How to stretch a picturebox to a window while maintaining an aspect ratio?

[#1]

I'm writing a script that will generate a GUI for displaying images, using a rowstate handler to pass the images over to the window.

Is there a way to set a picture box object to:

1. Stretch with window size (with a minimum and maximum size defined)
2. Maintain it's original aspect ratio (e.g. square) (see script 2)
3. Forbid direct user re-sizing.

Here's some JSL that uses the sample table of images.

Clear Globals();
Names Default To Here(1);

dt = Open( "$SAMPLE_DATA/Big Class Families.jmp" );

//Set the picture equal to selected row
rs_updateviewer = Expr(
	
	SelectedRows = (dt << Get Selected Rows());
	i = If(N Items(SelectedRows) == 0, 1, SelectedRows[1]);
	
	img = column(dt, "pet")[i];
	pb << Set Image(img);
);

//Viewer Window
Viewer = New Window(
	"Viewer",
	Show Menu( 0 ),
	<< On Close(Clear Globals(rs);
	),
	<< Size Window( 1000, 700),
	
	vb = V List Box("Center",
	H Center Box( Text Box( "Viewer" ) ),
	H List Box(
//	tb = dt << New Data Box(),
	tb = Data Grid Box(),
	pb = Picture Box()
	)
	)
	,
	pb << Set Stretch( "Fill", "Fill" );
	pb << Border( 1 );
	
	tb << Set Stretch( "Off", "Off" );
	tb << Set Data Table( dt );
	tb << Close Side Panels( 1 );
	
);

//Initiate image
rs_updateviewer;

// Define the handler function
f = Function( {a},
	rs_updateviewer
);

// Register the row state handler to the table
set_rowstate = Expr(
	rs = dt << Make Row State Handler( f );
);

set_rowstate;

Here's an script index example of a graph with it's aspect ratio fixed, the behaviour I'd like on the picture

Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
gb = Graph Builder( Show Control Panel( 0 ), Variables( X( :height ), Y( :weight ) ), Elements( Points( X, Y ), Smoother( X, Y ) ) );
gb << Fit to Window( "Maintain Aspect Ratio" );

[#2]

Which min/max size has been determined (window or picture)? Should user be allowed to resize the window but not the picture? And is allowed to resize the window, should picture be able to resize to this new window size?