Adding a gap buffer to a text editor

x0.c

#include <SDL2/SDL.h>
#include <stdio.h>

int error(char *msg, const char *err) {
	printf("Error %s: %s\n", msg, err);
	return 0;
}

#define HOR 32
#define VER 16
#define PAD 8

#define TEXTSZ 1024 * 32

char text[TEXTSZ+1];
int text_len = 0;
int cursor = 0;

void pushchar(char c) {
	int i;
	if(text_len >= TEXTSZ)
		return;
	for(i = text_len-1; i >= cursor; --i)
		text[i + 1] = text[i];
	text_len++;
	text[cursor] = c;
	cursor++;
}

void left() {
	if(cursor > 0) --cursor;
}

void right() {
	if(cursor < text_len-1) ++cursor;
}

int loadtxt(char *name) {
	char line[256];
	FILE *f = fopen(name, "r");
	if(!f) return error("Load", "Invalid input file");
	text_len = 0;
	while(fgets(line, 256, f)) {
		int i = 0;
		char c;
		while((c = line[i++]))
			pushchar(c);
	}
	/* reset cursor */
	cursor = 0;
	printf("Loaded: %s\n", name);
	fclose(f);
	return 1;
}

int cursorcol() {
	int result = 0;
	int c;
	for(c = cursor-1; c >= 0; --c) {
		if(text[c] == '\n') break;
		++result;
	}
	return result;
}

void down() {
	int col = cursorcol();
	/* skip rest of line */
	for(; cursor < text_len && text[cursor] != '\n'; ++cursor)
		right();
	/* scan forward on next line */
	right();
	for(; col > 0 && cursor < text_len && text[cursor] != '\n'; --col)
		right();
}

void up() {
	int col = cursorcol();
	/* scan back to end of previous line */
	left();
	while(cursor > 0 && text[cursor] != '\n')
		left();
	/* scan back to start of previous line */
	left();
	while(cursor > 0 && text[cursor] != '\n')
		left();
	/* scan forward on previous line */
	for(; col > 0 && cursor < text_len && text[cursor] != '\n'; --col)
		right();
}

int WIDTH = 8 * HOR + PAD * 2;
int HEIGHT = 8 * (VER + 2) + PAD * 2;
int FPS = 30, GUIDES = 1, ZOOM = 2;

Uint8 chrbuf[2048];
SDL_Window *gWindow = NULL;
SDL_Renderer *gRenderer = NULL;
SDL_Texture *gTexture = NULL;
Uint32 *pixels;

void clear(Uint32 *dst) {
	int i, j;
	for(i = 0; i < HEIGHT; i++)
		for(j = 0; j < WIDTH; j++)
			dst[i * WIDTH + j] = 0;
}

void putpixel(Uint32 *dst, int x, int y) {
	if(x >= 0 && x < WIDTH - 8 && y >= 0 && y < HEIGHT - 8)
		dst[(y + PAD) * WIDTH + (x + PAD)] = 0xffffffff;
}

void drawletter(Uint32 *dst, int x, int y, int id) {
	int v, h, offset = id * 16;
	for(v = 0; v < 8; v++)
		for(h = 0; h < 8; h++) {
			int px = (x * 8) + (8 - h);
			int py = (y * 8) + v;
			int ch1 = chrbuf[offset + v];
			int ch2 = chrbuf[offset + v + 8];
			int clr = ((ch1 >> h) & 0x1) + (((ch2 >> h) & 0x1) << 1);
			if(clr)
				putpixel(dst, px, py);
		}
}

void drawbody(Uint32 *dst) {
	int i, x = 0, line = 0;
	for(i = 0; i < text_len; ++i) {
		char c = text[i];
		drawletter(dst, x, line, (int)c);
		x++;
		if(c == '\n') {
			x = 0;
			line++;
		}
	}
}

void redraw(Uint32 *dst) {
	clear(dst);
	drawbody(dst);
	SDL_UpdateTexture(gTexture, NULL, dst, WIDTH * sizeof(Uint32));
	SDL_RenderClear(gRenderer);
	SDL_RenderCopy(gRenderer, gTexture, NULL, NULL);
	SDL_RenderPresent(gRenderer);
}

void dotext(SDL_Event *event) {
	int i;
	for(i = 0; i < SDL_TEXTINPUTEVENT_TEXT_SIZE; ++i) {
		char c = event->text.text[i];
		if(c < ' ' || c > '~') break;
		pushchar(c);
	}
	redraw(pixels);
}

void dokey(SDL_Event *event) {
	switch(event->key.keysym.sym) {
	case SDLK_RETURN: pushchar('\n'); break;
	case SDLK_DOWN: down(); break;
	case SDLK_UP: up(); break;
	case SDLK_LEFT: left(); break;
	case SDLK_RIGHT: right(); break;
	}
}

int loadchr(FILE *f) {
	if(!f) return error("Load", "Invalid font file");
	if(!fread(chrbuf, sizeof(chrbuf), 1, f))
		return error("Load", "Invalid font file size");
	puts("Load: Complete");
	fclose(f);
	return 1;
}

int init(void) {
	if(SDL_Init(SDL_INIT_VIDEO) < 0)
		return error("Init", SDL_GetError());
	gWindow = SDL_CreateWindow("Moogle",
		SDL_WINDOWPOS_UNDEFINED,
		SDL_WINDOWPOS_UNDEFINED,
		WIDTH * ZOOM,
		HEIGHT * ZOOM,
		SDL_WINDOW_SHOWN);
	if(gWindow == NULL)
		return error("Window", SDL_GetError());
	gRenderer = SDL_CreateRenderer(gWindow, -1, 0);
	if(gRenderer == NULL)
		return error("Renderer", SDL_GetError());
	gTexture = SDL_CreateTexture(gRenderer,
		SDL_PIXELFORMAT_ARGB8888,
		SDL_TEXTUREACCESS_STATIC,
		WIDTH,
		HEIGHT);
	if(gTexture == NULL)
		return error("Texture", SDL_GetError());
	pixels = (Uint32 *)malloc(WIDTH * HEIGHT * sizeof(Uint32));
	if(pixels == NULL)
		return error("Pixels", "Failed to allocate memory");
	clear(pixels);
	return 1;
}

void quit(void) {
	free(pixels);
	SDL_DestroyTexture(gTexture);
	gTexture = NULL;
	SDL_DestroyRenderer(gRenderer);
	gRenderer = NULL;
	SDL_DestroyWindow(gWindow);
	gWindow = NULL;
	SDL_Quit();
	exit(0);
}

int main(int argc, char *argv[]) {
	int ticknext = 0;
	if(!init())
		return error("Init", "Failure");
	loadchr(fopen("type.chr", "r"));
	if(argc > 1)
		loadtxt(argv[1]);
	redraw(pixels);
	while(1) {
		int tick = SDL_GetTicks();
		SDL_Event event;
		if(tick < ticknext)
			SDL_Delay(ticknext - tick);
		ticknext = tick + (1000 / FPS);
		while(SDL_PollEvent(&event) != 0) {
			switch(event.type) {
			case SDL_QUIT: quit(); break;
			case SDL_TEXTINPUT: dotext(&event); break;
			case SDL_KEYDOWN: dokey(&event); break;
			}
		}
	}
	quit();
	return 0;
}

x1.c

#include <SDL2/SDL.h>
#include <stdio.h>

int error(char *msg, const char *err) {
	printf("Error %s: %s\n", msg, err);
	return 0;
}

#define HOR 32
#define VER 16
#define PAD 8

#define TEXTSZ 1024 * 32

char text_before[TEXTSZ+1];  /* index 0 = start of file */
int text_before_len = 0;  /* where the next char typed will go */
char text_after[TEXTSZ+1];  /* index 0 = end of file */
int text_after_len = 0;

void pushchar(char c) {
	if(text_before_len + text_after_len >= TEXTSZ)
		return;
	text_before[text_before_len++] = c;
}

void left() {
	if(text_before_len == 0) return;
	text_after[text_after_len] = text_before[text_before_len-1];
	++text_after_len;
	--text_before_len;
	text_before[text_before_len] = '\0';
}

void right() {
	if(text_after_len == 0) return;
	text_before[text_before_len] = text_after[text_after_len-1];
	++text_before_len;
	--text_after_len;
	text_before[text_after_len] = '\0';
}

int loadtxt(char *name) {
	char line[256];
	FILE *f = fopen(name, "r");
	if(!f) return error("Load", "Invalid input file");
	text_before_len = 0;
	text_after_len = 0;
	while(fgets(line, 256, f)) {
		int i = 0;
		char c;
		while((c = line[i++]))
			pushchar(c);
	}
	/* reset cursor */
	while(text_before_len > 0)
		left();
	printf("Loaded: %s\n", name);
	fclose(f);
	return 1;
}

int cursorcol() {
	int result = 0;
	int c;
	for(c = text_before_len-1; c >= 0; --c) {
		if(text_before[c] == '\n') break;
		++result;
	}
	return result;
}

void down() {
	int col = cursorcol();
	/* skip rest of line */
	while(text_after_len > 0 && text_after[text_after_len-1] != '\n')
		right();
	/* scan forward on next line */
	right();
	for(; col > 0 && text_after_len > 0 && text_after[text_after_len-1] != '\n'; --col)
		right();
}

void up() {
	int col = cursorcol();
	/* scan back to end of previous line */
	left();
	while(text_before_len > 0 && text_before[text_before_len-1] != '\n')
		left();
	/* scan back to start of previous line */
	left();
	while(text_before_len > 0 && text_before[text_before_len-1] != '\n')
		left();
	/* scan forward on previous line */
	for(; col > 0 && text_after_len > 0 && text_after[text_after_len-1] != '\n'; --col)
		right();
}

int WIDTH = 8 * HOR + PAD * 2;
int HEIGHT = 8 * (VER + 2) + PAD * 2;
int FPS = 30, GUIDES = 1, ZOOM = 2;

Uint8 chrbuf[2048];
SDL_Window *gWindow = NULL;
SDL_Renderer *gRenderer = NULL;
SDL_Texture *gTexture = NULL;
Uint32 *pixels;

void clear(Uint32 *dst) {
	int i, j;
	for(i = 0; i < HEIGHT; i++)
		for(j = 0; j < WIDTH; j++)
			dst[i * WIDTH + j] = 0;
}

void putpixel(Uint32 *dst, int x, int y) {
	if(x >= 0 && x < WIDTH - 8 && y >= 0 && y < HEIGHT - 8)
		dst[(y + PAD) * WIDTH + (x + PAD)] = 0xffffffff;
}

void drawletter(Uint32 *dst, int x, int y, int id) {
	int v, h, offset = id * 16;
	for(v = 0; v < 8; v++)
		for(h = 0; h < 8; h++) {
			int px = (x * 8) + (8 - h);
			int py = (y * 8) + v;
			int ch1 = chrbuf[offset + v];
			int ch2 = chrbuf[offset + v + 8];
			int clr = ((ch1 >> h) & 0x1) + (((ch2 >> h) & 0x1) << 1);
			if(clr)
				putpixel(dst, px, py);
		}
}

void drawbody(Uint32 *dst) {
	int i, x = 0, line = 0;
	for(i = 0; i < text_before_len; ++i) {
		char c = text_before[i];
		drawletter(dst, x, line, (int)c);
		x++;
		if(c == '\n') {
			x = 0;
			line++;
		}
	}
	for(i = text_after_len-1; i >= 0; --i) {
		char c = text_after[i];
		drawletter(dst, x, line, (int)c);
		x++;
		if(c == '\n') {
			x = 0;
			line++;
		}
	}
}

void redraw(Uint32 *dst) {
	clear(dst);
	drawbody(dst);
	SDL_UpdateTexture(gTexture, NULL, dst, WIDTH * sizeof(Uint32));
	SDL_RenderClear(gRenderer);
	SDL_RenderCopy(gRenderer, gTexture, NULL, NULL);
	SDL_RenderPresent(gRenderer);
}

void dotext(SDL_Event *event) {
	int i;
	for(i = 0; i < SDL_TEXTINPUTEVENT_TEXT_SIZE; ++i) {
		char c = event->text.text[i];
		if(c < ' ' || c > '~') break;
		pushchar(c);
	}
	redraw(pixels);
}

void dokey(SDL_Event *event) {
	switch(event->key.keysym.sym) {
	case SDLK_RETURN: pushchar('\n'); break;
	case SDLK_DOWN: down(); break;
	case SDLK_UP: up(); break;
	case SDLK_LEFT: left(); break;
	case SDLK_RIGHT: right(); break;
	}
}

int loadchr(FILE *f) {
	if(!f) return error("Load", "Invalid font file");
	if(!fread(chrbuf, sizeof(chrbuf), 1, f))
		return error("Load", "Invalid font file size");
	puts("Load: Complete");
	fclose(f);
	return 1;
}

int init(void) {
	if(SDL_Init(SDL_INIT_VIDEO) < 0)
		return error("Init", SDL_GetError());
	gWindow = SDL_CreateWindow("Moogle",
		SDL_WINDOWPOS_UNDEFINED,
		SDL_WINDOWPOS_UNDEFINED,
		WIDTH * ZOOM,
		HEIGHT * ZOOM,
		SDL_WINDOW_SHOWN);
	if(gWindow == NULL)
		return error("Window", SDL_GetError());
	gRenderer = SDL_CreateRenderer(gWindow, -1, 0);
	if(gRenderer == NULL)
		return error("Renderer", SDL_GetError());
	gTexture = SDL_CreateTexture(gRenderer,
		SDL_PIXELFORMAT_ARGB8888,
		SDL_TEXTUREACCESS_STATIC,
		WIDTH,
		HEIGHT);
	if(gTexture == NULL)
		return error("Texture", SDL_GetError());
	pixels = (Uint32 *)malloc(WIDTH * HEIGHT * sizeof(Uint32));
	if(pixels == NULL)
		return error("Pixels", "Failed to allocate memory");
	clear(pixels);
	return 1;
}

void quit(void) {
	free(pixels);
	SDL_DestroyTexture(gTexture);
	gTexture = NULL;
	SDL_DestroyRenderer(gRenderer);
	gRenderer = NULL;
	SDL_DestroyWindow(gWindow);
	gWindow = NULL;
	SDL_Quit();
	exit(0);
}

int main(int argc, char *argv[]) {
	int ticknext = 0;
	if(!init())
		return error("Init", "Failure");
	loadchr(fopen("type.chr", "r"));
	if(argc > 1)
		loadtxt(argv[1]);
	redraw(pixels);
	while(1) {
		int tick = SDL_GetTicks();
		SDL_Event event;
		if(tick < ticknext)
			SDL_Delay(ticknext - tick);
		ticknext = tick + (1000 / FPS);
		while(SDL_PollEvent(&event) != 0) {
			switch(event.type) {
			case SDL_QUIT: quit(); break;
			case SDL_TEXTINPUT: dotext(&event); break;
			case SDL_KEYDOWN: dokey(&event); break;
			}
		}
	}
	quit();
	return 0;
}