feature: ability to highlight selected NPC with declared spawn (AscensionGameDev#2223)

* feature: ability to highlight selected NPC with declared spawn

(Editor feature and QoL update)
- Adds the ability to highlight selected NPC with declared spawn within the map grid
- Adds configurable pulsating color for selected NPC spawns
- QoL enhancements and fixes for declared/random spawns:
  - Differently colored text as visual aid
  - Pressing the random checkbox for spawn location updates the grid preview
- QoL enhancements on forms organization within the NPCs map layers tab
- Adds a spawn counter under the NPC list

(day's review)
- Cached repeated global calls
- Simplified code, less nesting
- Adjusted Color Pulse calculation to use Intersect's Timing system
- HotPink is easier to read with dark background for random location label

(chore: UI changes and fixes)
- prevents an ArgumentOutOfRangeException at Graphics.cs L:1007 with a check to ensure that selectedNpcIndex is less than the size of tmpMap.Spawns before using it to access an element in the list.
- Reorganizes things a bit, added border style to the spawn counter.

Author: Arufonsu

Intersect.Editor/Core/Graphics.cs

@@ -7,6 +7,7 @@
 using Intersect.Editor.Content;
 using Intersect.Editor.Entities;
 using Intersect.Editor.Forms.DockingElements;
+using Intersect.Editor.Forms.Helpers;
 using Intersect.Editor.General;
 using Intersect.Editor.Maps;
 using Intersect.Enums;
@@ -100,6 +101,10 @@ public static partial class Graphics
 
         public static bool TilePreviewUpdated;
 
+        private static long _lastNpcPulseColorUpdate;
+
+        private static float _npcColorPulseRatio;
+
         //Setup and Loading
         public static void InitMonogame()
         {
@@ -982,29 +987,51 @@ private static void DrawSelectionRect()
                 {
                     for (var i = 0; i < tmpMap.Spawns.Count; i++)
                     {
-                        if (tmpMap.Spawns[i].X >= 0 && tmpMap.Spawns[i].Y >= 0)
+                        if (tmpMap.Spawns[i].X < 0 || tmpMap.Spawns[i].Y < 0)
                         {
-                            var spawnTex = GameContentManager.GetTexture(
-                                GameContentManager.TextureType.Misc, "spawnicon.png"
-                            );
+                            continue;
+                        }
+
+                        var spawnTex = GameContentManager.GetTexture(
+                            GameContentManager.TextureType.Misc, "spawnicon.png"
+                        );
 
-                            if (spawnTex != null)
+                        if (spawnTex == null)
+                        {
+                            continue;
+                        }
+
+                        // Check if the current spawn is selected
+                        var spawnColor = System.Drawing.Color.White;
+                        var selectedNpcIndex = Globals.MapLayersWindow.lstMapNpcs.SelectedIndex;
+                        if (selectedNpcIndex > -1 && selectedNpcIndex < tmpMap.Spawns.Count &&
+                            tmpMap.Spawns[i] == tmpMap.Spawns[selectedNpcIndex])
+                        {
+                            // Calculate pulsating color: adjusts denominator to change speed of pulsation.
+                            var currentTime = Timing.Global.MillisecondsUtc;
+                            if ((currentTime - _lastNpcPulseColorUpdate) >= 50) // Update every 50ms.
                             {
-                                DrawTexture(
-                                    spawnTex, new RectangleF(0, 0, spawnTex.Width, spawnTex.Height),
-                                    new RectangleF(
-                                        CurrentView.Left + tmpMap.Spawns[i].X * Options.TileWidth,
-                                        CurrentView.Top + tmpMap.Spawns[i].Y * Options.TileHeight, Options.TileWidth,
-                                        Options.TileHeight
-                                    ), System.Drawing.Color.White, null
-                                );
+                                _npcColorPulseRatio = (float)(Math.Sin(2 * Math.PI * (currentTime / 1000.0)) + 1) / 2;
+                                _lastNpcPulseColorUpdate = currentTime;
+                            }
+                            if (FrmMapLayers.NpcPulseColor == default)
+                            {
+                                FrmMapLayers.NpcPulseColor = System.Drawing.Color.Red;
                             }
+
+                            spawnColor = GridHelper.ColorInterpolate(spawnColor, FrmMapLayers.NpcPulseColor, _npcColorPulseRatio);
                         }
+
+                        DrawTexture(
+                            spawnTex, new RectangleF(0, 0, spawnTex.Width, spawnTex.Height),
+                            new RectangleF(
+                                CurrentView.Left + tmpMap.Spawns[i].X * Options.TileWidth,
+                                CurrentView.Top + tmpMap.Spawns[i].Y * Options.TileHeight, Options.TileWidth,
+                                Options.TileHeight
+                            ), spawnColor
+                        );
                     }
                 }
-                else
-                {
-                }
             }
 
             if (Globals.CurrentTool == EditingTool.Selection && Globals.Dragging)