Tab indentation can be set from the UI.

src/co/uproot/htabs/demo/HTabsDemoApp.java

@@ -39,6 +39,7 @@
 import javax.swing.JPanel;
 import javax.swing.JRadioButton;
 import javax.swing.JTabbedPane;
+import javax.swing.JTextField;
 import javax.swing.SwingConstants;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
@@ -47,6 +48,8 @@
 import javax.swing.border.EmptyBorder;
 import javax.swing.event.ChangeEvent;
 import javax.swing.event.ChangeListener;
+import javax.swing.event.DocumentEvent;
+import javax.swing.event.DocumentListener;
 
 import co.uproot.htabs.custom.tabbedpane.CustomTabbedPane;
 import co.uproot.htabs.demo.components.ColoredIcon;
@@ -170,7 +173,48 @@ public void actionPerformed(final ActionEvent e) {
     newTabButtons.add(newSiblingBtn, BorderLayout.CENTER);
     newTabButtons.add(newChildBtn, BorderLayout.EAST);
 
-    topBar.add(radioPanel, BorderLayout.WEST);
+    final JPanel tabIndentPanel = new JPanel();
+    tabIndentPanel.setLayout(new BorderLayout());
+
+    final JLabel tabIndentLabel = new JLabel("Tab indent: ");
+
+    final JTextField tabIndentField = new JTextField(String.valueOf(tabManager.getTabComponentIndent()), 5);
+    tabIndentField.getDocument().addDocumentListener(new DocumentListener() {
+      @Override
+      public void insertUpdate(DocumentEvent e) {
+        update();
+      }
+
+      @Override
+      public void removeUpdate(DocumentEvent e) {
+        update();
+      }
+
+      @Override
+      public void changedUpdate(DocumentEvent e) {
+
+      }
+
+      private void update() {
+        try {
+          int indent = Integer.parseInt(tabIndentField.getText());
+          tabManager.setIndent(indent);
+        } catch (NumberFormatException e) {
+          // do nothing
+        }
+      }
+    });
+
+    tabIndentPanel.add(tabIndentLabel, BorderLayout.WEST);
+    tabIndentPanel.add(tabIndentField, BorderLayout.EAST);
+
+    final JPanel upperLeftPanel = new JPanel();
+    upperLeftPanel.setLayout(new BorderLayout());
+
+    upperLeftPanel.add(radioPanel, BorderLayout.NORTH);
+    upperLeftPanel.add(tabIndentPanel, BorderLayout.SOUTH);
+
+    topBar.add(upperLeftPanel, BorderLayout.WEST);
     topBar.add(newTabButtons, BorderLayout.EAST);
 
 

src/co/uproot/htabs/tabmanager/TabManager.java

@@ -38,6 +38,7 @@
 import java.awt.geom.GeneralPath;
 import java.awt.geom.Path2D;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import javax.swing.AbstractButton;
@@ -172,6 +173,29 @@ private int getTabComponentIndent(final Component tabComponent) {
     final int tabLevel = getTabLevel(tab);
     return getTabComponentIndent(tabLevel);
   }
+
+  public void setIndent(int indent){
+    if (!(tabbedPane.getUI() instanceof CustomMetalTabbedPaneUI)){
+      setTabIndent(indent);
+    }
+    setTabComponentIndent(indent);
+    redraw();
+  }
+
+  private void redraw() {
+    tabbedPane.revalidate();
+    tabbedPane.repaint();
+    for(final Tab tab: tabs){
+      tab.removeTabContentPane();
+    }
+
+    // TODO: use Google's Collection library to foreach through the original list in reversed order.
+    List<Tab> reversedTabs = new ArrayList<>(tabs);
+    Collections.reverse(reversedTabs);
+    for(final Tab tab: reversedTabs){
+      tab.addTabContentPane();
+    }
+  }
 
   private static int getTabLevel(final Tab tab) {
     return tab == null ? 0 : tab.tabLevel;
@@ -778,7 +802,28 @@ public void collapseTab() {
       }
       this.setCollapsed(true);
     }
+
+    private void addTabContentPane() {
+      List<Tab> reversedChildren = new ArrayList<>(children);
+      // TODO: use Google's Collection library to foreach through the original list in reversed order.
+      Collections.reverse(reversedChildren);
+      for (final Tab child : reversedChildren) {
+        child.addTabContentPane();
+      }
+      addTab(Tab.this, 0);
+    }
+
+    private void removeTabContentPane() {
+      tabbedPane.remove(tabContentPane);
+      for (final Tab child : this.children) {
+        child.removeTabContentPane();
+      }
+    }
+
+  }
 
+  public int getTabComponentIndent() {
+    return tabComponentIndent;
   }
 
 }