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Thread View: comp.windows.ms.programmer
2 messages
2 total messages Started by Samuelson S. Rehman Wed, 26 Aug 1992 03:40
Question about Listbox 64K barrier
#492
Author: Samuelson S. Rehman
Date: Wed, 26 Aug 1992 03:40
32 lines
1686 bytes
I'm a M2 UNIX programmer and programming in MS Windows is pretty new to me.

I'm writing a program that can allow a user to select a record from
a listbox. Now this list of record can easily exceed the 64K barrier.
So my questions are:

	1. How can I interrupt the user when he's trying to scroll down/up,
	so I can load the next/prev 64K segment from the file ?

	2. And even if that can be done, how do I maintain the scrollbar to
	show the position of the bar within the whole database, but not
	just within the 64K segment ??

	3. If that is totally impossible, can anyone tell me where can
	I find information (books maybe) about writing a widget ( or
	whatever it's called in MS Windows ) ?

Thanks!

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							    sam@netcom.com
Re: Question about Listbox 64K barrier
#493
Author: Tom W. Brown
Date: Wed, 26 Aug 1992 18:14
43 lines
2489 bytes
In article <k+bn2wq.sam@netcom.com>, sam@netcom.com (Samuelson S. Rehman) writes:
|> 
|> I'm a M2 UNIX programmer and programming in MS Windows is pretty new to me.
|> 
|> I'm writing a program that can allow a user to select a record from
|> a listbox. Now this list of record can easily exceed the 64K barrier.
|> So my questions are:
|> 
|> 	1. How can I interrupt the user when he's trying to scroll down/up,
|> 	so I can load the next/prev 64K segment from the file ?
|> 
|> 	2. And even if that can be done, how do I maintain the scrollbar to
|> 	show the position of the bar within the whole database, but not
|> 	just within the 64K segment ??
|> 

Both of these concerns can be addressed by using an "OWNERDRAW" listbox.  Check
the documentation for CreateWindow with regard to the LBS_OWNERDRAWFIXED or
LBS_OWNERDRAWVARIABLE styles.

In a nutshell, these styles allow you to have a listbox where Windows does
not need to store strings for each item in the list, rather a message is
sent back to your application whenever a list item needs to be displayed (c.f.
WM_DRAWITEM) allowing you to perform whatever file/memory buffering you
desire.

|> 	3. If that is totally impossible, can anyone tell me where can
|> 	I find information (books maybe) about writing a widget ( or
|> 	whatever it's called in MS Windows ) ?

The definitive documentation is probably the SDK (Software Developer's Kit)
manual set from Microsoft Press, but there are plenty of books available that 
do a better job of "teaching" windows programming -- one of my favorites has
always been Charles Petzold's book.

Good luck,


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