SWT: remove the invisible component space in composite - eclipse

Question

I put three composite(1,2,3) inside one composite0, so they all set their layout based on the composite0.setLayout(new FormLayout()). The problem I have now is, I make the composite3 invisible: composite3.setVisible(false); (I dont want to delete the data, still need that component, but just doesn't want it shows on the UI), and there's a big gap after componite2 now. How to remove the big gap(which use to put the composite2)? thank you in advanced!

Answer 1

Snippet 313 of the official SWT examples should help you with that. You basically set a different FormData on composite3 depending on whether you want to show or hide it.

Answer 2

I have a databinding observable for that, but it assumes the controls to be within a GridLayout. I use it to show and hide composites and widgets within a wizard page, depending on the selection state of a checkbox.
To use it, set it up with something like this:
DataBindingContext dbc = new DataBindingContext();
Button button = new Button(composite, SWT.CHECK);
IObservableValue target = SWTObservables.observeSelection(button);
dbc.bindValue(target, new HideControlObservable(someControl));
Here is the observable:
/**
* Observable to control the presence (visibility and size) of any control
* within a grid layout.
* <p>
* Changing the value of this observable will do two things:
* <ol>
* <li>Set the visibility of the control</li>
* <li>Set the size of the control to zero when the control is invisible.</li>
* </ol>
* So, when using this observable, the control will not only be invisible,
* but it will be gone, completely. Normally, when setting the visibility of
* a control to <code>false</code>, the control will not be displayed but
* will still take all the space on the screen.
* </p>
* <p>
* <strong>Note:</strong> this observable works for controls within a
* <strong>GridLayout only</strong>.
* </p>
*/
public class HideControlObservable extends WritableValue implements IValueChangeListener {
private final DataBindingContext dbc = new DataBindingContext();
private final ISWTObservableValue sizeObservable;
private final Point size = new Point(0, 0);
private final Control control;
public HideControlObservable(Control control) {
super(control.getVisible(), Boolean.class);
this.control = control;
UpdateValueStrategy never = new UpdateValueStrategy(UpdateValueStrategy.POLICY_NEVER);
dbc.bindValue(SWTObservables.observeVisible(control), this, never, null);
sizeObservable = SWTObservables.observeSize(control);
sizeObservable.addValueChangeListener(this);
if (!control.isVisible()) {
GridData gd = (GridData) control.getLayoutData();
if (gd == null) {
gd = new GridData();
}
gd.exclude = true;
control.setLayoutData(gd);
control.setSize(new Point(0, 0));
}
}
#Override
public void doSetValue(Object value) {
super.doSetValue(value);
Boolean bool = (Boolean) value;
if (bool) {
GridData gd = (GridData) control.getLayoutData();
if (gd == null) {
gd = new GridData();
}
gd.exclude = false;
control.setLayoutData(gd);
control.setSize(size);
control.getParent().layout();
} else {
GridData gd = (GridData) control.getLayoutData();
if (gd == null) {
gd = new GridData();
}
gd.exclude = true;
control.setLayoutData(gd);
control.setSize(new Point(0, 0));
control.getParent().layout();
}
}
#Override
public synchronized void dispose() {
sizeObservable.dispose();
super.dispose();
}
#Override
public void handleValueChange(ValueChangeEvent event) {
Point newSize = (Point) event.getObservableValue().getValue();
if (newSize.x > size.x) {
size.x = newSize.x;
}
if (newSize.y > size.y) {
size.y = newSize.y;
}
}
}

Answer 3

FormData data = new FormData();
data.left = new FormAttachment(0, 100, EditorPanel.SPACING);
data.top = new FormAttachment(section1, EditorPanel.SPACING);
data.height = 0;
data.width = 0;
addSectionFormData(a, b, c);
a.setLayoutData(data);
b.setLayoutData(data);
this solve the problem! :)