/* gcc -framework Cocoa -lobjc `pkg-config --cflags --libs cairo` cairo.m -o cairo
 * Draws a ring using a surface with a data buffer, and then using as
 * a source for a translated cr, which exposes what I believe is a
 * bug. At least the same code works for X11.
 */


#import <Cocoa/Cocoa.h>
#include <cairo/cairo-quartz.h>

static void
paint_ring (cairo_t *cr,
	    int     x,
	    int     y,
	    int     width,
	    int     height)
{
  int xx, yy;
  double size, ring_width;
  double dx, dy, dist;
  double cx, cy;
  double inner, outer;
  uint32 *buf, *p;
  cairo_surface_t *source;

  size = MIN (width, height) / 2.0;
  ring_width = 20;

  cx = width / 2.0;
  cy = height / 2.0;
  
  outer = size / 2.0;
  inner = outer - ring_width;
  
  buf = calloc (width * height, sizeof (uint32));
  for (yy = 0; yy < height; yy++)
    {
      p = buf + yy * width;
      
      dy = -(yy + y - cy);
      
      for (xx = 0; xx < width; xx++)
	{
	  dx = xx + x - cx;
	  
	  dist = dx * dx + dy * dy;
	  if (dist < ((inner-1) * (inner-1)) || dist > ((outer+1) * (outer+1)))
	    {
	      *p++ = 0;
	      continue;
	    }
	  
	  *p++ = (255 << 16) | (65 << 8) | 24;
	}
    }

  source = cairo_image_surface_create_for_data ((unsigned char *) buf,
						CAIRO_FORMAT_RGB24,
						width, height, 4 * width);

  cairo_save (cr);
    
  cairo_set_source_surface (cr, source, x, y);
  cairo_surface_destroy (source);

  cairo_set_line_width (cr, ring_width);
  cairo_new_path (cr);
  cairo_arc (cr,
	     cx, cy,
	     size / 2.0 - ring_width / 2.0,
	     0, 2 * M_PI);
  cairo_stroke (cr);
  
  cairo_restore (cr);
  
  free (buf);
}

@interface TestView: NSView
{
}
@end

@implementation TestView

- (id)initWithFrame:(NSRect)frameRect
{
  self = [super initWithFrame:frameRect];

  return self;
}

- (BOOL)isOpaque
{
  return NO;
}

- (void)drawRect:(NSRect)rect
{
  NSRect bounds = [self bounds];
  int width = bounds.size.width;
  int height = bounds.size.height;

  CGContextRef ctx = (CGContextRef)[[NSGraphicsContext
                                      currentContext] graphicsPort];

  CGContextTranslateCTM (ctx, 0.0, height);
  CGContextScaleCTM (ctx, 1.0, -1.0);

  cairo_surface_t *surface = cairo_quartz_surface_create_for_cg_context (ctx, width, height);
  cairo_t *cr = cairo_create (surface);
  
  /* Commenting this will make the ring look as intented. */
  //cairo_translate (cr, 10, 10);

  paint_ring (cr, 0, 0, width, height);

  cairo_destroy (cr);
  cairo_surface_destroy (surface);
}

@end

int
main (int argc, char **argv)
{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    [NSApplication sharedApplication];
    
    int style = NSClosableWindowMask | NSResizableWindowMask |
      NSTitledWindowMask | NSMiniaturizableWindowMask;
    NSWindow *win = [[NSWindow alloc] initWithContentRect:NSMakeRect(50, 50, 600, 400)
                                      styleMask:style
                                      backing:NSBackingStoreBuffered
                                      defer:NO];

    NSView *view = [[TestView alloc] init];
    
    [win setContentView: view];

    [win makeKeyAndOrderFront:win];
    [NSApp run];

    [pool release];
  
    return 0;
}