I have nearly finished my Applet and I'm now left only to finalize the
layout. So far I've used a GridLayout(3, 1) but now want to change to
something else. I played around with a GridBagLayout() but I'm getting
unexpected resizing effects.

My applet consists of 3 areas in a single column, from top to bottom :

 a) a tab pane
 b) a JLabel wrapped in a ScrollPane used as message area
 c) a scrollPane originally wrapped around a dummy Jlabel, and
    later dynamically removed and replaced by a scrollPane wrapped
    around a JTable

The first tab of the tab pane contains a ScrollPane wrapped around a
customized "myDisplay extends JPanel implements Scrollable", the other
tabs are just static control menus.

With the test grid layout the 3 areas a/b/c are (of course) of the same
vertical size.

 The myDisplay in (a) is initialized to a 256x256 ramp image (which
 appears to be definitely narrower than the applet width, and slightly
 not tall enough to contain the image, so a vertical scroll bar appears.

 Later I load images in it, which can be smaller or larger. They can
 also be zoomed 2x, 3x, 4x etc. so they will soon become larger and
 scroll bars appear as appropriate.

 (b) is initialized to an empty area, messages appear in it and scroll
 bar appears when it's full

 (c) as I said is initialized to a "nothing loaded" message. As soon
 as I load an image in (a) a table of "regions" is loaded in (c), which
 can have more or less rows, therefore causing a scroll bar to appear or
 not.

The only component for which a setPreferredSize is set is the myDisplay
inside the scroll pane in the first tab of (a).

In the test configuration (GridLayout(3, 1)) everything goes fine (the
three pieces a/b/c are never auto-resized, ... scroll bars in them
appear when appropriate ...

... but I'm NOT SATISFIED because the three pieces have the same height.

What I'd wish to achieve is 3 components of DIFFERENT height (say that
I'd wish (a) to be tall enough to contain a 512x512 image plus the tabs,
(b) to be only 3-4 text lines, and (c) to occupy the rest of the page,
a bit less than the height of (a).

I tried with GridBagLayout, but that has SIDE EFFECTS ... as the various
components dynamically resize.  Sometimes the myDisplay in (a) resizes
and loses the scrollbars, and this pushes the bottom of the Jtable in
(c) offscreen. While the message area in (b) grows higher than wished
and then remains like that.

This is the latest set of GridBagConstrains I tried (c1 c2 c3 for the
components (a) (b) (c) from top to bottom), but I tried several
variations.

     c1.gridx=0 ; c1.gridy=0 ;
     c1.gridwidth=GridBagConstraints.REMAINDER ;
     c1.gridheight=10 ;
     c1.fill=GridBagConstraints.BOTH ;
     c1.anchor=GridBagConstraints.PAGE_START;
     c1.weightx=1.0 ; c1.weighty=0.0 ;
     c2.gridx=0 ; c1.gridy=11  ;
     c2.gridwidth=GridBagConstraints.REMAINDER ;
     c2.gridheight=5 ;
     c2.fill=GridBagConstraints.BOTH ;
     c2.anchor=GridBagConstraints.LINE_END ;
     c2.weightx=1.0 ; c2.weighty=0.0 ;
     c3.gridx=0 ; c1.gridy=16 ;
     c3.gridwidth=GridBagConstraints.REMAINDER ;
     c3.gridheight=GridBagConstraints.REMAINDER ;
     c3.fill=GridBagConstraints.BOTH ;
     c3.anchor=GridBagConstraints.PAGE_END;
     c3.weightx=1.0 ; c3.weighty=0.0 ;

How can I achieve what I want i.e. three vertical sections of FIXED
DIFFERENT heights, which never resize, but in which scroll bars appear
when needed ?