TabbedPane: support hiding tab area if it contains only one tab

CHANGELOG.md

@@ -10,7 +10,8 @@ FlatLaf Change Log
   - Added "Gradianto Nature Green" theme.
   - Updated "Arc Dark", "Cyan", "Dark purple", "Gradianto", "Gray", "Gruvbox"
     and "One Dark" themes.
-
+- TabbedPane: Support hiding tab area if it contains only one tab. (set client
+  property `JTabbedPane.hideTabAreaWithOneTab` to `true`)
 
 #### Fixed bugs
 

flatlaf-core/src/main/java/com/formdev/flatlaf/FlatClientProperties.java

@@ -219,7 +219,7 @@ public interface FlatClientProperties
 	 */
 	String MENU_BAR_EMBEDDED = "JRootPane.menuBarEmbedded";
 
-	//---- JScrollBar ---------------------------------------------------------
+	//---- JScrollBar / JScrollPane -------------------------------------------
 
 	/**
 	 * Specifies whether the decrease/increase arrow buttons of a scrollbar are shown.
@@ -263,6 +263,14 @@ public interface FlatClientProperties
 	 */
 	String TABBED_PANE_HAS_FULL_BORDER = "JTabbedPane.hasFullBorder";
 
+	/**
+	 * Specifies whether the tab area should be hidded if it contains only one tab.
+	 * <p>
+	 * <strong>Component</strong> {@link javax.swing.JTabbedPane}<br>
+	 * <strong>Value type</strong> {@link java.lang.Boolean}
+	 */
+	String TABBED_PANE_HIDE_TAB_AREA_WITH_ONE_TAB = "JTabbedPane.hideTabAreaWithOneTab";
+
 	/**
 	 * Specifies the minimum width of a tab.
 	 * <p>

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java

@@ -693,6 +693,26 @@ public class FlatTabbedPaneUI
 		return Math.max( tabHeight, scale( clientPropertyInt( tabPane, TABBED_PANE_TAB_HEIGHT, this.tabHeight ) ) );
 	}
 
+	@Override
+	protected int calculateMaxTabWidth( int tabPlacement ) {
+		return hideTabArea() ? 0 : super.calculateMaxTabWidth( tabPlacement );
+	}
+
+	@Override
+	protected int calculateMaxTabHeight( int tabPlacement ) {
+		return hideTabArea() ? 0 : super.calculateMaxTabHeight( tabPlacement );
+	}
+
+	@Override
+	protected int calculateTabAreaWidth( int tabPlacement, int vertRunCount, int maxTabWidth ) {
+		return hideTabArea() ? 0 : super.calculateTabAreaWidth( tabPlacement, vertRunCount, maxTabWidth );
+	}
+
+	@Override
+	protected int calculateTabAreaHeight( int tabPlacement, int horizRunCount, int maxTabHeight ) {
+		return hideTabArea() ? 0 : super.calculateTabAreaHeight( tabPlacement, horizRunCount, maxTabHeight );
+	}
+
 	@Override
 	protected Insets getTabInsets( int tabPlacement, int tabIndex ) {
 		Object value = getTabClientProperty( tabIndex, TABBED_PANE_TAB_INSETS );
@@ -752,7 +772,7 @@ public class FlatTabbedPaneUI
 	 */
 	@Override
 	protected Insets getContentBorderInsets( int tabPlacement ) {
-		if( contentSeparatorHeight == 0 || !clientPropertyBoolean( tabPane, TABBED_PANE_SHOW_CONTENT_SEPARATOR, true ) )
+		if( hideTabArea() || contentSeparatorHeight == 0 || !clientPropertyBoolean( tabPane, TABBED_PANE_SHOW_CONTENT_SEPARATOR, true ) )
 			return new Insets( 0, 0, 0, 0 );
 
 		boolean hasFullBorder = clientPropertyBoolean( tabPane, TABBED_PANE_HAS_FULL_BORDER, this.hasFullBorder );
@@ -787,6 +807,9 @@ public class FlatTabbedPaneUI
 
 	@Override
 	public void paint( Graphics g, JComponent c ) {
+		if( hideTabArea() )
+			return;
+
 		ensureCurrentLayout();
 
 		int tabPlacement = tabPane.getTabPlacement();
@@ -1226,6 +1249,13 @@ public class FlatTabbedPaneUI
 		return UIManager.getBoolean( "ScrollPane.smoothScrolling" );
 	}
 
+	protected boolean hideTabArea() {
+		return tabPane.getTabCount() == 1 &&
+			leadingComponent == null &&
+			trailingComponent == null &&
+			clientPropertyBoolean( tabPane, TABBED_PANE_HIDE_TAB_AREA_WITH_ONE_TAB, false );
+	}
+
 	protected int getTabsPopupPolicy() {
 		Object value = tabPane.getClientProperty( TABBED_PANE_TABS_POPUP_POLICY );
 
@@ -2193,6 +2223,7 @@ public class FlatTabbedPaneUI
 				case TABBED_PANE_SHOW_TAB_SEPARATORS:
 				case TABBED_PANE_SHOW_CONTENT_SEPARATOR:
 				case TABBED_PANE_HAS_FULL_BORDER:
+				case TABBED_PANE_HIDE_TAB_AREA_WITH_ONE_TAB:
 				case TABBED_PANE_MINIMUM_TAB_WIDTH:
 				case TABBED_PANE_MAXIMUM_TAB_WIDTH:
 				case TABBED_PANE_TAB_HEIGHT:

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatContainerTest.java

@@ -78,6 +78,11 @@ public class FlatContainerTest
 		putTabbedPanesClientProperty( TABBED_PANE_SHOW_CONTENT_SEPARATOR, showContentSeparator );
 	}
 
+	private void hideTabAreaWithOneTabChanged() {
+		boolean hideTabAreaWithOneTab = hideTabAreaWithOneTabCheckBox.isSelected();
+		putTabbedPanesClientProperty( TABBED_PANE_HIDE_TAB_AREA_WITH_ONE_TAB, hideTabAreaWithOneTab );
+	}
+
 	private void hasFullBorderChanged() {
 		Boolean hasFullBorder = hasFullBorderCheckBox.isSelected() ? true : null;
 		putTabbedPanesClientProperty( TABBED_PANE_HAS_FULL_BORDER, hasFullBorder );
@@ -461,6 +466,7 @@ public class FlatContainerTest
 		maximumTabWidthCheckBox = new JCheckBox();
 		showTabSeparatorsCheckBox = new JCheckBox();
 		secondTabWiderCheckBox = new JCheckBox();
+		hideTabAreaWithOneTabCheckBox = new JCheckBox();
 		CellConstraints cc = new CellConstraints();
 
 		//======== this ========
@@ -579,6 +585,7 @@ public class FlatContainerTest
 					"[]" +
 					"[]para" +
 					"[]" +
+					"[]" +
 					"[]"));
 
 				//---- tabScrollCheckBox ----
@@ -800,6 +807,11 @@ public class FlatContainerTest
 				secondTabWiderCheckBox.setText("Second Tab insets wider (4,20,4,20)");
 				secondTabWiderCheckBox.addActionListener(e -> secondTabWiderChanged());
 				tabbedPaneControlPanel.add(secondTabWiderCheckBox, "cell 2 9");
+
+				//---- hideTabAreaWithOneTabCheckBox ----
+				hideTabAreaWithOneTabCheckBox.setText("Hide tab area with one tab");
+				hideTabAreaWithOneTabCheckBox.addActionListener(e -> hideTabAreaWithOneTabChanged());
+				tabbedPaneControlPanel.add(hideTabAreaWithOneTabCheckBox, "cell 1 10");
 			}
 			panel9.add(tabbedPaneControlPanel, cc.xywh(1, 11, 3, 1));
 		}
@@ -844,6 +856,7 @@ public class FlatContainerTest
 	private JCheckBox maximumTabWidthCheckBox;
 	private JCheckBox showTabSeparatorsCheckBox;
 	private JCheckBox secondTabWiderCheckBox;
+	private JCheckBox hideTabAreaWithOneTabCheckBox;
 	// JFormDesigner - End of variables declaration  //GEN-END:variables
 
 	private JTabbedPane[] allTabbedPanes;

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatContainerTest.jfd

@@ -132,7 +132,7 @@ new FormModel {
 				add( new FormContainer( "com.formdev.flatlaf.testing.FlatTestFrame$NoRightToLeftPanel", new FormLayoutManager( class net.miginfocom.swing.MigLayout ) {
 					"$layoutConstraints": "insets 0,hidemode 3"
 					"$columnConstraints": "[][fill][]"
-					"$rowConstraints": "[center][][][][][]para[][]para[][]"
+					"$rowConstraints": "[center][][][][][]para[][]para[][][]"
 				} ) {
 					name: "tabbedPaneControlPanel"
 					"opaque": false
@@ -547,6 +547,16 @@ new FormModel {
 					}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 						"value": "cell 2 9"
 					} )
+					add( new FormComponent( "javax.swing.JCheckBox" ) {
+						name: "hideTabAreaWithOneTabCheckBox"
+						"text": "Hide tab area with one tab"
+						auxiliary() {
+							"JavaCodeGenerator.variableLocal": false
+						}
+						addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "hideTabAreaWithOneTabChanged", false ) )
+					}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+						"value": "cell 1 10"
+					} )
 				}, new FormLayoutConstraints( class com.jgoodies.forms.layout.CellConstraints ) {
 					"gridY": 11
 					"gridWidth": 3