NSUInteger increment is not consistent when moving with Touches Moved with different hand speeds

Question

I've created a NSUInteger that increments per pixel moved in Touches Moved method. However the increment is not consistent. It appears that moving your finger fast will increase the number slowly whereas moving your finger slowly will increase the number fast.

Essentially I'm creating a ink bottle effect, so that drawing on the screen will decrease the ink in line with finger movement, but with different speeds of drawing, this wont be always the same.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    SKLabelNode *touchedNode = (SKLabelNode *)[self nodeAtPoint:positionInScene];

    pathToDraw = CGPathCreateMutable();
    CGPathMoveToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
    lineNode = [[SKShapeNode alloc] init];
    lineNode.path = pathToDraw;
    [_gameNode addChild:lineNode];
}

- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    UITouch* touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    CGPathAddLineToPoint(pathToDraw, NULL, positionInScene.x, positionInScene.y);
    lineNode.path = pathToDraw;
    lineNode.name = lineNodeCategoryName;
    lineNode.physicsBody = [SKPhysicsBody bodyWithEdgeChainFromPath:pathToDraw];
    lineNode.physicsBody.categoryBitMask = lineNodeCategory;
    lineNode.physicsBody.contactTestBitMask = bubble1Category|bubble2Category|bubble3Category|bubble4Category|bubble5Category;
    lineNode.physicsBody.collisionBitMask = ballCategory;
    lineNode.physicsBody.dynamic = YES;
    lineNode.strokeColor = [SKColor blackColor];
    lineNode.glowWidth = 3.0;

    testNumber ++;
    testLabel.text = [NSString stringWithFormat:@"%lu",(unsigned long)testNumber];

    }

Answer 1

touchesMoved:withEvent: is called when a move event is detected. You won't be able to rely on the number of times this method is called to detect how far the user's finger moved.

You should rather try to rely on the distance the finger has travelled between two events to increment your test number.