A semi-transparent popup dialog (JFrame, actually) in Scala (or Java)

By Alvin Alexander. Last updated: August 7, 2022

As a brief note to self, I used the following Scala source code to build a semi-transparent dialog (a Java JFrame, actually) for the second version of Sarah:

import java.awt._
import javax.swing._

/**
 * How to use:
 *
 *   val b = new TextWindowBuilder("Hello, world")
 *   b.setVisible(true)
 *  
 *   // later
 *   b.setVisible(false)
 *
 */
class TextWindowBuilder (
        textToDisplay: String,
        windowSize: Dimension = new Dimension(400, 300),
        location: Point = new Point(200, 200),
        textAreaRows: Int = 10,
        textAreaColumns: Int = 40,
        alpha: Float = 0.8f
        ) {

    // textarea and scrollpane
    val textArea = new JTextArea(textAreaRows, textAreaColumns)
    textArea.setFont(new Font("Helvetica Neue", Font.PLAIN, 20))
    textArea.setEditable(false)
    textArea.setMargin(new Insets(12, 12, 12, 12))
    val scrollPane = new JScrollPane(textArea)
    textArea.setText(textToDisplay)
    scrollPane.setPreferredSize(windowSize)
    scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS)
    scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS)
 
    // jframe
    val f = new JFrame()
    f.setUndecorated(true)
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
    f.getRootPane.putClientProperty("Window.alpha", alpha)
    f.getContentPane.add(scrollPane, BorderLayout.CENTER)
    f.setLocation(location)
   
    def setText(text: String) {
        val code = textArea.setText(text)
        invokeLater(code)
    }

    def setVisible(makeVisible: Boolean) {
        if (makeVisible) {
            val block = {
                f.pack
                f.setVisible(true)
            }
            invokeLater(block)
        } else {
            val block = f.setVisible(false)
            invokeLater(block)
        }
    }
   
    private def invokeLater[A](blockOfCode: => A) = {
        SwingUtilities.invokeLater(new Runnable {
            def run {
                blockOfCode
            }
        })
    }
 
}

As one example of how to create a semi-transparent popup window with this code, I instantiated a new window in Sarah like this:

// this is the secondary window i use in Sarah2 to display output
val textWindow = new TextWindowBuilder(
    "",
    new Dimension(mainFrame.getWidth, 400),
    new Point(372, 395)
)

This code shows several things, including: