[project structure dialog] properly handle selection changes after reopening the dialog (IJPL-161905)

After e7b38952621668, AutoScrollToSourceHandler remembers the modality state which it uses for processing events on the first invocation. However, it's used in BaseStructureConfigurable instances, which are reused each time the Project Structure dialog is opened (see IJPL-21800). And then the dialog is opened for the second time, it stops processing auto-scroll events. It's not that simple to fix IJPL-21800. So as a temporary solution, an internal 'resetAlarm' function was added and called when the dialog is closed to reset the instance and ensure that it'll be recreated with the proper modality state the next time the dialog is opened.

GitOrigin-RevId: 68af8a98a7d73a50d8cbc7889e4ab9a229d3ad54

java/idea-ui/src/com/intellij/openapi/roots/ui/configuration/projectRoot/BaseStructureConfigurable.java

@@ -144,6 +144,7 @@ public abstract class BaseStructureConfigurable extends MasterDetailsComponent i
     myUiDisposed = true;
 
     myAutoScrollHandler.cancelAllRequests();
+    myAutoScrollHandler.resetAlarm();
 
     myContext.getDaemonAnalyzer().clear();
 

platform/platform-api/src/com/intellij/ui/AutoScrollToSourceHandler.kt

@@ -32,21 +32,28 @@ abstract class AutoScrollToSourceHandler {
   private var scheduledNavigationData: WeakReference<Component>? = null
 
   // access only from EDT
-  private val autoScrollAlarm = lazy(LazyThreadSafetyMode.NONE) {
-    SingleAlarm(
-      task = {
-        val component = scheduledNavigationData?.get() ?: return@SingleAlarm
-        scheduledNavigationData = null
-        // for tests
-        if (component.isShowing && (!needToCheckFocus() || UIUtil.hasFocus(component))) {
-          scrollToSource(component)
-        }
-      },
-      delay = Registry.intValue("ide.autoscroll.to.source.delay", 100),
-      parentDisposable = null,
-      threadToUse = Alarm.ThreadToUse.SWING_THREAD,
-      modalityState = ModalityState.defaultModalityState(),
-    )
+  private var autoScrollAlarm: SingleAlarm? = null 
+    
+  private fun getOrCreateAutoScrollAlarm(): SingleAlarm {
+    var alarm = autoScrollAlarm
+    if (alarm == null) {
+      alarm = SingleAlarm(
+        task = {
+          val component = scheduledNavigationData?.get() ?: return@SingleAlarm
+          scheduledNavigationData = null
+          // for tests
+          if (component.isShowing && (!needToCheckFocus() || UIUtil.hasFocus(component))) {
+            scrollToSource(component)
+          }
+        },
+        delay = Registry.intValue("ide.autoscroll.to.source.delay", 100),
+        parentDisposable = null,
+        threadToUse = Alarm.ThreadToUse.SWING_THREAD,
+        modalityState = ModalityState.defaultModalityState(),
+      )
+      autoScrollAlarm = alarm
+    }
+    return alarm
   }
 
   fun install(tree: JTree) {
@@ -114,9 +121,17 @@ abstract class AutoScrollToSourceHandler {
   }
 
   fun cancelAllRequests() {
-    if (autoScrollAlarm.isInitialized()) {
-      autoScrollAlarm.value.cancel()
-    }
+    autoScrollAlarm?.cancel()
+  }
+
+  /**
+   * Resets the internal instance to ensure that it'll be recreated properly if the component is reused in a different modal dialog.
+   * This is a temporary solution specifically for the Project Structure dialog, it's better to recreate components instead of reusing them.
+   */
+  @ApiStatus.Internal
+  @ApiStatus.Obsolete
+  fun resetAlarm() {
+    autoScrollAlarm = null
   }
 
   fun onMouseClicked(component: Component) {
@@ -129,7 +144,7 @@ abstract class AutoScrollToSourceHandler {
   private fun onSelectionChanged(component: Component?) {
     if (component != null && component.isShowing && isAutoScrollMode()) {
       scheduledNavigationData = WeakReference(component)
-      autoScrollAlarm.value.cancelAndRequest()
+      getOrCreateAutoScrollAlarm().cancelAndRequest()
     }
   }