Drawing in circle clipping region

[Yuriy Rusinov <yrusinov mnsspb ru>]

Hello, colleagues !

I have to draw something in circle, I draw black circle on my event box
by cairo as a presented on screen shot, try to make
Glib::RefPtr<Gdk::Pixmap> pgPixmap such this

  Glib::RefPtr<Gdk::Drawable> pDr = eBox->get_window ();
  int w = eBox->get_allocation().get_width();
  int h = eBox->get_allocation().get_height();
  if (pDr)
      pgPixmap = Gdk::Pixmap::create (pDr, w, h);
  //
  // set colors
  //
  Gdk::Color bgCol;
  bgCol.set_rgb_p (0.0, 0.0, 0.0);
  Gdk::Color fgCol;
  fgCol.set_rgb_p (1.0, 1.0, 1.0);
  Glib::RefPtr<Gdk::GC> pGC = Gdk::GC::create (pDr);
  pGC->set_background (bgCol);
  pGC->set_foreground (fgCol);
  int radius = w < h ? w-40 : h-40;
  radius /= 2.0;

  pgPixmap->draw_arc (pGC, true, w/2, h/2, radius, radius, 0.0, 64*360);

get image from pgPixmap such this

  Glib::RefPtr<Gdk::Image> pIm = pgPixmap->get_image (0, 0, w, h);
  const void* data = pIm->get_mem ();

make Bitmap

  Glib::RefPtr<Gdk::Bitmap> pgBitmap = Gdk::Bitmap::create (pDr, (const
char*)data, w, h);

put it onto my event box

  eBox->add_pixmap (pgPixmap, pgBitmap);

but nothing changes, where is my error and which way I have to do it ?

Thanks a lot,
Yuriy Rusinov.

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