// Sweeps one scanline with one style index. The style ID can be
// determined by calling style().
//template<class Scanline>
public bool sweep_scanline(IScanlineCache sl, int style_idx)
{
int scan_y = m_scan_y - 1;
if (scan_y > m_Rasterizer.max_y()) return false;
sl.reset_spans();
int master_alpha = aa_mask;
if (style_idx < 0)
{
style_idx = 0;
}
else
{
style_idx++;
master_alpha = m_master_alpha[(int)(m_ast[(int)style_idx] + m_min_style - 1)];
}
style_info st = m_styles[m_ast[style_idx]];
int num_cells = (int)st.num_cells;
int CellOffset = st.start_cell;
cell_aa cell = m_cells[CellOffset];
int cover = 0;
while (num_cells-- != 0)
{
int alpha;
int x = cell.x;
int area = cell.area;
cover += cell.cover;
cell = m_cells[++CellOffset];
if (area != 0)
{
alpha = calculate_alpha((cover << (poly_subpixel_shift + 1)) - area,
master_alpha);
sl.add_cell(x, alpha);
x++;
}
if (num_cells != 0 && cell.x > x)
{
alpha = calculate_alpha(cover << (poly_subpixel_shift + 1),
master_alpha);
if (alpha != 0)
{
sl.add_span(x, cell.x - x, alpha);
}
}
}
if (sl.num_spans() == 0) return false;
sl.finalize(scan_y);
return true;
}