Button: make icon-only buttons square (no minimum width, smaller left/right insets)

CHANGELOG.md

@@ -5,6 +5,9 @@ FlatLaf Change Log
 
 - Use new chevron arrows in "Flat Light" and "Flat Dark" themes, but keep
   triangle arrows in "Flat IntelliJ" and "Flat Darcula" themes. (issue #7)
+- If a JButton has an icon and no text, then it does not get a minimum width
+  (usually 72 pixel) and the left and right insets are same as top/bottom insets
+  so that it becomes square (if the icon is square).
 - Added Java 9 module descriptor `module-info.class` to `flatlaf.jar` (in
   `META-INF/versions/9`). But FlatLaf remains Java 8 compatible. (issue #1)
 - Support specifying custom scale factor in system properties `flatlaf.uiScale`

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

@@ -20,8 +20,11 @@ import static com.formdev.flatlaf.util.UIScale.scale;
 import java.awt.Color;
 import java.awt.Component;
 import java.awt.Graphics;
+import java.awt.Insets;
 import java.awt.Paint;
+import javax.swing.JButton;
 import javax.swing.UIManager;
+import javax.swing.plaf.UIResource;
 
 /**
  * Border for {@link javax.swing.JButton}.
@@ -73,6 +76,17 @@ public class FlatButtonBorder
 			null );
 	}
 
+	@Override
+	public Insets getBorderInsets( Component c, Insets insets ) {
+		insets = super.getBorderInsets( c, insets );
+
+		// use smaller left and right insets for icon-only buttons (so that they are square)
+		if( FlatButtonUI.isIconOnlyButton( c ) && ((JButton)c).getMargin() instanceof UIResource )
+			insets.left = insets.right = Math.min( insets.top, insets.bottom );
+
+		return insets;
+	}
+
 	@Override
 	protected float getArc() {
 		return scale( (float) arc );

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

@@ -146,6 +146,13 @@ public class FlatButtonUI
 		return c instanceof JButton && ((JButton)c).isDefaultButton();
 	}
 
+	static boolean isIconOnlyButton( Component c ) {
+		String text;
+		return c instanceof JButton &&
+			((JButton)c).getIcon() != null &&
+			((text = ((JButton)c).getText()) == null || text.isEmpty());
+	}
+
 	static boolean isHelpButton( Component c ) {
 		return c instanceof JButton && clientPropertyEquals( (JButton) c, BUTTON_TYPE, BUTTON_TYPE_HELP );
 	}
@@ -259,8 +266,11 @@ public class FlatButtonUI
 			return new Dimension( helpButtonIcon.getIconWidth(), helpButtonIcon.getIconHeight() );
 
 		Dimension prefSize = super.getPreferredSize( c );
-		if( !isToolBarButton( c ) )
+
+		// apply minimum width, if not in toolbar and not a icon-only button
+		if( !isToolBarButton( c ) && !isIconOnlyButton( c ) )
 			prefSize.width = Math.max( prefSize.width, scale( minimumWidth + (focusWidth * 2) ) );
+
 		return prefSize;
 	}
 }

flatlaf-core/src/test/java/com/formdev/flatlaf/FlatComponentsTest.java

@@ -55,6 +55,7 @@ public class FlatComponentsTest
 		FlatComponentsTest.TestDefaultButton button5 = new FlatComponentsTest.TestDefaultButton();
 		JButton button3 = new JButton();
 		JButton button12 = new JButton();
+		JButton button13 = new JButton();
 		JLabel toggleButtonLabel = new JLabel();
 		JToggleButton toggleButton1 = new JToggleButton();
 		JToggleButton toggleButton2 = new JToggleButton();
@@ -246,6 +247,10 @@ public class FlatComponentsTest
 		button12.setEnabled(false);
 		add(button12, "cell 4 1");
 
+		//---- button13 ----
+		button13.setIcon(UIManager.getIcon("Tree.closedIcon"));
+		add(button13, "cell 5 1");
+
 		//---- toggleButtonLabel ----
 		toggleButtonLabel.setText("JToggleButton:");
 		add(toggleButtonLabel, "cell 0 2");

flatlaf-core/src/test/java/com/formdev/flatlaf/FlatComponentsTest.jfd

@@ -76,6 +76,12 @@ new FormModel {
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 4 1"
 			} )
+			add( new FormComponent( "javax.swing.JButton" ) {
+				name: "button13"
+				"icon": new com.jformdesigner.model.SwingIcon( 2, "Tree.closedIcon" )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 5 1"
+			} )
 			add( new FormComponent( "javax.swing.JLabel" ) {
 				name: "toggleButtonLabel"
 				"text": "JToggleButton:"

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/BasicComponentsPanel.java

@@ -39,6 +39,7 @@ class BasicComponentsPanel
 		JButton button2 = new JButton();
 		JButton button3 = new JButton();
 		JButton button4 = new JButton();
+		JButton button13 = new JButton();
 		JLabel checkBoxLabel = new JLabel();
 		JCheckBox checkBox1 = new JCheckBox();
 		JCheckBox checkBox2 = new JCheckBox();
@@ -169,6 +170,10 @@ class BasicComponentsPanel
 		button4.setEnabled(false);
 		add(button4, "cell 4 1");
 
+		//---- button13 ----
+		button13.setIcon(UIManager.getIcon("Tree.closedIcon"));
+		add(button13, "cell 5 1");
+
 		//---- checkBoxLabel ----
 		checkBoxLabel.setText("JCheckBox");
 		add(checkBoxLabel, "cell 0 2");

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/BasicComponentsPanel.jfd

@@ -69,6 +69,12 @@ new FormModel {
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 4 1"
 			} )
+			add( new FormComponent( "javax.swing.JButton" ) {
+				name: "button13"
+				"icon": new com.jformdesigner.model.SwingIcon( 2, "Tree.closedIcon" )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 5 1"
+			} )
 			add( new FormComponent( "javax.swing.JLabel" ) {
 				name: "checkBoxLabel"
 				"text": "JCheckBox"