Failing test + initialCssState impl

modules/javafx.graphics/src/main/java/com/sun/javafx/scene/NodeHelper.java

@@ -286,6 +286,10 @@ public static void reapplyCSS(Node node) {
         nodeAccessor.reapplyCSS(node);
     }
 
+    public static boolean isInitialCssState(Node node) {
+        return nodeAccessor.isInitialCssState(node);
+    }
+
     public static void recalculateRelativeSizeProperties(Node node, Font fontForRelativeSizes) {
         nodeAccessor.recalculateRelativeSizeProperties(node, fontForRelativeSizes);
     }
@@ -391,6 +395,7 @@ boolean doComputeIntersects(Node node, PickRay pickRay,
         void setLabeledBy(Node node, Node labeledBy);
         Accessible getAccessible(Node node);
         void reapplyCSS(Node node);
+        boolean isInitialCssState(Node node);
         void recalculateRelativeSizeProperties(Node node, Font fontForRelativeSizes);
         boolean isTreeVisible(Node node);
         BooleanExpression treeVisibleProperty(Node node);

modules/javafx.graphics/src/main/java/javafx/scene/Node.java

@@ -595,6 +595,11 @@ public void reapplyCSS(Node node) {
                 node.reapplyCSS();
             }
 
+            @Override
+            public boolean isInitialCssState(Node node) {
+                return node.initialCssState;
+            }
+
             @Override
             public void recalculateRelativeSizeProperties(Node node, Font fontForRelativeSizes) {
                 node.recalculateRelativeSizeProperties(fontForRelativeSizes);
@@ -1010,6 +1015,8 @@ protected void invalidated() {
                     }
                     updateDisabled();
                     computeDerivedDepthTest();
+                    resetInitialCssStateFlag();
+
                     final Parent newParent = get();
 
                     // Update the focus bits before calling reapplyCss(), as the focus bits can affect CSS styling.
@@ -1106,6 +1113,8 @@ private void invalidatedScenes(Scene oldScene, SubScene oldSubScene) {
         if (sceneChanged) {
             if (newScene == null) {
                 completeTransitionTimers();
+            } else {
+                resetInitialCssStateFlag();
             }
             updateCanReceiveFocus();
             if (isFocusTraversable()) {
@@ -10066,6 +10075,25 @@ private void doProcessCSS() {
         }
     }
 
+    /**
+     * A node is considered to be in its initial CSS state if it wasn't shown in a scene graph before.
+     * This flag is cleared after CSS processing was completed in a Scene pulse event. Note that manual
+     * calls to {@link #applyCss()} or similar methods will not clear this flag, since we consider all
+     * CSS processing before the Scene pulse to be part of the node's initial state.
+     */
+    private boolean initialCssState = true;
+
+    private void resetInitialCssStateFlag() {
+        initialCssState = true;
+        Scene scene = getScene();
+        if (scene != null) {
+            scene.registerClearInitialCssStateFlag(this);
+        }
+    }
+
+    void clearInitialCssStateFlag() {
+        initialCssState = false;
+    }
 
     /**
      * A StyleHelper for this node.

modules/javafx.graphics/src/main/java/javafx/scene/Scene.java

@@ -589,6 +589,25 @@ private void doCSSPass() {
             sceneRoot.clearDirty(com.sun.javafx.scene.DirtyBits.NODE_CSS);
             sceneRoot.processCSS();
         }
+
+        if (!clearInitialCssStateNodes.isEmpty()) {
+            for (var node : clearInitialCssStateNodes) {
+                node.clearInitialCssStateFlag();
+            }
+
+            clearInitialCssStateNodes.clear();
+        }
+    }
+
+    /**
+     * A list of nodes that have expressed their interest to be notified when the next CSS pass
+     * is completed. Nodes will use this event to determine whether they are in their initial
+     * CSS state (see {@link Node#initialCssState}.
+     */
+    private final List<Node> clearInitialCssStateNodes = new ArrayList<>();
+
+    void registerClearInitialCssStateFlag(Node node) {
+        clearInitialCssStateNodes.add(node);
     }
 
     void doLayoutPass() {

modules/javafx.graphics/src/test/java/test/javafx/scene/Node_transition_Test.java

@@ -67,7 +67,6 @@ public void startup() {
         scene = new Scene(new Group(node));
         stage = new Stage();
         stage.setScene(scene);
-        stage.show();
     }
 
     @AfterEach
@@ -188,6 +187,10 @@ public void testRunningTimersAreTrackedInNode() {
         Map<String, TransitionTimer> timers = NodeShim.getTransitionTimers(node);
         assertNull(timers);
 
+        // Showing the stage causes the first Scene CSS pass, after which the node is
+        // eligible for CSS transitions.
+        stage.show();
+
         // The hover state starts the timer.
         node.pseudoClassStateChanged(PseudoClass.getPseudoClass("hover"), true);
         node.applyCss();
@@ -213,6 +216,10 @@ public void testRunningTimerIsCompletedWhenNodeIsRemovedFromSceneGraph() {
         node.applyCss();
         assertNull(NodeShim.getTransitionTimers(node));
 
+        // Showing the stage causes the first Scene CSS pass, after which the node is
+        // eligible for CSS transitions.
+        stage.show();
+
         // The hover state starts the timer.
         node.pseudoClassStateChanged(PseudoClass.getPseudoClass("hover"), true);
         node.applyCss();
@@ -238,6 +245,10 @@ public void testRunningTimerIsCompletedWhenNodeBecomesInvisible() {
         node.applyCss();
         assertNull(NodeShim.getTransitionTimers(node));
 
+        // Showing the stage causes the first Scene CSS pass, after which the node is
+        // eligible for CSS transitions.
+        stage.show();
+
         // The hover state starts the timer.
         node.pseudoClassStateChanged(PseudoClass.getPseudoClass("hover"), true);
         node.applyCss();
@@ -251,4 +262,71 @@ public void testRunningTimerIsCompletedWhenNodeBecomesInvisible() {
         assertEquals(1, node.getOpacity(), 0.001);
     }
 
+    @Test
+    public void testTransitionIsStartedWhenInitialPropertyIsNotSpecifiedInStylesheet() {
+        String url = "data:text/css;base64," + Base64.getUrlEncoder().encodeToString("""
+            .testClass { transition: all 1s; }
+            .testClass:hover { -fx-opacity: 0.5; }
+            """.getBytes(StandardCharsets.UTF_8));
+
+        scene.getStylesheets().add(url);
+        node.getStyleClass().add("testClass");
+        node.applyCss();
+        assertNull(NodeShim.getTransitionTimers(node));
+
+        stage.show();
+        node.pseudoClassStateChanged(PseudoClass.getPseudoClass("hover"), true);
+        toolkit.firePulse();
+        assertEquals(1, NodeShim.getTransitionTimers(node).size());
+    }
+
+    @Test
+    public void testTransitionIsOnlyStartedAfterSceneHasProcessedCSS() {
+        String url = "data:text/css;base64," + Base64.getUrlEncoder().encodeToString("""
+            .testClass { -fx-opacity: 0; transition: all 1s; }
+            .testClass:hover { -fx-opacity: 1; }
+            """.getBytes(StandardCharsets.UTF_8));
+
+        scene.getStylesheets().add(url);
+        node.getStyleClass().add("testClass");
+        node.applyCss();
+        assertNull(NodeShim.getTransitionTimers(node));
+
+        // Even though we apply CSS here, no transition is started because the Scene has not
+        // processed CSS in response to a pulse event yet.
+        node.pseudoClassStateChanged(PseudoClass.getPseudoClass("hover"), true);
+        node.applyCss();
+        assertNull(NodeShim.getTransitionTimers(node));
+
+        // This will fire the first pulse event, which also does not start the transition
+        // because the initial CSS pass only establishes the initial CSS state for the node.
+        node.pseudoClassStateChanged(PseudoClass.getPseudoClass("hover"), false);
+        stage.show();
+        assertNull(NodeShim.getTransitionTimers(node));
+
+        // This will fire the second pulse event, which will start the transition.
+        node.pseudoClassStateChanged(PseudoClass.getPseudoClass("hover"), true);
+        toolkit.firePulse();
+        assertEquals(1, NodeShim.getTransitionTimers(node).size());
+    }
+
+    @Test
+    public void testInitialCssStateFlagIsSetWhenAddedToOrRemovedFromScene() {
+        stage.show();
+
+        // The initial CSS pass is already done, so the initialCssState flag is cleared.
+        assertFalse(NodeHelper.isInitialCssState(node));
+
+        // Removing the node from the scene resets the initialCssState flag.
+        ((Group)scene.getRoot()).getChildren().remove(0);
+        assertTrue(NodeHelper.isInitialCssState(node));
+
+        // The initialCssState flag is set on a newly-created node.
+        var node2 = new Rectangle();
+        assertTrue(NodeHelper.isInitialCssState(node2));
+
+        // The flag is also set when the new node is added to the scene.
+        ((Group)scene.getRoot()).getChildren().add(node2);
+        assertTrue(NodeHelper.isInitialCssState(node));
+    }
 }