Scroll DXDraw

I don''t fully understand what you''re after...
but here''s how you would so scrolling:

Let''s say this is your drawing routine

for J := 0 to 100 do
for I := 0 to 100 do
Draw(I * 30, J * 30, MyTile);

so if you wanted to implement scrolling, you''d alter it like this:

for J := 0 to 100 do
for I := 0 to 100 do
Draw(I * 30 + ScrollX, J * 30 + ScrollY, MyTile);

Now if you scroll to the left, you would increase ScrollX. If you scroll to the right you would decrease ScrollX.
If you scroll up, you would increase ScrollY and if you want to sroll down you would decrease ScrollY.

Make sure you only draw what''s on the screen by altering your drawing routine like this

for J := 0 to 100 do
for I := 0 to 100 do
if (I * 30 >= 0) and (I * 30 + 30 <= DXDraw.Width) and (J * 30 > 0) and (J * 30 + 30 <= DXDraw.Height) then
Draw(I * 30 + ScrollX, J * 30 + ScrollY, MyTile);

hope that helped.

You might find the modified line

Draw((I * 30 + ScrollX) mod DXDraw.Width, (J * 30 + ScrollY) mod DXDraw.Height, MyTile);

executes a little faster and, instead of directly decrementing the scroll variables (mod does not like negative values), writing

ScrollX:=(ScrollX+DXDraw.Width -1) mod DXDraw.Width;
and
ScrollY:=(ScrollY+DXDraw.Height -1) mod DXDraw.Height;

will do the job.

Hope I haven't muddied the water.





Stevie

Don't follow me, I'm lost.
(Editted to correct a typo)

[edited by - Stevie56 on March 9, 2003 7:56:45 AM]

I think you may find the following link

http://www.gameprogrammer.net/index.php?fuseaction=tutorial.tutorial3

Covers your question.



Stevie

Don''t follow me, I''m lost.

Scroll the surface.

WhiteBlobs