Allow hidden blocks to be revealed by plugins (#4017)

* Add revealedBlocks rule

(1/2)

* Use revealedBlocks rule

(2/2)

core/src/mindustry/game/Rules.java

@@ -80,6 +80,8 @@ public class Rules{
     public Seq<WeatherEntry> weather = new Seq<>(1);
     /** Blocks that cannot be placed. */
     public ObjectSet<Block> bannedBlocks = new ObjectSet<>();
+    /** Reveals blocks normally hidden by build visibility */
+    public ObjectSet<Block> revealedBlocks = new ObjectSet<>();
     /** Unlocked content names. Only used in multiplayer when the campaign is enabled. */
     public ObjectSet<String> researched = new ObjectSet<>();
     /** Whether ambient lighting is enabled. */

core/src/mindustry/world/Block.java

@@ -522,7 +522,7 @@ public class Block extends UnlockableContent{
     }
 
     public boolean isVisible(){
-        return buildVisibility.visible() && !isHidden();
+        return (buildVisibility.visible() || state.rules.revealedBlocks.contains(this)) && !isHidden();
     }
 
     public boolean isPlaceable(){
@@ -718,7 +718,7 @@ public class Block extends UnlockableContent{
 
     @Override
     public boolean isHidden(){
-        return !buildVisibility.visible();
+        return !buildVisibility.visible() && !state.rules.revealedBlocks.contains(this);
     }
 
     @Override