From:	"Anthony.Appleyard" <MCLSSAA2 AT fs2 DOT mt DOT umist DOT ac DOT uk>
Organization:	Materials Science Centre
To:	DJGPP AT delorie DOT com
Date:	Tue, 6 Jan 1998 09:45:25 GMT
Subject:	Re: Getting the fastest running
Reply-to:	Anthony DOT Appleyard AT umist DOT ac DOT uk
Message-ID:	<1B174837C8E@fs2.mt.umist.ac.uk>

  On Mon, 5 Jan 1998, Anthony.Appleyard wrote:
> Due to the nature of the work I must set up a screen display in an array and
> then bulk copy it to screen (in a 256-color mode: VESA 0x101, 0x103, 0x105,
> 0x107), by dosmemput()'ing it 0x10000 bytes at a time to the graphics screen
> address 0xa0000 etseq. Is this the fastest way to copy bulk matter to the
> graphics screen in djgpp? If not, what is?

  Geza Herman <geza AT inf DOT bme DOT hu> replied:-
> Why must you copy? You can write directly to vid.mem. ...

I must copy because setting up the screen display involves writing and then
overwriting (1) parts of the background which are hidden by objects, (2) parts
of objects which are hidden by other objects. Compare the old and troublesome
`hidden line' problem. If I wrote directly to screen, this hidden matter would
keep flashing in and out of view. How can I tell the PC's graphics card not to
redisplay the screen while I am writing a display to it?

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