ComboBox: made popup list wider if list item texts are longer than combo box width

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

@@ -341,6 +341,22 @@ public class FlatComboBoxUI
 			super( combo );
 		}
 
+		@Override
+		protected Rectangle computePopupBounds( int px, int py, int pw, int ph ) {
+			// get maximum display size of all items, ignoring prototype value
+			Object prototype = comboBox.getPrototypeDisplayValue();
+			if( prototype != null )
+				comboBox.setPrototypeDisplayValue( null );
+			Dimension displaySize = getDisplaySize();
+			if( prototype != null )
+				comboBox.setPrototypeDisplayValue( prototype );
+
+			// make popup wider if necessary
+			pw = Math.max( pw, displaySize.width );
+
+			return super.computePopupBounds( px, py, pw, ph );
+		}
+
 		@Override
 		protected void configurePopup() {
 			super.configurePopup();

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

@@ -75,6 +75,7 @@ public class FlatComponentsTest
 		JComboBox<String> comboBox2 = new JComboBox<>();
 		JComboBox<String> comboBox3 = new JComboBox<>();
 		JComboBox<String> comboBox4 = new JComboBox<>();
+		JComboBox<String> comboBox5 = new JComboBox<>();
 		JLabel spinnerLabel = new JLabel();
 		JSpinner spinner1 = new JSpinner();
 		JSpinner spinner2 = new JSpinner();
@@ -365,6 +366,16 @@ public class FlatComponentsTest
 		comboBox4.setEnabled(false);
 		add(comboBox4, "cell 4 5,growx");
 
+		//---- comboBox5 ----
+		comboBox5.setPrototypeDisplayValue("12345");
+		comboBox5.setModel(new DefaultComboBoxModel<>(new String[] {
+			"wide popup if text is longer",
+			"aa",
+			"bbb",
+			"cccc"
+		}));
+		add(comboBox5, "cell 5 5,growx");
+
 		//---- spinnerLabel ----
 		spinnerLabel.setText("JSpinner:");
 		add(spinnerLabel, "cell 0 6");

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

@@ -240,6 +240,19 @@ new FormModel {
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 4 5,growx"
 			} )
+			add( new FormComponent( "javax.swing.JComboBox" ) {
+				name: "comboBox5"
+				"prototypeDisplayValue": "12345"
+				"model": new javax.swing.DefaultComboBoxModel {
+					selectedItem: "wide popup if text is longer"
+					addElement( "wide popup if text is longer" )
+					addElement( "aa" )
+					addElement( "bbb" )
+					addElement( "cccc" )
+				}
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 5 5,growx"
+			} )
 			add( new FormComponent( "javax.swing.JLabel" ) {
 				name: "spinnerLabel"
 				"text": "JSpinner:"

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

@@ -54,6 +54,7 @@ class BasicComponentsPanel
 		JComboBox<String> comboBox2 = new JComboBox<>();
 		JComboBox<String> comboBox3 = new JComboBox<>();
 		JComboBox<String> comboBox4 = new JComboBox<>();
+		JComboBox<String> comboBox5 = new JComboBox<>();
 		JLabel spinnerLabel = new JLabel();
 		JSpinner spinner1 = new JSpinner();
 		JSpinner spinner2 = new JSpinner();
@@ -264,6 +265,16 @@ class BasicComponentsPanel
 		comboBox4.setEnabled(false);
 		add(comboBox4, "cell 4 4,growx");
 
+		//---- comboBox5 ----
+		comboBox5.setPrototypeDisplayValue("12345");
+		comboBox5.setModel(new DefaultComboBoxModel<>(new String[] {
+			"wide popup if text is longer",
+			"aa",
+			"bbb",
+			"cccc"
+		}));
+		add(comboBox5, "cell 5 4,growx");
+
 		//---- spinnerLabel ----
 		spinnerLabel.setText("JSpinner:");
 		add(spinnerLabel, "cell 0 5");

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

@@ -199,6 +199,19 @@ new FormModel {
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 4 4,growx"
 			} )
+			add( new FormComponent( "javax.swing.JComboBox" ) {
+				name: "comboBox5"
+				"prototypeDisplayValue": "12345"
+				"model": new javax.swing.DefaultComboBoxModel {
+					selectedItem: "wide popup if text is longer"
+					addElement( "wide popup if text is longer" )
+					addElement( "aa" )
+					addElement( "bbb" )
+					addElement( "cccc" )
+				}
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 5 4,growx"
+			} )
 			add( new FormComponent( "javax.swing.JLabel" ) {
 				name: "spinnerLabel"
 				"text": "JSpinner:"