- Table: detect whether component is used in cell editor and automatically disable round border style and reduce cell editor outer border width (used for focus indicator) to zero

- ComboBox, Spinner and TextField: support disabling round border style per component, if globally enabled
(issue #148)

CHANGELOG.md

@@ -3,6 +3,15 @@ FlatLaf Change Log
 
 ## Unreleased
 
+#### New features
+
+- Table: Detect whether component is used in cell editor and automatically
+  disable round border style and reduce cell editor outer border width (used for
+  focus indicator) to zero. (issue #148)
+- ComboBox, Spinner and TextField: Support disabling round border style per
+  component, if globally enabled (set client property `JComponent.roundRect` to
+  `false`). (issue #148)
+
 #### Fixed bugs
 
 - Custom window decorations: Embedded menu bar did not always respond to mouse

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

@@ -314,6 +314,15 @@ public interface FlatClientProperties
 		return (value instanceof Boolean) ? (boolean) value : defaultValue;
 	}
 
+	/**
+	 * Checks whether a client property of a component is a {@link Boolean} and returns its value.
+	 * If the client property is not set, or not a {@link Boolean}, defaultValue is returned.
+	 */
+	static Boolean clientPropertyBooleanStrict( JComponent c, String key, Boolean defaultValue ) {
+		Object value = c.getClientProperty( key );
+		return (value instanceof Boolean) ? (Boolean) value : defaultValue;
+	}
+
 	/**
 	 * Checks whether a client property of a component is an integer and returns its value.
 	 * If the client property is not set, or not an integer, defaultValue is returned.

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

@@ -87,15 +87,14 @@ public class FlatBorder
 		try {
 			FlatUIUtils.setRenderingHints( g2 );
 
-			boolean isCellEditor = isCellEditor( c );
-			float focusWidth = isCellEditor ? 0 : scale( (float) getFocusWidth( c ) );
+			float focusWidth = scale( (float) getFocusWidth( c ) );
 			float borderWidth = scale( (float) getBorderWidth( c ) );
-			float arc = isCellEditor ? 0 : scale( (float) getArc( c ) );
+			float arc = scale( (float) getArc( c ) );
 			Color outlineColor = getOutlineColor( c );
 
 			// paint outer border
 			if( outlineColor != null || isFocused( c ) ) {
-				float innerWidth = !isCellEditor && !(c instanceof JScrollPane)
+				float innerWidth = !isCellEditor( c ) && !(c instanceof JScrollPane)
 					? (outlineColor != null ? innerOutlineWidth : innerFocusWidth)
 					: 0;
 
@@ -204,8 +203,7 @@ public class FlatBorder
 
 	@Override
 	public Insets getBorderInsets( Component c, Insets insets ) {
-		boolean isCellEditor = isCellEditor( c );
-		float focusWidth = isCellEditor ? 0 : scale( (float) getFocusWidth( c ) );
+		float focusWidth = scale( (float) getFocusWidth( c ) );
 		float ow = focusWidth + scale( (float) getLineWidth( c ) );
 
 		insets = super.getBorderInsets( c, insets );
@@ -214,7 +212,7 @@ public class FlatBorder
 		insets.bottom = Math.round( scale( (float) insets.bottom ) + ow );
 		insets.right = Math.round( scale( (float) insets.right ) + ow );
 
-		if( isCellEditor ) {
+		if( isCellEditor( c ) ) {
 			// remove top and bottom insets if used as cell editor
 			insets.top = insets.bottom = 0;
 
@@ -232,6 +230,9 @@ public class FlatBorder
 	 * Returns the (unscaled) thickness of the outer focus border.
 	 */
 	protected int getFocusWidth( Component c ) {
+		if( isCellEditor( c ) )
+			return 0;
+
 		return focusWidth;
 	}
 

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

@@ -141,6 +141,9 @@ public class FlatButtonBorder
 
 	@Override
 	protected int getArc( Component c ) {
+		if( isCellEditor( c ) )
+			return 0;
+
 		switch( FlatButtonUI.getButtonType( c ) ) {
 			case FlatButtonUI.TYPE_SQUARE: return 0;
 			case FlatButtonUI.TYPE_ROUND_RECT: return Short.MAX_VALUE;

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

@@ -33,6 +33,10 @@ public class FlatRoundBorder
 
 	@Override
 	protected int getArc( Component c ) {
-		return FlatUIUtils.isRoundRect( c ) ? Short.MAX_VALUE : arc;
+		if( isCellEditor( c ) )
+			return 0;
+
+		Boolean roundRect = FlatUIUtils.isRoundRect( c );
+		return roundRect != null ? (roundRect ? Short.MAX_VALUE : 0) : arc;
 	}
 }

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

@@ -33,6 +33,10 @@ public class FlatTextBorder
 
 	@Override
 	protected int getArc( Component c ) {
-		return FlatUIUtils.isRoundRect( c ) ? Short.MAX_VALUE : arc;
+		if( isCellEditor( c ) )
+			return 0;
+
+		Boolean roundRect = FlatUIUtils.isRoundRect( c );
+		return roundRect != null ? (roundRect ? Short.MAX_VALUE : 0) : arc;
 	}
 }

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

@@ -37,6 +37,7 @@ import java.awt.geom.Rectangle2D;
 import java.awt.geom.RoundRectangle2D;
 import java.util.function.Consumer;
 import javax.swing.JComponent;
+import javax.swing.JTable;
 import javax.swing.LookAndFeel;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
@@ -137,11 +138,21 @@ public class FlatUIUtils
 	}
 
 	public static boolean isCellEditor( Component c ) {
-		// check whether used as cell editor in file chooser
-		//   Tree.cellEditor is set in sun.swing.FilePane.editFileName()
+		// check whether used in cell editor (check 3 levels up)
+		Component c2 = c;
+		for( int i = 0; i <= 2 && c2 != null; i++ ) {
+			Container parent = c2.getParent();
+			if( parent instanceof JTable && ((JTable)parent).getEditorComponent() == c2 )
+				return true;
+
+			c2 = parent;
+		}
+
+		// check whether used as cell editor
 		//   Table.editor is set in JTable.GenericEditor constructor
+		//   Tree.cellEditor is set in sun.swing.FilePane.editFileName()
 		String name = c.getName();
-		if( "Tree.cellEditor".equals( name ) || "Table.editor".equals( name ) )
+		if( "Table.editor".equals( name ) || "Tree.cellEditor".equals( name ) )
 			return true;
 
 		// for using combo box as cell editor in table
@@ -159,9 +170,11 @@ public class FlatUIUtils
 			keyboardFocusManager.getActiveWindow() == SwingUtilities.windowForComponent( c );
 	}
 
-	public static boolean isRoundRect( Component c ) {
-		return c instanceof JComponent && FlatClientProperties.clientPropertyBoolean(
-			(JComponent) c, FlatClientProperties.COMPONENT_ROUND_RECT, false );
+	public static Boolean isRoundRect( Component c ) {
+		return (c instanceof JComponent)
+			? FlatClientProperties.clientPropertyBooleanStrict(
+				(JComponent) c, FlatClientProperties.COMPONENT_ROUND_RECT, null )
+			: null;
 	}
 
 	/**