View that implements marching ants selection

MarchingAntsView.plain_text

@interface MarchingAntsView : NSView {
    NSPoint     clickLoc;
    NSRect      selection;
}

@end

@implementation MarchingAntsView

NSRect RectFromPoints(NSPoint pt1, NSPoint pt2)
{
    float minX = MIN(pt1.x, pt2.x);
    float minY = MIN(pt1.y, pt2.y);
    float maxX = MAX(pt1.x, pt2.x);
    float maxY = MAX(pt1.y, pt2.y);
    
    float height = maxY - minY;
    float width = maxX - minX;
    
    return NSMakeRect(minX, minY, width, height);
}

- (void)mouseDown:(NSEvent *)theEvent
{
    NSPoint eventLocation = [theEvent locationInWindow];
    clickLoc = [self convertPoint:eventLocation fromView:nil];
    selection = NSZeroRect;
}

- (void)mouseDragged:(NSEvent *)theEvent
{
    NSPoint pt = [self convertPoint:[theEvent locationInWindow] fromView:nil];
    NSRect oldSelection = selection;
    selection = RectFromPoints(pt, clickLoc);
    [self setNeedsDisplayInRect:NSInsetRect(NSUnionRect(selection, oldSelection), -1, -1)];
}

- (void)mouseUp:(NSEvent *)theEvent
{
    Element *added = nil;
    NSPoint pt = [self convertPoint:[theEvent locationInWindow] fromView:nil];

    // do something here when the mouse is released

    selection = NSZeroRect;
}

@end