[Editor] Improve MainView's TabPane binding to the mainController.openItems

editor/src/main/kotlin/com/bartlomiejpluta/base/editor/main/view/MainView.kt

@@ -23,6 +23,8 @@ class MainView : View("BASE Game Editor") {
    private val projectStructureView = find<ProjectStructureView>()
    private val codeStructure = find<CodeStructureView>()
 
+   private val openTabs = mutableMapOf<Scope, Tab>()
+
    init {
       projectContext.projectProperty.addListener { _, _, project ->
          val projectName = project?.let { " :: ${it.name} (${it.sourceDirectory.absolutePath})" } ?: ""
@@ -34,8 +36,38 @@ class MainView : View("BASE Game Editor") {
       top = mainMenuView.root
 
       center = tabpane {
-         tabs.bind(mainController.openItems) { scope, item ->
-            when (item) {
+
+         // FIXME
+         // For some reason the plain object binding does not work between tabs and mainController.openItems.
+         // Because of that, the cache openTabs map has been created and the binding is done by following listener:
+         mainController.openItems.addListener(MapChangeListener {
+            when {
+               it.wasAdded() -> createTab(it.key, it.valueAdded).let { tab ->
+                  openTabs[it.key] = tab
+                  tabs += tab
+               }
+
+               it.wasRemoved() -> {
+                  val tab = openTabs[it.key]
+                  tabs -= tab
+                  openTabs.remove(it.key)
+               }
+            }
+         })
+      }
+
+      left = drawer(multiselect = true) {
+         item("Code Structure", expanded = true) {
+            this += codeStructure
+         }
+
+         item("Project Structure", expanded = true) {
+            this += projectStructureView
+         }
+      }
+   }
+
+   private fun createTab(scope: Scope, item: Any) = when (item) {
       is GameMap -> Tab().apply {
          val vm = GameMapVM(item)
          setInScope(vm, scope)
@@ -57,26 +89,4 @@ class MainView : View("BASE Game Editor") {
 
       else -> throw IllegalStateException("Unsupported tab item")
    }
-         }
-
-         // FIXME
-         // For some reason cleaning mainController.openMaps just takes off the tabs content keeping open themselves.
-         // The workaround is to detect if map is cleaned and the clean the tabs by hand.
-         mainController.openItems.addListener(MapChangeListener {
-            if (it.map.isEmpty()) {
-               tabs.clear()
-            }
-         })
-      }
-
-      left = drawer(multiselect = true) {
-         item("Code Structure", expanded = true) {
-            this += codeStructure
-         }
-
-         item("Project Structure", expanded = true) {
-            this += projectStructureView
-         }
-      }
-   }
 }