Question

This is a simple executable snippet that shows the issue.

When using the ExpandBar the desired outcome is to resize the window when there is a collapse or expand. It works properly on Mac but does not on Linux.

It looks like the ExpandListener is called before the collapse/expand actually occurs and therefore the pack() resizes incorrectly.

The async execution is merely a bandage to have it work on Mac but this does not work on Linux.

import org.eclipse.swt.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.events.ExpandEvent;
import org.eclipse.swt.events.ExpandListener;

public class ExpandBarExample {
    public static void main(String[] args) {
        Shell shell = new Shell(SWT.DIALOG_TRIM | SWT.MIN
                | SWT.APPLICATION_MODAL);
        shell.setLayout(new FormLayout());
        shell.setText("Expand Bar");
        final ExpandBar bar = new ExpandBar(shell, SWT.NONE);
        FormData fd = new FormData();
        fd.top = new FormAttachment(0);
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        fd.bottom = new FormAttachment(100);
        bar.setLayoutData(fd);

        bar.addExpandListener(new ExpandListener() {

            public void itemCollapsed(ExpandEvent arg0) {
                Display.getCurrent().asyncExec(new Runnable() {
                    public void run() {
                        bar.getShell().pack();
                    }
                });
            }

            public void itemExpanded(ExpandEvent arg0) {
                bar.getShell().pack();

                Display.getCurrent().asyncExec(new Runnable() {
                    public void run() {
                        bar.getShell().pack();
                    }
                });
            }

        });

        Composite composite = new Composite(bar, SWT.NONE);
        fd = new FormData();
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        composite.setLayoutData(fd);

        FormLayout layout = new FormLayout();
        layout.marginLeft = layout.marginTop = layout.marginRight = layout.marginBottom = 8;

        composite.setLayout(layout);
        Label label = new Label(composite, SWT.NONE);
        label.setText("This is Bar 1");
        ExpandItem item1 = new ExpandItem(bar, SWT.NONE, 0);
        item1.setText("Bar 1");
        item1.setHeight(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
        item1.setControl(composite);
        item1.setExpanded(true);

        composite = new Composite(bar, SWT.NONE);
        fd = new FormData();
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        composite.setLayoutData(fd);

        layout = new FormLayout();
        layout.marginLeft = layout.marginTop = layout.marginRight = layout.marginBottom = 8;
        composite.setLayout(layout);
        label = new Label(composite, SWT.NONE);
        label.setText("This is Bar2");
        ExpandItem item2 = new ExpandItem(bar, SWT.NONE, 1);
        item2.setText("Bar 2");
        item2.setHeight(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
        item2.setControl(composite);
        item2.setExpanded(true);

        composite = new Composite(bar, SWT.NONE);
        fd = new FormData();
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        composite.setLayoutData(fd);

        layout = new FormLayout();
        layout.marginLeft = layout.marginTop = layout.marginRight = layout.marginBottom = 8;
        composite.setLayout(layout);
        label = new Label(composite, SWT.NONE);
        label.setText("This is Bar3");
        ExpandItem item3 = new ExpandItem(bar, SWT.NONE, 2);
        item3.setText("Bar 3");
        item3.setHeight(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
        item3.setControl(composite);
        item3.setExpanded(true);

        bar.setSpacing(6);
        shell.pack();
        shell.open();
        Display display = shell.getDisplay();

        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }

}

Answer 1

I am unhappy with this solution but it works.

Definitely a XXX solution

Use XXX in a comment to flag something that is bogus but works. Use FIXME to flag something that is bogus and broken.
– java.sun.com

without further ado

import org.eclipse.swt.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.events.ExpandEvent;
import org.eclipse.swt.events.ExpandListener;

public class ExpandBarExample {
    public static void main(String[] args) {
        Shell shell = new Shell(SWT.DIALOG_TRIM | SWT.MIN
                | SWT.APPLICATION_MODAL);
        shell.setLayout(new FormLayout());
        shell.setText("Expand Bar");
        final ExpandBar bar = new ExpandBar(shell, SWT.NONE);
        FormData fd = new FormData();
        fd.top = new FormAttachment(0);
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        fd.bottom = new FormAttachment(100);
        bar.setLayoutData(fd);

        bar.addExpandListener(new ExpandListener() {

            private void resize(final ExpandEvent event, final boolean expand){

                final Display display = Display.getCurrent();

                new Thread(new Runnable() {
                    public void run() {

                        final int[] orgSize = new int[1];
                        final int[] currentSize = new int[1];

                        final Object lock = new Object();

                        if (display.isDisposed() || bar.isDisposed()){
                            return;
                        }

                        display.syncExec(new Runnable() {
                            public void run() {
                                if (bar.isDisposed() || bar.getShell().isDisposed()){
                                    return;
                                }

                                synchronized(lock){
                                    bar.getShell().pack(true);
                                    orgSize[0] = bar.getShell().getSize().y;
                                    currentSize[0] = orgSize[0];
                                }
                            }
                        });     

                        while (currentSize[0] == orgSize[0]){
                            if (display.isDisposed() || bar.isDisposed()){
                                return;
                            }

                            display.syncExec(new Runnable() {
                                public void run() {

                                    synchronized(lock){
                                        if (bar.isDisposed() || bar.getShell().isDisposed()){
                                            return;
                                        }

                                        currentSize[0] = bar.getShell().getSize().y;

                                        if (currentSize[0] != orgSize[0]){
                                            return;
                                        }
                                        else{
                                            bar.getShell().layout(true);
                                            bar.getShell().pack(true);
                                        }
                                    }
                                }
                            });                             
                        }
                    }
                }).start();
        }

        public void itemCollapsed(ExpandEvent event) {
            resize(event, false);
        }

        public void itemExpanded(ExpandEvent event) {        
            resize(event, true);
        }

        });

        Composite composite = new Composite(bar, SWT.NONE);
        fd = new FormData();
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        composite.setLayoutData(fd);

        FormLayout layout = new FormLayout();
        layout.marginLeft = layout.marginTop = layout.marginRight = layout.marginBottom = 8;

        composite.setLayout(layout);
        Label label = new Label(composite, SWT.NONE);
        label.setText("This is Bar 1");
        ExpandItem item1 = new ExpandItem(bar, SWT.NONE, 0);
        item1.setText("Bar 1");
        item1.setHeight(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
        item1.setControl(composite);
        item1.setExpanded(true);

        composite = new Composite(bar, SWT.NONE);
        fd = new FormData();
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        composite.setLayoutData(fd);

        layout = new FormLayout();
        layout.marginLeft = layout.marginTop = layout.marginRight = layout.marginBottom = 8;
        composite.setLayout(layout);
        label = new Label(composite, SWT.NONE);
        label.setText("This is Bar2");
        ExpandItem item2 = new ExpandItem(bar, SWT.NONE, 1);
        item2.setText("Bar 2");
        item2.setHeight(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
        item2.setControl(composite);
        item2.setExpanded(true);

        composite = new Composite(bar, SWT.NONE);
        fd = new FormData();
        fd.left = new FormAttachment(0);
        fd.right = new FormAttachment(100);
        composite.setLayoutData(fd);

        layout = new FormLayout();
        layout.marginLeft = layout.marginTop = layout.marginRight = layout.marginBottom = 8;
        composite.setLayout(layout);
        label = new Label(composite, SWT.NONE);
        label.setText("This is Bar3");
        ExpandItem item3 = new ExpandItem(bar, SWT.NONE, 2);
        item3.setText("Bar 3");
        item3.setHeight(composite.computeSize(SWT.DEFAULT, SWT.DEFAULT).y);
        item3.setControl(composite);
        item3.setExpanded(true);

        bar.setSpacing(6);
        shell.pack();
        shell.open();
        Display display = shell.getDisplay();

        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) {
                display.sleep();
            }
        }
        display.dispose();
    }

}

If anyone wants to know what this is doing and doesn’t want to look at the code.

Basically the ExpandListener looks at the original height of the shell, and issues syncExec’s to pack() the shell until the shell actually changes size. A very busy waiting approach.