Develop Reference

Java JTextPane changes line height when UTF8 character is added

I am using Java JDK 1.6 and have a problem using JTextPane to show text with a monospaced font. As soon as I add a UTF8-character like 😂, the line height in the textpane is reduced (for all the text already in the pane and also all text added later). How can I avoid this? I would like to have the normal line height.
Here is some sample code:
class AttributedTextPane extends JTextPane
{
private DefaultStyledDocument defaultStyledDocument;
protected AttributedTextPane()
{
this.defaultStyledDocument = new DefaultStyledDocument();
this.setDocument(defaultStyledDocument);
this.setContentType("text/plain");
...
}
}
...
This pane is integrated into an JInternalFrame. Creating the panel and setting the desired monospaced font:
Font font = new Font("DejaVu Sans Mono", Font.PLAIN, 11);
AttributedTextPane pane = new AttributedTextPane();
pane.setFont(font);
To display the desired text, I call pane.setText(...); As soon as I add the UTF8 character, the line height changes, see screenshot at http://i.imgur.com/Fq7XBJB.png. Is there a way to avoid that the line height is changed?
Thanks, Deejay

You could try setting/forcing a line height like so:
MutableAttributeSet jTextPaneSet = new SimpleAttributeSet(pane.getParagraphAttributes());
StyleConstants.setLineSpacing(jTextPaneSet, 1.5f); //replace float 1.5f with your desired line spacing/height
Source:
http://docs.oracle.com/javase/8/docs/api/javax/swing/JTextPane.html#setParagraphAttributes(javax.swing.text.AttributeSet,%20boolean)
https://docs.oracle.com/javase/7/docs/api/javax/swing/text/StyleConstants.html#setLineSpacing(javax.swing.text.MutableAttributeSet,%20float)

Old question but I have been struggling with it for some time, though with a JTextArea. The solution is to have either a VM param -Di18n=true or put the i18n property in the document.
My test code:
import javax.swing.JTextArea;
public class Test {
public static void main(String[] argv) {
JTextArea ta = new JTextArea();
//ta.getDocument().putProperty("i18n", Boolean.TRUE);
ta.setText("A");
System.out.println(ta.getPreferredSize()); // - height 16 without i18n and using default font, 15 with i18n
ta.setText("\ud8ff\udc05"); // surrogate pair
System.out.println(ta.getPreferredSize()); // - height 15
ta.setText("A");
System.out.println(ta.getPreferredSize()); // - height 15
}
}
When i18n is not enabled and the document is appended, the elements that are created are PlainView/WrappedPlainView that return the height based on the FontMetrics height.
When i18n is enabled the elements are PlainParagraph that contain GlyphView that calculates the height differently.
When i18n is not enabled and the document is appended with a surrogate pair then due to SwingUtilities2.isComplexLayout returning true, the i18n property is automatically set to true for the document and then all elements are created as PlainParagraph containing GlyphView that return the different (always smaller?) height.

Making JLable in JTextPane Undeletable

I currently have a JLabel embedded in a JTextPane using this:
import javax.swing.*;
import javax.swing.text.*;
public class MainFrame
{
JFrame mainFrame = new JFrame("Main Frame");
JTextPane textPane = new JTextPane();
public MainFrame()
{
String[] components = {"Title", "\n"};
String[] styles = {"LABEL_ALIGN", "LEFT_ALIGN"};
StyledDocument sd = textPane.getStyledDocument();
Style DEFAULT_STYLE = StyleContext.getDefaultStyleContext().getStyle(StyleContext.DEFAULT_STYLE);
Style LEFT_STYLE = sd.addStyle("LEFT_ALIGN", DEFAULT_STYLE);
StyleConstants.setAlignment(LEFT_STYLE, StyleConstants.ALIGN_LEFT);
Style CENTER_STYLE = sd.addStyle("CENTER_ALIGN", DEFAULT_STYLE);
StyleConstants.setAlignment(CENTER_STYLE, StyleConstants.ALIGN_CENTER);
JLabel titleLbl = new JLabel("Title");
Style LABEL_STYLE = sd.addStyle("LABEL_ALIGN", DEFAULT_STYLE);
StyleConstants.setAlignment(LABEL_STYLE, StyleConstants.ALIGN_CENTER);
StyleConstants.setComponent(LABEL_STYLE, titleLbl);
for(int i = 0; i < components.length; i++)
{
try
{
sd.insertString(sd.getLength(), components[i], sd.getStyle(styles[i]));
sd.setLogicalStyle(sd.getLength(), sd.getStyle(styles[i]));
}
catch(BadLocationException e)
{
e.printStackTrace();
}
}
mainFrame.add(textPane);
mainFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
mainFrame.setLocationRelativeTo(null);
mainFrame.setExtendedState(JFrame.MAXIMIZED_BOTH);
mainFrame.pack();
mainFrame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(MainFrame::new);
}
}
How can I make the label un-deletable? Because whenever I hold backspace, the label ends up getting removed from the JTextPane

You might be able to use a NavigationFilter to prevent the removal of the component at the beginning of the text pane. Check out: How to make part of a JTextField uneditable for an example of this approach. In this case the label represents a single character so the prefix length would be set to 1. Or maybe you can just use the prefix concept itself and don't even use the JLabel.
Otherwise, you might be able to create a custom DocumentFilter. Check out the section from the Swing tutorial on Implementing a DocumentFilter for the basics.
So you would need to track the offset off the location of the component. Then in the remove(...) method of the filter you would need to check if you are removing data in the range of your offset. If so you would ignore the remove.
Of course the offset can dynamically change if you add or remove text before the label so you would need to manage that as well.
Or you can check out the Protected Text Component which attempts to manage all of that for you.

Why not just put your title label outside the text area? That seems more intuitive.
It looks like there's no real way to avoid this while still allowing the textarea to be editable. You could place the label above the text frame so that it occupies the same space, or above the text frame so that it behaves like a proper title.
Unfortunately, the nature of the textarea is that all of its subcomponents are editable or none of them are.

How do I underline text "text" when text is a field?

public class Text extends JPanel {
private String text;
public Text()
{
this.setPreferredSize(new Dimension(20,20));
setFont (new Font(text, Font.PLAIN, 24));
text = "";
}
public void showUnderline()
{
Hashtable<TextAttribute, Object> map = new Hashtable
<TextAttribute, Object>();
map.put(TextAttribute.UNDERLINE, TextAttribute.UNDERLINE_ON);
}
the text object will be created within another class. in that class I will need to underline it with the showUnderline method. The method seems incomplete.I'm shooting for the java exclusive approach, meaning no HTML.
How do I link the text to the showUnderline method?

What do you mean 'java exclusive approach, meaning no HTML' ? You probably are looking for a JLabel, and you can put very simple html in it. Here's the first result on google:
http://www.apl.jhu.edu/~hall/java/Swing-Tutorial/Swing-Tutorial-JLabel.html
It has an example of making text different colors, fonts, and bold or italicized. You could probably just do something like:
JLabel label = new JLabel("<u>MY TEXT</u>",JLabel.CENTER);
From there, you can place it like you would place any other JComponent.
If you really don't want HTML, you could use a JTextPane. Here's an example:
http://www.exampledepot.com/egs/javax.swing.text/style_hilitewords2.html

JEditorPane, is preferredSize tracking parent width?

JEditorPane seems to have a very interesting feature: it seems to track its parent width, and determines the preferred height accordingly, also if the parent IS NOT a JViewport.
By track i mean that the preferred width of the component is set to the one of its parent (maybe apart from some insets).
The ScrollableTracksViewportWidth is false.
This is the very simple code that demonstrates this fact (just copy and fix imports):
When the JFrame is resized, the preferred width of the JEditorPane (in my environement) is always frame.width-14 (of course 14 may be graphical-system specific).
q1) Tracking the parent (non viewport) width is good. Can I rely on it? As far as i know this is an undocumented feature.More! Just replace new JEditorPane() with new JTextPane(), a richer subclass of JEditorPane, and the feature disappear.
q2) It seems to me that this "tracking" happens through the "setting" of the JEditorPane size. This means that FIRST the size (width) must be set, then the preferred size height will be ok. Is it right?
q3) Why JTextPane has not this feature?
public class SSCE01 extends JFrame {
public static void main(String[] a) {
new SSCE01().setVisible(true);
}
public SSCE01() {
final JEditorPane ep = new JEditorPane();
add(ep);
addComponentListener(new ComponentAdapter() {
public void componentResized(ComponentEvent e) {
Dimension ps = getSize();
System.out.println("Frame size : " + ps.width + " x " + ps.height);
ps = ep.getPreferredSize();
System.out.println("JEditorPane preferredSize: " + ps.width + " x " + ps.height);
}
});
pack();
}
}
q4) More clear question. As hypothesized in q2, setting the size allows the tracking. But just for JEditorPane, NOT for JTextPane. How can I accomplish this for the JTextPane too?
this works:
public SSCE02() {
JEditorPane ep = new JEditorPane();
ep.setText("this is a very very long text. veeeeery long, so long that it will never fit into one 100 pixels width row");
ep.setSize(new Dimension(100,Integer.MAX_VALUE));
add(ep);
pack();
}
this doesn't. It has been used a JTextPane in place of JEditorPane:
public SSCE02() {
JEditorPane ep = new JTextPane();
ep.setText("this is a very very long text. veeeeery long, so long that it will never fit into one 100 pixels width row");
ep.setSize(new Dimension(100,Integer.MAX_VALUE));
add(ep);
pack();
}
UPDATE 1
Summary: the "track Size property" is observed in JEditorPane but nothing similar exists in JTextPane.
A little but significative step further:
Loading an HTML document into JEditorPane lets the feature disappear from JEditorPane too.
At this point, the feature seems implemented by the Document implementation and not by the JEditorPane (or JTextPane) itself! In the case of JEditorPane, the Document is javax.swing.text.PlainDocument. When you do:
URL url = HTMLInComponents01.class.getResource("sample.html");
jEditorPane1.setPage(url);
System.out.println(jEditorPane1.getDocument().getClass().getName());
you'll get:
javax.swing.text.html.HTMLDocument
I also notice that the good javax.swing.text.PlainDocument that gives us this great service of "calculating the height" of a component when the width is given through setSize" isn't assignable to a JTextPane, that expects a StyledDocument instance!
Now I'll verify which other text components are capable of using PlainDocument.

I recommend you add the component to the JFrame's content pane instead of using the add() method. Also set a layout on the content pane and it will all resize automatically.
JFrame f = new JFrame();
f.getContentPane().setLayout(new BorderLayout());
f.getContentPane().add(new JTextPane());
Regards

Selecting text from a JLabel?

Is it possible to enable the selection of text from a JLabel? If not, what's the best alternative control to use, and how can it be configured to appear like a JLabel?

A JTextField doesn't allow html-formatted text like a JLabel. If you want selectable html text you could alternatively try a JTextPane set to html formatting:
JTextPane f = new JTextPane();
f.setContentType("text/html"); // let the text pane know this is what you want
f.setText("<html>Hello World</html>"); // showing off
f.setEditable(false); // as before
f.setBackground(null); // this is the same as a JLabel
f.setBorder(null); // remove the border

You can use a JTextField without enabling the editing
JTextField f=new JTextField("Hello World");
f.setEditable(false);
content.add(f);
Pierre

Building on the answers:
You can use a JTextField without enabling the editing
JTextField f=new JTextField("Hello World");
f.setEditable(false);
f.setBackground(null); //this is the same as a JLabel
f.setBorder(null); //remove the border
I don't know how to stop the text from "Jumping" when you select it, or replace the text (programmatically). Maybe it is just my computer...

When using JTextField, you will also want to remove the border:
f.setBorder(null);
and set the disabled text color: f.setDisabledTextColor(Color.black);

As variant below CopyableLabel supports html tags and Fonts as JLabel.
public class CopyableLabel extends JTextPane {
private static final long serialVersionUID = -1;
private static final Font DEFAULT_FONT;
static {
Font font = UIManager.getFont("Label.font");
DEFAULT_FONT = (font != null) ? font: new Font("Tahoma", Font.PLAIN, 11);
}
public CopyableLabel() {
construct();
}
private void construct() {
setContentType("text/html");
setEditable(false);
setBackground(null);
setBorder(null);
putClientProperty(JEditorPane.HONOR_DISPLAY_PROPERTIES, true);
setFont(DEFAULT_FONT);
}
}

JLabels cannot be editable.
However, you could use a JTextField and just change the foreground / background colors to make it appear as a JLabel. If you wanted to be really fancy you could add code to change the colors when it's selected to indicate that it's editable.

Besides the changes suggested in other responses (setEditable, setContentType, setOpaque or setBackground, maybe setEnabled + setDisabledTextColor(Color.black), maybe setBorder(null) and/or setMargin(new Insets(0,0,0,0))
To get the font of a JTextPane to look like a JLabel, see the suggestion from this blog post:
"Unfortunately, simply calling set font on JEditorPane will have no effect, as the default font is pulled from a style sheet rather than the JComponent. There is, however, a clever way around the errant font default. The best way to change the default font in an HTML rendering JEditorPane, is to alter the style sheet like this:"
// create a JEditorPane that renders HTML and defaults to the system font.
JEditorPane editorPane =
new JEditorPane(new HTMLEditorKit().getContentType(),text);
// set the text of the JEditorPane to the given text.
editorPane.setText(text);
// add a CSS rule to force body tags to use the default label font
// instead of the value in javax.swing.text.html.default.csss
Font font = UIManager.getFont("Label.font");
String bodyRule = "body { font-family: " + font.getFamily() + "; " +
"font-size: " + font.getSize() + "pt; }";
((HTMLDocument)editorPane.getDocument()).getStyleSheet().addRule(bodyRule);