Date   : Sun, 13 Aug 2006 01:26:45
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: Cursor sizes

>Message-ID: <02c601c6bc08$7b562040$800101df@...>

"Richard Wilson" <rich@...> wrote:
> The 6845 HSYNC position is changed to suit teletext mode by only 2 character
> periods. On a real BBC, this may cause the display to shift right by one
> character in teletext mode. Is this actually observed?

Yep. In programs I tend to do:

MODE 7:VDU 23;2,53;0;0;0

to move the display right a bit to centre the display.

> Another quick question though.. How does the palette affect the cursor
> display in the different modes? Can you change the colour of the cursor?

The cursor purely inverts whatever is on the screen underneath it.
If the display would be black, the cursor is white. If the display
would be blue, the cursor is yellow.

Try the following:

MODE 1
GCOL 0,0:MOVE 0,0:DRAW 0,1024
GCOL 0,1:MOVE 4,0:DRAW 4,1024
GCOL 0,2:MOVE 6,0:DRAW 6,1024
GCOL 0,3:MOVE 8,0:DRAW 8,1024
VDU 23;10,0;0;0;0
and then move the editing cursor over the coloured bars.

> Is it possible to change the palette and get a red cursor (for example)
> in Mode 7?

Yes. Move the cursor over a (white-red)=yellow background. Try:

FOR A9 TO 135:VDU A,157,10,13:NEXT
VDU 23;10,0;0;0;0

and then move the editing cursor over the coloured bars


--
J.G.Harston - jgh@...                - mdfs.net/User/JGH
Sheffield Boundary Review at http://mdfs.net/User/JGH/Docs/Politics/ParlReview