ExpandBar is not requesting layout after expand/collapse breaking the layout

[laeubi]

Describe the bug
I have a layout that dynamically grow/shrink according to the content, and an ExpandBar widget to show/hide content.
When the user expand/collapse content, the UI is not updated appropriately:

• If the item is collapsed and user expands it, the content is cut of
• If the item is expanded and the user collapse it, space is not reclaimed
• If the users change the size of the window, the layout is updated (so this is not a bug in the layout itself).

To Reproduce
The following snippet can be used to reproduce the behavior (derived from Snippet223):

package test.me;

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.BorderData;
import org.eclipse.swt.layout.BorderLayout;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.ExpandBar;
import org.eclipse.swt.widgets.ExpandItem;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

public class Snippet223_Bug {

public static void main (String [] args) {
	Display display = new Display ();
	Shell shell = new Shell (display);
  shell.setLayout(new BorderLayout());
	shell.setText("ExpandBar Example");
  ExpandBar bar = new ExpandBar(shell, SWT.NONE);
  bar.setLayoutData(new BorderData(SWT.TOP));
  Text text = new Text(shell, SWT.V_SCROLL);
  text.setLayoutData(new BorderData(SWT.CENTER));
	Image image = display.getSystemImage(SWT.ICON_QUESTION);
	Composite composite = new Composite (bar, SWT.NONE);
  GridLayout layout = new GridLayout();
  layout.marginLeft = layout.marginTop = layout.marginRight = layout.marginBottom = 10;
  layout.verticalSpacing = 10;
	composite.setLayout(layout);
	Button button = new Button (composite, SWT.PUSH);
	button.setText("SWT.PUSH");
	button = new Button (composite, SWT.RADIO);
	button.setText("SWT.RADIO");
	button = new Button (composite, SWT.CHECK);
	button.setText("SWT.CHECK");
	button = new Button (composite, SWT.TOGGLE);
	button.setText("SWT.TOGGLE");
	ExpandItem item0 = new ExpandItem (bar, SWT.NONE, 0);
	item0.setText("What is your favorite button");
	item0.setHeight(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
	item0.setControl(composite);
	item0.setImage(image);
  item0.setExpanded(true);
	bar.setSpacing(8);
  bar.setBackground(display.getSystemColor(SWT.COLOR_CYAN));
	shell.setSize(400, 350);
	shell.open();
	while (!shell.isDisposed ()) {
		if (!display.readAndDispatch ()) {
			display.sleep ();
		}
	}
	image.dispose();
	display.dispose();
}

}

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
After starting the snippet it looks like this:

The collapsing the item looks like this:

Now make the window a bit larger:

Now expand the item and it looks like this:

Now make the window a bit smaller:

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Debian 4.19.194-3 (2021-07-18) x86_64 GNU/Linux
3. Java 17

Version since
Eclipse or SWT version since when the behavior is seen [e.g. 4.23]: Current SWT release

Workaround (or) Additional context
If I register a listener and request layout manually everything works as expected without a glitch:

  bar.addExpandListener(new ExpandListener() {

    @Override
    public void itemExpanded(ExpandEvent e) {
      forceLayoutUpdate();
    }

    @Override
    public void itemCollapsed(ExpandEvent e) {
      forceLayoutUpdate();
    }

    private void forceLayoutUpdate() {
      bar.requestLayout();
    }
  });

This is really annoying, as it has two consequences:

1. Developers must install workarounds and use try-and-error to find out what makes the layout broke, if noticed at all at development time (e.g. problem might only become visible with larger inputs)
2. Users are getting bad experience with SWT application not reacting to size changes, probably even flicker if they try to resize windows

[Phillipus]

FWIW, also happens on Windows 11 and macOS 13.2.1.

[laeubi]

@Phillipus thanks for verify this, I updated the description!

[deepika-u]

@laeubi
I have tried your snippet(derived from Snippet223) on windows 11 with java 11, java 17, java19 versions - seeing the same problem across versions.
To be specific on the problem,

• when the content is collapsed and window size is increased, then content is expanded we are not seeing the buttons section.
• when the content is expanded and window size is increased/decreased, then when content is expanded/collapsed we are seeing the buttons section properly.

But when i tried to do the same set of steps with Snippet223 - not able to see the problem.

[laeubi]

Snippet223 uses different layout that do not grow/shrink but always shows at 100% of the window and uses the scrollbar of the ExpandBar instead.

[elsazac]

@laeubi I can see the same issue in Mac OS Ventura as well in all the three jdk versions ,11 19 and 17.Only when the content is put back to the original size (the size of the widget when it appeared after the run)only we could see the content of the drop down .In all other cases the content of the drop down is not visible when we resize the widget with the drop down collapsed.