Need help for modifying an assembly routine

[bfg.gamepassion]

Hi,

 

i really need BIG help. In the Newcoleco coding library is a superb fonction called put_frame. Here is the source code :

 

; gpfram0.s

 

.module put_frame

 

; global from this code

.globl _put_frame

; put_frame (void *table, byte x, byte y, byte width, byte height)

 

.area _CODE

 

_put_frame:

exx

pop hl

exx

pop hl

pop de

pop bc

push bc

push de

push hl

exx

push hl

exx

push ix

push iy

call 0x080b

pop iy

pop ix

ret

 

It take a memory zone (*table) of characters of widht and height, an display it at position x,y. If it's out of the screen, it's okay, it don't crash anything.

 

I really can't read assembly. But What i'd like to to, is if this routine want to put a char

at a position x > 24, then, it don't do put the char.

 

Can somebody change easily this assembly routine to do that ?! Or is it not possible because it call a bios routine at 0X080b ???

 

By the way, there is the put_frame0 routine, who don't check "boundary" ... Maybe it's possible to modify ...

 

; gp9fram0.s

 

.module put_frame0

 

.globl calc_offset

 

; global from this code

.globl _put_frame0

; put_frame0 (void *table, byte x, byte y, byte width, byte height)

 

.area _CODE

 

_put_frame0:

exx

pop hl

exx

pop hl

pop de

call calc_offset

pop bc

push bc

push de

push hl

exx

push hl

exx

loop:

push bc

push de

push hl

ld b,#0

xor a

call 0x1fdf

pop hl

pop de

pop bc

push bc

ld b,#0

add hl,bc

ex de,hl

ld bc,#0x0020

add hl,bc

ex de,hl

pop bc

dec b

ld a,b

jr nz,loop

ret

Edited December 8, 2011 by bfg.gamepassion

[youki]

<ul>

<li>Hi Michel,</li>

</ul>

<p>The put_frame , as you stated, make call to coleco bios routine put_frame , so you won't be able to modify the routine . (Or do you want create your own bios on chip and patch your coleco???)</p>

<p> </p>

<p>concerning the put_frame0 , i have to check .  But i didn't not understand what you want do exactly?  I think put_frame don't put the char if x is > at 24 already no?</p>

<p> </p>

<p>Contact me per mail ou on my forums , to explain me your problem. </p>

<p> </p>

<p> </p>

 

[hardhat]

That first routine just puts the parameters in the correct registers and calls the OS7 function to do the work. The second function just calls write_vram() for each line. So it could be modified to do the clipping I suppose.

 

The best way to do this, is to do the clipping at column 24 in C (I call it maxx), or use double buffering, and draw to the off screen buffer where ever you like, then draw your menu or whatever at column 24 and beyond, then show the whole screen at once.

 

To do the clipping in C you'd say:

 

void put_frame_clipped(void *table, byte maxx, byte x, byte y, byte width, byte height)
{
byte j;
byte w=width;
if( x>=maxx) return; /* off screen. */
if( x+w>maxx) w=maxx-x;
for( j=y; j<y+height && j<24; j++) {
   put_frame( table, x, j, w, 1);
   table+=width;
}
}

This could use write_vram even more efficiently, if speed is an issue.

 

For double buffering, you set it up with:

void setup()
{
screen( name_table1, name_table2);
}

 

Then draw what you like, then redraw the menu at column 24 and beyond, and your drawing will only be visible when you call:

swap_screen();

[bfg.gamepassion]

Thanks for advices !!

 

Here's the routine i've decided to use :

 

void put_frameS(byte *tile,char x,char y,char w,char h)
{
char i;
char cw; // calculated weight
//char px;
int offset_deplacement;
char tmp;

if (x>23) return;
if (y>23) return;

tmp = x+w;

if (tmp<24) // Il n'y aura pas de clipping à droite
{
 if ( (x>=0) && ((y+h)<24) && (y>=0) )  // Et il n'y aura pas de clipping tout court
 {
  put_frame0(tile,x,y,w,h);
 }
 else // Il y aura un clipping à gauche
 {
  put_frame(tile,x,y,w,h);
 }

 return;
}

 offset_deplacement = 0;

 // Si on dépasse du crop
 // Il faut calculer la nouvelle largeur
 if ((tmp) > 24)
  cw = 24-x;
 else
  cw = w;

 for (i=0;i<h;i++)
 {
  tmp = y+i; // Ligne courant de l'écran à écrire
  if ((tmp)>24) return;
  if ((tmp)>=0)
  {
   put_vram(chrtab+((tmp)<<5)+x,tile+offset_deplacement,cw);
  }
 
  offset_deplacement += w;
 }

}

 

It mixed 3 "techniques" to have the more optimized speed possible i think.

[hardhat]

Looks good. That should work well.