Add RSyntaxTextArea for stream content

This is one of the first steps of integrating RSyntaxTextArea for PDF
content stream editing. Tokenization is based on the parsing logic,
which was added in the previous commit.

Since PDF content streams are, in a general case, not text, but binary
data, some workarounds had to be made, as RSyntaxTextArea was designed
to work with text. A custom token type and painter was created, so that
we could render arbitrary characters not as text, but as hexadecimal
representations of the binary data.

Additionally, Latin1Filter was made so that we could somewhat trick
RSyntaxTextArea to work with binary data. It replaces any characters,
which are not representable in Latin-1 (i.e. U+0100 and beyond) with
their UTF-8 representation, but with bytes stored in chars. As a result
all chars in the document fit in one byte and the backing character
array for the document acts as an inflated byte array. This way we can
just decode the text with Latin-1 to get the expected output, which can
be put directly into PDF.

With how RSyntaxTextArea is structured, quite a lot of code from there
has to be copied, as inheritance is not "granular" enough to do what we
cant.

Since the input stream is no longer processed by iText, what you see in
the editor pane is the raw data in the stream itself unmodified. This
was one of the goals, as before opening a stream for editing would
make it pretty much impossible to save it without altering at least
whitespace in some way.

As of now, there are some regressions. For example:
1. Images are no longer render in the stream pane. For now, they are
   displayed as text.
2. Since stream is presented as-is, there is no indentation at the
   moment. This will be added later as an explicit prettifier option.

Code folding, static syntax analysis and RSTAUI dialog integrations will
be added later.

Author: Eswcvlad

pom.xml

@@ -81,6 +81,8 @@
     <itext.version>9.1.0</itext.version>
     <jackson.version>2.18.2</jackson.version>
     <logback.version>1.5.17</logback.version>
+    <rsyntaxtextarea.version>3.6.0</rsyntaxtextarea.version>
+    <rstaui.version>3.3.1</rstaui.version>
 
     <!-- Test dependencies -->
     <junit-jupiter-api.version>5.12.0</junit-jupiter-api.version>
@@ -134,6 +136,16 @@
       <artifactId>flatlaf</artifactId>
       <version>${flatlaf.version}</version>
     </dependency>
+    <dependency>
+      <groupId>com.fifesoft</groupId>
+      <artifactId>rsyntaxtextarea</artifactId>
+      <version>${rsyntaxtextarea.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>com.fifesoft</groupId>
+      <artifactId>rstaui</artifactId>
+      <version>${rstaui.version}</version>
+    </dependency>
     <dependency>
       <groupId>com.itextpdf</groupId>
       <artifactId>pdftest</artifactId>

src/main/java/com/itextpdf/rups/controller/PdfReaderController.java

@@ -73,7 +73,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.rups.view.itext.PdfTree;
 import com.itextpdf.rups.view.itext.PlainText;
 import com.itextpdf.rups.view.itext.StructureTree;
-import com.itextpdf.rups.view.itext.SyntaxHighlightedStreamPane;
+import com.itextpdf.rups.view.itext.StreamTextEditorPane;
 import com.itextpdf.rups.view.itext.XRefTable;
 import com.itextpdf.rups.view.itext.treenodes.PdfObjectTreeNode;
 
@@ -135,7 +135,7 @@ public class PdfReaderController implements IPdfObjectPanelEventListener, IRupsE
     /**
      * A panel that will show a stream.
      */
-    protected SyntaxHighlightedStreamPane streamPane;
+    protected StreamTextEditorPane streamPane;
 
     /**
      * The factory producing tree nodes.
@@ -205,7 +205,7 @@ public PdfReaderController(TreeSelectionListener treeSelectionListener,
 
         objectPanel = new PdfObjectPanel();
         objectPanel.addEventListener(this);
-        streamPane = new SyntaxHighlightedStreamPane(this);
+        streamPane = new StreamTextEditorPane(this);
         JScrollPane debug = new JScrollPane(DebugView.getInstance().getTextArea());
         editorTabs = new JTabbedPane();
         editorTabs.addTab(Language.STREAM.getString(), null, streamPane, Language.STREAM.getString());
@@ -261,7 +261,7 @@ public JTabbedPane getEditorTabs() {
      *
      * @return a SyntaxHighlightedStreamPane
      */
-    public SyntaxHighlightedStreamPane getStreamPane() {
+    public StreamTextEditorPane getStreamPane() {
         return streamPane;
     }
 

src/main/java/com/itextpdf/rups/view/Language.java

@@ -95,6 +95,7 @@ public enum Language {
     ERROR_BUILDING_CONTENT_STREAM,
     ERROR_CANNOT_CHECK_NULL_FOR_INPUT_STREAM,
     ERROR_CANNOT_FIND_FILE,
+    ERROR_CHARACTER_ENCODING,
     ERROR_CLOSING_STREAM,
     ERROR_COMPARE_DOCUMENT_CREATION,
     ERROR_COMPARED_DOCUMENT_CLOSED,

src/main/java/com/itextpdf/rups/view/contextmenu/InspectObjectAction.java

@@ -45,7 +45,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.rups.view.Language;
 import com.itextpdf.rups.view.icons.FrameIconUtil;
 import com.itextpdf.rups.view.itext.PdfTree;
-import com.itextpdf.rups.view.itext.SyntaxHighlightedStreamPane;
+import com.itextpdf.rups.view.itext.StreamTextEditorPane;
 import com.itextpdf.rups.view.itext.treenodes.PdfObjectTreeNode;
 
 import javax.swing.AbstractAction;
@@ -83,10 +83,10 @@ public void actionPerformed(ActionEvent e) {
 
         final PdfObjectTreeNode node =
                 (PdfObjectTreeNode) ((PdfTree) invoker).getSelectionPath().getLastPathComponent();
-        final SyntaxHighlightedStreamPane syntaxHighlightedStreamPane = new SyntaxHighlightedStreamPane(null);
+        final StreamTextEditorPane streamPane = new StreamTextEditorPane(null);
 
-        frame.add(syntaxHighlightedStreamPane);
-        syntaxHighlightedStreamPane.render(node);
+        frame.add(streamPane);
+        streamPane.render(node);
 
         final Language dialogCancel = Language.DIALOG_CANCEL;
         frame.getRootPane().getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)

src/main/java/com/itextpdf/rups/view/contextmenu/SaveToPdfStreamJTextPaneAction.java

@@ -42,18 +42,18 @@ This file is part of the iText (R) project.
  */
 package com.itextpdf.rups.view.contextmenu;
 
-import com.itextpdf.rups.view.itext.SyntaxHighlightedStreamPane;
+import com.itextpdf.rups.view.itext.StreamTextEditorPane;
 
 import java.awt.event.ActionEvent;
 
 public class SaveToPdfStreamJTextPaneAction extends AbstractRupsAction {
 
-    public SaveToPdfStreamJTextPaneAction(String name, SyntaxHighlightedStreamPane invoker) {
+    public SaveToPdfStreamJTextPaneAction(String name, StreamTextEditorPane invoker) {
         super(name, invoker);
     }
 
     public void actionPerformed(ActionEvent event) {
-        final SyntaxHighlightedStreamPane pane = (SyntaxHighlightedStreamPane) invoker;
+        final StreamTextEditorPane pane = (StreamTextEditorPane) invoker;
         pane.saveToTarget();
     }
 }

src/main/java/com/itextpdf/rups/view/contextmenu/StreamPanelContextMenu.java

@@ -43,13 +43,13 @@ This file is part of the iText (R) project.
 package com.itextpdf.rups.view.contextmenu;
 
 import com.itextpdf.rups.view.Language;
-import com.itextpdf.rups.view.itext.SyntaxHighlightedStreamPane;
+import com.itextpdf.rups.view.itext.StreamTextEditorPane;
 
 import javax.swing.Action;
+import javax.swing.JComponent;
 import javax.swing.JMenuItem;
 import javax.swing.JPopupMenu;
 import javax.swing.JSeparator;
-import javax.swing.JTextPane;
 import javax.swing.text.DefaultEditorKit;
 
 /**
@@ -73,7 +73,7 @@ public final class StreamPanelContextMenu extends JPopupMenu {
      * @param textPane   the text pane
      * @param controller the controller
      */
-    public StreamPanelContextMenu(final JTextPane textPane, final SyntaxHighlightedStreamPane controller) {
+    public StreamPanelContextMenu(final JComponent textPane, final StreamTextEditorPane controller) {
         super();
 
         final JMenuItem copyItem = getJMenuItem(

src/main/java/com/itextpdf/rups/view/itext/BeepingUndoManager.java

@@ -0,0 +1,73 @@
+/*
+    This file is part of the iText (R) project.
+    Copyright (c) 1998-2025 Apryse Group NV
+    Authors: Apryse Software.
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License version 3
+    as published by the Free Software Foundation with the addition of the
+    following permission added to Section 15 as permitted in Section 7(a):
+    FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
+    APRYSE GROUP. APRYSE GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
+    OF THIRD PARTY RIGHTS
+
+    This program is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE.
+    See the GNU Affero General Public License for more details.
+    You should have received a copy of the GNU Affero General Public License
+    along with this program; if not, see http://www.gnu.org/licenses or write to
+    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+    Boston, MA, 02110-1301 USA, or download the license from the following URL:
+    http://itextpdf.com/terms-of-use/
+
+    The interactive user interfaces in modified source and object code versions
+    of this program must display Appropriate Legal Notices, as required under
+    Section 5 of the GNU Affero General Public License.
+
+    In accordance with Section 7(b) of the GNU Affero General Public License,
+    a covered work must retain the producer line in every PDF that is created
+    or manipulated using iText.
+
+    You can be released from the requirements of the license by purchasing
+    a commercial license. Buying such a license is mandatory as soon as you
+    develop commercial activities involving the iText software without
+    disclosing the source code of your own applications.
+    These activities include: offering paid services to customers as an ASP,
+    serving PDFs on the fly in a web application, shipping iText with a closed
+    source product.
+
+    For more information, please contact iText Software Corp. at this
+    address: [email protected]
+ */
+package com.itextpdf.rups.view.itext;
+
+import java.awt.Toolkit;
+import javax.swing.undo.CannotRedoException;
+import javax.swing.undo.CannotUndoException;
+import javax.swing.undo.UndoManager;
+
+/**
+ * A variation of an {@link UndoManager}, which will issue a beep instead of
+ * throwing {@link CannotUndoException} and {@link CannotRedoException}
+ * exceptions.
+ */
+public final class BeepingUndoManager extends UndoManager {
+    @Override
+    public void redo() {
+        try {
+            super.redo();
+        } catch (CannotRedoException ignored) {
+            Toolkit.getDefaultToolkit().beep();
+        }
+    }
+
+    @Override
+    public void undo() {
+        try {
+            super.undo();
+        } catch (CannotUndoException ignored) {
+            Toolkit.getDefaultToolkit().beep();
+        }
+    }
+}