Flush queued IDE writes and restart validation after host revision changes

designer-kit-ui/src/main/java/de/neitzel/fxdesigner/kit/DesignerPane.java

@@ -554,6 +554,11 @@ public final class DesignerPane extends BorderPane implements AutoCloseable {
 
   private void load(DocumentSnapshot value) {
     if (closed) return;
+    // A newer host revision can have identical text (edit/revert or native reload).
+    // Its predecessor's validation reply will be rejected by revision, so it must
+    // not leave an in-flight marker that absorbs every subsequent render request.
+    if (draft == null || draft.revision() != value.revision() || !draft.text().equals(value.text()))
+      invalidateBindings("Document synchronized; target validation outdated.");
     loading = true;
     layoutPasses = 0;
     canvasCommitQueued = false;
@@ -635,6 +640,9 @@ public final class DesignerPane extends BorderPane implements AutoCloseable {
       report(error);
     } finally {
       loading = false;
+      // The change debounce may already have fired against the previous draft.
+      // Render only after the authoritative revision and its projection agree.
+      if (projection != null && examples.getValue() != null) resize.playFromStart();
       if (pendingSourceOffset != null) {
         int offset = pendingSourceOffset;
         pendingSourceOffset = null;

designer-kit-ui/src/test/java/de/neitzel/fxdesigner/kit/ProjectionHostChecks.java

@@ -1604,7 +1604,72 @@ public final class ProjectionHostChecks {
     await(() -> fx(() -> source(pane).getText().equals(original)));
   }
 
+  private static Object field(DesignerPane pane, String name) throws Exception {
+    var field = DesignerPane.class.getDeclaredField(name);
+    field.setAccessible(true);
+    return field.get(pane);
+  }
+
+  /** Force a host revision to arrive after validation starts, with identical final text. */
+  public static void renderRevisionRace(DesignerPane pane, DocumentSession document)
+      throws Exception {
+    String original = document.snapshot().toCompletableFuture().get().text();
+    var poll = (javafx.animation.Timeline) field(pane, "poll");
+    var resize = (javafx.animation.PauseTransition) field(pane, "resize");
+    fx(
+        () -> {
+          poll.stop();
+          resize.stop();
+          return null;
+        });
+    try {
+      set(document, original + "<!-- transient external edit -->");
+      set(document, original);
+      long revision = document.snapshot().toCompletableFuture().get().revision();
+      fx(
+          () -> {
+            resize.stop();
+            pane.render();
+            check(original.equals(field(pane, "validatingSource")), "Validation was not in flight");
+            // Deliver the real host-poll callback before the worker validation reply.
+            poll.getKeyFrames().getFirst().getOnFinished().handle(new javafx.event.ActionEvent());
+            return null;
+          });
+      await(() -> fx(() -> ((DocumentSnapshot) field(pane, "draft")).revision() == revision));
+      long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(10);
+      boolean rendered = false;
+      while (System.nanoTime() < deadline) {
+        rendered =
+            fx(
+                () ->
+                    List.of("card", "second").stream()
+                        .allMatch(
+                            id -> {
+                              var region = (SnapshotRegion) object(pane, id).getSceneGraphObject();
+                              return region.image() != null
+                                  && region.statusText().equals("Target runtime");
+                            }));
+        if (rendered) break;
+        Thread.sleep(25);
+      }
+      check(rendered, "Host revision stranded target validation/rendering");
+      check(
+          document.snapshot().toCompletableFuture().get().text().equals(original),
+          "Render edited source");
+      System.out.println(
+          "PASS host revision during validation: identical text, fresh target pixels, no extra"
+              + " action");
+    } finally {
+      fx(
+          () -> {
+            poll.playFromStart();
+            return null;
+          });
+    }
+  }
+
   public static void run(DesignerPane pane, DocumentSession document) throws Exception {
+    renderRevisionRace(pane, document);
     String original = document.snapshot().toCompletableFuture().get().text();
     // The same real application, now with nested, fully-qualified Component declarations.
     String nested =