path: root/graftest/graftest.c

#include "SDL.h"

/* atari GTIA palette, currently only for NTSC */
#include "colortable.h"

/* ROM data. rom.h and rom.c are generated from jumpmanjr.rom */
#include "rom.h"

/* load address of the ROM image */
#define ROM_START 0x8000

/* address within ROM where the level descriptors start */
#define LEVEL_BASE 0xa000

/* size of each level descriptor in the ROM */
#define LEVEL_SIZE 0x40

/* address within ROM where the GR.1/2 font starts */
#define FONT 0x9e00

/* where the level names start in the ROM */
#define LEVEL_NAMES 0xbb00

/* length of each level name */
#define LEVEL_NAME_SIZE 20

/* pixels to blit to our texture. modify these at will,
	they will be blitted once per frame. */
Uint32 texture_pixels[160 * 200];

/* color registers for the 4 playfield colors on each level.
	these hold indices into colortable. */
Uint8 color_regs[4];

/* read 1 byte at atari address from the ROM */
Uint8 peek(int addr) {
	return jumpmanjr_rom[addr - ROM_START];
}

/* read 1 word at atari address from the ROM */
Uint16 dpeek(int addr) {
	return (peek(addr) | (peek(addr + 1) << 8));
}

/* get a pointer within the ROM, give an atari address */
Uint8 *romptr(int addr) {
	return jumpmanjr_rom + (addr - ROM_START);
}

/* deltas are stored in ROM as twos-complement. we'll
	interpret them programatically instead of casting them
	to signed chars. */
int getdelta(Uint8 d) {
	return (d < 128) ? (d) : (d - 256);
}

/* clear out texture_pixels. generally only needs doing just before
	rendering a new level. */
void clear_pixels(void) {
	memset(texture_pixels, 0, sizeof(texture_pixels));
}

/* draw one copy of a shape (see ../level_maps.txt) */
void draw_shape(int shapeaddr, int xpos, int ypos) {
	int w = 0, xoffs = 0, yoffs = 0, c = 0;
	Uint8 *p = romptr(shapeaddr);
	ypos *= 2;

	fprintf(stderr, "draw_shape(%04x, %d, %d);\n", shapeaddr, xpos, ypos);

	while(1) {
		if(*p == 0xff) break;

		w = *p++;
		xoffs = *p++;
		yoffs = 2 * (*p++);
		for(c = 0; c < w; c++) {
			Uint8 reg = *p++;
			fprintf(stderr, "drawing pixel reg %d at %d, %d\n", reg, xpos + xoffs, ypos + yoffs);
			texture_pixels[xpos + xoffs + c + (160 * (ypos + yoffs))] = colortable[color_regs[reg]];
			texture_pixels[xpos + xoffs + c + (160 * (ypos + yoffs + 1))] = colortable[color_regs[reg]];
		}
	}
}

/* draw multiple copies of a shape, separated by dx/dy pixels */
void draw_shapes(int shapeaddr, int dx, int dy, int xpos, int ypos, int copies) {
	fprintf(stderr, "draw_shapes(%04x, %d, %d, %d, %d, %d);\n", shapeaddr, dx, dy, xpos, ypos, copies);
	while(copies--) {
		draw_shape(shapeaddr, xpos, ypos);
		xpos += dx;
		ypos += dy;
	}
}

/* draw map data. this just takes a rom address, so it can
	be used for map changes and such (doesn't have to be in the
	level descriptor even). basically this is a C port of draw_map
	from the disassembly. */
void draw_map(int addr) {
	Uint8 *p = romptr(addr);
	int shapeaddr = 0, dx = 0, dy = 0, xpos = 0, ypos = 0, copies = 0;

	while(1) {
		switch(*p) {
			case 0xff: /* end opcode */
				return;

			case 0xfe: /* set shape */
				shapeaddr = p[1] | ( p[2] << 8);
				p += 3;
				break;

			case 0xfd: /* set delta */
				dx = getdelta(p[1]);
				dy = getdelta(p[2]);
				p += 3;
				break;

			case 0xfc: /* jump */
				p = romptr(p[1] | ( p[2] << 8));
				break;

			default:  /* draw shape */
				xpos = p[0];
				ypos = p[1];
				copies = p[2];
				draw_shapes(shapeaddr, dx, dy, xpos, ypos, copies);
				p += 3;
		}
	}

}

/* there are only 64 chars in the font! */
void gr1_char(int x, int y, Uint8 color, Uint8 chr) {
	int row, pix;
	Uint8 *p;

	chr -= 32;
	chr %= 64;
	p = romptr(FONT + chr * 8);

	for(row = 0; row < 8; row++) {
		int b = *p++;
		for(pix = 0; pix < 8; pix++) {
			if(b & 0x80) {
				texture_pixels[x + pix + 160 * y] = colortable[color];
			} else {
				texture_pixels[x + pix + 160 * y] = colortable[0];
			}
			b <<= 1;
		}
		y++;
	}
}

void gr1_text(int x, int y, Uint8 color, int addr, int len) {
	Uint8 *p = romptr(addr);

	while(len--) {
		gr1_char(x, y, color, *p++);
		x += 8;
	}
}

/* draw the initial map for a level, given the *zero based* level
	number (range 0 to 11). eventually this should play the level
	intro music and mess with the color regs. */
void render_level(int levelnum) {
	int leveldesc = LEVEL_BASE + LEVEL_SIZE * levelnum;
	int mapaddr = dpeek(leveldesc + 22);
	int levelname = LEVEL_NAMES + LEVEL_NAME_SIZE * levelnum;
	Uint32 start = SDL_GetTicks();

	color_regs[0] = 0;
	color_regs[1] = peek(leveldesc + 47);
	color_regs[2] = peek(leveldesc + 48);
	color_regs[3] = peek(leveldesc + 49);

	clear_pixels();
	gr1_text(0, 178, 12, levelname, LEVEL_NAME_SIZE);

	fprintf(stderr, "leveldesc %04x, mapaddr %04x\n", leveldesc, mapaddr);
	draw_map(mapaddr);
	fprintf(stderr, "render_level(%d) took %dms\n", levelnum, SDL_GetTicks() - start);
}

int main(int argc, char **argv) {
	int lev = 0, done = 0, fullscreen = 0;
	Uint32 start, end, now;
	SDL_Window *window;
	SDL_Renderer *renderer;
	SDL_Texture *texture;
	SDL_Event event;

	if(SDL_Init(SDL_INIT_VIDEO) < 0) {
		SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't initialize SDL: %s", SDL_GetError());
		return 3;
	}

	if(SDL_CreateWindowAndRenderer(320, 200, 0, &window, &renderer)) {
		SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create window and renderer: %s", SDL_GetError());
		return 3;
	}

	texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB888, SDL_TEXTUREACCESS_STREAMING, 160, 200);

	SDL_RenderSetLogicalSize(renderer, 320, 200);

	render_level(lev);
	while(!done) {
		start = SDL_GetTicks();
		end = start + 167; // NTSC timing

		while(SDL_PollEvent(&event)) {
			if(event.type == SDL_QUIT) {
				break;
			}

			if(event.type == SDL_KEYDOWN) {
				switch(event.key.keysym.sym) {
					case SDLK_SPACE:
						lev++;
						if(lev == 12) lev = 0;
						render_level(lev);
						break;

					case SDLK_BACKSPACE:
						lev--;
						if(lev < 0) lev = 11;
						render_level(lev);
						break;

					case SDLK_ESCAPE:
						done = 1;
						break;

					case SDLK_RETURN:
						fullscreen = !fullscreen;
						SDL_SetWindowFullscreen(window, fullscreen ? SDL_WINDOW_FULLSCREEN_DESKTOP : 0);
						break;

					default:
						break;
				}
			}
		}

		SDL_SetRenderDrawColor(renderer, 0x00, 0x00, 0x00, 0x00);
		SDL_RenderClear(renderer);

		SDL_UpdateTexture(texture, NULL, texture_pixels, 160 * 4);
		SDL_RenderCopy(renderer, texture, NULL, NULL);
		SDL_RenderPresent(renderer);

		now = SDL_GetTicks();
		if(now < end) {
			SDL_Delay(end - now);
			// fprintf(stderr, "frame took %d ms\n", now - start);
		} else {
			// fprintf(stderr, "!! frame took too long, %d ms\n", now - end);
		}
	}

	SDL_DestroyTexture(texture);
	SDL_DestroyRenderer(renderer);
	SDL_DestroyWindow(window);

	SDL_Quit();

	return 0;
}