Avoid Tree Resize after Section expand

Question

I've got a question I couldn't resolve myself for quite a while now.

I have a RCP ViewPage containing two sections. The sections are inside a SashForm so that the user is able to resize the expanded sections. In the bottom section there is a Tree which is empty after initialization. Through user interaction (i.e. removing a filter) the tree gets filled and has a lot of data in it. If the user now collapses the bottom view and expands it again the tree gets resized which causes ScrollBars in my form. What I want is scrollbars in the tree view.

Here is how the view is build:

- ScrolledForm
  - Form Body
    - Sash
      - Section 1
        - Composite
          - Some View
      - Section 2
        - Composite
          - Tree

I hope you understand what I'm trying to achieve.

UPDATE: Here is some source code to play with. It uses a Table instead of a tree but produces the same issue.

public class MyPersonPageEditor extends FormPage {

    public static final String ID = "some.ID"; 

    TableViewer tableViewer;

    public MyPersonPageEditor(FormEditor editor) {
        super(editor, ID, "Some Title");
    }

    @Override
    protected void createFormContent(IManagedForm managedForm) {
        FormToolkit toolkit = managedForm.getToolkit();
        ScrolledForm form = managedForm.getForm();
        Composite formBody = form.getBody();
        formBody.setLayout(new GridLayout());

        form.setText("Some Title");
        toolkit.decorateFormHeading(form.getForm());

        SashForm sfForm = new SashForm(formBody, SWT.VERTICAL);
        sfForm.setLayout(new GridLayout());
        sfForm.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

        Section topSection = new Section(sfForm, Section.TITLE_BAR | Section.EXPANDED | Section.TWISTIE);
        topSection.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        topSection.setText("Section 1 Title");
        Composite topSectionComposite = toolkit.createComposite(topSection);
        topSectionComposite.setLayout(new GridLayout());
        toolkit.createLabel(topSectionComposite, "Just some content. Doesn't need to be much");
        Button btn = toolkit.createButton(topSectionComposite, "Create Table Content", SWT.PUSH);
        btn.addSelectionListener(new SelectionListener() {
            @Override
            public void widgetSelected(SelectionEvent e) {
                for (int i = 0 ; i < 10 ; i++) {
                    tableViewer.add("Element " + i);
                }
            }

            @Override
            public void widgetDefaultSelected(SelectionEvent e) {

            }
        });
        topSection.setClient(topSectionComposite);

        Section bottomSection = new Section(sfForm, Section.TITLE_BAR | Section.EXPANDED | Section.TWISTIE);
        bottomSection.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        bottomSection.setText("Section 2 Title");
        Composite bottomSectionComposite = toolkit.createComposite(bottomSection);
        bottomSectionComposite.setLayout(new GridLayout());
        bottomSectionComposite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        bottomSection.setClient(bottomSectionComposite);
        Table table = toolkit.createTable(bottomSectionComposite, SWT.BORDER | SWT.MULTI | SWT.FULL_SELECTION | 
                 SWT.V_SCROLL | SWT.H_SCROLL | SWT.RESIZE);
        table.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        table.setHeaderVisible(true);

        tableViewer = new TableViewer(table);
        tableViewer.add("New Element");
        new TableColumn(table, SWT.LEFT).setText("Spalte 1");

        TableLayout layoutDefault = new TableLayout();
        layoutDefault.addColumnData(new ColumnWeightData(1));
        table.setLayout(layoutDefault);

        form.reflow(true);
    }
}

If you click the button after start the table looks like the left picture. After you collapse and expand the second section it looks like the right one.

Answer 1

Here is the code that works: you just have to tweak the size of the Tree/Table and make sure it will not span across the vertical space:

public void createPartControl(Composite parent) {

    FormToolkit toolkit = new FormToolkit(parent.getDisplay());
    final ScrolledForm form = toolkit.createScrolledForm(parent);
    Composite formBody = form.getBody();
    formBody.setLayout(new GridLayout());
    form.setText("Some Title");
    toolkit.decorateFormHeading(form.getForm());

    SashForm sfForm = new SashForm(formBody, SWT.VERTICAL);
    sfForm.setLayout(new GridLayout());
    sfForm.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

    //top section
    Section topSection = new Section(sfForm, Section.TITLE_BAR | Section.EXPANDED | Section.TWISTIE);
    topSection.setLayout(new GridLayout());
    topSection.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
    topSection.setText("Section 1 Title");
    Composite topSectionComposite = toolkit.createComposite(topSection);
    topSectionComposite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
    topSectionComposite.setLayout(new TableWrapLayout());

    toolkit.createLabel(topSectionComposite, "Just some content. Doesn't need to be much");
    Button btn = toolkit.createButton(topSectionComposite, "Create Table Content", SWT.PUSH);
    btn.addSelectionListener(new SelectionListener() {

        @Override
        public void widgetSelected(SelectionEvent e) {
            for (int i = 0 ; i < 10 ; i++) {
                tableViewer.add("Element " + i);
            }
            form.reflow(true);
        }

        @Override
        public void widgetDefaultSelected(SelectionEvent e) {

        }
    });
    topSection.setClient(topSectionComposite);

    //bottom section
    Section bottomSection = new Section(sfForm, Section.TITLE_BAR | Section.EXPANDED | Section.TWISTIE);
    bottomSection.setLayout(new GridLayout());
    bottomSection.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
    bottomSection.setText("Section 2 Title");
    Composite bottomSectionComposite = toolkit.createComposite(bottomSection);
    bottomSectionComposite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
    bottomSectionComposite.setLayout(new TableWrapLayout());

    Table table = toolkit.createTable(bottomSectionComposite, SWT.BORDER | SWT.MULTI | SWT.FULL_SELECTION | 
            SWT.V_SCROLL | SWT.H_SCROLL | SWT.RESIZE);

    TableWrapData ttd222 = new TableWrapData(TableWrapData.FILL_GRAB, TableWrapData.FILL_GRAB);
    ttd222.maxHeight =200;
    table.setLayoutData(ttd222);
    table.setHeaderVisible(true);

    tableViewer = new TableViewer(table);
    tableViewer.add("New Element");
    new TableColumn(table, SWT.LEFT).setText("Spalte 1");

    TableLayout layoutDefault = new TableLayout();
    layoutDefault.addColumnData(new ColumnWeightData(1));
    table.setLayout(layoutDefault);

    bottomSection.setClient(bottomSectionComposite);
    form.reflow(true);
}

Answer 2

-make sure the Tree has the SWT.H_SCROLL style (if I remember correctly), that is has a minimum size (for example with GridLayout and GridData set the minHeight to X or with TableWrapLayout and TableData heightHint to X) -if you don't manage to make it work just tell me and I'll try to make the code; also, a picture with the layout would be great