REQ: *VERY* Long List & paging methods 
Author Message
 REQ: *VERY* Long List & paging methods

I'm translating an existing C-language database search engine to a
combination of Tcl/Tk for the GUI and C for the search/retrieval.  The
databases on which it will run can have *very* long lists, i.e. tens of
thousands to millions of list items.  Because of the potential length of
the lists of retrieved data records as well as the overhead in
processing the full records to abbreviated browse formats for the
display list, I know that I'll need to page through the list, only
keeping a hundred or so records in the actual list, but with the
scrollbar representing the number of items in the "virtual" list.  Can
anyone point me to any examples of list paging of this sort?  

Thanks in advance.
--
Kim Buttleman
U. S. Geological Survey, Reston, Va., USA



Fri, 27 Apr 2001 03:00:00 GMT  
 REQ: *VERY* Long List & paging methods

Quote:

> [logical clipping or "paging" for listboxes]

Two options:

 1.(easier) Use a canvas, with a scrollregion of the real size of the
list, but delete/add just enough items for the current view at the time
you call the scrollbar's callback [.c yview]. In this case the canvas's
yscrollcommand is the standard {.s set}, thanks to the big scrollregion.

 2. (harder, but maybe more efficient?) Use a (small) list, and modify
both the scrollbar's callback and the lists's yscrollcommand so that
they have a false idea of the list's size and position. This is
basically the same as one of the solutions suggested to Lindsay
Marshall's white-at-bottom-of-text problem.

-Alex



Sat, 28 Apr 2001 03:00:00 GMT  
 
 [ 2 post ] 

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