/***************************************************************************
Atari Sky Raider video emulation
***************************************************************************/
#include "emu.h"
#include "includes/skyraid.h"
VIDEO_START( skyraid )
{
skyraid_state *state = machine.driver_data<skyraid_state>();
state->m_helper = auto_bitmap_alloc(machine, 128, 240, machine.primary_screen->format());
}
static void draw_text(running_machine &machine, bitmap_t* bitmap, const rectangle* cliprect)
{
skyraid_state *state = machine.driver_data<skyraid_state>();
const UINT8* p = state->m_alpha_num_ram;
int i;
for (i = 0; i < 4; i++)
{
int x;
int y;
y = 136 + 16 * (i ^ 1);
for (x = 0; x < bitmap->width; x += 16)
drawgfx_transpen(bitmap, cliprect, machine.gfx[0], *p++, 0, 0, 0, x, y, 0);
}
}
static void draw_terrain(running_machine &machine, bitmap_t* bitmap, const rectangle *cliprect)
{
skyraid_state *state = machine.driver_data<skyraid_state>();
const UINT8* p = machine.region("user1")->base();
int x;
int y;
for (y = 0; y < bitmap->height; y++)
{
int offset = (16 * state->m_scroll + 16 * ((y + 1) / 2)) & 0x7FF;
x = 0;
while (x < bitmap->width)
{
UINT8 val = p[offset++];
int color = val / 32;
int count = val % 32;
rectangle r;
r.min_y = y;
r.min_x = x;
r.max_y = y + 1;
r.max_x = x + 31 - count;
bitmap_fill(bitmap, &r, color);
x += 32 - count;
}
}
}
static void draw_sprites(running_machine &machine, bitmap_t* bitmap, const rectangle* cliprect)
{
skyraid_state *state = machine.driver_data<skyraid_state>();
int i;
for (i = 0; i < 4; i++)
{
int code = state->m_obj_ram[8 + 2 * i + 0] & 15;
int flag = state->m_obj_ram[8 + 2 * i + 1] & 15;
int vert = state->m_pos_ram[8 + 2 * i + 0];
int horz = state->m_pos_ram[8 + 2 * i + 1];
vert -= 31;
if (flag & 1)
drawgfx_transpen(bitmap, cliprect, machine.gfx[1],
code ^ 15, code >> 3, 0, 0,
horz / 2, vert, 2);
}
}
static void draw_missiles(running_machine &machine, bitmap_t* bitmap, const rectangle* cliprect)
{
skyraid_state *state = machine.driver_data<skyraid_state>();
int i;
/* hardware is restricted to one sprite per scanline */
for (i = 0; i < 4; i++)
{
int code = state->m_obj_ram[2 * i + 0] & 15;
int vert = state->m_pos_ram[2 * i + 0];
int horz = state->m_pos_ram[2 * i + 1];
vert -= 15;
horz -= 31;
drawgfx_transpen(bitmap, cliprect, machine.gfx[2],
code ^ 15, 0, 0, 0,
horz / 2, vert, 0);
}
}
static void draw_trapezoid(running_machine &machine, bitmap_t* dst, bitmap_t* src)
{
const UINT8* p = machine.region("user2")->base();
int x;
int y;
for (y = 0; y < dst->height; y++)
{
UINT16* pSrc = BITMAP_ADDR16(src, y, 0);
UINT16* pDst = BITMAP_ADDR16(dst, y, 0);
int x1 = 0x000 + p[(y & ~1) + 0];
int x2 = 0x100 + p[(y & ~1) + 1];
for (x = x1; x < x2; x++)
pDst[x] = pSrc[128 * (x - x1) / (x2 - x1)];
}
}
SCREEN_UPDATE( skyraid )
{
skyraid_state *state = screen->machine().driver_data<skyraid_state>();
bitmap_fill(bitmap, cliprect, 0);
draw_terrain(screen->machine(), state->m_helper, NULL);
draw_sprites(screen->machine(), state->m_helper, NULL);
draw_missiles(screen->machine(), state->m_helper, NULL);
draw_trapezoid(screen->machine(), bitmap, state->m_helper);
draw_text(screen->machine(), bitmap, cliprect);
return 0;
}