#include "emu.h"
#include "video/taitoic.h"
#include "includes/volfied.h"
/******************************************************
INITIALISATION AND CLEAN-UP
******************************************************/
VIDEO_START( volfied )
{
volfied_state *state = machine.driver_data<volfied_state>();
state->m_video_ram = auto_alloc_array(machine, UINT16, 0x40000);
state->m_video_ctrl = 0;
state->m_video_mask = 0;
state->save_pointer(NAME(state->m_video_ram), 0x40000);
state->save_item(NAME(state->m_video_ctrl));
state->save_item(NAME(state->m_video_mask));
}
/*******************************************************
READ AND WRITE HANDLERS
*******************************************************/
READ16_HANDLER( volfied_video_ram_r )
{
volfied_state *state = space->machine().driver_data<volfied_state>();
return state->m_video_ram[offset];
}
WRITE16_HANDLER( volfied_video_ram_w )
{
volfied_state *state = space->machine().driver_data<volfied_state>();
mem_mask &= state->m_video_mask;
COMBINE_DATA(&state->m_video_ram[offset]);
}
WRITE16_HANDLER( volfied_video_ctrl_w )
{
volfied_state *state = space->machine().driver_data<volfied_state>();
COMBINE_DATA(&state->m_video_ctrl);
}
READ16_HANDLER( volfied_video_ctrl_r )
{
/* Could this be some kind of hardware collision detection? If bit 6 is
set the game will check for collisions with the large enemy, whereas
bit 5 does the same for small enemies. Bit 7 is also used although
its purpose is unclear. This register is usually read during a VBI
and stored in work RAM for later use. */
return 0x60;
}
WRITE16_HANDLER( volfied_video_mask_w )
{
volfied_state *state = space->machine().driver_data<volfied_state>();
COMBINE_DATA(&state->m_video_mask);
}
WRITE16_HANDLER( volfied_sprite_ctrl_w )
{
volfied_state *state = space->machine().driver_data<volfied_state>();
pc090oj_set_sprite_ctrl(state->m_pc090oj, (data & 0x3c) >> 2);
}
/*******************************************************
SCREEN REFRESH
*******************************************************/
static void refresh_pixel_layer( running_machine &machine, bitmap_t *bitmap )
{
int x, y;
/*********************************************************
VIDEO RAM has 2 screens x 256 rows x 512 columns x 16 bits
x--------------- select image
-x-------------- ? (used for 3-D corners)
--x------------- ? (used for 3-D walls)
---xxxx--------- image B
-------xxx------ palette index bits #8 to #A
----------x----- ?
-----------x---- ?
------------xxxx image A
'3d' corners & walls are made using unknown bits for each
line the player draws. However, on the pcb they just
appear as solid black. Perhaps it was prototype code that
was turned off at some stage.
*********************************************************/
volfied_state *state = machine.driver_data<volfied_state>();
UINT16* p = state->m_video_ram;
int width = machine.primary_screen->width();
int height = machine.primary_screen->height();
if (state->m_video_ctrl & 1)
p += 0x20000;
for (y = 0; y < height; y++)
{
for (x = 1; x < width + 1; x++) // Hmm, 1 pixel offset is needed to align properly with sprites
{
int color = (p[x] << 2) & 0x700;
if (p[x] & 0x8000)
{
color |= 0x800 | ((p[x] >> 9) & 0xf);
if (p[x] & 0x2000)
color &= ~0xf; /* hack */
}
else
color |= p[x] & 0xf;
*BITMAP_ADDR16(bitmap, y, x - 1) = color;
}
p += 512;
}
}
SCREEN_UPDATE( volfied )
{
volfied_state *state = screen->machine().driver_data<volfied_state>();
bitmap_fill(screen->machine().priority_bitmap, cliprect, 0);
refresh_pixel_layer(screen->machine(), bitmap);
pc090oj_draw_sprites(state->m_pc090oj, bitmap, cliprect, 0);
return 0;
}