/*
 
 File: arcs.c
 
 Abstract: //	These are the functions that implement equivalents to the QuickDraw arc drawing APIs,
		   //   FrameArc and PaintArc.
		   //	See DrawProcs.c for sample usage
 
 Version: 1.0
 
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 */ 

#define _BSD_SOURCE
#include <math.h>
#include <stdbool.h>

#ifdef __APPLE__
#include <ApplicationServices/ApplicationServices.h>
#else
#include <CoreGraphics/CoreGraphics.h>
#endif

/*
pathForArc : Adds an arc (a segment of an oval) fitting inside a rectangle to the path.

Parameter Descriptions
context : The CG context to render to.
r : The CG rectangle that defines the arc's boundary..
startAngle : The angle indicating the start of the arc.
arcAngle : The angle indicating the arcÕs extent.
*/

void pathForArc(CGContextRef context, CGRect r, int startAngle, int arcAngle)
{
    CGFloat start, end;
    CGAffineTransform matrix;
	
	// Save the context's state because we are going to scale it
    CGContextSaveGState(context);
	
	// Create a transform to scale the context so that a radius of 1 maps to the bounds
	// of the rectangle, and transform the origin of the context to the center of
	// the bounding rectangle.
    matrix = CGAffineTransformMake(r.size.width/2, 0,
								   0, r.size.height/2,
								   r.origin.x + r.size.width/2,
								   r.origin.y + r.size.height/2);
								   
	// Apply the transform to the context
    CGContextConcatCTM(context, matrix);
		
	// Calculate the start and ending angles
    if (arcAngle > 0) {
		start = (90 - startAngle - arcAngle) * M_PI / 180;
		end = (90 - startAngle) * M_PI / 180;
    } else {
		start = (90 - startAngle) * M_PI / 180;
		end = (90 - startAngle - arcAngle) * M_PI / 180;
    }
	
	// Add the Arc to the path
    CGContextAddArc(context, 0, 0, 1, start, end, false);
	
	// Restore the context's state. This removes the translation and scaling
	// but leaves the path, since the path is not part of the graphics state.
    CGContextRestoreGState(context);
}

/*
frameArc : Draws an arc of the oval that fits inside a rectangle.

Parameter Descriptions
context : The CG context to render to.
r : The CG rectangle that defines the arc's boundary..
startAngle : The angle indicating the start of the arc.
arcAngle : The angle indicating the arcÕs extent.
*/

void frameArc(CGContextRef context, CGRect r, int startAngle, int arcAngle)
{

	// Signal the start of a path
    CGContextBeginPath(context);

	// Add to the path the arc of the oval that fits inside the rectangle.
	pathForArc(context,r,startAngle,arcAngle);
	
	// Stroke the path
    CGContextStrokePath(context);
}

/*
paintArc : Paints a wedge of the oval that fits inside a rectangle.

Parameter Descriptions
context : The CG context to render to.
r : The CG rectangle that defines the arc's boundary..
startAngle : The angle indicating the start of the arc.
arcAngle : The angle indicating the arcÕs extent.
*/

void paintArc(CGContextRef context, CGRect r, int startAngle, int arcAngle)
{
	// Signal the start of a path
    CGContextBeginPath(context);
	
	// Set the start of the path to the arcs focal point
    CGContextMoveToPoint(context, r.origin.x + r.size.width/2, r.origin.y + r.size.height/2);
	
	// Add to the path the arc of the oval that fits inside the rectangle.
	pathForArc(context,r,startAngle,arcAngle);

	// Complete the path closing the arc at the focal point
    CGContextClosePath(context);
	
	// Fill the path
    CGContextFillPath(context);
}
