I present this "wall 'o code" as a (mostly) complete means of doing an area selection inside a custom NSView with the ability to subsequently expand/move the "marching ants" rectangle.
Hopefully someone out there finds it useful.
A initial call to "introThumbRect" gets the ball rolling. The sides of the rectangle can be expanded, with the mouse cursor changing appropriately. The selection rectangle can also be moved. The initial/resulting rectangle is in the view's "thumbRect" property (relative to the "fullImage" coordinate system). The "cropPt" value is the upper-left of the displayed image "fullImage"; for the purposes here, assume it's (0,0).
The one issue I'm having is that, once a mouse drag is happening (ie. the sides are being expanded or the rectangle is being moved), I'm fighting with the mouse cursor to maintain it in it's original drag state. It wants to revert to an arrow cursor whereas it should maintain itself as, say, an open-hand cursor. I believe this is happening as a result of re-calculating the tracking areas, but such a problem is practically impossible to debug as XCode doesn't "track" the cursor state.
If anyone can assist with fixing that minor bug, that'd be great.
#import <Cocoa/Cocoa.h>
@interface ThumbNailView : NSView
@property (nonatomic, strong) NSImage *fullImage;
@property (nonatomic) CGPoint cropPt;
@property (nonatomic) CGRect thumbRect;
- (void)introThumbRect;
@end
@implementation ThumbNailView
{
NSMutableArray *trackingAreas;
NSCursor *dragCursor;
NSTimer *antTimer;
NSInteger antPhase;
NSString *dragMode;
CGRect origThumbRect;
CGPoint thumbPt;
CGPoint mouseLoc;
BOOL thumbVisible;
BOOL updatedTracking;
BOOL amDragging;
}
- (id)initWithFrame:(NSRect)frame
{
self = [super initWithFrame:frame];
if (self)
[self setThumbRect:CGRectZero];
return self;
}
-(BOOL) isFlipped
{
return YES;
}
- (void)setupTrackingOnRect:(CGRect)r
{
CGRect trackRects[5];
int d=5;
// these are tracking rectangles for the interior + 4 sides of the rectangle
trackRects[0] = CGRectMake(r.origin.x+d,r.origin.y+d,
r.size.width-d*2,r.size.height-d*2); // main interior
trackRects[1] = CGRectMake(r.origin.x-d,r.origin.y+d,
d*2,r.size.height-d*2); // left side
trackRects[2] = CGRectMake(r.origin.x+r.size.width-d,r.origin.y+d,
d*2,r.size.height-d*2); // right side
trackRects[3] = CGRectMake(r.origin.x+d,r.origin.y-d,
r.size.width-d*2,d*2); // top side
trackRects[4] = CGRectMake(r.origin.x+d,r.origin.y+r.size.height-d,
r.size.width-d*2,d*2); // bottom inside
NSMutableArray *dicts = [[NSMutableArray alloc] init];
[dicts addObject:[[NSDictionary alloc] initWithObjectsAndKeys:
NSStringFromRect(CGRectMake(1,1,0,0)),@"moveMode",
[NSCursor openHandCursor], @"cursor",nil]];
[dicts addObject:[[NSDictionary alloc] initWithObjectsAndKeys:
NSStringFromRect(CGRectMake(1,0,-1,0)),@"moveMode",
[NSCursor resizeLeftRightCursor],@"cursor",nil]];
[dicts addObject:[[NSDictionary alloc] initWithObjectsAndKeys:
NSStringFromRect(CGRectMake(0,0,1,0)),@"moveMode",
[NSCursor resizeLeftRightCursor],@"cursor",nil]];
[dicts addObject:[[NSDictionary alloc] initWithObjectsAndKeys:
NSStringFromRect(CGRectMake(0,1,0,-1)),@"moveMode",
[NSCursor resizeUpDownCursor], @"cursor",nil]];
[dicts addObject:[[NSDictionary alloc] initWithObjectsAndKeys:
NSStringFromRect(CGRectMake(0,0,0,1)),@"moveMode",
[NSCursor resizeUpDownCursor], @"cursor",nil]];
NSTrackingAreaOptions myOptions = NSTrackingMouseEnteredAndExited |
NSTrackingMouseMoved;
NSMutableArray *tracks = [[NSMutableArray alloc] init];
for (int i=0; i<5; i++) {
NSDictionary *dict = [dicts objectAtIndex:i];
[tracks addObject:[[NSTrackingArea alloc] initWithRect:trackRects[i]
options:myOptions | NSTrackingActiveInKeyWindow
owner:self
userInfo:dict]];
[self addTrackingArea:[tracks objectAtIndex:i]];
}
trackingAreas=tracks;
}
- (void)updateTrackingAreas
{
if (dragCursor)
[dragCursor set];
[super updateTrackingAreas];
if (dragCursor)
[dragCursor set];
for (NSTrackingArea *t in [self trackingAreas])
[self removeTrackingArea:t];
trackingAreas=nil;
if (thumbVisible) {
CGRect tRect = CGRectOffset([self thumbRect],
thumbPt.x-[self cropPt].x,
thumbPt.y-[self cropPt].y);
[self setupTrackingOnRect:tRect];
}
}
- (void)mouseEntered:(NSEvent *)theEvent
{
if (amDragging)
return;
NSDictionary *userDict = [theEvent userData];
if (userDict) {
NSCursor *newCursor = [userDict objectForKey:@"cursor"];
if (newCursor) {
[newCursor set];
dragCursor=newCursor;
}
NSString *newMode = [userDict objectForKey:@"moveMode"];
if (newMode)
dragMode=newMode;
}
}
- (void)mouseExited:(NSEvent *)theEvent
{
if (!amDragging) {
[[NSCursor arrowCursor] set];
dragMode=nil;
dragCursor=nil;
}
}
- (void)mouseDragged:(NSEvent *)theEvent
{
if (dragMode) {
amDragging=YES;
if (dragCursor)
[dragCursor set];
CGPoint newLoc = [NSEvent mouseLocation];
NSInteger deltaX = mouseLoc.x - newLoc.x;
NSInteger deltaY = mouseLoc.y - newLoc.y;
CGRect moveMode = NSRectFromString(dragMode);
CGRect trect = CGRectOffset(origThumbRect,-moveMode.origin.x*deltaX,moveMode.origin.y*deltaY);
trect.size.width -= moveMode.size.width*deltaX;
trect.size.height += moveMode.size.height*deltaY;
[self setThumbRect:trect];
updatedTracking=NO;
[self setNeedsDisplay:YES];
}
}
- (void)mouseMoved:(NSEvent *)theEvent
{
if (dragCursor)
[dragCursor set];
}
- (void)mouseDown:(NSEvent *)theEvent
{
mouseLoc=[NSEvent mouseLocation];
origThumbRect = [self thumbRect];
}
- (void)mouseUp:(NSEvent *)theEvent
{
amDragging=NO;
dragCursor=nil;
[self setNeedsDisplay:YES];
}
- (void)introThumbRect
{
NSInteger h = [self frame].size.height;
if (!h)
return;
CGRect thumbRect = CGRectMake(0,0,140.0*h/64.0,h);
thumbPt = [self cropPt];
[self setThumbRect:thumbRect];
[self setNeedsDisplay:YES];
}
- (void) antMarch:(NSTimer *)timer
{
antPhase = (antPhase+1)%7;
[self setNeedsDisplay:YES];
}
- (void)drawRect:(NSRect)dirtyRect
{
[super drawRect:dirtyRect];
// Drawing code here.
[[NSColor greenColor] set];
[NSBezierPath fillRect:dirtyRect];
CGRect cropRect = CGRectMake([self cropPt].x,
[self cropPt].y,
[self frame].size.width,
[self frame].size.height);
CGRect myRect = CGRectMake(0,0,cropRect.size.width,cropRect.size.height);
[[self fullImage] drawInRect:myRect
fromRect:cropRect
operation:NSCompositeCopy
fraction:1.0
respectFlipped:YES
hints:nil];
if (CGRectEqualToRect(CGRectZero,[self thumbRect]))
return;
CGRect tRect = CGRectOffset([self thumbRect],
thumbPt.x-[self cropPt].x,
thumbPt.y-[self cropPt].y);
CGRect iRect = CGRectIntersection(myRect,tRect);
if (CGRectIsNull(iRect)) {
if (thumbVisible) {
thumbVisible=NO;
[self updateTrackingAreas];
}
if (antTimer) {
[antTimer invalidate];
antTimer=nil;
}
return;
}
thumbVisible=YES;
[self drawThumbBox];
if (!antTimer) {
antTimer = [NSTimer scheduledTimerWithTimeInterval:0.1
target:self
selector:@selector(antMarch:)
userInfo:nil
repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:antTimer forMode: NSDefaultRunLoopMode];
[[NSRunLoop currentRunLoop] addTimer:antTimer forMode: NSEventTrackingRunLoopMode];
}
//if (![self inDrag])
if (dragCursor)
[dragCursor set];
if (!updatedTracking) {
updatedTracking=YES;
[self updateTrackingAreas];
}
}
- (void)drawThumbBox
{
NSInteger deltaX = thumbPt.x-[self cropPt].x;
NSInteger deltaY = thumbPt.y-[self cropPt].y;
CGRect tRect = CGRectOffset([self thumbRect],deltaX,deltaY);
NSCompositingOperation curComp = [[NSGraphicsContext currentContext] compositingOperation];
[[NSGraphicsContext currentContext] setCompositingOperation:NSCompositeXOR];
// draw marching ants
[[NSColor blackColor] set];
NSBezierPath *selectionPath = [NSBezierPath bezierPathWithRect:tRect];
CGFloat dashArray[2] = {5.0, 2.0};
[selectionPath setLineDash:dashArray
count:sizeof(dashArray)/sizeof(CGFloat)
phase:antPhase];
[selectionPath stroke];
[[NSGraphicsContext currentContext] setCompositingOperation:curComp];
}
@end