Resolved #3401, Resolved #3598, possibly resolved #3643 - game can be instantly closed and reopened on Android

From a practical standpoint - Reset all GL objects upon create(), since they lose all relevance when we have a new GL context

core/src/com/unciv/UncivGame.kt

@@ -5,6 +5,7 @@ import com.badlogic.gdx.Game
 import com.badlogic.gdx.Gdx
 import com.badlogic.gdx.Input
 import com.badlogic.gdx.audio.Music
+import com.badlogic.gdx.graphics.g2d.TextureAtlas
 import com.badlogic.gdx.scenes.scene2d.actions.Actions
 import com.badlogic.gdx.utils.Align
 import com.unciv.logic.GameInfo
@@ -14,10 +15,7 @@ import com.unciv.models.metadata.GameSettings
 import com.unciv.models.ruleset.RulesetCache
 import com.unciv.models.translations.Translations
 import com.unciv.ui.LanguagePickerScreen
-import com.unciv.ui.utils.CameraStageBaseScreen
-import com.unciv.ui.utils.CrashController
-import com.unciv.ui.utils.ImageGetter
-import com.unciv.ui.utils.center
+import com.unciv.ui.utils.*
 import com.unciv.ui.worldscreen.PlayerReadyScreen
 import com.unciv.ui.worldscreen.WorldScreen
 import java.util.*
@@ -79,9 +77,23 @@ class UncivGame(parameters: UncivGameParameters) : Game() {
         // Whatever needs graphics needs to be done on the main thread,
         // So it's basically a long set of deferred actions.
         settings = GameSaver.getGeneralSettings() // needed for the screen
-        screen = LoadingScreen()
+
+
+        /** When we recreate the GL context for whatever reason (say - we moved to a split screen on Android),
+         * ALL objects that were related to the old context - need to be recreated.
+         * So far we have:
+         * - All textures (hence the texture atlas)
+         * - SpriteBatch (hence CameraStageBaseScreen uses a new SpriteBatch for each screen)
+         * - Skin (hence CameraStageBaseScreen.setSkin())
+         * - Font (hence Fonts.resetFont() inside setSkin())
+         */
+        ImageGetter.atlas = TextureAtlas("game.atlas")
+        ImageGetter.setNewRuleset(ImageGetter.ruleset)
+        CameraStageBaseScreen.setSkin() // needs to come AFTER the Texture reset, since the buttons depend on it
 
         Gdx.graphics.isContinuousRendering = settings.continuousRendering
+        screen = LoadingScreen()
+
 
         thread(name = "LoadJSON") {
             RulesetCache.loadRulesets(printOutput = true)
@@ -96,6 +108,8 @@ class UncivGame(parameters: UncivGameParameters) : Game() {
             // This stuff needs to run on the main thread because it needs the GL context
             Gdx.app.postRunnable {
                 ImageGetter.ruleset = RulesetCache.getBaseRuleset() // so that we can enter the map editor without having to load a game first
+
+
                 thread(name="Music") { startMusic() }
                 restoreSize()
 

core/src/com/unciv/ui/utils/CameraStageBaseScreen.kt

@@ -41,7 +41,7 @@ open class CameraStageBaseScreen : Screen {
         val width = resolutions[0]
         val height = resolutions[1]
 
-        stage = Stage(ExtendViewport(width, height), batch)
+        stage = Stage(ExtendViewport(width, height), SpriteBatch())
 
 
         stage.addListener(
@@ -91,8 +91,10 @@ open class CameraStageBaseScreen : Screen {
     }
 
     companion object {
-        val skin by lazy {
-            val skin = Skin().apply {
+        lateinit var skin:Skin
+        fun setSkin() {
+            Fonts.resetFont()
+            skin = Skin().apply {
                 add("Nativefont", Fonts.font, BitmapFont::class.java)
                 add("Button", ImageGetter.getRoundedEdgeTableBackground(), Drawable::class.java)
                 addRegions(TextureAtlas("skin/flat-earth-ui.atlas"))

core/src/com/unciv/ui/utils/Fonts.kt

@@ -107,11 +107,11 @@ class NativeBitmapFontData(val fontImplementation: NativeFontImplementation) : B
 }
 
 object Fonts {
-    val font by lazy {
+    lateinit var font:BitmapFont
+    fun resetFont() {
         val fontData = NativeBitmapFontData(UncivGame.Current.fontImplementation!!)
-        val font = BitmapFont(fontData, fontData.regions, false)
+        font = BitmapFont(fontData, fontData.regions, false)
         font.setOwnsTexture(true)
-        font
     }
 
     // From https://stackoverflow.com/questions/29451787/libgdx-textureregion-to-pixmap