resize - SWT Why is parent Composite resized after I create a new Composite in parent?

Question

I want to recreate the functionality and look of ExpandItem. I am creating a Composite which has a StyledText widget and a Button. When the Button is pressed, a new Composite is created below these two, and when it is pressed again, this new Composite is hidden. However, after creating the new Composite, my parent Composite resizes for no reason. I am attaching my code and pictures of my work. I would appreciate any kind of help.

Shell shell = new Shell();
//    shell.setSize(400, 400);
Display display = shell.getDisplay();
shell.setLayout(new FillLayout());

//create outerComp
GridLayout gridLayoutOuterComp = new GridLayout();

GridData gridDataOuterComp = new GridData(SWT.FILL, SWT.FILL, true, true);
gridDataOuterComp.heightHint = 150;

Composite outerComp = new Composite(shell, SWT.NONE);
outerComp.setLayout(gridLayoutOuterComp);
outerComp.setLayoutData(gridDataOuterComp);

//create innerComp
GridLayout gridLayoutInnerComposite = new GridLayout();
gridLayoutInnerComposite.numColumns = 5;

GridData gridDataInnerComposite = new GridData(SWT.FILL, SWT.FILL, true, false);
gridDataInnerComposite.heightHint = 40;

Composite composite = new Composite(outerComp, SWT.NONE);
composite.setLayout(gridLayoutInnerComposite);
composite.setLayoutData(gridDataInnerComposite);
composite.setBackground(display.getSystemColor(SWT.COLOR_GREEN));

// create the styled text widget
GridData gridDataStyledText = new GridData();
gridDataStyledText.grabExcessHorizontalSpace = true;
gridDataStyledText.horizontalSpan = 4;
gridDataStyledText.horizontalAlignment = SWT.FILL;
gridDataStyledText.heightHint = 30;

StyledText widget = new StyledText(composite, SWT.BORDER);
String textNew = "This is StyledText in Composite";
widget.setText(textNew);
widget.setLayoutData(gridDataStyledText);

//create Button
GridData gridDataButton = new GridData();
gridDataStyledText.horizontalSpan = 1;
gridDataButton.heightHint = 30;
gridDataButton.grabExcessHorizontalSpace = false;
gridDataButton.horizontalAlignment = SWT.END;

Button button = new Button(composite, SWT.PUSH);
button.setText("B1");
button.setLayoutData(gridDataButton);

button.addSelectionListener(new SelectionListener() {
  @Override
  public void widgetSelected(SelectionEvent e) {
    GridData newCompGridData = new GridData();
    if (counter % 2 == 1) {
      if (newComp != null && !newComp.isVisible()) {
        newComp.setVisible(true);

        GridData newData = new GridData();
        newData.heightHint = 100;
        composite.setLayoutData(newData);

        counter++;
      } else {
        newComp = new Composite(composite, SWT.BORDER);
        newCompGridData.horizontalAlignment = SWT.FILL;
        newCompGridData.grabExcessHorizontalSpace = true;
        newCompGridData.horizontalSpan = 5;
        newCompGridData.verticalAlignment = SWT.FILL;
        newComp.setLayoutData(newCompGridData);

        GridData newData = new GridData();
        newData.heightHint = 100;
        composite.setLayoutData(newData);

        Color red = display.getSystemColor(SWT.COLOR_RED);
        newComp.setBackground(red);


        counter++;
      }
    } else {
      newComp.setVisible(false);

      GridData newData = new GridData();
      newData.heightHint = 40;
      composite.setLayoutData(newData);

      counter++;
    }
    composite.getParent().layout();
    composite.layout();
    newComp.layout();
  }

question from:https://stackoverflow.com/questions/65923406/swt-why-is-parent-composite-resized-after-i-create-a-new-composite-in-parent

Answer 1

The lines:

GridData newData = new GridData();
newData.heightHint = 100;
composite.setLayoutData(newData);

are changing the layout data for composite to the default alignment and grab values. They should be:

GridData newData = new GridData(SWT.FILL, SWT.FILL, true, false);
newData.heightHint = 100;
composite.setLayoutData(newData);

Note: the line

outerComp.setLayoutData(gridDataOuterComp);

doesn't do anything because the parent of outerComp is using FillLayout.