ltnant.c: forgot to adjust index cut off, also refined the code a bit

src/animations/ltn_ant.c

@@ -35,13 +35,13 @@
 #define NX (UNUM_COLS - 1u)
 #define NY (UNUM_ROWS - 1u)
 
-static coord_t const xdcomp[] = {0, P,  0, NX};
-static coord_t const ydcomp[] = {P, 0, NY,  0};
+static coord_t const xdcomp[] = {0, NX,  0, P};
+static coord_t const ydcomp[] = {P,  0, NY, 0};
 
 typedef struct ant_s {
-	coord_t  x,  y;
-	coord_t ox, oy; /* Used to set old pixels to brightness 2 */
-	unsigned char vector_index;
+	coord_t  x,  y; /* current postion */
+	coord_t ox, oy; /* previous position, used to dim out old pixels */
+	unsigned char vector_index; /* index to one of (0,1),(1,0),(0,-1),(-1,0) */
 } ant_t;
 
 void ltn_ant() {
@@ -51,43 +51,35 @@ void ltn_ant() {
 
 	unsigned int cycles = 500;
 
-	/* Random start position and direction */
-	ant.x = random8() % UNUM_COLS;
-	ant.y = random8() % UNUM_ROWS;
+	/* random start position and direction */
+	ant.x = ant.ox = random8() % UNUM_COLS;
+	ant.y = ant.oy = random8() % UNUM_ROWS;
 
-	/* Make sure we do have a valid vector */
+	/* make sure we have a valid vector */
 	ant.vector_index = random8() % 4u;
 
-	ant.ox = ant.x;
-	ant.oy = ant.y;
-
-	while(cycles != 0) {
-		/* If the pixel is not set turn it on */
+	while(cycles--) {
+		/* if the pixel is turned off turn it on */
 		if(get_pixel((pixel) {ant.x, ant.y}) == 0) {
-			setpixel((pixel) {ant.x, ant.y}, 3);
-			
-			// turn right
-			ant.vector_index = (ant.vector_index + 1u) % 8u;
+			setpixel((pixel) {ant.x, ant.y}, NUMPLANE);
+			ant.vector_index = (ant.vector_index + 3u) % 4u; // turn left
 
-			/* Lets the last pixel be darker than the latest */
-			if((ant.ox != ant.x) || (ant.oy != ant.y))
-				setpixel((pixel) {ant.ox, ant.oy}, 2);
+			/* dim the previous pixel */
+			setpixel((pixel){ant.ox, ant.oy}, NUMPLANE - 1);
 
+			/* memorize this position */
 			ant.ox = ant.x;
 			ant.oy = ant.y;
+		/* if the pixel is turned on turn it off */
 		} else {
 			setpixel((pixel) {ant.x, ant.y}, 0);
-			// turn left
-			ant.vector_index = (ant.vector_index + 3u) % 8u;
+			ant.vector_index = (ant.vector_index + 1u) % 4u; // turn right
 		}
 
-		wait(100);
+		/* move to next pixel, playing field is modeled after a torus */
+		ant.x = (ant.x + xdcomp[ant.vector_index]) % UNUM_COLS;
+		ant.y = (ant.y + ydcomp[ant.vector_index]) % UNUM_ROWS;
 
-		/* Playing field is modeled after a torus */
-		ant.x = (coord_t)(ant.x + xdcomp[ant.vector_index]) % UNUM_COLS;
-		ant.y = (coord_t)(ant.y + ydcomp[ant.vector_index]) % UNUM_ROWS;
-
-		cycles--;
+		wait(100);
 	}
-	wait(300);
 }