Question

I’m trying to display an SWT table inside a form section, but am having problems with column resizing and scrolling.

I’ve attached some sample code that can be placed in a ViewPart of an Eclipse pluging (3.7 is the version I’m using). If you run the code, and resize the column to the right, the table gains a horizontal scrollbar (which is what I want).

Now if I collapse the section (click the arrow to the left of “Section Title”), the view gains a horizontal scrollbar (which i don’t want). Expanding the section again, the view scroll remains, and now the table no longer has one.

I’m looking for a way (probably some awful combination of nested composites) to stop the table being wider than the view, and would appreciate any suggestions.

public class ExampleView extends ViewPart {
  /** Note: other fields / methods removed to condense snippet */

  private FormToolkit toolkit;
  private ScrolledForm scrolledForm;

  public void createPartControl(Composite parent) {
            parent.setLayout(new FillLayout());

    toolkit = new FormToolkit(parent.getDisplay());
    scrolledForm = toolkit.createScrolledForm(parent);
    scrolledForm.setExpandHorizontal(true);
    scrolledForm.setText("Form Title");

    scrolledForm.getBody().setLayout(new FillLayout());
    // here's the modification for the solution
    scrolledForm.getBody().setLayout(
            new BoundedLayout(new FillLayout(), true));

    final Section section = toolkit.createSection(scrolledForm.getBody(),
            Section.DESCRIPTION | Section.TITLE_BAR | Section.TWISTIE
                    | Section.EXPANDED);

    section.addExpansionListener(new ExpansionAdapter() {
        public void expansionStateChanged(ExpansionEvent e) {
            scrolledForm.reflow(true);
        }
    });
    section.setText("Section Title");

    final Table table = toolkit.createTable(section, SWT.FULL_SELECTION);
    TableViewer viewer = new TableViewer(table);

    table.setLinesVisible(true);
    table.setHeaderVisible(true);
    table.setItemCount(10);

    TableColumn col = new TableColumn(table, SWT.NONE);
    col.setText("Column A");
    col.setWidth(150);
    col.setResizable(true);
    col.setMoveable(true);

    TableColumn col2 = new TableColumn(table, SWT.NONE);
    col2.setText("Column B");
    col2.setWidth(150);
    col2.setResizable(true);
    col2.setMoveable(true);

    section.setClient(table);
  }
}

Answer 1

So here’s a solution i’ve come up with using a custom Layout. It wraps another layout, but can bound the computeSize to either the width or height of the parent composite – basically only allowing scrolling in one direction (if there is an easier way to force the ScrolledForm to do this please let me know!).

There are some nasty-ish reflection hacks that need to be applied as the computeSize and layout methods are protected

import java.lang.reflect.Method;

import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Layout;

public class BoundedLayout extends Layout {
  protected Layout delegateLayout;

  protected Method computeSizeMethod;
  protected Method layoutMethod;

  protected boolean widthBound;

  public BoundedLayout(Layout delegateLayout, boolean widthBound) {
      setDelegateLayout(delegateLayout);
      this.widthBound = widthBound;
  }

  public Layout getDelegateLayout() {
      return delegateLayout;
  }

  public void setDelegateLayout(Layout delegateLayout) {
      this.delegateLayout = delegateLayout;

      try {
          computeSizeMethod = delegateLayout.getClass().getDeclaredMethod(
                "computeSize", Composite.class, int.class, int.class,
                boolean.class);
          computeSizeMethod.setAccessible(true);

          layoutMethod = delegateLayout.getClass().getDeclaredMethod(
                "layout", Composite.class, boolean.class);
          layoutMethod.setAccessible(true);
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
  }

  @Override
  protected Point computeSize(Composite composite, int wHint, int hHint,
        boolean flushCache) {
    // get comp size to make sure we don't let any children exceed it
    Point compSize = composite.getSize();

    try {
        Point layoutComputedSize = (Point) computeSizeMethod.invoke(
                delegateLayout, composite, wHint, hHint, flushCache);

        if (widthBound) {
            layoutComputedSize.x = Math.min(compSize.x,
                    layoutComputedSize.x);
        } else {
            layoutComputedSize.y = Math.min(compSize.y,
                    layoutComputedSize.y);
        }

        return layoutComputedSize;
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
  }

  @Override
  protected void layout(Composite composite, boolean flushCache) {
    try {
        layoutMethod.invoke(delegateLayout, composite, flushCache);
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
  }
}