[Plib-devel] [PATCH] puListBox::setTopItem(): don't scroll off the list

[Melchior F. <mf...@us...>]

This isn't really a bug, but still something that should be "fixed":
puListBox::setTopItem() allows to scroll off a list until only one
entry is left on the top and the rest empty(C). This is useless and
doesn't buy us anything -- on the contrary: it's very annoying
because you shoot over the goal and have to scroll back for no reason.
The list view is really a viewport to the list, so there's no reason
to display anything else than list members. Empty space doesn't
belong to the list. And if leaving the list is possible on the bottom
then why not on top? (C) & (D)? This would at least be consistent. :-}

Current behavior:  (A) & (C)
Desired behavior:  (A) & (B)


(A) correct with top=0        (B) correct with top=max (but not in plib)
                                
                                       aaaaa
  _________                          __bbbbb__
  | aaaaa |                          | ccccc |
  | bbbbb |                          | ddddd |
  | ccccc |                          | eeeee |
  | ddddd |                          | fffff |
  ---------                          ---------
    eeeee
    fffff


(C) silly (current plib)       (D) even sillier, but consistent with (C)!

    aaaaa                             _________
    bbbbb                             |       |
    ccccc                             |       |
    ddddd                             |       |
  __eeeee__                           |_aaaaa_|
  | fffff |                             bbbbb
  |       |                             ccccc
  |       |                             ddddd
  |       |                             eeeee
  ---------                             fffff


Index: src/pui/puListBox.cxx
===================================================================
RCS file: /cvsroot/plib/plib/src/pui/puListBox.cxx,v
retrieving revision 1.26
diff -u -p -r1.26 puListBox.cxx
--- src/pui/puListBox.cxx       18 Apr 2006 16:50:17 -0000      1.26
+++ src/pui/puListBox.cxx       21 May 2006 08:45:08 -0000
@@ -74,10 +74,11 @@ void puListBox::newList ( char ** _list
 void puListBox::setTopItem( int item_index )
 {
   top = item_index ;
-  if ( top < 0 )
+  int visible = getNumVisible();
+  if ( top < 0 || num <= visible )
     top = 0 ;
-  else if ( num > 0 && top > num-1 )
-    top = num-1;
+  else if ( num > 0 && top > num-visible )
+    top = num-visible;

   puPostRefresh () ;
 }