/*

     File: DotView.m

 Abstract:  Simple NSView subclass showing how to draw, handle simple events, and target/action methods. This version also adds ability to undo all changes by simple use of NSUndoManager in the setters.

  Version: 1.2

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#import <Cocoa/Cocoa.h>

#import "DotView.h"

@implementation DotView

@synthesize color, radius, center;

// initWithFrame: is NSView's designated initializer (meaning it should be overridden in the

// subclassers if needed, and it should call super, that is NSView's implementation).  

// In DotView we do just that, and also set the instance variables.

//

// Note that we initialize the instance variables here in the same way they are

// initialized in the nib file. This is adequate, but a better solution is to make

// sure the two places are initialized from the same place. An even better approach is to

// simply use Cocoa Bindings, where the values are kept in sync automatically. For purposes

// of illustration and transparency (since this is a mod of the DotView example), we

// do not use bindings here.

static NSString *DotViewUndoAndRedisplay;

- (id)initWithFrame:(NSRect)frame {

    if (self = [super initWithFrame:frame]) {

        self.center = NSMakePoint(50, 50);

        self.radius = 10.0;

        self.color = [NSColor redColor];

        [self addObserver:self forKeyPath:@"color" options:NSKeyValueObservingOptionOld context:DotViewUndoAndRedisplay];

        [self addObserver:self forKeyPath:@"radius" options:NSKeyValueObservingOptionOld context:DotViewUndoAndRedisplay];

        [self addObserver:self forKeyPath:@"center" options:NSKeyValueObservingOptionOld context:DotViewUndoAndRedisplay];

    }

    return self;

}

// dealloc is the method called when objects are being freed. (Note that "release"

// is called to release objects; when the number of release calls reduce the

// total reference count on an object to zero, dealloc is called to free

// the object.  dealloc should free any memory allocated by the subclass

// and then call super to get the superclass to do additional cleanup.

- (void)dealloc {

    [self removeObserver:self forKeyPath:@"color" context:DotViewUndoAndRedisplay];

    [self removeObserver:self forKeyPath:@"radius" context:DotViewUndoAndRedisplay];

    [self removeObserver:self forKeyPath:@"center" context:DotViewUndoAndRedisplay];    

    self.color = nil;

    [super dealloc];

}

// drawRect: should be overridden in subclassers of NSView to do necessary

// drawing in order to recreate the the look of the view. It will be called

// to draw the whole view or parts of it (pay attention the rect argument);

// it will also be called during printing if your app is set up to print.

// In DotView we first clear the view to white, then draw the dot at its

// current location and size.

- (void)drawRect:(NSRect)rect {

    // Draw the background

    [[NSColor whiteColor] set];

    NSRectFill([self bounds]);

    // Draw the dot

    NSPoint c = self.center;

    CGFloat r = self.radius;

    NSRect dotRect = NSMakeRect(c.x - r, c.y - r, 2 * r, 2 * r);

    [self.color set];

    [[NSBezierPath bezierPathWithOvalInRect:dotRect] fill];

}

// Views which totally redraw their whole bounds without needing any of the

// views behind it should override isOpaque to return YES. This is a performance

// optimization hint for the display subsystem. This applies to DotView, whose

// drawRect: does fill the whole rect its given with a solid, opaque color.

- (BOOL)isOpaque {

    return YES;

}

// Rather than creating accessor methods for every single property we want react 

// to changes in, we observe them using KVO.

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

    if (context == DotViewUndoAndRedisplay) {

        NSUndoManager *undoManager = [[self window] undoManager];

        if ([keyPath isEqual:@"center"]) [[undoManager prepareWithInvocationTarget:self] setCenter:[[change objectForKey:NSKeyValueChangeOldKey] pointValue]];

        else if ([keyPath isEqual:@"radius"]) [[undoManager prepareWithInvocationTarget:self] setRadius:[[change objectForKey:NSKeyValueChangeOldKey] doubleValue]];

        else if ([keyPath isEqual:@"color"]) [undoManager registerUndoWithTarget:self selector:@selector(setColor:) object:[change objectForKey:NSKeyValueChangeOldKey]];

    [self setNeedsDisplay:YES];

    }

}

// Recommended way to handle events is to override NSResponder (superclass

// of NSView) methods in the NSView subclass. One such method is mouseUp:.

// These methods get the event as the argument. The event has the mouse

// location in window coordinates; use convertPoint:fromView: (with "nil"

// as the view argument) to convert this point to local view coordinates.

- (void)mouseUp:(NSEvent *)event {

    NSPoint eventLocationInViewCoords = [self convertPoint:[event locationInWindow] fromView:nil];

    self.center = eventLocationInViewCoords;

}

// Target/action methods. In this version of DotView the action methods simply call the 

// setters. Using Cocoa Bindings would eliminate the need for these two methods.

- (void)changeSize:(id)sender {

    self.radius = [sender doubleValue];

}

- (void)changeColor:(id)sender {

    self.color = [sender color];

}

@end