags(0x1|0x2|0x4|0x10|0x20|0x80|0x400) , plane 0 , depthBufferSize 24 , accumBufferSize 64 , stencilBufferSize 8 , redBufferSize 8 , greenBufferSize 8 , blueBufferSize 8 , alphaBufferSize -1 , samples -1 , swapInterval 1 , majorVersion 4 , minorVersion 2 , profile 2 ) @

I'm using QGLContext::getProcAddress() method to get GL_NV_Path_rendering extension functions adresses and they are also returned correctly. But when I try to use them (basing in NVIDIA example) in paintGL() method, nothing is rendered.
Could someone look at my source code and tell me what's wrong?

@
#include "glwidget.h"
#include <stdio.h>

#include "glextensions.h"

int hasPathRendering = 1;
int hasDirectStateAccess = 1;
const char *programName = "nvpr_basic";
GLuint pathObj = 42;
int path_specification_mode = 0;
int filling = 1;
int stroking = 1;
int even_odd = 0;

GLWidget::GLWidget(QWidget *parent) :
QGLWidget(parent)
{
}

void GLWidget::initializeGL()
{
qDebug() << "OpenGL Versions Supported: " << QGLFormat::openGLVersionFlags();
QString versionString(QLatin1String(reinterpret_cast<const char*>(glGetString(GL_VERSION))));
qDebug() << "Driver Version String:" << versionString;
qDebug() << "Current Context:" << format();

if (!getGLExtensionFunctions().resolve(context())) {
      QMessageBox::critical(0, "OpenGL features missing",
          "Failed to resolve OpenGL functions required to run this demo.\n"
          "The program will now exit.");
      delete this;
      return;
  }

initGraphics();

glViewport(0, 0, width(), height());
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
//glOrtho(-50, 50, -50, 50, -50, 50);
glMatrixMode(GL_MODELVIEW);

glClearColor(0.2, 0.2, 0.2, 1);

}

void initGraphics()
{
initPathFromSVG();

glPathParameteriNV(pathObj, GL_PATH_JOIN_STYLE_NV, GL_ROUND_NV);
glPathParameterfNV(pathObj, GL_PATH_STROKE_WIDTH_NV, 6.5);

}

void
initPathFromSVG()
{
const char *svgPathString =
//star
"M100,180 L40,10 L190,120 L10,120 L160,10 z";
// heart
"M300 300 C 100 400,100 200,300 100,500 200,500 400,300 300Z";
glPathStringNV(pathObj, GL_PATH_FORMAT_SVG_NV,
(GLsizei)strlen(svgPathString), svgPathString);
}

void GLWidget::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
doGraphics();
//swapBuffers();
}

void
doGraphics(void)
{
glClearStencil(0);
glClearColor(0,0,0,0);
glStencilMask(~0);
glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

glMatrixLoadIdentityEXT(GL_PROJECTION);
glMatrixLoadIdentityEXT(GL_MODELVIEW);
glMatrixOrthoEXT(GL_MODELVIEW, 0, 500, 0, 400, -1, 1);

filling = true;
stroking = true;

if (filling) {
    qDebug("filling");

    glStencilFillPathNV(pathObj, GL_COUNT_UP_NV, 0x1F);

    glEnable(GL_STENCIL_TEST);
    int even_odd = 0;
    if (even_odd) {
        glStencilFunc(GL_NOTEQUAL, 0, 0x1);
    } else {
        glStencilFunc(GL_NOTEQUAL, 0, 0x1F); // make viewport black !?
    }
    glStencilOp(GL_KEEP, GL_KEEP, GL_ZERO);
    glColor3f(0,1,0); // green
    glCoverFillPathNV(pathObj, GL_BOUNDING_BOX_NV);

    glBegin(GL_TRIANGLES); //this renders correctly !
    glVertex3f(0.8,0.9,0);
    glVertex3f(0.9,0.9,0);
    glVertex3f(0,0.4,0);
    glEnd();
}

if (stroking) {
    qDebug("stroking");
    glStencilStrokePathNV(pathObj, 0x1, ~0);
    glColor3f(1,1,0); // yellow
    glCoverStrokePathNV(pathObj, GL_CONVEX_HULL_NV);
}

}

void GLWidget::resizeGL()
{
}
@

Complete source code with comments: http://www.sendspace.com/file/jdrjsx