Table: optionally paint alternating rows below table if table is smaller than scroll pane (issue #504)

CHANGELOG.md

@@ -5,6 +5,9 @@ FlatLaf Change Log
 
 #### New features and improvements
 
+- Table: Optionally paint alternating rows below table if table is smaller than
+  scroll pane. Set UI value `Table.paintOutsideAlternateRows` to `true`.
+  Requires that `Table.alternateRowColor` is set to a color. (issue #504)
 - ToggleButton: Made the underline placement of tab-style toggle buttons
   configurable. (PR #530; issue #529)
 - Added spanish translation. (PR #525)
@@ -155,7 +158,7 @@ FlatLaf Change Log
   - Possibility to hide window title bar icon (for single window set client
     property `JRootPane.titleBarShowIcon` to `false`; for all windows set UI
     value `TitlePane.showIcon` to `false`).
-  - OptionPane: Hide window title bar icon by default. Can be be made visibly by
+  - OptionPane: Hide window title bar icon by default. Can be made visibly by
     setting UI default `OptionPane.showIcon` to `true`. (issue #416)
   - No longer show the Java "duke/cup" icon if no window icon image is set.
     (issue #416)

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

@@ -80,6 +80,7 @@ import com.formdev.flatlaf.util.UIScale;
  * @uiDefault Table.intercellSpacing					Dimension
  * @uiDefault Table.selectionInactiveBackground			Color
  * @uiDefault Table.selectionInactiveForeground			Color
+ * @uiDefault Table.paintOutsideAlternateRows			boolean
  *
  * <!-- FlatTableCellBorder -->
  *
@@ -95,7 +96,7 @@ import com.formdev.flatlaf.util.UIScale;
  */
 public class FlatTableUI
 	extends BasicTableUI
-	implements StyleableUI
+	implements StyleableUI, FlatViewportUI.ViewportPainter
 {
 	protected boolean showHorizontalLines;
 	protected boolean showVerticalLines;
@@ -421,4 +422,38 @@ public class FlatTableUI
 			? (viewport != rowHeader)
 			: (viewport == rowHeader || rowHeader == null);
 	}
+
+	/** @since 2.3 */
+	@Override
+	public void paintViewport( Graphics g, JComponent c, JViewport viewport ) {
+		int viewportWidth = viewport.getWidth();
+		int viewportHeight = viewport.getHeight();
+
+		// fill viewport background in same color as table background
+		if( viewport.isOpaque() ) {
+			g.setColor( table.getBackground() );
+			g.fillRect( 0, 0, viewportWidth, viewportHeight );
+		}
+
+		// paint alternating empty rows
+		boolean paintOutside = UIManager.getBoolean( "Table.paintOutsideAlternateRows" );
+		Color alternateColor;
+		if( paintOutside && (alternateColor = UIManager.getColor( "Table.alternateRowColor" )) != null ) {
+			g.setColor( alternateColor );
+
+			int rowCount = table.getRowCount();
+
+			// paint alternating empty rows below the table
+			int tableHeight = table.getHeight();
+			if( tableHeight < viewportHeight ) {
+				int tableWidth = table.getWidth();
+				int rowHeight = table.getRowHeight();
+
+				for( int y = tableHeight, row = rowCount; y < viewportHeight; y += rowHeight, row++ ) {
+					if( row % 2 != 0 )
+						g.fillRect( 0, y, tableWidth, rowHeight );
+				}
+			}
+		}
+	}
 }

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

@@ -18,8 +18,8 @@ package com.formdev.flatlaf.ui;
 
 import java.awt.Component;
 import java.awt.Graphics;
+import java.lang.reflect.Method;
 import javax.swing.JComponent;
-import javax.swing.JTable;
 import javax.swing.JViewport;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicViewportUI;
@@ -43,15 +43,28 @@ public class FlatViewportUI
 	}
 
 	@Override
-	public void update( Graphics g, JComponent c ) {
-		Component view = ((JViewport)c).getView();
-		if( c.isOpaque() && view instanceof JTable ) {
-			// paint viewport background in same color as table background
-			g.setColor( view.getBackground() );
-			g.fillRect( 0, 0, c.getWidth(), c.getHeight() );
+	public void paint( Graphics g, JComponent c ) {
+		super.paint( g, c );
 
-			paint( g, c );
-		} else
-			super.update( g, c );
+		Component view = ((JViewport)c).getView();
+		if( view instanceof JComponent ) {
+			try {
+				Method m = view.getClass().getMethod( "getUI" );
+				Object ui = m.invoke( view );
+				if( ui instanceof ViewportPainter )
+					((ViewportPainter)ui).paintViewport( g, (JComponent) view, (JViewport) c );
+			} catch( Exception ex ) {
+				// ignore
+			}
+		}
+	}
+
+	//---- interface ViewportPainter ------------------------------------------
+
+	/**
+	 * @since 2.3
+	 */
+	public interface ViewportPainter {
+		void paintViewport( Graphics g, JComponent c, JViewport viewport );
 	}
 }

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatComponents2Test.java

@@ -336,6 +336,16 @@ public class FlatComponents2Test
 			table.setSurrendersFocusOnKeystroke( focusCellEditorCheckBox.isSelected() );
 	}
 
+	private void alternatingRowsChanged() {
+		UIManager.put( "Table.alternateRowColor", alternatingRowsCheckBox.isSelected() ? Color.orange : null );
+		table1ScrollPane.repaint();
+	}
+
+	private void paintOutsideAlternateRowsChanged() {
+		UIManager.put( "Table.paintOutsideAlternateRows", paintOutsideAlternateRowsCheckBox.isSelected() ? true : null );
+		table1ScrollPane.repaint();
+	}
+
 	private void treeRendererChanged() {
 		Object sel = treeRendererComboBox.getSelectedItem();
 		if( !(sel instanceof String) )
@@ -493,8 +503,10 @@ public class FlatComponents2Test
 		focusCellEditorCheckBox = new JCheckBox();
 		showVerticalLinesCheckBox = new JCheckBox();
 		columnSelectionCheckBox = new JCheckBox();
+		alternatingRowsCheckBox = new JCheckBox();
 		intercellSpacingCheckBox = new JCheckBox();
 		rowHeaderCheckBox = new JCheckBox();
+		paintOutsideAlternateRowsCheckBox = new JCheckBox();
 		redGridColorCheckBox = new JCheckBox();
 		tableHeaderButtonCheckBox = new JCheckBox();
 
@@ -875,6 +887,11 @@ public class FlatComponents2Test
 			columnSelectionCheckBox.addActionListener(e -> columnSelectionChanged());
 			tableOptionsPanel.add(columnSelectionCheckBox, "cell 1 2");
 
+			//---- alternatingRowsCheckBox ----
+			alternatingRowsCheckBox.setText("alternating rows");
+			alternatingRowsCheckBox.addActionListener(e -> alternatingRowsChanged());
+			tableOptionsPanel.add(alternatingRowsCheckBox, "cell 2 2");
+
 			//---- intercellSpacingCheckBox ----
 			intercellSpacingCheckBox.setText("intercell spacing");
 			intercellSpacingCheckBox.addActionListener(e -> intercellSpacingChanged());
@@ -885,6 +902,11 @@ public class FlatComponents2Test
 			rowHeaderCheckBox.addActionListener(e -> rowHeaderChanged());
 			tableOptionsPanel.add(rowHeaderCheckBox, "cell 1 3");
 
+			//---- paintOutsideAlternateRowsCheckBox ----
+			paintOutsideAlternateRowsCheckBox.setText("outside alternating rows");
+			paintOutsideAlternateRowsCheckBox.addActionListener(e -> paintOutsideAlternateRowsChanged());
+			tableOptionsPanel.add(paintOutsideAlternateRowsCheckBox, "cell 2 3");
+
 			//---- redGridColorCheckBox ----
 			redGridColorCheckBox.setText("red grid color");
 			redGridColorCheckBox.addActionListener(e -> redGridColorChanged());
@@ -927,8 +949,10 @@ public class FlatComponents2Test
 	private JCheckBox focusCellEditorCheckBox;
 	private JCheckBox showVerticalLinesCheckBox;
 	private JCheckBox columnSelectionCheckBox;
+	private JCheckBox alternatingRowsCheckBox;
 	private JCheckBox intercellSpacingCheckBox;
 	private JCheckBox rowHeaderCheckBox;
+	private JCheckBox paintOutsideAlternateRowsCheckBox;
 	private JCheckBox redGridColorCheckBox;
 	private JCheckBox tableHeaderButtonCheckBox;
 	// JFormDesigner - End of variables declaration  //GEN-END:variables

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatComponents2Test.jfd

@@ -1,4 +1,4 @@
-JFDML JFormDesigner: "7.0.5.0.382" Java: "16" encoding: "UTF-8"
+JFDML JFormDesigner: "7.0.5.0.404" Java: "17.0.2" encoding: "UTF-8"
 
 new FormModel {
 	contentType: "form/swing"
@@ -485,6 +485,16 @@ new FormModel {
 				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 					"value": "cell 1 2"
 				} )
+				add( new FormComponent( "javax.swing.JCheckBox" ) {
+					name: "alternatingRowsCheckBox"
+					"text": "alternating rows"
+					auxiliary() {
+						"JavaCodeGenerator.variableLocal": false
+					}
+					addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "alternatingRowsChanged", false ) )
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 2 2"
+				} )
 				add( new FormComponent( "javax.swing.JCheckBox" ) {
 					name: "intercellSpacingCheckBox"
 					"text": "intercell spacing"
@@ -505,6 +515,16 @@ new FormModel {
 				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 					"value": "cell 1 3"
 				} )
+				add( new FormComponent( "javax.swing.JCheckBox" ) {
+					name: "paintOutsideAlternateRowsCheckBox"
+					"text": "outside alternating rows"
+					auxiliary() {
+						"JavaCodeGenerator.variableLocal": false
+					}
+					addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "paintOutsideAlternateRowsChanged", false ) )
+				}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+					"value": "cell 2 3"
+				} )
 				add( new FormComponent( "javax.swing.JCheckBox" ) {
 					name: "redGridColorCheckBox"
 					"text": "red grid color"