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// license:BSD-3-Clause
// copyright-holders:Nicola Salmoria,Chris Hardy
/***************************************************************************

  video.c

  Functions to emulate the video hardware of the machine.

***************************************************************************/

#include "emu.h"
#include "video/resnet.h"
#include "includes/circusc.h"


/***************************************************************************

  Convert the color PROMs into a more useable format.

  Circus Charlie has one 32x8 palette PROM and two 256x4 lookup table PROMs
  (one for characters, one for sprites).
  The palette PROM is connected to the RGB output this way:

  bit 7 -- 220 ohm resistor  -- BLUE
        -- 470 ohm resistor  -- BLUE
        -- 220 ohm resistor  -- GREEN
        -- 470 ohm resistor  -- GREEN
        -- 1  kohm resistor  -- GREEN
        -- 220 ohm resistor  -- RED
        -- 470 ohm resistor  -- RED
  bit 0 -- 1  kohm resistor  -- RED

***************************************************************************/

void circusc_state::circusc_palette(palette_device &palette) const
{
	const uint8_t *color_prom = memregion("proms")->base();
	static constexpr int resistances_rg[3] = { 1000, 470, 220 };
	static constexpr int resistances_b [2] = { 470, 220 };

	// compute the color output resistor weights
	double rweights[3], gweights[3], bweights[2];
	compute_resistor_weights(0, 255, -1.0,
			3, &resistances_rg[0], rweights, 0, 0,
			3, &resistances_rg[0], gweights, 0, 0,
			2, &resistances_b[0],  bweights, 0, 0);

	// create a lookup table for the palette
	for (int i = 0; i < 0x20; i++)
	{
		int bit0, bit1, bit2;

		// red component
		bit0 = BIT(color_prom[i], 0);
		bit1 = BIT(color_prom[i], 1);
		bit2 = BIT(color_prom[i], 2);
		int const r = combine_weights(rweights, bit0, bit1, bit2);

		// green component
		bit0 = BIT(color_prom[i], 3);
		bit1 = BIT(color_prom[i], 4);
		bit2 = BIT(color_prom[i], 5);
		int const g = combine_weights(gweights, bit0, bit1, bit2);

		// blue component
		bit0 = BIT(color_prom[i], 6);
		bit1 = BIT(color_prom[i], 7);
		int const b = combine_weights(bweights, bit0, bit1);

		palette.set_indirect_color(i, rgb_t(r, g, b));
	}

	// color_prom now points to the beginning of the lookup table
	color_prom += 32;

	// characters map to the upper 16 palette entries
	for (int i = 0; i < 0x100; i++)
	{
		uint8_t const ctabentry = color_prom[i] & 0x0f;
		palette.set_pen_indirect(i, ctabentry + 0x10);
	}

	// sprites map to the lower 16 palette entries
	for (int i = 0x100; i < 0x200; i++)
	{
		uint8_t const ctabentry = color_prom[i] & 0x0f;
		palette.set_pen_indirect(i, ctabentry);
	}
}



/***************************************************************************

  Callbacks for the TileMap code

***************************************************************************/

TILE_GET_INFO_MEMBER(circusc_state::get_tile_info)
{
	uint8_t const attr = m_colorram[tile_index];
	tileinfo.category = BIT(attr, 4);

	SET_TILE_INFO_MEMBER(
			0,
			m_videoram[tile_index] + ((attr & 0x20) << 3),
			attr & 0x0f,
			TILE_FLIPYX((attr & 0xc0) >> 6));
}



/***************************************************************************

  Start the video hardware emulation.

***************************************************************************/

void circusc_state::video_start()
{
	m_bg_tilemap = &machine().tilemap().create(*m_gfxdecode, tilemap_get_info_delegate(*this, FUNC(circusc_state::get_tile_info)), TILEMAP_SCAN_ROWS, 8, 8, 32, 32);

	m_bg_tilemap->set_scroll_cols(32);

	save_item(NAME(m_spritebank));
}



/***************************************************************************

  Memory handlers

***************************************************************************/

WRITE8_MEMBER(circusc_state::circusc_videoram_w)
{
	m_videoram[offset] = data;
	m_bg_tilemap->mark_tile_dirty(offset);
}

WRITE8_MEMBER(circusc_state::circusc_colorram_w)
{
	m_colorram[offset] = data;
	m_bg_tilemap->mark_tile_dirty(offset);
}

WRITE_LINE_MEMBER(circusc_state::flipscreen_w)
{
	flip_screen_set(state);
}

WRITE_LINE_MEMBER(circusc_state::spritebank_w)
{
	m_spritebank = state;
}



/***************************************************************************

  Display refresh

***************************************************************************/

void circusc_state::draw_sprites( bitmap_ind16 &bitmap, const rectangle &cliprect )
{
	int offs;
	uint8_t *sr = m_spritebank ? m_spriteram : m_spriteram_2;

	for (offs = 0; offs < m_spriteram.bytes(); offs += 4)
	{
		int code = sr[offs + 0] + 8 * (sr[offs + 1] & 0x20);
		int color = sr[offs + 1] & 0x0f;
		int sx = sr[offs + 2];
		int sy = sr[offs + 3];
		int flipx = sr[offs + 1] & 0x40;
		int flipy = sr[offs + 1] & 0x80;

		if (flip_screen())
		{
			sx = 240 - sx;
			sy = 240 - sy;
			flipx = !flipx;
			flipy = !flipy;
		}


		m_gfxdecode->gfx(1)->transmask(bitmap,cliprect,
				code, color,
				flipx,flipy,
				sx,sy,
				m_palette->transpen_mask(*m_gfxdecode->gfx(1), color, 0));
	}
}

uint32_t circusc_state::screen_update_circusc(screen_device &screen, bitmap_ind16 &bitmap, const rectangle &cliprect)
{
	int i;

	for (i = 0; i < 10; i++)
		m_bg_tilemap->set_scrolly(i, 0);
	for (i = 10; i < 32; i++)
		m_bg_tilemap->set_scrolly(i, *m_scroll);

	bitmap.fill(0, cliprect);
	m_bg_tilemap->draw(screen, bitmap, cliprect, 1, 0);
	draw_sprites(bitmap, cliprect);
	m_bg_tilemap->draw(screen, bitmap, cliprect, 0, 0);
	return 0;
}