componentPanel.setLayoutData(componentGridData);
// set a background to let user see limits of the component
componentPanel.setBackground(new Color(Display.getCurrent(), 255, 175, 175));// PINK as in awt
final ImageViewer theComponent = new ImageViewer(componentPanel, SWT.NONE);
// ----------
Group testPanel = getTestPanel(mainComposite, theComponent);
GridData testPanelGridData = new GridData();
testPanelGridData.grabExcessHorizontalSpace = true;