Better Layer Mask Drawer for Unity with Odin.

LayerMaskDrawer.cs

// ===============================
// AUTHOR     :	      John Leonard
// CREATE DATE     :    25.04.2020
// NOTE     :  Always include this 
//	  Header when copying the file
// ===============================
// Licence: MIT (https://opensource.org/licenses/MIT)
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
// BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// ===============================

using Sirenix.OdinInspector.Editor;
using Sirenix.Utilities.Editor;
using System;
using System.Collections.Generic;
using UnityEditor;
using UnityEngine;

public class LayerMaskDrawer : OdinValueDrawer<LayerMask>
{
	Rect buttonRect;
	List<string> layerNames = new List<string>();
	List<int> layerIndexes = new List<int>();
	List<bool> selectedLayers = new List<bool>();
	string buttonText = null;

	protected override void DrawPropertyLayout(GUIContent label)
	{
		GetAllLayerNames(layerNames, layerIndexes);

		EditorGUILayout.BeginHorizontal();

		EditorGUILayout.PrefixLabel(label);

		// get a list of selected layers with bitwise operations
		selectedLayers.Clear();
		int layerBitVal = ValueEntry.SmartValue;
		for (int i = 0; i < layerNames.Count; i++)
		{
			int bitVal = (int)Mathf.Pow(2, layerIndexes[i]);
			bool isSelected = (layerBitVal & bitVal) == bitVal;
			selectedLayers.Add(isSelected);
		}


		if (string.IsNullOrEmpty(buttonText))
		{
			bool all = true;
			bool none = true;
			buttonText = "";
			for (int i = 0; i < layerNames.Count; i++)
			{
				if (selectedLayers[i])
				{
					none = false;
					buttonText += layerNames[i] + ", ";
				}
				else { all = false; }
			}

			if (none) buttonText = "Nothing";
			else if (all) buttonText = "Everything";
			else if (buttonText.Length > 1) buttonText = buttonText.Remove(buttonText.Length - 2);
		}

		if (GUILayout.Button(buttonText, SirenixGUIStyles.DropDownMiniButton))
		{
			buttonText = null;
			PopupWindow.Show(buttonRect, new LayerMaskPopupSelector()
			{
				layerNames = layerNames,
				layerIndexes = layerIndexes,
				selectedLayers = selectedLayers,
				bitmask = ValueEntry.SmartValue,
				OnSet = (bitmask) => { ValueEntry.SmartValue = bitmask; buttonText = null; }
			});
		}

		// get the rectangle for the popup window
		if (Event.current.type == EventType.Repaint)
			buttonRect = GUILayoutUtility.GetLastRect();

		EditorGUILayout.EndHorizontal();
	}


	public class LayerMaskPopupSelector : PopupWindowContent
	{
		public List<string> layerNames = new List<string>();
		public List<int> layerIndexes = new List<int>();
		public List<bool> selectedLayers = new List<bool>();
		public Action<int> OnSet;
		public int bitmask;

		public override Vector2 GetWindowSize()
		{
			// every button is 30 but the label is only 22 so we substract 8
			float heightOfOne = 30;
			float height = heightOfOne * (2 + layerNames.Count) - 8;

			return new Vector2(200, height);
		}

		public override void OnGUI(Rect rect)
		{
			GUILayout.Label("Layers", EditorStyles.boldLabel);

			// check if all or none are selected
			bool all = true;
			bool none = true;
			foreach (bool b in selectedLayers)
			{
				if (b)
					none = false;
				else
					all = false;
				if (!all && !none) break;
			}

			// none button
			Texture2D noneIcon = none ? EditorIcons.TestPassed : EditorIcons.TestNormal;
			if (SirenixEditorGUI.MenuButton(0, " None", false, noneIcon))
			{
				SetBitmask(-1, true);
				OnSet(bitmask);
				for (int i = 0; i < selectedLayers.Count; i++)
				{
					selectedLayers[i] = false;
				}
			}

			// layer buttons
			for (int i = 0; i < layerNames.Count; i++)
			{
				Texture2D currentIcon =
					selectedLayers[i] ? EditorIcons.TestPassed : EditorIcons.TestNormal;
				if (SirenixEditorGUI.MenuButton(0, " " + layerNames[i],
					false, currentIcon))
				{
					selectedLayers[i] = !selectedLayers[i];
					SetBitmask(layerIndexes[i], selectedLayers[i]);
					OnSet(bitmask);
				}
			}

			// all button
			Texture2D allIcon = all ? EditorIcons.TestPassed : EditorIcons.TestNormal;
			if (SirenixEditorGUI.MenuButton(0, " All", false, allIcon))
			{
				SetBitmask(-2, true);
				OnSet(bitmask);
				for (int i = 0; i < selectedLayers.Count; i++)
				{
					selectedLayers[i] = true;
				}
			}

			OnSet(bitmask);

			// faster update of this window, otherwise the highlight of buttons lags
			editorWindow.Repaint();
		}

		void SetBitmask(int index, bool set)
		{
			// -1 = none
			if (index == -1) { bitmask = 0; return; }
			// -2 = all
			if (index == -2) { bitmask = ~0; return; }
			int bitVal = (int)Mathf.Pow(2, index);
			if (set)
				// or "|" will add the value, the 1 at the right position
				bitmask |= bitVal;
			else
				// and "&" will multiply the value, but we take the inverse
				// so the bit position is 0 while all others are 1
				// everything stays as it is, except for the one value
				// which will be set to 0
				bitmask &= ~bitVal;
		}

		public override void OnOpen()
		{
		}

		public override void OnClose()
		{
			OnSet(bitmask);
		}
	}

	// simple function to return the names of all layers and their corresponding index
	List<string> GetAllLayerNames(List<string> layerNames, List<int> layerIndexes)
	{
		layerNames.Clear();
		layerIndexes.Clear();
		//user defined layers start with layer 8 and unity
		//supports 31 layers
		for (int i = 0; i <= 31; i++)
		{
			//get the name of the layer
			var layerN = LayerMask.LayerToName(i);

			//only add the layer if it has been named
			if (layerN.Length > 0)
			{
				layerIndexes.Add(i);
				layerNames.Add(layerN);
			}
		}
		return layerNames;
	}

}