Pan Gesture basic example wrong behaviour about c4ios

[traviskirton]

Got it.

You should do this:

square.addPanGestureRecognizer { locations, center, translation, velocity, state in
    let p = self.canvas.convert(center, from: square)
    square.center = p
}

This converts the gesture's center point to it's relative position in the canvas.

Reasoning...

The demo attaches the gesture to the canvas. However, you're attaching the gesture to the shape itself, which causes the flicker because of this:

1. your touch starts in the center of the shape {50,50}
2. square.center = center sets the shape's actual center to {50, 50}
3. your touch doesn't move relative to the canvas, and...
4. your touch is now at a relative point outside the shape, let's say ~{200,200}
5. square.center = center sets the shape's center to ~{200,200}
6. your touch is now in the shape again, and measured relative to the shape's top-right corner
7. square.center = center sets the shape's actual center to ~{50, 50}
8. repeat...

[traviskirton]

The warning you get is something that comes with Xcode8, we get it too... Doesn't seem to affect anything.