canWithdraw() + changes to displayable() (#6902)

* `shouldDiplay()` + `canWithdraw()`

* Better implementation of `displayable()`

core/src/mindustry/entities/comp/BuildingComp.java

@@ -613,6 +613,10 @@ abstract class BuildingComp implements Posc, Teamc, Healthc, Buildingc, Timerc,
         Fx.unitDrop.at(unit);
     }
 
+    public boolean canWithdraw(){
+        return true;
+    }
+
     public boolean canUnload(){
         return block.unloadable;
     }
@@ -1342,11 +1346,6 @@ abstract class BuildingComp implements Posc, Teamc, Healthc, Buildingc, Timerc,
     public ItemModule flowItems(){
         return items;
     }
-
-    public boolean displayable(){
-        return true;
-    }
-
     @Override
     public void display(Table table){
         //display the block stuff

core/src/mindustry/ui/Displayable.java

@@ -4,5 +4,9 @@ import arc.scene.ui.layout.*;
 
 /** An interface for things that can be displayed when hovered over. */
 public interface Displayable{
+    default boolean displayable(){
+        return true;
+    }
+
     void display(Table table);
 }

core/src/mindustry/ui/fragments/BlockInventoryFragment.java

@@ -70,6 +70,8 @@ public class BlockInventoryFragment{
     }
 
     private void takeItem(int requested){
+        if(!build.canWithdraw()) return;
+
         //take everything
         int amount = Math.min(requested, player.unit().maxAccepted(lastItem));
 

core/src/mindustry/ui/fragments/PlacementFragment.java

@@ -577,7 +577,7 @@ public class PlacementFragment{
         if(Core.scene.hasMouse() || topTable.hit(v.x, v.y, false) != null) return null;
 
         //check for a unit
-        Unit unit = Units.closestOverlap(player.team(), Core.input.mouseWorldX(), Core.input.mouseWorldY(), 5f, u -> !u.isLocal());
+        Unit unit = Units.closestOverlap(player.team(), Core.input.mouseWorldX(), Core.input.mouseWorldY(), 5f, u -> !u.isLocal() && u.displayable());
         //if cursor has a unit, display it
         if(unit != null) return unit;