Bug 31395 Child window of Preferences dialog centers between screens
On the Preferences->Java->Code Generation->Names tab, the Edit button opens a dialog that is split between multiple monitors, instead of centering on the main Preference window like the rest of its child windows do.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/TodoTaskConfigurationBlock.java
private boolean canEdit(ListDialogField field) {
			return field.getSelectedElements().size() == 1;
		}
		public void customButtonPressed(ListDialogField field, int index) {
			doTodoButtonPressed(index);
		}
		public void selectionChanged(ListDialogField field) {
			field.enableButton(3, canEdit(field));
		}
			
		public void doubleClicked(ListDialogField field) {
			if (canEdit(field)) {
				doTodoButtonPressed(3);
			}
		}
		public void dialogFieldChanged(DialogField field) {
			validateSettings(PREF_COMPILER_TASK_TAGS, null);
		}			
		
	}
		
	protected Control createContents(Composite parent) {
		fPixelConverter= new PixelConverter(parent);