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The visible state of a control may change depending on the visible state of its parent control, how do I know this?

For example

Display display = Display.getDefault() ;
Shell shell = new Shell( display ) ;
shell.setSize( 400, 600 ) ;
shell.setLayout( new FillLayout( SWT.VERTICAL ) ) ;

Composite composite = new  Composite( shell, SWT.NONE ) ;
composite.setLayout( new FillLayout() ) ;
Button test = new Button( composite, SWT.NONE ) ;
test.setText( "test" ) ;

composite.addListener( SWT.Show, e -> System.out.println( "Composite Show" ) ) ;
composite.addListener( SWT.Hide, e -> System.out.println( "Composite Hide" ) ) ;
test.addListener( SWT.Show, e -> System.out.println( "Button Show" ) ) ;
test.addListener( SWT.Hide, e -> System.out.println( "Button Hide" ) ) ;

Button btn = new Button( shell, SWT.TOGGLE ) ;
btn.setText( "Show / Hide" ) ;
btn.addListener( SWT.Selection, e -> {
    composite.setVisible( btn.getSelection() ) ;
    System.out.println( test.isVisible() ) ;
} ) ;

shell.open() ;
while ( !shell.isDisposed() ) {
    if ( !display.readAndDispatch() ) {
        display.sleep() ;
     }
}

I can't get the Button's Show/Hide event.

Improve this question
4
  • The Show/Hide event is only sent on the Composite. Looking at the source there is no attempt to propogate the event to its children. Commented Aug 17, 2024 at 9:35
  • Yes, but is there any other way to know the change of visible state from the child Control level? Commented Aug 18, 2024 at 7:36
  • Not that I know off, but I have never had a need to respond to visibility changes. You would have to listen to the Composite event and go though the children of the composite. Commented Aug 18, 2024 at 7:43
  • What would knowing the state of visibility, setting aside that it could be partially visible in different amounts ms to ms, let you do? Commented Aug 19, 2024 at 17:06
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