// Unity C# reference source

// Copyright (c) Unity Technologies. For terms of use, see

// https://unity3d.com/legal/licenses/Unity_Reference_Only_License

using System;

namespace UnityEngine.UIElements

{

internal class ClampedDragger<T> : Clickable

where T : IComparable<T>

{

[Flags]

public enum DragDirection

{

None = 0,

LowToHigh = 1 << 0, // i.e. left-to-right, or top-to-bottom drag

HighToLow = 1 << 1, // i.e. right-to-left, or bottom-to-top

Free = 1 << 2 // i.e. user is dragging using the drag element, free of any direction constraint

}

public event System.Action dragging;

public DragDirection dragDirection { get; set; }

BaseSlider<T> slider { get; set; }

public Vector2 startMousePosition { get; private set; }

public Vector2 delta => (lastMousePosition - startMousePosition);

public ClampedDragger(BaseSlider<T> slider, System.Action clickHandler, System.Action dragHandler)

:

base(clickHandler, ScrollWaitDefinitions.firstWait, ScrollWaitDefinitions.regularWait)

{

dragDirection = DragDirection.None;

this.slider = slider;

dragging += dragHandler;

}

protected override void RegisterCallbacksOnTarget()

{

target.RegisterCallback<MouseDownEvent>(OnMouseDown);

target.RegisterCallback<MouseMoveEvent>(OnMouseMove);

target.RegisterCallback<MouseUpEvent>(OnMouseUp);

}

protected override void UnregisterCallbacksFromTarget()

{

target.UnregisterCallback<MouseDownEvent>(OnMouseDown);

target.UnregisterCallback<MouseMoveEvent>(OnMouseMove);

target.UnregisterCallback<MouseUpEvent>(OnMouseUp);

}

new void OnMouseDown(MouseDownEvent evt)

{

if (CanStartManipulation(evt))

{

startMousePosition = evt.localMousePosition;

dragDirection = DragDirection.None;

base.OnMouseDown(evt);

}

}

new void OnMouseMove(MouseMoveEvent evt)

{

if (active)

{

// Let base class Clickable handle the mouse event first

// (although nothing much happens in the base class on mouse drags)

base.OnMouseMove(evt);

// The drag element does the real work

// Take control if we can

if (dragDirection == DragDirection.None)

dragDirection = DragDirection.Free;

// If and when we have control, set value from drag element

if (dragDirection == DragDirection.Free)

{

dragging?.Invoke();

}

}

}

}

}