Python for Bioinformatics: Dragging

Sunday, October 18, 2009

Dragging

This post and the next show a simple example of dragging in Cocoa. We make a single simple shape, and position it randomly within the view. This code makes use of the C functions srand() and random(), and I wrote a short function to encapsulate this: - (NSUInteger)randomIntInRange:(NSRange)r.

I noticed something unexpected. When I set the contentView of the window to be of class "MyView", its initWithFrame: method does not get called. This only happens if a put a custom view in the window. I don't know why.

In the code listing, I've tacked on the instance variables, for convenience. Some of these are only used next time.

#import "MyView.h"

@implementation MyView
@synthesize shape;

- (id)initWithFrame:(NSRect)frameRect {
    NSLog(@"myView initWithFrame");
    self = [super initWithFrame:frameRect];
    if (nil == self) { return nil; }
    srandom(time(0));
    CL = [NSColorList 
        colorListNamed:@"Crayons"];
    [CL retain];
    [self setShape:[self makeShape]];
    return self;
}

- (NSUInteger)randomIntInRange:(NSRange)r {
    int j = r.location - 1;
    do { j = random() % r.length; }
    while (j < r.location);
    return (NSUInteger) j;
}

- (NSPoint)
randomStartingPointShapeOfW:(NSUInteger)wd 
                          h:(NSUInteger)ht {
    x = [self randomIntInRange:
         NSMakeRange(0,
            [self bounds].size.width - wd)];
    y = [self randomIntInRange:
         NSMakeRange(0,
            [self bounds].size.height - ht)];
    return NSMakePoint(x,y);
}

- (NSBezierPath *)makeShape {
    w = 100;
    h = 100;
    p = [self 
        randomStartingPointShapeOfW:w h:h];
    return [NSBezierPath bezierPathWithOvalInRect:
            NSMakeRect(p.x,p.y,w,h) ];
}

- (void)drawRect:(NSRect)rect{
    c = [CL colorWithKey:@"Lemon"];
    [c set];
    NSRectFill([self bounds]);
    c = [CL colorWithKey:@"Plum"];
    [c set];
    [shape fill];
}

@end

    NSBezierPath *shape;
    
    NSColor *c;
    NSColorList *CL;
    NSRect R;
    NSRect bo;
    NSRect bn;
    NSPoint p;
    NSPoint lastPoint;
    NSAffineTransform *t;

    NSUInteger i;
    NSUInteger x;
    NSUInteger y;
    NSUInteger w;
    NSUInteger h;
    float dx;
    float dy;
    
    BOOL draggingInProgress;
    BOOL didMove;