Draw editable angles using drawRect?

Question 1

You're not handling the editing flag properly. You call in touchesBegan:

        if(yDistance2 <= 25 || editing){
            NSLog(@"It's editing time, yo");
            editing = TRUE; // Here's your problem

Which means in touchesMoved, when you hit:

if(xDistance <= 25 || editing) // Note the "Or editing"

editing equals true, which means it will move point 1 instead, since it hits that if statement first, no matter which point set that.

Conclusion

You need to use a specific editing flag for each point. Not a shared one. At least not with an or check. Or better yet, handle touchesMoved a little nicer. You don't need to almost completely duplicate your code from touchesBegan

Side Note

Although not completely related to your problem, I believe you are also swaping point2 and point3 in your if statements. In checking xDistance2:

else if(xDistance2 <= 25 || editing){
            NSLog(@"X is pretty close");
            if(yDistance2 <= 25 || editing){
                NSLog(@"It's editing time, yo");
                editing = TRUE;
                first = currentSegment.firstPoint;
                second = currentSegment.secondPoint;
                third = point; // <- Why are you setting third to point and not second to point.
                self.segmentBeingEdited = currentSegment;
                [self setNeedsDisplay];
                return;
            }
    }

Ditto when you check XDistance3. You set second to point, instead of third.

Question 2

Ok--This may not be exactly what you wanted... I created an editable angle UI which I think is a pretty good way to put together what you want to do. (I like projects like this)

There's a canvas, view controller, angle view and angle handle view. Taps on the canvas are recorded. When 3 taps happen an angle view (with handles inside it) is created. Tapping on an existing angle selects it (revealing the handles and selection UI)

The project is on github.

edit

I didn't use gesture recognizers, but that might be a good alternative.

enter image description here

Question 3

There's one obvious and one non-obvious bug in your code.

The obvious one is that in your touchesBegan method, you are mistakenly setting the values of second and third - when you are close to the second point, you are assigning the touch point value to the third variable and vice versa.

The non-obvious one is that you have a global variable, editing, which is set in touchesBegan for whichever point you are editing, and then used in an or condition in touchesMoved, meaning that as soon as you drag anything, it immediately falls through to the first point of the first item in the array.

You've got too much going on in your touchesMoved method. You should be determining which point of which segment is being edited in touchesBegan, and then in touchesMoved only doing anything if you are editing a particular point - don't try and work out what you are editing again. You also don't really need to maintain all that separate state - you've got a segmentBeingEdited property, just use that, and a flag to say which point you are editing, and update the values directly while you are dragging.

This was obvious almost immediately by including a bit of context in your log messages - copy-pasting the same log message everywhere will always confuse you in the end.

Here's an adapted version of your touchesXX methods. I've removed a lot of unnecessary code and state for you. It still isn't working quite right - there are problems with drawing the edited segments. At some point you will need to add in code for a full redraw, or keep each image separate and remove the unneeded ones, but hopefully the principles I'm explaining will be straightforward.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    self.segmentBeingEdited = nil;
    pointBeingEdited = 0;

    UITouch *touch = [touches anyObject];

    CGPoint point = [touch locationInView:self];

    // Are we editing an existing segment?
    for(int i = 0;i<self.tapArray.count;i++){
        Segment *currentSegment = [self.tapArray objectAtIndex:i];

        int xDistance = abs(point.x - currentSegment.firstPoint.x);
        int yDistance = abs(point.y - currentSegment.firstPoint.y);
        int xDistance2 = abs(point.x - currentSegment.secondPoint.x);
        int yDistance2 = abs(point.y - currentSegment.secondPoint.y);
        int xDistance3 = abs(point.x - currentSegment.thirdPoint.x);
        int yDistance3 = abs(point.y - currentSegment.thirdPoint.y);

        if(xDistance <= 25){
            if(yDistance <= 25){
                pointBeingEdited = 1;
            }
        }
        else if(xDistance2 <= 25 ){
            if(yDistance2 <= 25){
                pointBeingEdited = 2;
            }
        }
        else if(xDistance3 <= 25){
            if(yDistance3 <= 25){
                pointBeingEdited = 3;
            }
        }

        if (pointBeingEdited != 0)
        {
            NSLog(@"editing point %d",pointBeingEdited);
            self.segmentBeingEdited = currentSegment;
            return;
        }
    }

    // Creating a new segment. Update data.
    if (pointBeingAdded == 0)
    {
        first = [touch locationInView:self];
        second = CGPointZero;
        third = CGPointZero;
    }
    else if (pointBeingAdded == 1)
    {
        second = [touch locationInView:self];
    }
    else if (pointBeingAdded == 2)
    {
        third = [touch locationInView:self];
    }
    pointBeingAdded++;

    [self setNeedsDisplay];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    if (!self.segmentBeingEdited)
        return;

    UITouch *touch = [touches anyObject];

    CGPoint point = [touch locationInView:self];
    if (pointBeingEdited == 1)
    {
        self.segmentBeingEdited.firstPoint = point;
    }
    else if (pointBeingEdited == 2)
    {
        self.segmentBeingEdited.secondPoint = point;
    }
    else if (pointBeingEdited == 3)
    {
        self.segmentBeingEdited.thirdPoint = point;
    }
    [self drawBitmap];
    [self setNeedsDisplay];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    if(self.segmentBeingEdited){
        first = CGPointZero;
        second = CGPointZero;
        third = CGPointZero;
    }

    if(pointBeingAdded == 3){
        // Add new segment
        Segment *segment = [[Segment alloc] init];
        segment.firstPoint = first;
        segment.secondPoint = second;
        segment.thirdPoint = third;

        if(self.tapArray == nil){
            self.tapArray = [[NSMutableArray alloc] init];
        }
        [self.tapArray addObject:segment];
        pointBeingAdded = 0;
    }
    [self drawBitmap];
    self.segmentBeingEdited = nil;
}

Question 4

I would like to say some things about your code:

1- It's not necessary but, you could use a tap and a pan gesture recognizers, I think that would simplify your code.

2- When you try to find the point being edited you repeat a lot of code, you could iterate the points for each segment like this:

- (void)tapAction:(UITapGestureRecognizer *)recognizer {
CGPoint point = [recognizer locationInView:self];
self.segmentBeingEdited = nil;
CGPoint currentPoint;
for (Segment *segment in self.tapArray) {
    for (NSInteger p = 0; p < 3; p++) {
        currentPoint = [segment pointAtIndex:p];
        CGFloat distance = fDistance(point, currentPoint);
        if (distance <= 25.0) {
            self.segmentBeingEdited = segment;
            self.pointBeingEdited = p;
            [self setNeedsDisplay];
            return;
        }
    }
}
Segment *segment = [self.tapArray lastObject];
if (!segment || segment.points == 3) {
    segment = [[Segment alloc] init];
    [self.tapArray addObject:segment];
}
[segment setPoint:point atIndex:segment.points];
segment.points = segment.points + 1;
[self setNeedsDisplay];

}

3- The Segment class could have methods to get and set the points based on the index 0,1,2 and the number of points already added, I think this would increase cohesion and simplify your code.

4- The algorithm you use to determine if the distance from the tap location to some point is less than 25... well, it works but it's technically incorrect, you should use something like this:

static inline CGFloat fDistance(CGPoint point1, CGPoint point2) {
CGFloat dx = point1.x - point2.x;
CGFloat dy = point1.y - point2.y;
return sqrtf(dx * dx + dy * dy); }

5- I noticed that you use CGPointEqualToPoint(point, CGPointZero) in some if's, again, it works but there is better ways to do that, you could use a flag to find the next point being added.

Finally you could use the pan gesture recognizer to edit the selected point:

- (void)panAction:(UIPanGestureRecognizer *)recognizer {
CGPoint location = [recognizer locationInView:self];

switch (recognizer.state) {
    case UIGestureRecognizerStateBegan:
    {
        CGPoint point = [self.segmentBeingEdited pointAtIndex:self.pointBeingEdited];
        CGFloat distance = fDistance(location, point);
        if (distance > 25.0) {
            self.segmentBeingEdited = nil;
        }
        break;
    }
    case UIGestureRecognizerStateChanged:
    {
        if (self.segmentBeingEdited) {
            [self.segmentBeingEdited setPoint:location atIndex:self.pointBeingEdited];
            [self setNeedsDisplay];
        }
    }

    default:
        break;
}
}

I hope this can be useful.