Implement buff icon sync capability (#6838)

Author: lL1l1

changelog/snippets/features.6838.md

@@ -0,0 +1 @@
+- (#6838) Implement the previously non-functional `BlueprintBuff.Icon` field which syncs the buff name to the UI when it affects a unit.

lua/SimSync.lua

@@ -20,6 +20,7 @@ end
 
 ---@class UnitSyncData
 ---@field WepPriority? UnitSyncWepPriority
+---@field Buffs? BuffName[] # Buffs affecting this unit
 
 -- UnitData that has been synced. We keep a separate copy of this so when we change
 -- focus army we can resync the data.

lua/sim/Buff.lua

@@ -623,13 +623,13 @@ function RemoveBuff(unit, buffName, removeAllCounts, instigator)
         def:OnBuffRemove(unit, instigator)
     end
 
-    -- FIXME: This doesn't work because the magic sync table doesn't detect
-    -- the change. Need to give all child tables magic meta tables too.
     if def.Icon then
         -- If the user layer was displaying an icon, remove it from the sync table
-        local newTable = unit.Sync.Buffs
-        table.removeByValue(newTable, buffName)
-        unit.Sync.Buffs = table.copy(newTable)
+        local oldTable = unit.Sync.Buffs
+        if oldTable then
+            table.removeByValue(oldTable, buffName)
+            unit.Sync.Buffs = oldTable
+        end
     end
 
     BuffAffectUnit(unit, buffName, unit, true)
@@ -810,6 +810,16 @@ function ApplyBuff(unit, buffName, instigator)
         def:OnApplyBuff(unit, instigator)
     end
 
+    if def.Icon then
+        local currentBuffs = unit.Sync.Buffs
+        if currentBuffs then
+            table.insert(currentBuffs, buffName)
+            unit.Sync.Buffs = currentBuffs
+        else
+            unit.Sync.Buffs = { buffName }
+        end
+    end
+
     BuffAffectUnit(unit, buffName, instigator, false)
 end
 

lua/system/BuffBlueprints.lua

@@ -113,6 +113,7 @@ Buffs = {}
 --- table of VFX (not the how the buff affects units)
 ---@field Effects? FileName[]
 ---@field EffectsScale? number
+---@field Icon? boolean # Syncs the buff name to UnitData when it affects a unit so that the UI can display an icon
 BuffDefMeta = {}
 BuffDefMeta.__index = BuffDefMeta
 BuffDefMeta.__call = function(...)