{
    if ( ! UI::HasSpecialWidget(`Slider) )
    {
	UI::OpenDialog(
		   `VBox( 
			 `Label("Error: This UI doesn't support the Slider widget!"),
			 `PushButton(`opt(`default), "&OK")
			 )
		   );
	UI::UserInput();
	UI::CloseDialog();
	
	return;
    }
    
    UI::OpenDialog(
	       `VBox(
		     `Slider( "Percentage", 0, 100, 50),
		     `PushButton(`opt(`default), "&OK")
		     )
	       );
    UI::UserInput();
    UI::CloseDialog();
}

          

        

          // Advanced Slider + BarGraph example:
//
// Display a dialog with a bar graph for RGB color percentages
// and 3 sliders for the RGB percentage.
// Update the bar graph while the user adjusts the RGB values.
//
// Unfortunately the colors don't match any more in the BarGraph widget - they
// used to be red, blue and green. You need to use a bit of imagination
// here. ;-)

{
    // Check for availability of required widgets
    
    if ( ! UI::HasSpecialWidget(`Slider) ||
	 ! UI::HasSpecialWidget(`BarGraph ) )
    {
	UI::OpenDialog(
		   `VBox( 
			 `Label("Error: This UI doesn't support the required special widgets!"),
			 `PushButton(`opt(`default), "&OK")
			 )
		   );
	UI::UserInput();
	UI::CloseDialog();
	
	return;
    }

    
    // Initialize RGB values
    
    integer red   = 128;
    integer blue  = 128;
    integer green = 128;


    // Create the dialog
    
    UI::OpenDialog(
	       `VBox(
		     `HSpacing(50),	// force width
		     `BarGraph( `id(`graph),
				[ red, green, blue ],
				[ "Red\n%1", "Green\n%1", "Blue\n%1" ] ),
		     `Slider( `id(`red),   `opt(`notify), "Red",   0, 255, red   ),
		     `Slider( `id(`green), `opt(`notify), "Green", 0, 255, green ),
		     `Slider( `id(`blue),  `opt(`notify), "Blue",  0, 255, blue  ),
		     `PushButton(`id(`close), `opt(`default), "&Close")
		     )
	       );

    
    // Event processing loop - left only via the "close" button
    // or the window manager close button / function.
    any widget = nil;

    do
    {
	widget = UI::UserInput();

	if ( widget == `red   ||	// any of the sliders?
	     widget == `blue  ||
	     widget == `green   )
	{
	    // Get all slider values
	    
	    red   = (integer) UI::QueryWidget(`id(`red),   `Value );
	    green = (integer) UI::QueryWidget(`id(`green), `Value );
	    blue  = (integer) UI::QueryWidget(`id(`blue),  `Value );

	    
	    // Update bar graph
	    
	    UI::ChangeWidget(`id(`graph), `Values, [ red, green, blue ] );
	}
    } while ( widget != `close &&	// the real "Close" button
	      widget != `cancel );	// the window manager close function/button
	
    UI::CloseDialog();
}