Compat for Vanilla Christmas Expanded (#501)

Syncs a (graphical only) gizmo and fixes the overlay overlapping MP buttons. Nothing major or necessary to use the mod in MP, but nice to have.

Source/Mods/VanillaChristmasExpanded.cs

@@ -0,0 +1,78 @@
+using System.Collections.Generic;
+using System.Reflection;
+using System.Reflection.Emit;
+using HarmonyLib;
+using Multiplayer.API;
+using Verse;
+
+namespace Multiplayer.Compat;
+
+/// <summary>Vanilla Christmas Expanded by Oskar Potocki, Sarg Bjornson, Taranchuk</summary>
+/// <see href="https://github.com/Vanilla-Expanded/VanillaChristmasExpanded"/>
+/// <see href="https://steamcommunity.com/sharedfiles/filedetails/?id=3380695249"/>
+[MpCompatFor("VE.VanillaChristmasExpanded")]
+public class VanillaChristmasExpanded
+{
+    public VanillaChristmasExpanded(ModContentPack mod)
+    {
+        LongEventHandler.ExecuteWhenFinished(LatePatch);
+
+        // Change graphic
+        MpCompat.RegisterLambdaMethod("VanillaChristmasExpanded.GrandFestiveTree", nameof(Building.GetGizmos), 0);
+    }
+
+    private static void LatePatch()
+    {
+        MpCompatPatchLoader.LoadPatch<VanillaChristmasExpanded>();
+    }
+
+    private static int ModifyScreenWidthValue(int screenWidth)
+    {
+        // Constant values taken directly from MP's code.
+        const int mpBtnMargin = 8;
+        const int mpBtnWidth = 80;
+        // If we don't offset it further the text will be covered by the
+        // indicator rectangle (its width isn't stored as a constant).
+        // Slightly winging it here with a value that doesn't fully match
+        // MP size but results in the overlay looking alright (as in, it
+        // doesn't overlap and there isn't too much of a gap between it
+        // and the MP UI).
+        const int extraOffset = 20;
+
+        if (MP.IsInMultiplayer)
+            return screenWidth - (mpBtnWidth + 2 * mpBtnMargin + extraOffset);
+        return screenWidth;
+    }
+
+    [MpCompatTranspiler("VanillaChristmasExpanded.FestiveFavorManager", "DrawUI")]
+    private static IEnumerable<CodeInstruction> MoveFestiveOverlayPosition(IEnumerable<CodeInstruction> instr, MethodBase baseMethod)
+    {
+        // Same issue as Vanilla Factions Insectoid 2. The overlay overlaps MP buttons. Since
+        // both overlays depend on a specific storyteller, they won't overlap with themselves.
+        // Since this mod requires a bit more offset (as it's overlapping with the rectangle
+        // "ticks behind" indicator) the same method cannot be reused as for VFEI2.
+
+        var target = AccessTools.DeclaredField(typeof(UI), nameof(UI.screenWidth));
+        var replacement = MpMethodUtil.MethodOf(ModifyScreenWidthValue);
+        var replacedCount = 0;
+
+        foreach (var ci in instr)
+        {
+            yield return ci;
+
+            if (ci.LoadsField(target))
+            {
+                yield return new CodeInstruction(OpCodes.Call, replacement);
+
+                replacedCount++;
+            }
+        }
+
+        const int expected = 1;
+        if (replacedCount != expected)
+        {
+            var name = (baseMethod.DeclaringType?.Namespace).NullOrEmpty() ? baseMethod.Name : $"{baseMethod.DeclaringType!.Name}:{baseMethod.Name}";
+            Log.Warning($"Patched incorrect number of Find.CameraDriver.MapPosition calls (patched {replacedCount}, expected {expected}) for method {name}");
+        }
+    }
+}