Draw the maze seperately to generation

main.c

@@ -14,16 +14,22 @@
 #include <time.h>
 #include <unistd.h>
 
-#define MAZE_SIZE 24
+#define MAZE_WIDTH 958
+#define MAZE_HEIGHT 538
+#define PX(x) (x)
 
-#define GRID_SIZE (2 * MAZE_SIZE - 1)
-#define MARGIN 2
-#define WALL_THICKNESS 1
-#define WINDOW_SIZE (GRID_SIZE + 2 * (WALL_THICKNESS + MARGIN))
+#define GRID_WIDTH (2 * MAZE_WIDTH - 1)
+#define GRID_HEIGHT (2 * MAZE_HEIGHT - 1)
+#define WINDOW_WIDTH (GRID_WIDTH + 2)
+#define WINDOW_HEIGHT (GRID_HEIGHT + 2)
 
-#define PX(x) ((x) << 3)
+#define ENTRANCE_X (-1)
+#define ENTRANCE_Y 0
+#define EXIT_X GRID_WIDTH
+#define EXIT_Y (GRID_HEIGHT - 1)
 
-#define GOAL (GRID_SIZE - 1)
+#define MAX_PATH_LENGTH (MAZE_WIDTH * MAZE_HEIGHT)
+#define STACK_SIZE MAX_PATH_LENGTH
 
 typedef enum { LEFT, RIGHT, UP, DOWN } dir_t;
 
@@ -39,7 +45,7 @@ typedef struct {
 	bool visited : 1;
 } cell_t;
 
-static const struct timespec wait = { .tv_nsec = 5000000 };
+static const struct timespec path_draw_pause = { .tv_nsec = 100000 };
 
 static const vec2_t steps[] = {
 	[LEFT] = { .x = -2, .y = 0 },
@@ -48,90 +54,112 @@ static const vec2_t steps[] = {
 	[DOWN] = { .x = 0, .y = 2 },
 };
 
+static const vec2_t start = { 0, 0 };
+static const vec2_t end = { GRID_WIDTH - 1, GRID_HEIGHT - 1 };
+
+static cell_t maze[GRID_WIDTH][GRID_HEIGHT];
 static Display *dpy;
 static Window window;
 static GC ctx;
-static cell_t maze[GRID_SIZE][GRID_SIZE];
-static int bg_col, wall_col, visited_col;
 
-static void clear_path(vec2_t p)
+static void draw_cell(int x, int y)
 {
-	const int margin_px = PX(MARGIN + WALL_THICKNESS);
-	const int left = margin_px + PX(p.x);
-	const int top = margin_px + PX(p.y);
-	XFillRectangle(dpy, window, ctx, left, top, PX(1), PX(1));
-	XClearArea(dpy, window, left, top, PX(1), PX(1), false);
-	XFlush(dpy);
+	XFillRectangle(
+	    dpy, window, ctx, 1 + PX(x + 1), 1 + PX(y + 1), PX(1), PX(1));
 }
 
-static void draw_visited(vec2_t p)
+static void clear_cell(int x, int y)
 {
-	const int margin_px = PX(MARGIN + WALL_THICKNESS);
-	const int left = margin_px + PX(p.x);
-	const int top = margin_px + PX(p.y);
-	XFillRectangle(dpy, window, ctx, left, top, PX(1), PX(1));
-	XFlush(dpy);
+	XClearArea(
+	    dpy, window, 1 + PX(x + 1), 1 + PX(y + 1), PX(1), PX(1), false);
 }
 
-static bool
-random_walk(coord_pred_t should_visit, visit_fn_t visit_fn, vec2_t start)
+static bool in_bounds(int x, int y)
 {
-	dir_t visit[] = { LEFT, RIGHT, UP, DOWN };
-	for (int i = 3; i > 0; --i) {
-		const int r = rand() % (i + 1);
-		const dir_t tmp = visit[r];
-		visit[r] = visit[i];
-		visit[i] = tmp;
-	}
+	const bool valid_x = x >= 0 && x < GRID_WIDTH;
+	const bool valid_y = y >= 0 && y < GRID_HEIGHT;
+	return valid_x && valid_y;
+}
 
-	vec2_t next, im;
+static bool finished_gen(int x, int y)
+{
+	int nx, ny;
 	for (int i = 0; i < 4; ++i) {
-		next.x = start.x + steps[visit[i]].x;
-		next.y = start.y + steps[visit[i]].y;
-		im.x = (start.x + next.x) / 2;
-		im.y = (start.y + next.y) / 2;
-
-		const bool x_in_bounds = next.x >= 0 && next.x < GRID_SIZE;
-		const bool y_in_bounds = next.y >= 0 && next.y < GRID_SIZE;
-		if (x_in_bounds && y_in_bounds && should_visit(next, im)) {
-			if (visit_fn(next, im)
-			    || random_walk(should_visit, visit_fn, next))
-				return true;
-		}
+		nx = x + steps[i].x;
+		ny = y + steps[i].y;
+		if (in_bounds(nx, ny) && !maze[nx][ny].is_path)
+			return false;
 	}
-
-	return false;
+	return true;
 }
 
-static bool is_wall(vec2_t c, vec2_t im)
+static void generate(vec2_t p)
 {
-	(void)im;
-	return !maze[c.x][c.y].is_path;
+	vec2_t stack[STACK_SIZE], *sp = stack;
+	maze[p.x][p.y].is_path = true;
+
+	do {
+		if (finished_gen(p.x, p.y)) {
+			p = *(--sp);
+			continue;
+		}
+
+		int nx, ny;
+		do {
+			dir_t d = rand() % 4;
+			nx = p.x + steps[d].x;
+			ny = p.y + steps[d].y;
+		} while (!in_bounds(nx, ny) || maze[nx][ny].is_path);
+
+		const int imx = (p.x + nx) / 2;
+		const int imy = (p.y + ny) / 2;
+		maze[imx][imy].is_path = maze[nx][ny].is_path = true;
+
+		*sp++ = p;
+		p.x = nx;
+		p.y = ny;
+	} while (sp != stack);
 }
 
-static bool generation_visit(vec2_t c, vec2_t im)
+static void solve(vec2_t p, vec2_t *sp, vec2_t **top)
 {
-	maze[c.x][c.y].is_path = true;
-	maze[im.x][im.y].is_path = true;
-	clear_path(im);
-	clear_path(c);
-	nanosleep(&wait, NULL);
-	return false;
-}
+	maze[0][0].visited = true;
+	*sp++ = p;
 
-static bool accessible_and_unvisited(vec2_t c, vec2_t im)
-{
-	return maze[im.x][im.y].is_path && !maze[c.x][c.y].visited;
-}
+	while (1) {
+		if (end.x == p.x && end.y == p.y) {
+			*sp++ = p;
+			*top = sp;
+			return;
+		}
 
-static bool solve_visit(vec2_t c, vec2_t im)
-{
-	maze[c.x][c.y].visited = true;
-	maze[im.x][im.y].visited = true;
-	draw_visited(im);
-	draw_visited(c);
-	nanosleep(&wait, NULL);
-	return GOAL == c.x && GOAL == c.y;
+		int nx, ny, imx, imy;
+		bool done = true;
+		for (int i = 0; i < 4; ++i) {
+			nx = p.x + steps[i].x;
+			ny = p.y + steps[i].y;
+			if (!in_bounds(nx, ny))
+				continue;
+
+			imx = (p.x + nx) / 2;
+			imy = (p.y + ny) / 2;
+			if (maze[imx][imy].is_path && !maze[nx][ny].visited) {
+				done = false;
+				break;
+			}
+		}
+
+		if (done) {
+			p = *(--sp);
+			continue;
+		}
+
+		maze[imx][imy].visited = maze[nx][ny].visited = true;
+
+		*sp++ = p;
+		p.x = nx;
+		p.y = ny;
+	}
 }
 
 int main(void)
@@ -146,11 +174,11 @@ int main(void)
 	assert(dpy);
 
 	// Create window and configure graphics context
-	wall_col = BlackPixel(dpy, DefaultScreen(dpy));
-	bg_col = WhitePixel(dpy, DefaultScreen(dpy));
+	const int black = BlackPixel(dpy, DefaultScreen(dpy));
+	const int white = WhitePixel(dpy, DefaultScreen(dpy));
 	window = XCreateSimpleWindow(
-	    dpy, DefaultRootWindow(dpy), 0, 0, PX(WINDOW_SIZE), PX(WINDOW_SIZE),
-	    0, bg_col, bg_col);
+	    dpy, DefaultRootWindow(dpy), 0, 0, PX(WINDOW_WIDTH),
+	    PX(WINDOW_HEIGHT), 0, black, black);
 	Atom del = XInternAtom(dpy, "WM_DELETE_WINDOW", false);
 	XSetWMProtocols(dpy, window, &del, 1);
 	ctx = DefaultGC(dpy, DefaultScreen(dpy));
@@ -160,7 +188,7 @@ int main(void)
 	    dpy, window, DefaultVisual(dpy, DefaultScreen(dpy)), AllocNone);
 	XColor xcol = { .red = 55555, .green = 10000, .blue = 10000 };
 	XAllocColor(dpy, cm, &xcol);
-	visited_col = xcol.pixel;
+	const int red = xcol.pixel;
 
 	// Map window
 	XSelectInput(dpy, window, StructureNotifyMask);
@@ -169,34 +197,53 @@ int main(void)
 		XNextEvent(dpy, &evt);
 	while (MapNotify != evt.type);
 
-	while (1) {
-		// Draw black box for walls
-		XClearWindow(dpy, window);
-		XSetForeground(dpy, ctx, wall_col);
-		XFillRectangle(
-		    dpy, window, ctx, PX(MARGIN), PX(MARGIN), PX(GRID_SIZE + 2),
-		    PX(GRID_SIZE + 2));
-		const vec2_t exit = { GOAL + 1, GOAL };
-		clear_path(exit);
-		XFlush(dpy);
+	// Draw entrance and exit
+	XSetForeground(dpy, ctx, white);
+	draw_cell(ENTRANCE_X, ENTRANCE_Y);
+	draw_cell(EXIT_X, EXIT_Y);
+	XFlush(dpy);
 
+	while (1) {
 		// Generate
 		memset(&maze, 0, sizeof(maze));
-		const vec2_t gen_start = { GOAL, GOAL };
-		maze[GOAL][GOAL].is_path = true;
-		clear_path(gen_start);
-		random_walk(is_wall, generation_visit, gen_start);
+		generate(end);
+
+		// Draw maze
+		XSetForeground(dpy, ctx, white);
+		draw_cell(ENTRANCE_X, ENTRANCE_Y);
+		for (int y = 0; y < GRID_HEIGHT; ++y) {
+			for (int x = 0; x < GRID_WIDTH; ++x) {
+				if (maze[x][y].is_path)
+					draw_cell(x, y);
+				else
+					clear_cell(x, y);
+			}
+		}
+		draw_cell(EXIT_X, EXIT_Y);
+		XFlush(dpy);
+
+		sleep(1);
 
 		// Solve
-		const vec2_t solve_start = { 0, 0 };
-		maze[0][0].visited = true;
-		XSetForeground(dpy, ctx, visited_col);
-		draw_visited(solve_start);
-		random_walk(accessible_and_unvisited, solve_visit, solve_start);
+		vec2_t path[MAX_PATH_LENGTH], *path_end;
+		solve(start, path, &path_end);
 
-		// Draw exit path
-		const int x = PX(MARGIN + GRID_SIZE + 1), y = PX(MARGIN + GRID_SIZE);
-		XFillRectangle(dpy, window, ctx, x, y, PX(1), PX(1));
+		// Draw solution path
+		XSetForeground(dpy, ctx, red);
+		draw_cell(ENTRANCE_X, ENTRANCE_Y);
+		const vec2_t *prev = &start;
+		for (const vec2_t *p = path; p < path_end; ++p) {
+			const int imx = (prev->x + p->x) / 2;
+			const int imy = (prev->y + p->y) / 2;
+
+			draw_cell(imx, imy);
+			draw_cell(p->x, p->y);
+			XFlush(dpy);
+
+			nanosleep(&path_draw_pause, NULL);
+			prev = p;
+		}
+		draw_cell(EXIT_X, EXIT_Y);
 		XFlush(dpy);
 
 		sleep(1);