/*

     File: Rotater.m 

 Abstract: Rotater simulates an arm which rotates about the specified origin.

 It knows how much of an angle to rotate per frame, but doesn't know

 anything about real time -- you have to send -animate at the correct

 time to advance each frame. 

  Version: 1.1 

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 */

#import "Rotater.h"

#define PI              (2 * asin (1.0))

//  Number of animation frames for any point to catch up to "wheel"

#define FRAMES_TO_SYNC  50

#define DEFAULT_RADIANS_PER_FRAME   (PI/40)

#define DEFAULT_ARM_LENGTH          200

@implementation Rotater

@synthesize origin;

@synthesize radiansPerFrame;

@synthesize armLength;

#pragma mark PUBLIC INSTANCE METHODS -- OVERRIDES FROM NSObject

- (id) init

{

    self = [super init];

    if (self == nil) return self;       // tripped on our shoelaces?

    self.radiansPerFrame = DEFAULT_RADIANS_PER_FRAME;

    self.armLength = DEFAULT_ARM_LENGTH;

    return self;

}

#pragma mark PUBLIC INSTANCE METHODS

- (void) animate                        // move to the next angle

{

    //  Just move the angle; the client must ask for X and Y.

    angle += radiansPerFrame;

}

- (void) setXY:(NSSize)point

{

    NSPoint newPoint = NSMakePoint(point.width, point.height);

    if (NSEqualPoints (newPoint, mostRecentPoint))

        return;

    //  Remember where we are now

    mostRecentPoint = newPoint;

    //  Initialize the catch-up fraction to 100%

    syncFraction = 1.0;

}

- (NSSize) getXY

{

    CGFloat x, y;

    //  Figure where we OUGHT to be (high-school trig is useful, after all)

    x = origin.x + (armLength * cos (angle));

    y = origin.y + (armLength * sin (angle));

    //  If the client did a 'set' to some odd place, partially accomodate

    //  that displacement. And reduce that ÒaccomodationÓ a little bit each time.

    if (syncFraction > 0.0)

    {

        x += syncFraction * (mostRecentPoint.x - x);

        y += syncFraction * (mostRecentPoint.y - y);

        syncFraction -= (1.0 / FRAMES_TO_SYNC);

    }

    //  Round everything

    x = floor (x + 0.5);

    y = floor (y + 0.5);

    mostRecentPoint = NSMakePoint (x, y);

    return NSMakeSize(x, y);

}

@end