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video.c
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video.c
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// Commander X16 Emulator
// Copyright (c) 2019 Michael Steil
// Copyright (c) 2020 Frank van den Hoef
// All rights reserved. License: 2-clause BSD
#include "video.h"
#include "memory.h"
#include "ps2.h"
#include "glue.h"
#include "debugger.h"
#include "keyboard.h"
#include "gif.h"
#include "vera_spi.h"
#include "vera_psg.h"
#include "vera_pcm.h"
#include "icon.h"
#include "sdcard.h"
#include <limits.h>
#ifdef __EMSCRIPTEN__
#include "emscripten.h"
#endif
#define ADDR_VRAM_START 0x00000
#define ADDR_VRAM_END 0x20000
#define ADDR_PSG_START 0x1F9C0
#define ADDR_PSG_END 0x1FA00
#define ADDR_PALETTE_START 0x1FA00
#define ADDR_PALETTE_END 0x1FC00
#define ADDR_SPRDATA_START 0x1FC00
#define ADDR_SPRDATA_END 0x20000
#define NUM_SPRITES 128
// both VGA and NTSC
#define SCAN_WIDTH 800
#define SCAN_HEIGHT 525
// VGA
#define VGA_FRONT_PORCH_X 16
#define VGA_FRONT_PORCH_Y 10
#define VGA_PIXEL_FREQ 25.175
// NTSC: 262.5 lines per frame, lower field first
#define NTSC_FRONT_PORCH_X 80
#define NTSC_FRONT_PORCH_Y 22
#define NTSC_PIXEL_FREQ (15.750 * 800 / 1000)
#define TITLE_SAFE_X 0.067
#define TITLE_SAFE_Y 0.05
// visible area we're drawing
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
#define SCREEN_RAM_OFFSET 0x00000
#ifdef __APPLE__
#define LSHORTCUT_KEY SDL_SCANCODE_LGUI
#define RSHORTCUT_KEY SDL_SCANCODE_RGUI
#else
#define LSHORTCUT_KEY SDL_SCANCODE_LCTRL
#define RSHORTCUT_KEY SDL_SCANCODE_RCTRL
#endif
// When rendering a layer line, we can amortize some of the cost by calculating multiple pixels at a time.
#define LAYER_PIXELS_PER_ITERATION 8
static SDL_Window *window;
static SDL_Renderer *renderer;
static SDL_Texture *sdlTexture;
static bool is_fullscreen = false;
static uint8_t video_ram[0x20000];
static uint8_t palette[256 * 2];
static uint8_t sprite_data[128][8];
// I/O registers
static uint32_t io_addr[2];
static uint8_t io_rddata[2];
static uint8_t io_inc[2];
static uint8_t io_addrsel;
static uint8_t io_dcsel;
static uint8_t ien;
static uint8_t isr;
static uint16_t irq_line;
static uint8_t reg_layer[2][7];
static uint8_t reg_composer[8];
static uint8_t layer_line[2][SCREEN_WIDTH];
static uint8_t sprite_line_col[SCREEN_WIDTH];
static uint8_t sprite_line_z[SCREEN_WIDTH];
static uint8_t sprite_line_mask[SCREEN_WIDTH];
static uint8_t sprite_line_collisions;
static bool layer_line_enable[2];
static bool sprite_line_enable;
float scan_pos_x;
uint16_t scan_pos_y;
int frame_count = 0;
static uint8_t framebuffer[SCREEN_WIDTH * SCREEN_HEIGHT * 4];
static GifWriter gif_writer;
static const uint16_t default_palette[] = {
0x000,0xfff,0x800,0xafe,0xc4c,0x0c5,0x00a,0xee7,0xd85,0x640,0xf77,0x333,0x777,0xaf6,0x08f,0xbbb,0x000,0x111,0x222,0x333,0x444,0x555,0x666,0x777,0x888,0x999,0xaaa,0xbbb,0xccc,0xddd,0xeee,0xfff,0x211,0x433,0x644,0x866,0xa88,0xc99,0xfbb,0x211,0x422,0x633,0x844,0xa55,0xc66,0xf77,0x200,0x411,0x611,0x822,0xa22,0xc33,0xf33,0x200,0x400,0x600,0x800,0xa00,0xc00,0xf00,0x221,0x443,0x664,0x886,0xaa8,0xcc9,0xfeb,0x211,0x432,0x653,0x874,0xa95,0xcb6,0xfd7,0x210,0x431,0x651,0x862,0xa82,0xca3,0xfc3,0x210,0x430,0x640,0x860,0xa80,0xc90,0xfb0,0x121,0x343,0x564,0x786,0x9a8,0xbc9,0xdfb,0x121,0x342,0x463,0x684,0x8a5,0x9c6,0xbf7,0x120,0x241,0x461,0x582,0x6a2,0x8c3,0x9f3,0x120,0x240,0x360,0x480,0x5a0,0x6c0,0x7f0,0x121,0x343,0x465,0x686,0x8a8,0x9ca,0xbfc,0x121,0x242,0x364,0x485,0x5a6,0x6c8,0x7f9,0x020,0x141,0x162,0x283,0x2a4,0x3c5,0x3f6,0x020,0x041,0x061,0x082,0x0a2,0x0c3,0x0f3,0x122,0x344,0x466,0x688,0x8aa,0x9cc,0xbff,0x122,0x244,0x366,0x488,0x5aa,0x6cc,0x7ff,0x022,0x144,0x166,0x288,0x2aa,0x3cc,0x3ff,0x022,0x044,0x066,0x088,0x0aa,0x0cc,0x0ff,0x112,0x334,0x456,0x668,0x88a,0x9ac,0xbcf,0x112,0x224,0x346,0x458,0x56a,0x68c,0x79f,0x002,0x114,0x126,0x238,0x24a,0x35c,0x36f,0x002,0x014,0x016,0x028,0x02a,0x03c,0x03f,0x112,0x334,0x546,0x768,0x98a,0xb9c,0xdbf,0x112,0x324,0x436,0x648,0x85a,0x96c,0xb7f,0x102,0x214,0x416,0x528,0x62a,0x83c,0x93f,0x102,0x204,0x306,0x408,0x50a,0x60c,0x70f,0x212,0x434,0x646,0x868,0xa8a,0xc9c,0xfbe,0x211,0x423,0x635,0x847,0xa59,0xc6b,0xf7d,0x201,0x413,0x615,0x826,0xa28,0xc3a,0xf3c,0x201,0x403,0x604,0x806,0xa08,0xc09,0xf0b
};
uint8_t video_space_read(uint32_t address);
static void video_space_read_range(uint8_t* dest, uint32_t address, uint32_t size);
static void refresh_palette();
void
video_reset()
{
// init I/O registers
memset(io_addr, 0, sizeof(io_addr));
memset(io_inc, 0, sizeof(io_inc));
io_addrsel = 0;
io_dcsel = 0;
io_rddata[0] = 0;
io_rddata[1] = 0;
ien = 0;
isr = 0;
irq_line = 0;
// init Layer registers
memset(reg_layer, 0, sizeof(reg_layer));
// init composer registers
memset(reg_composer, 0, sizeof(reg_composer));
reg_composer[1] = 128; // hscale = 1.0
reg_composer[2] = 128; // vscale = 1.0
reg_composer[5] = 640 >> 2;
reg_composer[7] = 480 >> 1;
// init sprite data
memset(sprite_data, 0, sizeof(sprite_data));
// copy palette
memcpy(palette, default_palette, sizeof(palette));
for (int i = 0; i < 256; i++) {
palette[i * 2 + 0] = default_palette[i] & 0xff;
palette[i * 2 + 1] = default_palette[i] >> 8;
}
refresh_palette();
// fill video RAM with random data
for (int i = 0; i < 128 * 1024; i++) {
video_ram[i] = rand();
}
sprite_line_collisions = 0;
scan_pos_x = 0;
scan_pos_y = 0;
psg_reset();
pcm_reset();
}
bool
video_init(int window_scale, char *quality)
{
uint32_t window_flags = SDL_WINDOW_ALLOW_HIGHDPI;
#ifdef __EMSCRIPTEN__
// Setting this flag would render the web canvas outside of its bounds on high dpi screens
window_flags &= ~SDL_WINDOW_ALLOW_HIGHDPI;
#endif
video_reset();
SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, quality);
SDL_CreateWindowAndRenderer(SCREEN_WIDTH * window_scale, SCREEN_HEIGHT * window_scale, window_flags, &window, &renderer);
#ifndef __MORPHOS__
SDL_SetWindowResizable(window, true);
#endif
SDL_RenderSetLogicalSize(renderer, SCREEN_WIDTH, SCREEN_HEIGHT);
sdlTexture = SDL_CreateTexture(renderer,
SDL_PIXELFORMAT_RGB888,
SDL_TEXTUREACCESS_STREAMING,
SCREEN_WIDTH, SCREEN_HEIGHT);
SDL_SetWindowTitle(window, "Commander X16");
SDL_SetWindowIcon(window, CommanderX16Icon());
SDL_ShowCursor(SDL_DISABLE);
if (record_gif != RECORD_GIF_DISABLED) {
if (!strcmp(gif_path+strlen(gif_path)-5, ",wait")) {
// wait for POKE
record_gif = RECORD_GIF_PAUSED;
// move the string terminator to remove the ",wait"
gif_path[strlen(gif_path)-5] = 0;
} else {
// start now
record_gif = RECORD_GIF_ACTIVE;
}
if (!GifBegin(&gif_writer, gif_path, SCREEN_WIDTH, SCREEN_HEIGHT, 1, 8, false)) {
record_gif = RECORD_GIF_DISABLED;
}
}
if (debugger_enabled) {
DEBUGInitUI(renderer);
}
return true;
}
struct video_layer_properties
{
uint8_t color_depth;
uint32_t map_base;
uint32_t tile_base;
bool text_mode;
bool text_mode_256c;
bool tile_mode;
bool bitmap_mode;
uint16_t hscroll;
uint16_t vscroll;
uint8_t mapw_log2;
uint8_t maph_log2;
uint16_t tilew;
uint16_t tileh;
uint8_t tilew_log2;
uint8_t tileh_log2;
uint16_t mapw_max;
uint16_t maph_max;
uint16_t tilew_max;
uint16_t tileh_max;
uint16_t layerw_max;
uint16_t layerh_max;
uint8_t tile_size_log2;
int min_eff_x;
int max_eff_x;
uint8_t bits_per_pixel;
uint8_t first_color_pos;
uint8_t color_mask;
uint8_t color_fields_max;
};
struct video_layer_properties layer_properties[2];
static int
calc_layer_eff_x(const struct video_layer_properties *props, const int x)
{
return (x + props->hscroll) & (props->layerw_max);
}
static int
calc_layer_eff_y(const struct video_layer_properties *props, const int y)
{
return (y + props->vscroll) & (props->layerh_max);
}
static uint32_t
calc_layer_map_addr_base2(const struct video_layer_properties *props, const int eff_x, const int eff_y)
{
// Slightly faster on some platforms because we know that tilew and tileh are powers of 2.
return props->map_base + ((((eff_y >> props->tileh_log2) << props->mapw_log2) + (eff_x >> props->tilew_log2)) << 1);
}
//TODO: Unused in all current cases. Delete? Or leave commented as a reminder?
//static uint32_t
//calc_layer_map_addr(struct video_layer_properties *props, int eff_x, int eff_y)
//{
// return props->map_base + ((eff_y / props->tileh) * props->mapw + (eff_x / props->tilew)) * 2;
//}
static void
refresh_layer_properties(const uint8_t layer)
{
struct video_layer_properties* props = &layer_properties[layer];
uint16_t prev_layerw_max = props->layerw_max;
uint16_t prev_hscroll = props->hscroll;
props->color_depth = reg_layer[layer][0] & 0x3;
props->map_base = reg_layer[layer][1] << 9;
props->tile_base = (reg_layer[layer][2] & 0xFC) << 9;
props->bitmap_mode = (reg_layer[layer][0] & 0x4) != 0;
props->text_mode = (props->color_depth == 0) && !props->bitmap_mode;
props->text_mode_256c = (reg_layer[layer][0] & 8) != 0;
props->tile_mode = !props->bitmap_mode && !props->text_mode;
if (!props->bitmap_mode) {
props->hscroll = reg_layer[layer][3] | (reg_layer[layer][4] & 0xf) << 8;
props->vscroll = reg_layer[layer][5] | (reg_layer[layer][6] & 0xf) << 8;
} else {
props->hscroll = 0;
props->vscroll = 0;
}
uint16_t mapw = 0;
uint16_t maph = 0;
props->tilew = 0;
props->tileh = 0;
if (props->tile_mode || props->text_mode) {
props->mapw_log2 = 5 + ((reg_layer[layer][0] >> 4) & 3);
props->maph_log2 = 5 + ((reg_layer[layer][0] >> 6) & 3);
mapw = 1 << props->mapw_log2;
maph = 1 << props->maph_log2;
// Scale the tiles or text characters according to TILEW and TILEH.
props->tilew_log2 = 3 + (reg_layer[layer][2] & 1);
props->tileh_log2 = 3 + ((reg_layer[layer][2] >> 1) & 1);
props->tilew = 1 << props->tilew_log2;
props->tileh = 1 << props->tileh_log2;
} else if (props->bitmap_mode) {
// bitmap mode is basically tiled mode with a single huge tile
props->tilew = (reg_layer[layer][2] & 1) ? 640 : 320;
props->tileh = SCREEN_HEIGHT;
}
// We know mapw, maph, tilew, and tileh are powers of two in all cases except bitmap modes, and any products of that set will be powers of two,
// so there's no need to modulo against them if we have bitmasks we can bitwise-and against.
props->mapw_max = mapw - 1;
props->maph_max = maph - 1;
props->tilew_max = props->tilew - 1;
props->tileh_max = props->tileh - 1;
props->layerw_max = (mapw * props->tilew) - 1;
props->layerh_max = (maph * props->tileh) - 1;
// Find min/max eff_x for bulk reading in tile data during draw.
if (prev_layerw_max != props->layerw_max || prev_hscroll != props->hscroll) {
int min_eff_x = INT_MAX;
int max_eff_x = INT_MIN;
for (int x = 0; x < SCREEN_WIDTH; ++x) {
int eff_x = calc_layer_eff_x(props, x);
if (eff_x < min_eff_x) {
min_eff_x = eff_x;
}
if (eff_x > max_eff_x) {
max_eff_x = eff_x;
}
}
props->min_eff_x = min_eff_x;
props->max_eff_x = max_eff_x;
}
props->bits_per_pixel = 1 << props->color_depth;
props->tile_size_log2 = props->tilew_log2 + props->tileh_log2 + props->color_depth - 3;
props->first_color_pos = 8 - props->bits_per_pixel;
props->color_mask = (1 << props->bits_per_pixel) - 1;
props->color_fields_max = (8 >> props->color_depth) - 1;
}
struct video_sprite_properties
{
int8_t sprite_zdepth;
uint8_t sprite_collision_mask;
int16_t sprite_x;
int16_t sprite_y;
uint8_t sprite_width_log2;
uint8_t sprite_height_log2;
uint8_t sprite_width;
uint8_t sprite_height;
bool hflip;
bool vflip;
uint8_t color_mode;
uint32_t sprite_address;
uint16_t palette_offset;
};
struct video_sprite_properties sprite_properties[128];
static void
refresh_sprite_properties(const uint16_t sprite)
{
struct video_sprite_properties* props = &sprite_properties[sprite];
props->sprite_zdepth = (sprite_data[sprite][6] >> 2) & 3;
props->sprite_collision_mask = sprite_data[sprite][6] & 0xf0;
props->sprite_x = sprite_data[sprite][2] | (sprite_data[sprite][3] & 3) << 8;
props->sprite_y = sprite_data[sprite][4] | (sprite_data[sprite][5] & 3) << 8;
props->sprite_width_log2 = (((sprite_data[sprite][7] >> 4) & 3) + 3);
props->sprite_height_log2 = ((sprite_data[sprite][7] >> 6) + 3);
props->sprite_width = 1 << props->sprite_width_log2;
props->sprite_height = 1 << props->sprite_height_log2;
// fix up negative coordinates
if (props->sprite_x >= 0x400 - props->sprite_width) {
props->sprite_x -= 0x400;
}
if (props->sprite_y >= 0x400 - props->sprite_height) {
props->sprite_y -= 0x400;
}
props->hflip = sprite_data[sprite][6] & 1;
props->vflip = (sprite_data[sprite][6] >> 1) & 1;
props->color_mode = (sprite_data[sprite][1] >> 7) & 1;
props->sprite_address = sprite_data[sprite][0] << 5 | (sprite_data[sprite][1] & 0xf) << 13;
props->palette_offset = (sprite_data[sprite][7] & 0x0f) << 4;
}
struct video_palette
{
uint32_t entries[256];
bool dirty;
};
struct video_palette video_palette;
static void
refresh_palette() {
const uint8_t out_mode = reg_composer[0] & 3;
const bool chroma_disable = (reg_composer[0] >> 2) & 1;
for (int i = 0; i < 256; ++i) {
uint8_t r;
uint8_t g;
uint8_t b;
if (out_mode == 0) {
// video generation off
// -> show blue screen
r = 0;
g = 0;
b = 255;
} else {
uint16_t entry = palette[i * 2] | palette[i * 2 + 1] << 8;
r = ((entry >> 8) & 0xf) << 4 | ((entry >> 8) & 0xf);
g = ((entry >> 4) & 0xf) << 4 | ((entry >> 4) & 0xf);
b = (entry & 0xf) << 4 | (entry & 0xf);
if (chroma_disable) {
r = g = b = (r + b + g) / 3;
}
}
video_palette.entries[i] = (uint32_t)(r << 16) | ((uint32_t)g << 8) | ((uint32_t)b);
}
video_palette.dirty = false;
}
static void
expand_4bpp_data(uint8_t *dst, const uint8_t *src, int dst_size)
{
while (dst_size >= 2) {
*dst = (*src) >> 4;
++dst;
*dst = (*src) & 0xf;
++dst;
++src;
dst_size -= 2;
}
}
static void
render_sprite_line(const uint16_t y)
{
memset(sprite_line_col, 0, SCREEN_WIDTH);
memset(sprite_line_z, 0, SCREEN_WIDTH);
memset(sprite_line_mask, 0, SCREEN_WIDTH);
uint16_t sprite_budget = 800 + 1;
for (int i = 0; i < NUM_SPRITES; i++) {
// one clock per lookup
sprite_budget--; if (sprite_budget == 0) break;
const struct video_sprite_properties *props = &sprite_properties[i];
if (props->sprite_zdepth == 0) {
continue;
}
// check whether this line falls within the sprite
if (y < props->sprite_y || y >= props->sprite_y + props->sprite_height) {
continue;
}
const uint16_t eff_sy = props->vflip ? ((props->sprite_height - 1) - (y - props->sprite_y)) : (y - props->sprite_y);
int16_t eff_sx = (props->hflip ? (props->sprite_width - 1) : 0);
const int16_t eff_sx_incr = props->hflip ? -1 : 1;
const uint8_t *bitmap_data = video_ram + props->sprite_address + (eff_sy << (props->sprite_width_log2 - (1 - props->color_mode)));
uint8_t unpacked_sprite_line[64];
if (props->color_mode == 0) {
// 4bpp
expand_4bpp_data(unpacked_sprite_line, bitmap_data, props->sprite_width);
} else {
// 8bpp
memcpy(unpacked_sprite_line, bitmap_data, props->sprite_width);
}
for (uint16_t sx = 0; sx < props->sprite_width; ++sx) {
const uint16_t line_x = props->sprite_x + sx;
if (line_x >= SCREEN_WIDTH) {
eff_sx += eff_sx_incr;
continue;
}
// one clock per fetched 32 bits
if (!(sx & 3)) {
sprite_budget--; if (sprite_budget == 0) break;
}
// one clock per rendered pixel
sprite_budget--; if (sprite_budget == 0) break;
const uint8_t col_index = unpacked_sprite_line[eff_sx];
eff_sx += eff_sx_incr;
// palette offset
if (col_index > 0) {
sprite_line_collisions |= sprite_line_mask[line_x] & props->sprite_collision_mask;
sprite_line_mask[line_x] |= props->sprite_collision_mask;
if (props->sprite_zdepth > sprite_line_z[line_x]) {
sprite_line_col[line_x] = col_index + props->palette_offset;
sprite_line_z[line_x] = props->sprite_zdepth;
}
}
}
}
}
static void
render_layer_line_text(uint8_t layer, uint16_t y)
{
const struct video_layer_properties *props = &layer_properties[layer];
const uint8_t max_pixels_per_byte = (8 >> props->color_depth) - 1;
const int eff_y = calc_layer_eff_y(props, y);
const int yy = eff_y & props->tileh_max;
// additional bytes to reach the correct line of the tile
const uint32_t y_add = (yy << props->tilew_log2) >> 3;
const uint32_t map_addr_begin = calc_layer_map_addr_base2(props, props->min_eff_x, eff_y);
const uint32_t map_addr_end = calc_layer_map_addr_base2(props, props->max_eff_x, eff_y);
const int size = (map_addr_end - map_addr_begin) + 2;
uint8_t tile_bytes[512]; // max 256 tiles, 2 bytes each.
video_space_read_range(tile_bytes, map_addr_begin, size);
uint32_t tile_start;
uint8_t fg_color;
uint8_t bg_color;
uint8_t s;
uint8_t color_shift;
{
const int eff_x = calc_layer_eff_x(props, 0);
const int xx = eff_x & props->tilew_max;
// extract all information from the map
const uint32_t map_addr = calc_layer_map_addr_base2(props, eff_x, eff_y) - map_addr_begin;
const uint8_t tile_index = tile_bytes[map_addr];
const uint8_t byte1 = tile_bytes[map_addr + 1];
if (!props->text_mode_256c) {
fg_color = byte1 & 15;
bg_color = byte1 >> 4;
} else {
fg_color = byte1;
bg_color = 0;
}
// offset within tilemap of the current tile
tile_start = tile_index << props->tile_size_log2;
// additional bytes to reach the correct column of the tile
const uint16_t x_add = xx >> 3;
const uint32_t tile_offset = tile_start + y_add + x_add;
s = video_space_read(props->tile_base + tile_offset);
color_shift = max_pixels_per_byte - xx;
}
// Render tile line.
for (int x = 0; x < SCREEN_WIDTH; x++) {
// Scrolling
const int eff_x = calc_layer_eff_x(props, x);
const int xx = eff_x & props->tilew_max;
if ((eff_x & 0x7) == 0) {
if ((eff_x & props->tilew_max) == 0) {
// extract all information from the map
const uint32_t map_addr = calc_layer_map_addr_base2(props, eff_x, eff_y) - map_addr_begin;
const uint8_t tile_index = tile_bytes[map_addr];
const uint8_t byte1 = tile_bytes[map_addr + 1];
if (!props->text_mode_256c) {
fg_color = byte1 & 15;
bg_color = byte1 >> 4;
} else {
fg_color = byte1;
bg_color = 0;
}
// offset within tilemap of the current tile
tile_start = tile_index << props->tile_size_log2;
}
// additional bytes to reach the correct column of the tile
const uint16_t x_add = xx >> 3;
const uint32_t tile_offset = tile_start + y_add + x_add;
s = video_space_read(props->tile_base + tile_offset);
color_shift = max_pixels_per_byte;
}
// convert tile byte to indexed color
const uint8_t col_index = (s >> color_shift) & 1;
--color_shift;
layer_line[layer][x] = col_index ? fg_color : bg_color;
}
}
static void
render_layer_line_tile(uint8_t layer, uint16_t y)
{
struct video_layer_properties *props = &layer_properties[layer];
const uint8_t max_pixels_per_byte = (8 >> props->color_depth) - 1;
const int eff_y = calc_layer_eff_y(props, y);
const uint8_t yy = eff_y & props->tileh_max;
const uint8_t yy_flip = yy ^ props->tileh_max;
const uint32_t y_add = (yy << (props->tilew_log2 + props->color_depth - 3));
const uint32_t y_add_flip = (yy_flip << (props->tilew_log2 + props->color_depth - 3));
const uint32_t map_addr_begin = calc_layer_map_addr_base2(props, props->min_eff_x, eff_y);
const uint32_t map_addr_end = calc_layer_map_addr_base2(props, props->max_eff_x, eff_y);
const int size = (map_addr_end - map_addr_begin) + 2;
uint8_t tile_bytes[512]; // max 256 tiles, 2 bytes each.
video_space_read_range(tile_bytes, map_addr_begin, size);
uint8_t palette_offset;
bool vflip;
bool hflip;
uint32_t tile_start;
uint8_t s;
uint8_t color_shift;
int8_t color_shift_incr;
{
const int eff_x = calc_layer_eff_x(props, 0);
// extract all information from the map
const uint32_t map_addr = calc_layer_map_addr_base2(props, eff_x, eff_y) - map_addr_begin;
const uint8_t byte0 = tile_bytes[map_addr];
const uint8_t byte1 = tile_bytes[map_addr + 1];
// Tile Flipping
vflip = (byte1 >> 3) & 1;
hflip = (byte1 >> 2) & 1;
palette_offset = byte1 & 0xf0;
// offset within tilemap of the current tile
const uint16_t tile_index = byte0 | ((byte1 & 3) << 8);
tile_start = tile_index << props->tile_size_log2;
color_shift_incr = hflip ? props->bits_per_pixel : -props->bits_per_pixel;
int xx = eff_x & props->tilew_max;
if (hflip) {
xx = xx ^ (props->tilew_max);
color_shift = 0;
} else {
color_shift = props->first_color_pos;
}
// additional bytes to reach the correct column of the tile
uint16_t x_add = (xx << props->color_depth) >> 3;
uint32_t tile_offset = tile_start + (vflip ? y_add_flip : y_add) + x_add;
s = video_space_read(props->tile_base + tile_offset);
}
// Render tile line.
for (int x = 0; x < SCREEN_WIDTH; x++) {
const int eff_x = calc_layer_eff_x(props, x);
if ((eff_x & max_pixels_per_byte) == 0) {
if ((eff_x & props->tilew_max) == 0) {
// extract all information from the map
const uint32_t map_addr = calc_layer_map_addr_base2(props, eff_x, eff_y) - map_addr_begin;
const uint8_t byte0 = tile_bytes[map_addr];
const uint8_t byte1 = tile_bytes[map_addr + 1];
// Tile Flipping
vflip = (byte1 >> 3) & 1;
hflip = (byte1 >> 2) & 1;
palette_offset = byte1 & 0xf0;
// offset within tilemap of the current tile
const uint16_t tile_index = byte0 | ((byte1 & 3) << 8);
tile_start = tile_index << props->tile_size_log2;
color_shift_incr = hflip ? props->bits_per_pixel : -props->bits_per_pixel;
}
int xx = eff_x & props->tilew_max;
if (hflip) {
xx = xx ^ (props->tilew_max);
color_shift = 0;
} else {
color_shift = props->first_color_pos;
}
// additional bytes to reach the correct column of the tile
const uint16_t x_add = (xx << props->color_depth) >> 3;
const uint32_t tile_offset = tile_start + (vflip ? y_add_flip : y_add) + x_add;
s = video_space_read(props->tile_base + tile_offset);
}
// convert tile byte to indexed color
uint8_t col_index = (s >> color_shift) & props->color_mask;
color_shift += color_shift_incr;
// Apply Palette Offset
if (palette_offset && col_index > 0 && col_index < 16) {
col_index += palette_offset;
}
layer_line[layer][x] = col_index;
}
}
static void
render_layer_line_bitmap(uint8_t layer, uint16_t y)
{
struct video_layer_properties *props = &layer_properties[layer];
int yy = y % props->tileh;
// additional bytes to reach the correct line of the tile
uint32_t y_add = (yy * props->tilew * props->bits_per_pixel) >> 3;
// Render tile line.
for (int x = 0; x < SCREEN_WIDTH; x++) {
int xx = x % props->tilew;
// extract all information from the map
uint8_t palette_offset = reg_layer[layer][4] & 0xf;
// additional bytes to reach the correct column of the tile
uint16_t x_add = (xx * props->bits_per_pixel) >> 3;
uint32_t tile_offset = y_add + x_add;
uint8_t s = video_space_read(props->tile_base + tile_offset);
// convert tile byte to indexed color
uint8_t col_index = (s >> (props->first_color_pos - ((xx & props->color_fields_max) << props->color_depth))) & props->color_mask;
// Apply Palette Offset
if (palette_offset && col_index > 0 && col_index < 16) {
col_index += palette_offset << 4;
}
layer_line[layer][x] = col_index;
}
}
static uint8_t calculate_line_col_index(uint8_t spr_zindex, uint8_t spr_col_index, uint8_t l1_col_index, uint8_t l2_col_index)
{
uint8_t col_index = 0;
switch (spr_zindex) {
case 3:
col_index = spr_col_index ? spr_col_index : (l2_col_index ? l2_col_index : l1_col_index);
break;
case 2:
col_index = l2_col_index ? l2_col_index : (spr_col_index ? spr_col_index : l1_col_index);
break;
case 1:
col_index = l2_col_index ? l2_col_index : (l1_col_index ? l1_col_index : spr_col_index);
break;
case 0:
col_index = l2_col_index ? l2_col_index : l1_col_index;
break;
}
return col_index;
}
static void
render_line(uint16_t y)
{
uint8_t out_mode = reg_composer[0] & 3;
uint8_t border_color = reg_composer[3];
uint16_t hstart = reg_composer[4] << 2;
uint16_t hstop = reg_composer[5] << 2;
uint16_t vstart = reg_composer[6] << 1;
uint16_t vstop = reg_composer[7] << 1;
int eff_y = (reg_composer[2] * (y - vstart)) >> 7;
uint8_t dc_video = reg_composer[0];
layer_line_enable[0] = dc_video & 0x10;
layer_line_enable[1] = dc_video & 0x20;
sprite_line_enable = dc_video & 0x40;
if (sprite_line_enable) {
render_sprite_line(eff_y);
}
if (warp_mode && (frame_count & 63)) {
// sprites were needed for the collision IRQ, but we can skip
// everything else if we're in warp mode, most of the time
return;
}
if (layer_line_enable[0]) {
if (layer_properties[0].text_mode) {
render_layer_line_text(0, eff_y);
} else if (layer_properties[0].bitmap_mode) {
render_layer_line_bitmap(0, eff_y);
} else {
render_layer_line_tile(0, eff_y);
}
}
if (layer_line_enable[1]) {
if (layer_properties[1].text_mode) {
render_layer_line_text(1, eff_y);
} else if (layer_properties[1].bitmap_mode) {
render_layer_line_bitmap(1, eff_y);
} else {
render_layer_line_tile(1, eff_y);
}
}
uint8_t col_line[SCREEN_WIDTH];
if (video_palette.dirty) {
refresh_palette();
}
// If video output is enabled, calculate color indices for line.
if (out_mode != 0) {
uint8_t spr_col_index[LAYER_PIXELS_PER_ITERATION];
uint8_t l1_col_index[LAYER_PIXELS_PER_ITERATION];
uint8_t l2_col_index[LAYER_PIXELS_PER_ITERATION];
uint8_t spr_zindex[LAYER_PIXELS_PER_ITERATION];
memset(spr_col_index, 0, sizeof(spr_col_index));
memset(l1_col_index, 0, sizeof(l1_col_index));
memset(l2_col_index, 0, sizeof(l2_col_index));
memset(spr_zindex, 0, sizeof(spr_zindex));
// Calculate color without border.
for (uint16_t x = 0; x < SCREEN_WIDTH; x+=LAYER_PIXELS_PER_ITERATION) {
uint8_t col_index[LAYER_PIXELS_PER_ITERATION];
memset(col_index, 0, sizeof(col_index));
int eff_x[LAYER_PIXELS_PER_ITERATION];
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
eff_x[i] = (reg_composer[1] * (x + i - hstart)) >> 7;
}
if (sprite_line_enable) {
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
spr_col_index[i] = sprite_line_col[eff_x[i]];
}
}
if (layer_line_enable[0]) {
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
l1_col_index[i] = layer_line[0][eff_x[i]];
}
}
if (layer_line_enable[1]) {
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
l2_col_index[i] = layer_line[1][eff_x[i]];
}
}
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
spr_zindex[i] = sprite_line_z[eff_x[i]];
}
bool same_sprite = true;
for (int i = 1; same_sprite && i < LAYER_PIXELS_PER_ITERATION; ++i) {
same_sprite &= spr_zindex[0] == spr_zindex[i];
}
if (same_sprite) {
switch (spr_zindex[0]) {
case 3:
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
col_index[i] = spr_col_index[i] ? spr_col_index[i] : (l2_col_index[i] ? l2_col_index[i] : l1_col_index[i]);
}
break;
case 2:
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
col_index[i] = l2_col_index[i] ? l2_col_index[i] : (spr_col_index[i] ? spr_col_index[i] : l1_col_index[i]);
}
break;
case 1:
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
col_index[i] = l2_col_index[i] ? l2_col_index[i] : (l1_col_index[i] ? l1_col_index[i] : spr_col_index[i]);
}
break;
case 0:
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
col_index[i] = l2_col_index[i] ? l2_col_index[i] : l1_col_index[i];
}
break;
}
} else {
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
col_index[i] = calculate_line_col_index(spr_zindex[i], spr_col_index[i], l1_col_index[i], l2_col_index[i]);
}
}
for (int i = 0; i < LAYER_PIXELS_PER_ITERATION; ++i) {
col_line[x+i] = col_index[i];
}
}
// Add border after if required.
if (y < vstart || y > vstop) {
uint32_t border_fill = border_color;
border_fill = border_fill | (border_fill << 8);
border_fill = border_fill | (border_fill << 16);
memset(col_line, border_fill, SCREEN_WIDTH);
} else {
for (uint16_t x = 0; x < hstart; ++x) {
col_line[x] = border_color;
}
for (uint16_t x = hstop; x < SCREEN_WIDTH; ++x) {
col_line[x] = border_color;
}
}
}
// Look up all color indices.
uint32_t* framebuffer4_begin = ((uint32_t*)framebuffer) + (y * SCREEN_WIDTH);
{
uint32_t* framebuffer4 = framebuffer4_begin;
for (uint16_t x = 0; x < SCREEN_WIDTH; x++) {
*framebuffer4++ = video_palette.entries[col_line[x]];
}
}
// NTSC overscan
if (out_mode == 2) {
uint32_t* framebuffer4 = framebuffer4_begin;
for (uint16_t x = 0; x < SCREEN_WIDTH; x++)
{
if (x < SCREEN_WIDTH * TITLE_SAFE_X ||
x > SCREEN_WIDTH * (1 - TITLE_SAFE_X) ||
y < SCREEN_HEIGHT * TITLE_SAFE_Y ||
y > SCREEN_HEIGHT * (1 - TITLE_SAFE_Y)) {
// Divide RGB elements by 4.
*framebuffer4 &= 0x00fcfcfc;
*framebuffer4 >>= 2;
}
framebuffer4++;
}
}
}
bool
video_step(float mhz)
{
uint8_t out_mode = reg_composer[0] & 3;
bool new_frame = false;
float advance = ((out_mode & 2) ? NTSC_PIXEL_FREQ : VGA_PIXEL_FREQ) / mhz;
scan_pos_x += advance;
if (scan_pos_x > SCAN_WIDTH) {
scan_pos_x -= SCAN_WIDTH;
uint16_t front_porch = (out_mode & 2) ? NTSC_FRONT_PORCH_Y : VGA_FRONT_PORCH_Y;
uint16_t y = scan_pos_y - front_porch;