Write maze generation procedure with no randomisation

main.c

@@ -18,10 +18,55 @@
 
 #define PX(x) ((x) << 3)
 
+#define GOAL (GRID_SIZE - 1)
+
+typedef enum { LEFT, RIGHT, UP, DOWN } dir_t;
+
 typedef struct {
 	bool cells[GRID_SIZE][GRID_SIZE];
 } maze_t;
 
+typedef struct {
+	int x, y;
+} vec2_t;
+
+static const vec2_t steps[] = {
+	[LEFT] = { .x = -2, .y = 0 },
+	[RIGHT] = { .x = 2, .y = 0 },
+	[UP] = { .x = 0, .y = -2 },
+	[DOWN] = { .x = 0, .y = 2 },
+};
+
+static void generate_step(maze_t *m, int x, int y)
+{
+	m->cells[x][y] = true;
+	if (GOAL == x && GOAL == y)
+		return;
+
+	dir_t visit[] = { LEFT, RIGHT, UP, DOWN };
+
+	for (int i = 0; i < 4; ++i) {
+		const int xp = x + steps[visit[i]].x;
+		const int yp = y + steps[visit[i]].y;
+
+		const bool x_in_bounds = xp >= 0 && xp < GRID_SIZE;
+		const bool y_in_bounds = yp >= 0 && yp < GRID_SIZE;
+		if (x_in_bounds && y_in_bounds && !m->cells[xp][yp]) {
+			const int xi = (x + xp) / 2;
+			const int yi = (y + yp) / 2;
+			m->cells[xi][yi] = true;
+
+			generate_step(m, xp, yp);
+		}
+	}
+}
+
+static void generate_maze(maze_t *m)
+{
+	memset(m, 0, sizeof(maze_t));
+	generate_step(m, 0, 0);
+}
+
 static void draw_maze(Display *dpy, Window w, GC gc, const maze_t *m)
 {
 	// Draw walls
@@ -76,8 +121,9 @@ int main(void)
 		XNextEvent(dpy, &evt);
 	while (MapNotify != evt.type);
 
+	// Generate and draw maze
 	maze_t m;
-	memset(&m, 0, sizeof(maze_t));
+	generate_maze(&m);
 	draw_maze(dpy, w, gc, &m);
 
 	// Wait for window exit