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// license:BSD-3-Clause
// copyright-holders:Olivier Galibert
/*
 * Sega System 24
 *
 */

#include "emu.h"
#include "includes/segas24.h"

#include <algorithm>
#include <vector>


namespace {
	struct layer_sort {
		layer_sort(segas24_mixer_device &_mixer) : mixer(_mixer) { }

		bool operator()(int l1, int l2) {
			static const int default_pri[12] = { 0, 1, 2, 3, 4, 5, 6, 7, -4, -3, -2, -1 };
			int p1 = mixer.get_reg(l1) & 7;
			int p2 = mixer.get_reg(l2) & 7;
			if(p1 != p2)
				return p1 - p2 < 0;
			return default_pri[l2] - default_pri[l1] < 0;
		}

		segas24_mixer_device &mixer;
	};
}

uint32_t segas24_state::screen_update(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	if(m_vmixer->get_reg(13) & 1) {
		bitmap.fill(m_palette->black_pen());
		return 0;
	}

	screen.priority().fill(0);
	bitmap.fill(0, cliprect);

	std::vector<int> order;
	order.resize(12);
	for(int i=0; i<12; i++)
		order[i] = i;

	std::sort(order.begin(), order.end(), layer_sort(*m_vmixer));

	int spri[4];
	int level = 0;
	for(int i=0; i<12; i++)
		if(order[i] < 8)
			m_vtile->draw(screen, bitmap, cliprect, order[i], level, 0);
		else {
			spri[order[i]-8] = level;
			level++;
		}

	m_vsprite->draw(bitmap, cliprect, screen.priority(), spri);
	return 0;
}