Here’s a simple demo. The main class displays a frame with a GridLayoutManager-managed panel. The panel contains a stack of JLabels with long text strings

I expect the labels to shrink as I shrink the window, like so

However, they don’t

import javax.swing.*;

public class FormDemoMain {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Form Demo");
        JPanel mainPanel = new LabelContainer().mainPanel;
        frame.setContentPane(mainPanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

import org.apache.commons.lang3.StringUtils;

import javax.swing.*;

public class LabelContainer {
    JPanel mainPanel;
    private JLabel labelOne;
    private JLabel labelTwo;
    private JLabel labelThree;

    LabelContainer() {
        // you may replace StringUtils.repeat("str", 20) with "str".repeat(20) if your JDK is 11+
        String longText = StringUtils.repeat("long ", 20) + "text";
        labelOne.setText("Label One: " + longText);
        labelTwo.setText("Label Two: " + longText);
        labelThree.setText("Label Three: " + longText);
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<form xmlns="http://www.intellij.com/uidesigner/form/" version="1" bind-to-class="stretchableLabel.form.LabelContainer">
  <grid id="27dc6" binding="mainPanel" layout-manager="GridLayoutManager" row-count="3" column-count="1" same-size-horizontally="false" same-size-vertically="false" hgap="10" vgap="10">
    <margin top="0" left="0" bottom="0" right="0"/>
    <constraints>
      <xy x="20" y="20" width="500" height="400"/>
    </constraints>
    <properties>
      <background color="-7563106"/>
    </properties>
    <border type="none"/>
    <children>
      <component id="cadde" class="javax.swing.JLabel" binding="labelOne">
        <constraints>
          <grid row="0" column="0" row-span="1" col-span="1" vsize-policy="0" hsize-policy="3" anchor="8" fill="0" indent="0" use-parent-layout="false"/>
        </constraints>
        <properties>
          <background color="-11841453"/>
          <foreground color="-1"/>
          <opaque value="true"/>
          <text value="Label"/>
        </properties>
      </component>
      <component id="36e79" class="javax.swing.JLabel" binding="labelTwo">
        <constraints>
          <grid row="1" column="0" row-span="1" col-span="1" vsize-policy="0" hsize-policy="0" anchor="8" fill="0" indent="0" use-parent-layout="false"/>
        </constraints>
        <properties>
          <background color="-11841453"/>
          <foreground color="-1"/>
          <opaque value="true"/>
          <text value="Label"/>
        </properties>
      </component>
      <component id="744ac" class="javax.swing.JLabel" binding="labelThree">
        <constraints>
          <grid row="2" column="0" row-span="1" col-span="1" vsize-policy="0" hsize-policy="0" anchor="8" fill="0" indent="0" use-parent-layout="false"/>
        </constraints>
        <properties>
          <autoscrolls value="false"/>
          <background color="-11841453"/>
          <foreground color="-1"/>
          <opaque value="true"/>
          <text value="Label"/>
        </properties>
      </component>
    </children>
  </grid>
</form>

The problem is not reproduced with the OOB GridLayout. Note the ellipsis

import org.apache.commons.lang3.StringUtils;

import javax.swing.*;
import java.awt.*;

public class GridLayoutDemo {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Grid Layout Demo");
        JPanel labelPanel = new JPanel();
        LayoutManager layout = new GridLayout(0,1,10,10);
        labelPanel.setLayout(layout);
        labelPanel.setBackground(Color.LIGHT_GRAY);
        String shortText = "Short label text";
        JLabel labelOne = new JLabel(shortText);
        labelOne.setOpaque(true);
        labelOne.setBackground(Color.DARK_GRAY);
        labelOne.setForeground(Color.WHITE);
        JLabel labelTwo = new JLabel(shortText);
        labelTwo.setOpaque(true);
        labelTwo.setBackground(Color.DARK_GRAY);
        labelTwo.setForeground(Color.WHITE);
        labelPanel.add(labelOne);
        labelPanel.add(labelTwo);
        frame.add(labelPanel);
        JButton makeShortButton = new JButton("Make short");
        makeShortButton.addActionListener(e -> {
            labelOne.setText("Label One: " + shortText);
            labelTwo.setText("Label Two: " + shortText);
            frame.pack();
        });
        JButton makeLongButton = new JButton("Make long");
        String longText = "Long" + StringUtils.repeat(" long", 30) + " label text";
        makeLongButton.addActionListener(e -> {
            labelOne.setText("Label One: " + longText);
            labelTwo.setText("Label Two: " + longText);
            frame.pack();
        });
        JPanel buttonPanel = new JPanel();
        buttonPanel.add(makeShortButton);
        buttonPanel.add(makeLongButton);
        frame.add(buttonPanel, BorderLayout.SOUTH);
        frame.pack();
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

The GUI Designer interface doesn’t allow a regular GridLayout, only JetBrains’ own com.intellij.uiDesigner.core.GridLayoutManager

What complicates things further, I can’t debug it. I can’t even open the source file of that layout manager

I know the drawbacks of GUI Designer only too well. But we’re so coupled with it, we can’t ever get uncoupled. The ability to see the approximate visual rendering of your components right in the source code is so appealing

How can I make the labels shrink as the containing window is shrinked with GUI Designer forms?