Move build range overlay creation to post-mod blueprint loading (FAFo…

…rever#6220)

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## Issue
There are frequently modded games with build range multiplier mods, but
the overlay is created before mod loading, so it's not possible to see
the new range without UI mods.

## Description of the proposed changes
<!-- A clear and concise description (or visuals) of what the changes
imply. -->
<!-- If it closes an issue, make sure to link the issue by using
"(Closes/Fixes/Resolves) #(Issue Number)" in your pull request. -->
- Moves the build range overlay to post mod blueprint loading so it is
compatible with mods.
- Adds engineering pods to the overlay since it shouldn't lag and it is
helpful to see their build range.
- Excludes engineer stations from the build range overlay since being
able to see what they will auto-assist is useful for not getting them
stuck on hard to assist things like SMD.
- Excludes engineers with air staging from the overlay just in case it
ever happens.

## Testing done on the proposed changes
<!-- List all relevant testing that you've done to confirm the changes
work. -->
- Enabled a 1.5x build range mod and made sure that the overlay updated
for engineers and not for engineer stations.
- Checked that guard scan radius for engineer stations works within the
exactly stated radius by disabling the blueprint overlay creation, using
the default 25 build range overlay from the blueprint, and placing t1 pd
inside/outside that overlay.
- Larger build skirts (visible with `dbg grid`) like t1 land facs need
to have 2 cells within range of the engineer station.
- Also tested placing an SMD nearby outside the guard radius at various
places and it has to clearly overlap the radius to be assisted
automatically.
- Checked that build radius works for engineers with the
`MaxBuildDistance+2` range by placing T1 PD 7/8 ogrids away from a t1
engi. It can build land factories even further away (8-9 ogrids away
from the build skirt max directly vertically/horizontally, but not
diagonally (7-8 max)).

## Checklist

- [x] Changes are annotated, including comments where useful
- [x] Changes are documented in the changelog for the next game version

---------

Co-authored-by: Josh <[email protected]>

changelog/snippets/features.6220.md

@@ -0,0 +1,5 @@
+- (#6220) Improve the build range overlay's compatibility.
+  - Add the overlay to engineer drones/pods.
+  - Correctly display build ranges modded through `ModBlueprints()`.
+  - Display the auto assist range of engineer stations instead of their build range.
+    - This is only a -2 displayed range difference without mods, but it will be a larger difference with mods.

lua/system/Blueprints.lua

@@ -787,15 +787,6 @@ function PreModBlueprints(all_bps)
                 bp.AddCategories = nil
             end
 
-            -- Build range overlay
-            if bp.CategoriesHash.ENGINEER then -- show build range overlay for engineers
-                if not bp.AI then bp.AI = {} end
-                bp.AI.StagingPlatformScanRadius = (bp.Economy.MaxBuildDistance or 5) + 2
-                if not (bp.CategoriesHash.POD or bp.CategoriesHash.INSIGNIFICANTUNIT) then -- excluding Build Drones
-                    bp.CategoriesHash.OVERLAYMISC = true
-                end
-            end
-
             -- Add common category values for easier lookup
 
             -- Add tech category

lua/system/blueprints-units.lua

@@ -223,6 +223,28 @@ local function PostProcessUnit(unit)
         end
     end
 
+    -- Build range overlay
+    -- only for engineers, excluding insignificant units such as Cybran build drones or air staging that has its own radius set
+    if isEngineer and not (unit.CategoriesHash['INSIGNIFICANTUNIT'] or unit.CategoriesHash['AIRSTAGINGPLATFORM']) then
+        -- guarantee that the table exists
+        if not unit.AI then unit.AI = {} end
+
+        -- Engine allows building +2 range outside the max distance (or even more for large buildings)
+        local overlayRadius = (unit.Economy.MaxBuildDistance or 5) + 2
+
+        -- Display auto-assist range for engineer stations instead of max build distance if it is smaller
+        if unit.CategoriesHash['ENGINEERSTATION'] then
+            local guardScanRadius = unit.AI.GuardScanRadius
+            if guardScanRadius < overlayRadius then
+                overlayRadius = guardScanRadius
+            end
+        end
+
+        unit.AI.StagingPlatformScanRadius = overlayRadius
+        table.insert(unit.Categories, 'OVERLAYMISC')
+        unit.CategoriesHash.OVERLAYMISC = true
+    end
+
     -- sanitize air unit footprints
 
     -- value used by formations to determine the distance between other air units. Note