8313424: JavaFX controls in the title bar

modules/javafx.graphics/src/main/java/javafx/scene/layout/HeaderBar.java

@@ -54,9 +54,10 @@
  * of leading or trailing children or the platform-specific placement of default window buttons.
  * <p>
  * All children will be resized to their preferred widths and extend the height of the {@code HeaderBar}.
- * {@code HeaderBar} honors the minimum, preferred, and maximum sizes of its children. If the child's
- * resizable range prevents it from be resized to fit within its position, it will be vertically centered
- * relative to the available space; this alignment can be customized with a layout constraint.
+ * {@code HeaderBar} honors the minimum, preferred, and maximum sizes of its children. As a consequence,
+ * its computed minimum width is sufficient to accommodate all of its children. If a child's resizable
+ * range prevents it from be resized to fit within its position, it will be vertically centered relative
+ * to the available space; this alignment can be customized with a layout constraint.
  * <p>
  * The default {@link #minHeightProperty() minHeight} of the {@code HeaderBar} is set to match the height
  * of the platform-specific default window buttons.
@@ -259,7 +260,9 @@ public final void setTrailing(Node value) {
 
     @Override
     protected double computeMinWidth(double height) {
-        Node leading = getLeading(), center = getCenter(), trailing = getTrailing();
+        Node leading = getLeading();
+        Node center = getCenter();
+        Node trailing = getTrailing();
         Insets insets = getInsets();
         double leftPrefWidth;
         double rightPrefWidth;
@@ -290,7 +293,9 @@ protected double computeMinWidth(double height) {
 
     @Override
     protected double computeMinHeight(double width) {
-        Node leading = getLeading(), center = getCenter(), trailing = getTrailing();
+        Node leading = getLeading();
+        Node center = getCenter();
+        Node trailing = getTrailing();
         Insets insets = getInsets();
         double leadingMinHeight = getAreaHeight(leading, -1, true);
         double trailingMinHeight = getAreaHeight(trailing, -1, true);
@@ -311,7 +316,9 @@ protected double computeMinHeight(double width) {
 
     @Override
     protected double computePrefHeight(double width) {
-        Node leading = getLeading(), center = getCenter(), trailing = getTrailing();
+        Node leading = getLeading();
+        Node center = getCenter();
+        Node trailing = getTrailing();
         Insets insets = getInsets();
         double leadingPrefHeight = getAreaHeight(leading, -1, false);
         double trailingPrefHeight = getAreaHeight(trailing, -1, false);

modules/javafx.graphics/src/main/java/javafx/scene/layout/HeaderBarBase.java

@@ -55,6 +55,7 @@
  */
 public abstract class HeaderBarBase extends Region {
 
+    private static final Dimension2D EMPTY = new Dimension2D(0, 0);
     private static final String DRAGGABLE = "headerbar-draggable";
 
     /**
@@ -135,21 +136,21 @@ private void onFullScreenChanged(boolean fullScreen) {
 
     private void updateInsets() {
         if (currentFullScreen || currentMetrics == null) {
-            leftSystemInset.set(new Dimension2D(0, 0));
-            rightSystemInset.set(new Dimension2D(0, 0));
+            leftSystemInset.set(EMPTY);
+            rightSystemInset.set(EMPTY);
             minSystemHeight.set(0);
             return;
         }
 
         if (currentMetrics.placement() == HorizontalDirection.LEFT) {
             leftSystemInset.set(currentMetrics.size());
-            rightSystemInset.set(new Dimension2D(0, 0));
+            rightSystemInset.set(EMPTY);
         } else if (currentMetrics.placement() == HorizontalDirection.RIGHT) {
-            leftSystemInset.set(new Dimension2D(0, 0));
+            leftSystemInset.set(EMPTY);
             rightSystemInset.set(currentMetrics.size());
         } else {
-            leftSystemInset.set(new Dimension2D(0, 0));
-            rightSystemInset.set(new Dimension2D(0, 0));
+            leftSystemInset.set(EMPTY);
+            rightSystemInset.set(EMPTY);
         }
 
         minSystemHeight.set(currentMetrics.minHeight());
@@ -188,7 +189,7 @@ public final Dimension2D getLeftSystemInset() {
      * independent of layout orientation.
      */
     private final ReadOnlyObjectWrapper<Dimension2D> rightSystemInset =
-        new ReadOnlyObjectWrapper<>(this, "rightInset", new Dimension2D(0, 0)) {
+        new ReadOnlyObjectWrapper<>(this, "rightInset", EMPTY) {
             @Override
             protected void invalidated() {
                 requestLayout();