FANodeDraw.m

// Draws a test finite automata node with CoreGraphics functions.

- (void)drawRect:(NSRect)rect
{
    // Obtain the current context.
    CGContextRef context = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];

    // Set the color space.
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextSetFillColorSpace(context, colorSpace);
    CGContextSetStrokeColorSpace(context, colorSpace);
    CGColorSpaceRelease(colorSpace);

    // Fill the view backgroud.
    CGFloat canvasBackgroundColor[] = {1.0f, 1.0f, 1.0f, 1.0f};
    CGContextSetFillColor(context, canvasBackgroundColor);
    CGContextFillRect(context, rect);

    // Define the node geometry.
    CGSize nodeSize = CGSizeMake(50.0f, 50.0f);
    CGPoint nodeCenterPosition = CGPointMake(100.0f, 150.0f);
    CGPoint nodePosition = CGPointMake(nodeCenterPosition.x - nodeSize.width / 2.0f,
                                       nodeCenterPosition.y - nodeSize.height / 2.0f);
    CGRect nodeRect = CGRectMake(nodePosition.x, nodePosition.y, nodeSize.width, nodeSize.height);

    // Stroke the node path.
    CGFloat nodeStrokeColor[] = {0.0f, 0.0f, 0.0f, 1.0f};
    CGContextSetLineWidth(context, 3.0);
    CGContextSetStrokeColor(context, nodeStrokeColor);
    CGContextAddEllipseInRect(context, nodeRect);
    CGContextStrokePath(context);

    // Fill the node background.
    CGFloat nodeBackgroundColor[] = {1.0f, 1.0f, 1.0f, 1.0f};
    CGContextSetFillColor(context, nodeBackgroundColor);
    CGContextFillEllipseInRect(context, nodeRect);

    // Draw the node label.
    NSString *nodeLabelText = @"s0";
    NSFont *font = [NSFont fontWithName:@"Helvetica" size:24.0];
    NSDictionary *textAttributes = @{NSFontAttributeName: font};
    CGSize labelSize = [nodeLabelText sizeWithAttributes:textAttributes];
    CGPoint labelPosition = CGPointMake(nodeCenterPosition.x - labelSize.width / 2.0f,
                                        nodeCenterPosition.y - labelSize.height / 2.0f);
    CGRect labelRect = CGRectMake(labelPosition.x, labelPosition.y, labelSize.width, labelSize.height);
    [nodeLabelText drawInRect:labelRect withAttributes:textAttributes];
}