/*

    File:       SillyBallsView.m

    Contains:   View class for drawing lots of silly balls.

    Written by: DTS

    Copyright:  Copyright (c) 1997-2011 Apple Inc. All Rights Reserved.

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                The Apple Software is provided by Apple on an "AS IS" basis. 

                APPLE MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

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*/

#import "SillyBallsView.h"

@interface SillyBallsView ()

@property (nonatomic, copy,   readonly ) NSString *     textString;     // the text we're drawing

@property (nonatomic, assign, readonly ) NSSize         textSize;       // the size of that text, cached for performance

@property (nonatomic, retain, readwrite) NSTimer *      drawingTimer;   // a timer for drawing the balls

@end

@implementation SillyBallsView

@synthesize running      = running_;

@synthesize ballInterval = ballInterval_;

@synthesize textString   = textString_;

@synthesize textSize     = textSize_;

@synthesize drawingTimer = drawingTimer_;

- (id)initWithFrame:(NSRect)frameRect

    // See comment in interface part.

{

    self = [super initWithFrame:frameRect];

    if (self != nil) {

        self->running_ = NO;

        self->ballInterval_ = 1.0;

        // Init some basic instance variables.

        self->textString_ = [@"Bo3b" copy];

        self->textSize_ = [self->textString_ sizeWithAttributes:nil];

        // Observe our own properties so that, when they change, we can respond.

        [self addObserver:self forKeyPath:@"running" options:0 context:&self->running_];

        [self addObserver:self forKeyPath:@"ballInterval" options:0 context:&self->ballInterval_];

    }

    return self;

}

- (void)dealloc

{

    // Remove our observers.

    [self removeObserver:self forKeyPath:@"running"];

    [self removeObserver:self forKeyPath:@"ballInterval"];

    // General clean up.

    [self->textString_ release];

    [self->drawingTimer_ invalidate];

    [self->drawingTimer_ release];

    [super dealloc];

}

#pragma mark * Drawing

- (CGFloat)randomCGFloat

    // Returns a random floating point number between 0.0 and 1.0.

{

    return ((CGFloat) rand() / (CGFloat) RAND_MAX);

}

static const CGFloat kBallSize = 32.0;

- (void)drawRandomBallInRect:(const NSRect *)rect

    // Draws Silly Ball(tm) at random coordinates within the specified 

    // rectangle.  This method can assume we're in a state ready to draw, 

    // either inside the view's -drawRect: routine, or otherwise having the 

    // focus locked on this view.

{

    NSRect          ballBounds;

    NSBezierPath *  oval;

    NSPoint         textOrigin;

    // Calculate where the ball should go.

    ballBounds.origin.x = rect->origin.x + rect->size.width  * [self randomCGFloat];

    ballBounds.origin.y = rect->origin.x + rect->size.height * [self randomCGFloat];

    ballBounds.size.width  = kBallSize;

    ballBounds.size.height = kBallSize;

    // Set the current colour to a random RGB value.

    [[NSColor colorWithDeviceRed:[self randomCGFloat] green:[self randomCGFloat] blue:[self randomCGFloat] alpha:1.0] set];

    // Now construct a bezier path for an circle and draw it.

    oval = [NSBezierPath bezierPath];

    [oval appendBezierPathWithOvalInRect:ballBounds];

    [oval fill];

    // Now set the current colour to black and draw the text centred in the ball.

    [[NSColor blackColor] set];

    textOrigin = ballBounds.origin;

    textOrigin.x += (ballBounds.size.width  - self.textSize.width ) / 2.0;

    textOrigin.y += (ballBounds.size.height - self.textSize.height) / 2.0;

    [self.textString drawAtPoint:textOrigin withAttributes:nil];

}

- (void)drawRect:(NSRect)rect

    // NSViews are expected to override this method to do their drawing.  We actually 

    // do nothing in this method, because we don't have any persistent state.  All our 

    // drawing is done in response to drawingTimer firing.  See the sample code read me 

    // for a more thorough explanation of this.

{

    #pragma unused(rect)

}

- (void)drawAnother:(NSTimer *)timer

    // This method is called in response to drawingTimer firing.  Its function is to 

    // lock focus on the view and then call -drawRandomBallInRect:.

{

    NSRect visRect;

    assert(timer == self.drawingTimer);

    #pragma unused(timer)

    // Lock focus on ourselves.  We need to do this because we're drawing

    // outside of the context of NSView's -drawRect: method.  This is relatively

    // unusual behaviour for a view.  See the discussion of this in the read me.

    [self lockFocus];

    // Draw a ball.

    visRect = [self visibleRect];

    [self drawRandomBallInRect:&visRect];

    // And unlock the focus.

    [self unlockFocus];

    [[self window] flushWindow];

}

#pragma mark * Responding to external events

- (void)clear

    // See comment in interface part.

{

    [self setNeedsDisplay:YES];

}

- (void)startDrawingTimer

{

    // Invalidate any previous repeat timer.

    [self.drawingTimer invalidate];

    // Start the new one.

    self.drawingTimer = [NSTimer scheduledTimerWithTimeInterval:self.ballInterval target:self selector:@selector(drawAnother:) userInfo:nil repeats:YES];

}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

    if (context == &self->running_) {

        assert([keyPath isEqual:@"running"]);

        assert(object == self);

        // When running changes, either start or stop the drawing timer.

        if (self.running) {

            [self startDrawingTimer];

        } else {

            [self.drawingTimer invalidate];

            self.drawingTimer = nil;

        }

    } else if (context == &self->ballInterval_) {

        // When ballInterval changes, and we're running, update the drawing 

        // timer to use the specified interval.

        if (self.running) {

            [self startDrawingTimer];

        }

    } else {

        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];

    }

}

@end