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8bitworkshop/presets/atari7800/dll.c
2019-12-16 11:17:57 -06:00

151 lines
3.4 KiB
C

#include "dll.h"
#include <string.h>
DLLEntry DLL[NUMSLOTS]; // display list list
byte DL[NUMSLOTS][SLOTSIZE]; // display list slots
byte DL_len[NUMSLOTS]; // current bytes in each slot
#ifdef DLSAVE
byte DL_save[NUMSLOTS]; // save lengths of each slot
#endif
byte slot0 = 0; // current page offset
// set display list list address registers
void dll_set_addr(const void* dpp) {
MARIA.DPPH = (word)dpp>>8;
MARIA.DPPL = (byte)dpp;
}
// clear the current page
void dll_clear() {
byte i;
for (i=slot0; i<slot0+SLOTSPERPAGE; i++) {
DL_len[i] = 0;
DL[i][1] = 0;
}
}
#ifdef DLSAVE
// save display list lengths of each slot
void dll_save() {
memcpy(DL_save, DL_len, sizeof(DL_save));
}
// restore display list lengths of current page
void dll_restore() {
byte i;
for (i=slot0; i<slot0+SLOTSPERPAGE; i++) {
DL_len[i] = DL_save[i]; // set slot length
DL[i][DL_len[i]+1] = 0; // set end marker
}
}
// restore all slots
void dll_restore_all() {
slot0 ^= SLOTSPERPAGE;
dll_restore();
slot0 ^= SLOTSPERPAGE;
dll_restore();
}
#endif
#ifdef DOUBLEBUFFER
// swap between pages
void dll_swap() {
slot0 ^= SLOTSPERPAGE;
if (!slot0) {
dll_set_addr(DLL+SLOTSPERPAGE);
} else {
dll_set_addr(DLL);
}
}
// copy offscreen page to current page
void dll_copy() {
memcpy(&DL[slot0], &DL[slot0 ^ SLOTSPERPAGE], SLOTSIZE*SLOTSPERPAGE);
memcpy(&DL_len[slot0], &DL_len[slot0 ^ SLOTSPERPAGE], SLOTSPERPAGE);
}
#endif
// set scroll position
void dll_set_scroll(byte y) {
static byte oldslot = 0;
byte slot = y / SLOTHEIGHT;
byte offset = 15 - (y & 15);
DLL[oldslot].offset_flags = DLL_FLAGS | (SLOTHEIGHT-1);
DLL[slot].offset_flags = DLL_FLAGS | offset;
dll_set_addr(DLL + slot);
oldslot = slot;
}
// allocate a given # of bytes in a slot
sbyte dll_bytesleft(byte slot) {
slot &= NUMSLOTS-1;
return SLOTSIZE - DL_len[slot];
}
// allocate a given # of bytes in a slot
void* dll_alloc(byte slot, byte len) {
byte dlofs;
register byte* dl;
slot &= NUMSLOTS-1;
dl = DL[slot];
dlofs = DL_len[slot];
DL_len[slot] += len;
dl[dlofs+len+1] = 0;
return &dl[dlofs];
}
// add a sprite to currently selected page
void dll_add_sprite(word addr, byte x, byte y, byte wpal) {
byte slot = (y / SLOTHEIGHT) | slot0;
register DL4Entry* dl = (DL4Entry*) dll_alloc(slot, 4);
dl->data_lo = (byte)addr;
dl->data_hi = (byte)(addr>>8) + (y & 15);
dl->xpos = x;
dl->width_pal = wpal;
if (y & 15) {
DL4Entry* dl2 = (DL4Entry*) dll_alloc(slot+1, 4);
*dl2 = *dl;
dl2->data_hi -= SLOTHEIGHT;
}
}
// add a string to currently selected page
// strings are aligned to top of slot
void dll_add_string(register const char* str, byte x, byte y, byte wpal) {
byte slot = (y / SLOTHEIGHT) | slot0;
register DL5Entry* dl = (DL5Entry*) dll_alloc(slot, 5);
dl->data_lo = (byte)str;
dl->data_hi = (word)str>>8;
dl->flags = DL5_INDIRECT;
dl->width_pal = wpal;
dl->xpos = x;
}
// set up display lists
void dll_setup() {
byte i;
byte* dlptr = &DL[0][0];
register DLLEntry *dll = &DLL[0];
for (i=0; i<NUMSLOTS; i++) {
dll->offset_flags = DLL_FLAGS | (SLOTHEIGHT-1);
dll->dl_hi = (word)dlptr>>8;
dll->dl_lo = (byte)dlptr;
dlptr += sizeof(DL[0]);
dll++;
}
dll_clear();
#ifdef DOUBLEBUFFER
dll_swap();
dll_clear();
dll_swap();
#else
dll_set_addr(DLL);
#endif
#ifdef DLSAVE
memset(DL_save, 0, sizeof(DL_save));
#endif
}