/*

 Copyright (C) 2017 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 The Drag Tracker tracks the changes of the mouse during a primary button drag. Tracking starts when the left mouse button is held down and the movement of the cursor exceeds a threshold value. Tracking ends when the mouse button is released. The owning view must route mouseDown:, mouseDragged: and mouseUp: responder messages to this tracker.

 */

#import "DragTracker.h"

@interface DragTracker()

@property BOOL isTrackingDrag;

@property(readwrite, nonatomic) NSPoint initialPoint;

@property (assign, nonatomic) NSPoint currentPoint;

@property(readwrite, nonatomic) NSUInteger modifiers;

@end

@implementation DragTracker

- (instancetype)init {

    if (self = [super init]) {

        self.threshold = 2.0;

    }

    return self;

}

#pragma mark NSResponder

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

    self.initialPoint = [self.view convertPoint:event.locationInWindow fromView:nil];    // convertPointFromBase:[event locationInWindow]];

    self.currentPoint = self.initialPoint;

}

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

    self.modifiers = event.modifierFlags;

    self.currentPoint = [self.view convertPoint:event.locationInWindow fromView:nil]; // [self.view convertPointFromBase:[event locationInWindow]];

    if (!self.isEnabled) return;

    if (!self.isTrackingDrag) {

        NSPoint delta = self.delta;

        if (fabs(delta.x) > self.threshold || fabs(delta.y) > self.threshold) {

            self.isTrackingDrag = YES;

            if (self.beginTrackingAction) [NSApp sendAction:self.beginTrackingAction to:self.view from:self];

        }

    } else {

        if (self.updateTrackingAction) [NSApp sendAction:self.updateTrackingAction to:self.view from:self];

    }

}

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

    if (self.isTrackingDrag) {

        self.modifiers = event.modifierFlags;

        if (self.endTrackingAction) [NSApp sendAction:self.endTrackingAction to:self.view from:self];

        self.isTrackingDrag = NO;

    }

}

#pragma mark InputTracker

- (void)cancelTracking {

    if (self.isTrackingDrag) {

        if (self.endTrackingAction) [NSApp sendAction:self.endTrackingAction to:self.view from:self];

        self.isTrackingDrag = NO;

    }

}

#pragma mark API

@synthesize isTrackingDrag = _trackingDrag;

@synthesize initialPoint = _initialPoint;

@synthesize currentPoint = _currentPoint;

@synthesize threshold = _threshold;

@synthesize beginTrackingAction = _beginTrackingAction;

@synthesize updateTrackingAction = _updateTrackingAction;

@synthesize endTrackingAction = _endTrackingAction;

@synthesize modifiers = _modifiers;

@synthesize userInfo = _userInfo;

- (NSPoint)delta;

{

    NSPoint delta;

    delta.x = self.currentPoint.x - self.initialPoint.x;

    delta.y = self.currentPoint.y - self.initialPoint.y;

    return delta;

}

@end