/*

 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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 */ 

#include "arcs.h"

/*

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)

{

    float 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)

{

    float start, end;

    // 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);

}