add much-needed optimizations and enhance the snake example game

src/examples/snake.c

@@ -11,7 +11,7 @@ typedef struct {
 	int32_t y;
 } v2;
 
-#define SNAKE_MAX_LENGTH 64
+#define SNAKE_MAX_LENGTH 10
 
 typedef struct {
 	// position of the head of the snake in the framebuffer
@@ -32,6 +32,9 @@ typedef struct {
 } snake_state_t;
 
 snake_state_t snake;
+bool put_string_game_over;
+bool put_string_win;
+bool redraw = false;
 
 bool
 is_opposite_direction(v2 a, v2 b)
@@ -156,11 +159,17 @@ calculate_snake_death_collisions()
 {
 	for (int i = 1; i < snake.length; i++) {
 		if (v2_eq(snake.body[0], snake.body[i])) {
-			game_state->is_running = false;
+			put_string_game_over = true;
 		}
 	}
 }
 
+void
+evaluate_win()
+{
+	put_string_win = (snake.length >= SNAKE_MAX_LENGTH);
+}
+
 /**
  * performed every frame
  * runs on a separate worker thread - you can take advantage
@@ -171,7 +180,7 @@ client_update_framebuffer()
 {
 	uint64_t now = SDL_GetTicks();
 
-	if (now >= snake.next_move_time) {
+	if (now >= snake.next_move_time && !put_string_game_over) {
 		
 		// ------- business logic --------
 
@@ -183,7 +192,62 @@ client_update_framebuffer()
 
 		calculate_snake_death_collisions();
 
+		evaluate_win();
+
+		v2 old_head = snake.body[0];
+		v2 old_tail = snake.body[snake.length - 1];
+
 		advance_snake_pos();
+
+		v2 new_head = snake.body[0];
+
+		clear_rect(
+		    old_tail.x,
+		    old_tail.y,
+		    snake.size,
+		    snake.size,
+		    0x000000
+		);
+
+		if (snake.length > 1) {
+			put_rect(
+			    old_head.x,
+			    old_head.y,
+			    snake.size,
+			    snake.size,
+			    0x00AA00
+			);
+		}
+
+		put_rect(
+		    new_head.x,
+		    new_head.y,
+		    snake.size,
+		    snake.size,
+		    0x00FF00
+		);
+
+		mark_dirty_rect(
+		    old_tail.x,
+		    old_tail.y,
+		    snake.size,
+		    snake.size
+		);
+
+		mark_dirty_rect(
+		    old_head.x,
+		    old_head.y,
+		    snake.size,
+		    snake.size
+		);
+
+		mark_dirty_rect(
+		    new_head.x,
+		    new_head.y,
+		    snake.size,
+		    snake.size
+		);
+
 		
 		// -------------------------------
 		
@@ -193,8 +257,11 @@ client_update_framebuffer()
 	    	snake.next_move_time = now + snake.move_interval;
 		}
 
-		clear_framebuffer(0x000000);
+		redraw = true;
+		game_state->framebuffer_dirty = true;
+	}
 
+	if (redraw) {
 		// draw the apple
 		if (snake.is_apple_alive) {
 			put_rect_v2(
@@ -210,6 +277,7 @@ client_update_framebuffer()
 			snake.body[0].x, snake.body[0].y, 
 			snake.size, snake.size, 0x00FF00
 		);
+
 		// draw the tail
 		for (int i = 1; i < snake.length; i++) {
 			put_rect(
@@ -217,6 +285,21 @@ client_update_framebuffer()
 				snake.size, snake.size, 0x00AA00
 			);
 		}
+
+		// draw the splash texts
+		if (put_string_game_over) {
+			put_string("GAME OVER!\n<q> to quit", 
+				0, 0, 5, 2, 3, 0xFF0000, 0x000000
+			);
+		}
+
+		if (put_string_win) {
+			put_string("YOU WIN!\n<q> to quit", 
+				0, 100, 5, 2, 3, 0x00FF00, 0x000000
+			);
+		}
+
+		redraw = false;
 	}
 }
 
@@ -230,11 +313,14 @@ snake_init()
 	snake.dir = (v2){1, 0};
 	snake.length = 1;
 	snake.size = 20;
-	snake.move_interval = 300;
+	snake.move_interval = 50;
 	snake.next_move_time = snake.move_interval;
 	snake.is_apple_alive = false;
 	snake.pending_dir = snake.dir;
 	snake.direction_pending = false;
+
+	put_string_game_over = false;
+	put_string_win = false;
 }
 
 int