[hatari-devel] 2 more falcon programs running better : Pinball dream and Killing impact

[Laurent Sallafranque <laurent.sallafranque@xxxxxxx>]

Hi,

I post here my current search for sharing with you.

I've worked on a memory address that is not used by the videl for now : 
the videl address counter.

At least, 2 programs write into it : killing impact and pinball dreams.

By adding only 3 lines of code into videl.c, I manage to remove 
(partially for now) the screen garbage for these 2 programs.

Now, the screens are correctly rendered and the games are playable.


With killing impact, there's another problem with vertical display (I 
think the screen may be doubled on real Falcon ?)


With Pinball Dreams, the game change twice the counter address : 1st 
time for score display and 2nd time for the game itself (that's why 
there's still garbage at bottom of the table now, the screen  should be 
displayed lower (the upper part of the screen should display the score 
panel).


For now, you can consider it as a proof of concept.

It renders better the 2 games, but that's not perfect.

And when you quit the games, the hack still operate, but it should not.

The good way to solve it would be to improve thye videl

The bad way (but with a good result) would just consist to add a new 
variable to videl, reset it to 0 at the brginning of a VBL and if a 
program changes the counter, set this variable to 1. like this, the hack 
would work cleanly.

Should I complete the temporary hack (for better rendering but not 
perfect) or shouldn't be add such a bad hack that may be hard to 
understand later is someone works on videl later (except if we add a ton 
of comments to explain it).

I'm interrested in your point of view.

Regards

Laurent


The proof of concept patch : diff -u

diff --git a/src/falcon/videl.c b/src/falcon/videl.c
index cf5ce874..e4019413 100644
--- a/src/falcon/videl.c
+++ b/src/falcon/videl.c
@@ -942,6 +942,10 @@ bool VIDEL_renderScreen(void)
        bool change = false;

        Uint32 videoBase = VIDEL_getVideoramAddress();
+       Uint32 videocounter = (IoMem_ReadByte(0xff8205)<<16) + 
(IoMem_ReadByte(0xff8207)<<8) + IoMem_ReadByte(0xff8209);
+
+       if (videocounter != 0)
+               videoBase = videocounter;

        if (vw > 0 && vw != videl.save_scrWidth) {
                LOG_TRACE(TRACE_VIDEL, "Videl : width change from %d to 
%d\n", videl.save_scrWidth, vw);