How do I ensure a consistent JavaFX Dialog header width with varying title lengths?
Context:
I'm using JavaFX's built-in Dialog extensively in our application. Additionally, all my dialogs and general UI scenes are dynamically wrapped and scaled using a custom utility called LetterBoxer.java (related question).
The utility places UI components into a StackPane, centers them, and scales them dynamically based on scene/window resizing.
Problem:
When displaying dialogs with varying title lengths, each Dialog header automatically adjusts its width, causing visual inconsistency from one dialog to another.
Minimal Reproducible Example (simplified):
package dynamicDialogFixedWidthExample;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
public class DynamicDialogFixedWidthExample extends Application {
@Override
public void start(Stage primaryStage) {
Label headerLabel = new Label("An Extremely Long Header Title for Testing");
headerLabel.setStyle("-fx-font-size: 16px; -fx-background-color: lightblue; -fx-padding: 10;");
headerLabel.setWrapText(true);
BorderPane borderPane = getBorderPane(headerLabel);
AnchorPane rootAnchorPane = new AnchorPane(borderPane);
AnchorPane.setTopAnchor(borderPane, 0.0);
AnchorPane.setBottomAnchor(borderPane, 0.0);
AnchorPane.setLeftAnchor(borderPane, 0.0);
AnchorPane.setRightAnchor(borderPane, 0.0);
LetterBoxer letterBoxer = new LetterBoxer();
Scene scene = letterBoxer.box(rootAnchorPane);
primaryStage.setScene(scene);
scene.setOnMouseClicked(event -> {
if (headerLabel.getText().equals("An Extremely Long Header Title for Testing")) {
headerLabel.setText("Short");
} else if (headerLabel.getText().equals("Short")) {
headerLabel.setText("This is a Title");
} else {
headerLabel.setText("An Extremely Long Header Title for Testing");
}
});
primaryStage.setTitle("Dynamic Width Dialog Example");
primaryStage.setWidth(250);
primaryStage.setHeight(250);
primaryStage.show();
}
private static BorderPane getBorderPane(Label headerLabel) {
Label centerContent = new Label("Centered Content Goes Here");
centerContent.setStyle("-fx-font-size: 14px; -fx-background-color: lightgray; -fx-padding: 20;");
Label footerLabel = new Label("Footer");
footerLabel.setStyle("-fx-font-size: 14px; -fx-background-color: lightgreen; -fx-padding: 10;");
BorderPane borderPane = new BorderPane();
borderPane.setTop(headerLabel);
borderPane.setCenter(centerContent);
borderPane.setBottom(footerLabel);
return borderPane;
}
public static void main(String[] args) {
launch(args);
}
}
LetterBoxer.java
package dynamicDialogFixedWidthExample;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Bounds;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.transform.Scale;
public class LetterBoxer {
public Scene box(final Parent content) {
return box(content, 1);
}
public Scene box(final Parent content, final double minScale) {
// the content is wrapped in a Group so that the stack centers
// the scaled node rather than the untransformed node.
Group group = new Group(content);
Scene scene = new Scene(group);
// generate a layout pass.
group.applyCss();
group.layout();
// determine the default ratio of laid out components.
final Bounds layoutBounds = group.getLayoutBounds();
final double initWidth = layoutBounds.getWidth();
final double initHeight = layoutBounds.getHeight();
final double ratio = initWidth / initHeight;
StackPane stackPane = new StackPane(group);
// place the root in a stack to keep it centered.
scene.setRoot(
stackPane
);
// configure a listener to adjust the size of the scene content (by scaling it).
BoxParams boxParams = new BoxParams(
scene, minScale, ratio, initHeight, initWidth, content
);
// adjust the size of the scene content (by scaling it) if the size changes.
BoxSizeAdjuster boxSizeAdjuster = new BoxSizeAdjuster(boxParams);
scene.widthProperty().addListener(boxSizeAdjuster);
scene.heightProperty().addListener(boxSizeAdjuster);
return scene;
}
private record BoxParams(
Scene scene,
double minScale,
double ratio,
double initHeight, double initWidth,
Parent content
) {
}
private static class BoxSizeAdjuster
implements ChangeListener<Number> {
private final BoxParams boxParams;
private final Scale scale = new Scale();
public BoxSizeAdjuster(BoxParams boxParams) {
this.boxParams = boxParams;
scale.setPivotX(0);
scale.setPivotY(0);
boxParams.content.getTransforms().setAll(scale);
}
@Override
public void changed(
ObservableValue<? extends Number> observableValue,
Number oldValue,
Number newValue
) {
final double newWidth = boxParams.scene.getWidth();
final double newHeight = boxParams.scene.getHeight();
final double scaleFactor =
Math.max(
newWidth / newHeight > boxParams.ratio
? newHeight / boxParams.initHeight
: newWidth / boxParams.initWidth,
boxParams.minScale
);
scale.setX(scaleFactor);
scale.setY(scaleFactor);
}
}
}
Due to varying title lengths, the header width fluctuates noticeably.
What I've tried (not working):
- Setting fixed widths or minimal widths on primary stage.
They didn't provide consistent dynamic adaptability considering the custom StackPane scaling wrapper.
Desirable Result/Question:
How can I consistently enforce a stable header width in JavaFX dialogs within dynamic scaling environments created by StackPane wrapping?
Any guidance or effective techniques for managing dynamic layout sizing in wrapped JavaFX UIs would be greatly appreciated.
Thanks everyone for the feedback—I’ve significantly clarified the question, added context around the scaling wrapper (LetterBoxer), and provided a minimal reproducible example. I'd appreciate if you could take another look!
How do I ensure a consistent JavaFX Dialog header width with varying title lengths?
Context:
I'm using JavaFX's built-in Dialog extensively in our application. Additionally, all my dialogs and general UI scenes are dynamically wrapped and scaled using a custom utility called LetterBoxer.java (related question).
The utility places UI components into a StackPane, centers them, and scales them dynamically based on scene/window resizing.
Problem:
When displaying dialogs with varying title lengths, each Dialog header automatically adjusts its width, causing visual inconsistency from one dialog to another.
Minimal Reproducible Example (simplified):
package dynamicDialogFixedWidthExample;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
public class DynamicDialogFixedWidthExample extends Application {
@Override
public void start(Stage primaryStage) {
Label headerLabel = new Label("An Extremely Long Header Title for Testing");
headerLabel.setStyle("-fx-font-size: 16px; -fx-background-color: lightblue; -fx-padding: 10;");
headerLabel.setWrapText(true);
BorderPane borderPane = getBorderPane(headerLabel);
AnchorPane rootAnchorPane = new AnchorPane(borderPane);
AnchorPane.setTopAnchor(borderPane, 0.0);
AnchorPane.setBottomAnchor(borderPane, 0.0);
AnchorPane.setLeftAnchor(borderPane, 0.0);
AnchorPane.setRightAnchor(borderPane, 0.0);
LetterBoxer letterBoxer = new LetterBoxer();
Scene scene = letterBoxer.box(rootAnchorPane);
primaryStage.setScene(scene);
scene.setOnMouseClicked(event -> {
if (headerLabel.getText().equals("An Extremely Long Header Title for Testing")) {
headerLabel.setText("Short");
} else if (headerLabel.getText().equals("Short")) {
headerLabel.setText("This is a Title");
} else {
headerLabel.setText("An Extremely Long Header Title for Testing");
}
});
primaryStage.setTitle("Dynamic Width Dialog Example");
primaryStage.setWidth(250);
primaryStage.setHeight(250);
primaryStage.show();
}
private static BorderPane getBorderPane(Label headerLabel) {
Label centerContent = new Label("Centered Content Goes Here");
centerContent.setStyle("-fx-font-size: 14px; -fx-background-color: lightgray; -fx-padding: 20;");
Label footerLabel = new Label("Footer");
footerLabel.setStyle("-fx-font-size: 14px; -fx-background-color: lightgreen; -fx-padding: 10;");
BorderPane borderPane = new BorderPane();
borderPane.setTop(headerLabel);
borderPane.setCenter(centerContent);
borderPane.setBottom(footerLabel);
return borderPane;
}
public static void main(String[] args) {
launch(args);
}
}
LetterBoxer.java
package dynamicDialogFixedWidthExample;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.geometry.Bounds;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.transform.Scale;
public class LetterBoxer {
public Scene box(final Parent content) {
return box(content, 1);
}
public Scene box(final Parent content, final double minScale) {
// the content is wrapped in a Group so that the stack centers
// the scaled node rather than the untransformed node.
Group group = new Group(content);
Scene scene = new Scene(group);
// generate a layout pass.
group.applyCss();
group.layout();
// determine the default ratio of laid out components.
final Bounds layoutBounds = group.getLayoutBounds();
final double initWidth = layoutBounds.getWidth();
final double initHeight = layoutBounds.getHeight();
final double ratio = initWidth / initHeight;
StackPane stackPane = new StackPane(group);
// place the root in a stack to keep it centered.
scene.setRoot(
stackPane
);
// configure a listener to adjust the size of the scene content (by scaling it).
BoxParams boxParams = new BoxParams(
scene, minScale, ratio, initHeight, initWidth, content
);
// adjust the size of the scene content (by scaling it) if the size changes.
BoxSizeAdjuster boxSizeAdjuster = new BoxSizeAdjuster(boxParams);
scene.widthProperty().addListener(boxSizeAdjuster);
scene.heightProperty().addListener(boxSizeAdjuster);
return scene;
}
private record BoxParams(
Scene scene,
double minScale,
double ratio,
double initHeight, double initWidth,
Parent content
) {
}
private static class BoxSizeAdjuster
implements ChangeListener<Number> {
private final BoxParams boxParams;
private final Scale scale = new Scale();
public BoxSizeAdjuster(BoxParams boxParams) {
this.boxParams = boxParams;
scale.setPivotX(0);
scale.setPivotY(0);
boxParams.content.getTransforms().setAll(scale);
}
@Override
public void changed(
ObservableValue<? extends Number> observableValue,
Number oldValue,
Number newValue
) {
final double newWidth = boxParams.scene.getWidth();
final double newHeight = boxParams.scene.getHeight();
final double scaleFactor =
Math.max(
newWidth / newHeight > boxParams.ratio
? newHeight / boxParams.initHeight
: newWidth / boxParams.initWidth,
boxParams.minScale
);
scale.setX(scaleFactor);
scale.setY(scaleFactor);
}
}
}
Due to varying title lengths, the header width fluctuates noticeably.
What I've tried (not working):
- Setting fixed widths or minimal widths on primary stage.
They didn't provide consistent dynamic adaptability considering the custom StackPane scaling wrapper.
Desirable Result/Question:
How can I consistently enforce a stable header width in JavaFX dialogs within dynamic scaling environments created by StackPane wrapping?
Any guidance or effective techniques for managing dynamic layout sizing in wrapped JavaFX UIs would be greatly appreciated.
Thanks everyone for the feedback—I’ve significantly clarified the question, added context around the scaling wrapper (LetterBoxer), and provided a minimal reproducible example. I'd appreciate if you could take another look!
Share Improve this question edited Mar 24 at 12:00 Billie asked Mar 10 at 7:48 BillieBillie 3592 silver badges13 bronze badges 6 | Show 1 more comment3 Answers
Reset to default 0We have to infer that the OP is looking to have what @James_D suggested. For the window to take on a width appropriate for the widest possible header text, and then remaining at that size regardless of the Label shown.
This, however, directly contradicts the sample code supplied, which explicitly resizes the window based on the length of the current value in the Label. And it expends a lot of effort to do this, which makes it less clear what the OP is asking.
Before looking at a solution, it's best to address some issues with the original code...
The main layout class is a BorderPane. For some reason, the BorderPane is then placed into an AnchorPane and anchored to each side of the AnchorPane. There are no other children in the AnchorPane. The AnchorPane used in this way doesn't add any functionality to the layout, and possibly suppresses some of the normal behaviours of the enclosed BorderPane.
Next, the AnchorPane is placed into a StackPane, with the comment, "to center". But it's not clear what this does since the rest of the code attempts to keep the BorderPane/AnchorPane/StackPane in a Stage which resizes based on the size of the Label. So centring shouldn't be an issue.
Finally, the original code uses a Text with the same content as the Label in order to recalculate the required size of the layout. This is generally not a good/reliable approach for this issue, and you'd be better of using bindings on the dimensional properties of the Nodes involved.
Additionally, I had issues with Scene/Stage/Window resizing on Linux, so I've just left them at their initial sizes and applied a unique colour to the Scene so that it's obvious where it's empty.
Cleaned up, and converted to Kotlin, a rough equivalent to the original code looks like this:
class ConsistentWidth : Application() {
override fun start(primaryStage: Stage) {
val headerText : StringProperty = SimpleStringProperty("This is a Title oetahutnsaoehuaoeust aoestuhoesusau nst ueoatnshuaoesual")
val borderPane = BorderPane().apply {
top = Label().apply {
textProperty().bind(headerText)
style = "-fx-font-size: 16px; -fx-background-color: lightblue; -fx-padding: 10;"
widthProperty().subscribe { _ -> [email protected]() }
}
center = Label("Centered Content Goes Here").apply {
style = "-fx-font-size: 14px; -fx-background-color: lightgray; -fx-padding: 20;"
}
bottom = Label("Footer").apply {
style = "-fx-font-size: 14px; -fx-background-color: lightgreen; -fx-padding: 10;"
}
style = "-fx-font-size: 14px; -fx-background-color: pink; -fx-padding: 10;"
autosize()
}
primaryStage.title = "Dynamic Width Dialog Example"
primaryStage.show()
val scene = Scene(borderPane, Color.AQUA)
primaryStage.scene = scene.apply {
onMouseClicked = EventHandler {
if (headerText.value == "This is a Title") {
headerText.value = "Short"
borderPane.autosize()
} else if (headerText.value == "Short") {
headerText.value = "An Extremely Long Header Title for Testing"
borderPane.autosize()
} else {
headerText.value = "This is a Title"
borderPane.autosize()
}
}
}
}
}
fun main() {
Application.launch(ConsistentWidth::class.java)
}
You can see that the layout is actually quite simple now, just 14 lines. The Label in BorderPane.top has now been decoupled from the logic code by binding it's value to a StringProperty.
When running, it looks like this. The original value of the StringProperty makes the Window quite wide:
If the goal is to have the layout at a single size which is big enough for the longest Label, and to stay at that size, then a number of Labels can be created and placed into a StackPane, with only one of them visible at a time, by manipulating their visible Property:
class ConsistentWidth : Application() {
override fun start(primaryStage: Stage) {
val whichLabel: IntegerProperty = SimpleIntegerProperty(0)
val borderPane = BorderPane().apply {
top = StackPane().apply {
children += Label("This is a Title").apply {
visibleProperty().bind(whichLabel.map { it == 0 })
style = "-fx-font-size: 16px; -fx-background-color: lightblue; -fx-padding: 10;"
}
children += Label("Short").apply {
visibleProperty().bind(whichLabel.map { it == 1 })
style = "-fx-font-size: 16px; -fx-background-color: lightblue; -fx-padding: 10;"
}
children += Label("An Extremely Long Header Title for Testing").apply {
visibleProperty().bind(whichLabel.map { it == 2 })
style = "-fx-font-size: 16px; -fx-background-color: lightblue; -fx-padding: 10;"
}
alignment = Pos.CENTER_LEFT
}
center = Label("Centered Content Goes Here").apply {
style = "-fx-font-size: 14px; -fx-background-color: lightgray; -fx-padding: 20;"
}
bottom = Label("Footer").apply {
style = "-fx-font-size: 14px; -fx-background-color: lightgreen; -fx-padding: 10;"
}
style = "-fx-font-size: 14px; -fx-background-color: pink; -fx-padding: 10;"
autosize()
}
primaryStage.title = "Dynamic Width Dialog Example"
primaryStage.show()
val scene = Scene(borderPane, Color.AQUA)
primaryStage.scene = scene.apply {
onMouseClicked = EventHandler {
val nextNum = if (whichLabel.value < 2) {whichLabel.value + 1} else 0
whichLabel.value = nextNum
}
}
}
}
fun main() {
Application.launch(ConsistentWidth::class.java)
}
Here the BorderPane.top is populated with a StackPane, which in turn is populated with three Labels, each of which has its visible Property bound through a map to the IntegerProperty, whichLabel.
The click action now just cycles through 0..2 in whichLabel.
Most importantly, the managed Property of each Label remains set as true, so the layout manager will continue to create space for them, even when they are not visible. This guarantees that the window will be wide enough for the longest Label.
It looks like this:
and this:
This achieves the effect without doing any direct manipulation of the sizes of the layouts at all.
As others said, it is not very clear about what is the required behavior for the question. I agree with all the suggestions.
Below is an approach to change the width of the stage to the widest label width. This is more or less like the way you approached, but with:
more precise code by including logic in layout computing pipeline instead of handling in listeners and initial manual computation,
considering all label widths,
no intermediate Text node for calculations.
The general idea is to use the prefWidth() method to get the max width of the Label irrespective of the surrounding node. Below is the code added in the layoutChildren method of the BorderPane to recompute the stage width, when ever the content changes.
BorderPane borderPane = new BorderPane() {
@Override
protected void layoutChildren() {
super.layoutChildren();
// Compute the width of all labels and get the max width.
double maxWidth = lookupAll(".label").stream().map(l -> l.prefWidth(-1)).max(Double::compareTo).get();
setPrefWidth(maxWidth);
primaryStage.setWidth(maxWidth + STAGE_PADDING);
}
};
As mentioned by @DaveB, it is always recommended to clean up the nodes that doesn't add any value. In your code the AnchorPane and StackPane are of no use here (atleast in this demo).
Please check the below full demo of the approach.
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
public class DynamicDialogFixedWidthExample extends Application {
/* Extra width required for the stage borders. This will be 0 if you are using a transparent stage. */
private static final double STAGE_PADDING = 16;
@Override
public void start(Stage primaryStage) {
// === Create Header (Top Section) ===
Label headerLabel = new Label("This is a Title");
headerLabel.setStyle("-fx-font-size: 16px; -fx-background-color: lightblue; -fx-padding: 10;");
// === Create Center (Content Section) ===
Label centerContent = new Label("Centered Content Goes Here");
centerContent.setStyle("-fx-font-size: 14px; -fx-background-color: lightgray; -fx-padding: 20;");
// === Create Footer (Bottom Section) ===
Label footerLabel = new Label("Footer");
footerLabel.setStyle("-fx-font-size: 14px; -fx-background-color: lightgreen; -fx-padding: 10;");
// === Assemble BorderPane ===
BorderPane borderPane = new BorderPane() {
@Override
protected void layoutChildren() {
super.layoutChildren();
// Compute the width of label's and get the max width.
double maxWidth = lookupAll(".label").stream().map(l -> l.prefWidth(-1)).max(Double::compareTo).get();
setPrefWidth(maxWidth);
primaryStage.setWidth(maxWidth + STAGE_PADDING);
}
};
borderPane.setTop(headerLabel);
borderPane.setCenter(centerContent);
borderPane.setBottom(footerLabel);
borderPane.setStyle("-fx-background-color: #f0f0f0;");
// === Set Scene ===
Scene scene = new Scene(borderPane);
primaryStage.setScene(scene);
primaryStage.setResizable(false);
// === Simulate Header Text Change for Testing ===
scene.setOnMouseClicked(event -> {
if (headerLabel.getText().equals("This is a Title")) {
headerLabel.setText("Short");
} else if (headerLabel.getText().equals("Short")) {
headerLabel.setText("An Extremely Long Header Title for Testing");
} else {
headerLabel.setText("This is a Title");
}
});
// === Set Stage Properties ===
primaryStage.setTitle("Dynamic Width Dialog Example");
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
UPDATE:
Based on @DaveB suggestion, calling autosize() method of BorderPane also does the trick.
BorderPane borderPane = new BorderPane() {
@Override
protected void layoutChildren() {
super.layoutChildren();
autosize();
primaryStage.setWidth(getWidth() + STAGE_PADDING);
}
};
Problem:
When using JavaFX’s Dialog class, the dialog width was changing dynamically based on the header text length, leading to inconsistent widths across different dialogs.
Cause:
JavaFX automatically adjusts the preferred size of a Label inside a DialogPane based on content length.
If the header text is short, the dialog shrinks.
If the header text is long, the dialog expands.
Without constraints, JavaFX does not wrap text correctly inside a DialogPane, which further contributes to unpredictable behavior.
Solution:
To enforce a consistent width while still allowing text to wrap properly, add this line:
headerLabel.setPrefWidth(250);
under the line
headerLabel.setWrapText(true);
✅ setWrapText(true); ensures long text doesn’t force the dialog to grow indefinitely.
✅ setPrefWidth(250); ensures the label stays at a consistent width instead of dynamically resizing.
Why This Works:
JavaFX doesn’t automatically wrap text in Label unless setWrapText(true); is set.
Without setPrefWidth(), the Label does not know when to wrap and just expands.
This fix works within JavaFX’s intended API behavior rather than trying to override it.
Thanks to this simple fix, my dialogs now maintain a consistent width, while still allowing longer titles to wrap properly instead of expanding the dialog size.
Additional Reference:
This answer was inspired by this discussion on javaFx Label wrapText doesn't work.
headerLabel.setMaxWidth(Double.MAX_VALUE);on all the labels. – SedJ601 Commented Mar 10 at 14:52