void draw_stars(bitmap_ind16 bitmap, rectangle cliprect)
{
/* draw the stars */
/* $a005 controls the stars ON/OFF */
if (m_videolatch.target.q5_r() == 1)
{
int star_cntr;
int set_a, set_b;
/* two sets of stars controlled by these bits */
set_a = m_videolatch.target.q3_r();
set_b = m_videolatch.target.q4_r() | 2;
for (star_cntr = 0; star_cntr < MAX_STARS; star_cntr++)
{
int x;
int y;
if ((set_a == s_star_seed_tab[star_cntr].set) || (set_b == s_star_seed_tab[star_cntr].set))
{
x = (int)((s_star_seed_tab[star_cntr].x + m_stars_scrollx) % 256 + 16);
y = (int)((112 + s_star_seed_tab[star_cntr].y + m_stars_scrolly) % 256);
/* 112 is a tweak to get alignment about perfect */
if (cliprect.contains(x, y))
{
//bitmap.pix16(y, x) = STARS_COLOR_BASE + m_star_seed_tab[ star_cntr ].col;
RawBuffer bitmapBuffer;
UInt32 bitmapBufferOffset = bitmap.pix16(out bitmapBuffer, y, x);
bitmapBuffer.set_uint16((int)bitmapBufferOffset, (UInt16)(STARS_COLOR_BASE + s_star_seed_tab[star_cntr].col));
}
}
}
}
}
public void draw_starfield(bitmap_ind16 bitmap, rectangle cliprect, int flip)
{
if (m_enable == 0)
{
return;
}
uint16_t pre_vis_cycle_count = m_pre_vis_cycle_count;
uint16_t post_vis_cycle_count = m_post_vis_cycle_count;
// Advance the LFSR during the pre-visible portion of the frame
do
{
m_lfsr = get_next_lfsr_state(m_lfsr);
} while ((--pre_vis_cycle_count) != 0);
// Now we are in visible portion of the frame - Output all LFSR hits here
for (int y = m_offset_y; y < VISIBLE_LINES + m_offset_y; y++)
{
for (int x = m_offset_x; x < STARFIELD_PIXEL_WIDTH + m_offset_x; x++)
{
// Check lfsr for hit
if ((m_lfsr & LFSR_HIT_MASK) == LFSR_HIT_VALUE)
{
uint8_t star_set = (uint8_t)bitswap(m_lfsr, 10, 8);
if ((m_set_a == star_set) || (m_set_b == star_set))
{
// don't draw the stars that are beyond the X limit
if (x < m_limit_x)
{
int dx = x;
if (flip != 0)
{
dx += 64;
}
if (cliprect.contains(dx, y))
{
uint8_t color;
color = (uint8_t)((m_lfsr >> 5) & 0x7);
color |= (uint8_t)((m_lfsr << 3) & 0x18);
color |= (uint8_t)((m_lfsr << 2) & 0x20);
color = (uint8_t)((~color) & 0x3F);
bitmap.pix(y, dx)[0] = (uint16_t)(STARS_COLOR_BASE + color);
}
}
}
}
// Advance LFSR
m_lfsr = get_next_lfsr_state(m_lfsr);
}
}
// Advance the LFSR during the post-visible portion of the frame
do
{
m_lfsr = get_next_lfsr_state(m_lfsr);
} while ((--post_vis_cycle_count) != 0);
}
