scrolling background

diff --git a/src/main.c b/src/main.c
index 9478ee8..81e60f8 100644 (file)
--- a/src/main.c
+++ b/src/main.c
@@ -30,6 +30,7 @@ int main(void)
        parts[0].update = dna_update;
        parts[1].start = simba_start;
        parts[1].update = simba_update;
+       parts[1].vblank = simba_vblank;
        part = parts;
 
        part->start();
@@ -44,6 +45,7 @@ int main(void)
                part->update();
 
                vdp_wait_vblank();
+               if(part->vblank) part->vblank();
                spr_submit();
                bnstate = pad_read(0);
                bndiff = bnstate ^ bnprev;

diff --git a/src/part_simba.c b/src/part_simba.c
index 7c2611d..a10e5fd 100644 (file)
--- a/src/part_simba.c
+++ b/src/part_simba.c
@@ -1,19 +1,22 @@
 #include <stdio.h>
 #include <stdint.h>
 #include "vdp.h"
+#include "pad.h"
 #include "parts.h"
 
 extern uint16_t simbabg_data[], simbabg_data_end[];
 extern unsigned char simbabg_cmap[], simbabg_cmap_end[];
 extern uint16_t simbabg_tmap[], simbabg_tmap_end[];
 
+static int scroll;
+
 void simba_init(void)
 {
        uint16_t *src;
 
        /* upload tiles */
        src = simbabg_data;
-       vdp_setup_addr(VDP_VRAM, 0);
+       vdp_setup_addr(VDP_VRAM, 32);   /* start from tile 1 32 bytes on */
        while(src < simbabg_data_end) {
                VDP_DATA = *src++;
        }
@@ -29,7 +32,7 @@ void simba_start(void)
        src = simbabg_tmap;
        vdp_setup_addr(VDP_VRAM, 0xe000);       /* nametable B */
        while(src < simbabg_tmap_end) {
-               VDP_DATA = VDP_TILENAME(*src++, 2, 0);
+               VDP_DATA = VDP_TILENAME(*src++ + 1, 2, 0);
        }
 
        /* setup colormaps */
@@ -38,8 +41,23 @@ void simba_start(void)
                vdp_setcolor(2, i, cptr[0] >> 4, cptr[1] >> 4, cptr[2] >> 4);
                cptr += 3;
        }
+
+       /* set scrolling to whole screen */
+       vdp_setreg(VDP_REG_MODE3, 0);
 }
 
 void simba_update(void)
 {
+       if(bnstate & PAD_LEFT) {
+               if(scroll > 0) scroll--;
+       } else if(bnstate & PAD_RIGHT) {
+               if(scroll < 511) scroll++;
+       }
+}
+
+void simba_vblank(void)
+{
+       vdp_setup_addr(VDP_VRAM, 0xf000);       /* hscroll table is at f000, see vdp.S */
+       VDP_DATA = 0;
+       VDP_DATA = scroll;
 }

diff --git a/src/parts.h b/src/parts.h
index 81ecaf6..40032f7 100644 (file)
--- a/src/parts.h
+++ b/src/parts.h
@@ -4,6 +4,7 @@
 struct part {
        void (*start)(void);
        void (*update)(void);
+       void (*vblank)(void);
 };
 
 extern struct part parts[];
@@ -15,5 +16,6 @@ void dna_update(void);
 void simba_init(void);
 void simba_start(void);
 void simba_update(void);
+void simba_vblank(void);
 
 #endif /* PARTS_H_ */