DockSash.cs

// <copyright file="DockSash.cs" company="Pixel Precision LLC">
// Copyright (c) 2020 All Rights Reserved
// </copyright>
// <author>William Leu</author>
// <date>04/12/2020</date>
// <summary>
// A sash to divide docked content and to give the user an interface
// to drag it.
// </summary>

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace PxPre.UIDock
{
    public class DockSash : 
        UnityEngine.UI.Image,
        UnityEngine.EventSystems.IDragHandler
    {
        /// <summary>
        /// The direction the sash is dividing.
        /// </summary>
        public enum Grain
        {
            /// <summary>
            /// The content being divided from the sash is separated horizontally.
            /// </summary>
            Horizontal,

            /// <summary>
            /// The content being divided from the sash is separated vertically.
            /// </summary>
            Vertical
        }

        /// <summary>
        /// The left or top content of the sash, depending on the grain.
        /// </summary>
        public Dock dockA;

        /// <summary>
        /// The right or bottom content of the sash, depending on the grain.
        /// </summary>
        public Dock dockB;

        /// <summary>
        /// The grain of the sash.
        /// </summary>
        public Grain grain;

        /// <summary>
        /// The system.
        /// </summary>
        public Root system;
            

        /// <summary>
        /// Assuming that the sash children are placed correctly, place the 
        /// dock sash in the middle of them.
        /// </summary>
        public void Align()
        {
            if(this.grain == Grain.Horizontal)
            {
                this.rectTransform.anchoredPosition =
                    new Vector2(
                        dockA.cachedPlace.xMax,
                        -dockA.cachedPlace.y);

                this.rectTransform.sizeDelta =
                    new Vector2(
                        dockB.cachedPlace.x - dockA.cachedPlace.xMax,
                        dockA.cachedPlace.height);
            }
            else
            { 
                this.rectTransform.anchoredPosition = 
                    new Vector2(
                        dockA.cachedPlace.x,
                        -dockA.cachedPlace.yMax);

                this.rectTransform.sizeDelta = 
                    new Vector2(
                        dockA.cachedPlace.width,
                        dockB.cachedPlace.y - dockA.cachedPlace.yMax);
            }
        }

        void UnityEngine.EventSystems.IDragHandler.OnDrag(UnityEngine.EventSystems.PointerEventData eventData)
        { 
            Vector2 delta = eventData.delta;
            if (this.grain == Grain.Horizontal)
            { 
                if(delta.x == 0.0f)
                    return;

                float moveAmt = 0.0f;
                if(delta.x < 0.0f)
                {
                    if(this.dockA.minSize.x >= this.dockA.cachedPlace.width)
                        return;

                    float endSize = this.dockA.cachedPlace.width + delta.x;
                    endSize = Mathf.Max(endSize, this.dockA.minSize.x);
                    moveAmt = Mathf.Min(0.0f, endSize - this.dockA.cachedPlace.width);
                }
                else
                { 
                    if(this.dockB.minSize.x >= this.dockB.cachedPlace.width)
                        return;

                    float endSize = this.dockB.cachedPlace.width - delta.x;
                    endSize = Mathf.Max(endSize, this.dockB.minSize.x);
                    moveAmt = Mathf.Max(0.0f, this.dockB.cachedPlace.width - endSize);
                }

                if(moveAmt == 0.0f)
                    return;

                this.dockA.cachedPlace.width += moveAmt;
                this.dockB.cachedPlace.width -= moveAmt;
                this.dockB.cachedPlace.x += moveAmt;
                this.system.UpdateDockedBranch(this.dockA);
                this.system.UpdateDockedBranch(this.dockB);

                this.system.RealignSashes();
            }
            else if(this.grain == Grain.Vertical)
            { 
                if(delta.y == 0.0)
                    return;
                    
                float moveAmt = 0.0f;
                if(delta.y > 0.0f)
                {
                    if(this.dockA.minSize.y >= this.dockA.cachedPlace.height)
                        return;

                    float endSize = this.dockA.cachedPlace.height - delta.y;
                    endSize = Mathf.Max(endSize, this.dockA.minSize.y);
                    moveAmt = Mathf.Min(0.0f, endSize - this.dockA.cachedPlace.height);
                }
                else
                { 
                    if(this.dockB.minSize.y >= this.dockB.cachedPlace.height)
                        return;

                    float endSize = this.dockB.cachedPlace.height + delta.y;
                    endSize = Mathf.Max(endSize, this.dockB.minSize.y);
                    moveAmt = Mathf.Max(0.0f, this.dockB.cachedPlace.height - endSize);
                }

                if(moveAmt == 0.0f)
                    return;

                this.dockA.cachedPlace.height += moveAmt;
                this.dockB.cachedPlace.height -= moveAmt;
                this.dockB.cachedPlace.y += moveAmt;
                this.system.UpdateDockedBranch(this.dockA);
                this.system.UpdateDockedBranch(this.dockB);

                this.system.RealignSashes();
            }
        }
    }
}