SIGNIFICANTLY decreased memory usage by only initializing overlay images when required

core/src/com/unciv/ui/components/tilegroups/layers/TileLayerOverlay.kt

@@ -2,6 +2,7 @@ package com.unciv.ui.components.tilegroups.layers
 
 import com.badlogic.gdx.graphics.Color
 import com.badlogic.gdx.scenes.scene2d.Actor
+import com.badlogic.gdx.scenes.scene2d.ui.Image
 import com.unciv.Constants
 import com.unciv.logic.civilization.Civilization
 import com.unciv.models.ruleset.unique.LocalUniqueCache
@@ -13,88 +14,126 @@ class TileLayerOverlay(tileGroup: TileGroup, size: Float) : TileLayer(tileGroup,
     override fun act(delta: Float) {}
     override fun hit(x: Float, y: Float, touchable: Boolean): Actor? = null
 
-    private val highlight = ImageGetter.getImage(strings().highlight).setHexagonSize() // for blue and red circles/emphasis on the tile
-    private val crosshair = ImageGetter.getImage(strings().crosshair).setHexagonSize() // for when a unit is targeted
-    private val goodCityLocationIndicator = ImageGetter.getImage("OtherIcons/Cities").setHexagonSize(0.25f)
-    private val fog = ImageGetter.getImage(strings().crosshatchHexagon ).setHexagonSize()
-    private val unexplored = ImageGetter.getImage(strings().unexploredTile ).setHexagonSize()
+    private var highlight: Image? = null // for blue and red circles/emphasis on the tile
+    private var crosshair: Image? = null // for when a unit is targeted
+    private var goodCityLocationIndicator: Image? = null
+    private var fog: Image? = null
+    private var unexplored: Image? = null
 
-    init {
-
-        highlight.isVisible = false
-        crosshair.isVisible = false
-        goodCityLocationIndicator.isVisible = false
-        fog.isVisible = false
-        fog.color = Color.WHITE.cpy().apply { a = 0.2f }
-
-        if (ImageGetter.imageExists(strings().unexploredTile))
-            addActor(unexplored)
-        addActor(highlight)
-        addActor(fog)
-        addActor(crosshair)
-        addActor(goodCityLocationIndicator)
+    private fun getHighlight() = ImageGetter.getImage(strings().highlight).setHexagonSize() // for blue and red circles/emphasis on the tile
+    private fun getCrosshair() = ImageGetter.getImage(strings().crosshair).setHexagonSize() // for when a unit is targeted
+    private fun getGoodCityLocationIndicator() = ImageGetter.getImage("OtherIcons/Cities").setHexagonSize(0.25f)
+    private fun getFog() = ImageGetter.getImage(strings().crosshatchHexagon ).setHexagonSize().apply { 
+        color = Color.WHITE.cpy().apply { a = 0.2f }
+    }
+    private fun getUnexplored() = ImageGetter.getImage(strings().unexploredTile ).setHexagonSize()
+    
+    fun orderToFront() {
+        unexplored?.toFront()
+        highlight?.toFront()
+        fog?.toFront()
+        crosshair?.toFront()
+        goodCityLocationIndicator?.toFront()
     }
 
     fun showCrosshair(alpha: Float = 1f) {
-        crosshair.isVisible = true
-        crosshair.color.a = alpha
-        determineVisibility()
+        if (crosshair != null){
+            crosshair = getCrosshair()
+            addActor(crosshair)
+            determineVisibility()
+        }
+        crosshair!!.color.a = alpha
     }
 
     fun hideCrosshair() {
-        crosshair.isVisible = false
+        if (crosshair == null) return
+        crosshair?.remove()
+        crosshair = null
         determineVisibility()
     }
 
-    fun showHighlight(color: Color, alpha: Float = 0.3f) {
-        highlight.isVisible = true
-        highlight.color = color.cpy().apply { a = alpha }
-        determineVisibility()
-    }
-
-    fun showHighlight() {
-        highlight.isVisible = true
-        determineVisibility()
+    fun showHighlight(color: Color = Color.WHITE, alpha: Float = 0.3f) {
+        if (highlight == null) {
+            highlight = getHighlight()
+            addActor(highlight)
+            determineVisibility()
+        }
+        highlight!!.color = color.cpy().apply { a = alpha }
     }
 
     fun hideHighlight() {
-        highlight.isVisible = false
+        if (highlight == null) return
+        highlight?.remove()
+        highlight = null
         determineVisibility()
     }
 
     fun showGoodCityLocationIndicator() {
-        goodCityLocationIndicator.isVisible = true
+        if (goodCityLocationIndicator != null) return
+        goodCityLocationIndicator = getGoodCityLocationIndicator()
+        addActor(goodCityLocationIndicator)
         determineVisibility()
     }
 
     fun hideGoodCityLocationIndicator() {
-        goodCityLocationIndicator.isVisible = false
+        if (goodCityLocationIndicator == null) return
+        goodCityLocationIndicator?.remove()
+        goodCityLocationIndicator = null
         determineVisibility()
     }
 
     fun reset() {
-        fog.isVisible = true
-        highlight.isVisible = false
-        crosshair.isVisible = false
-        goodCityLocationIndicator.isVisible = false
+        hideHighlight()
+        hideCrosshair()
+        hideGoodCityLocationIndicator()
         determineVisibility()
     }
 
     override fun doUpdate(viewingCiv: Civilization?, localUniqueCache: LocalUniqueCache) {
         val isViewable = viewingCiv == null || isViewable(viewingCiv)
-        fog.isVisible = !isViewable && !tileGroup.isForceVisible
+        
+        setFog(isViewable)
+        
+        if (viewingCiv == null) return
 
-        if (viewingCiv == null)
-            return
+        setUnexplored(viewingCiv)
 
-        unexplored.isVisible = !viewingCiv.hasExplored(tile())
         if (tile().getShownImprovement(viewingCiv) == Constants.barbarianEncampment
                 && tile().isExplored(viewingCiv))
             showHighlight(Color.RED)
     }
 
+    private fun setUnexplored(viewingCiv: Civilization) {
+        val unexploredShouldBeVisible = !viewingCiv.hasExplored(tile())
+        val unexploredIsVisible = unexplored != null
+        if (unexploredIsVisible && !unexploredShouldBeVisible) {
+            unexplored?.remove()
+            determineVisibility()
+        } else if (!unexploredIsVisible && unexploredShouldBeVisible
+                && ImageGetter.imageExists(strings().unexploredTile)) {
+            unexplored = getUnexplored()
+            addActor(unexplored)
+            determineVisibility()
+        }
+    }
+
+    private fun setFog(isViewable: Boolean) {
+        val fogShouldBeVisible = !isViewable && !tileGroup.isForceVisible
+        val fogIsVisible = fog != null
+        if (fogIsVisible && !fogShouldBeVisible) {
+            fog?.remove()
+            fog = null
+            determineVisibility()
+        } else if (!fogIsVisible && fogShouldBeVisible) {
+            fog = getFog()
+            addActor(fog)
+            determineVisibility()
+        }
+    }
+
     override fun determineVisibility() {
-        isVisible = fog.isVisible || highlight.isVisible || crosshair.isVisible || goodCityLocationIndicator.isVisible
+        isVisible = fog != null || unexplored != null || highlight != null || crosshair != null || goodCityLocationIndicator != null
+        orderToFront()
     }
 
 }