examples: add interpolated movement and input queue to snek/snek.v (#21798)

examples/snek/snek.v

@@ -1,9 +1,9 @@
-import os
+import datatypes
 import gg
 import gx
-// import sokol.sapp
-import time
+import os
 import rand
+import time
 
 // constants
 const top_height = 100
@@ -11,28 +11,20 @@ const canvas_size = 700
 const game_size = 17
 const tile_size = canvas_size / game_size
 const tick_rate_ms = 100
-
 const high_score_file_path = os.join_path(os.cache_dir(), 'v', 'examples', 'snek')
 
 // types
-struct Pos {
+struct Vec {
 	x int
 	y int
 }
 
-fn (a Pos) + (b Pos) Pos {
-	return Pos{a.x + b.x, a.y + b.y}
+fn (a Vec) + (b Vec) Vec {
+	return Vec{a.x + b.x, a.y + b.y}
 }
 
-fn (a Pos) - (b Pos) Pos {
-	return Pos{a.x - b.x, a.y - b.y}
-}
-
-enum Direction {
-	up
-	down
-	left
-	right
+fn (a Vec) - (b Vec) Vec {
+	return Vec{a.x - b.x, a.y - b.y}
 }
 
 type HighScore = int
@@ -48,30 +40,28 @@ fn (mut h HighScore) load() {
 
 struct App {
 mut:
-	gg         &gg.Context = unsafe { nil }
-	score      int
-	best       HighScore
-	snake      []Pos
-	dir        Direction
-	last_dir   Direction
-	food       Pos
-	start_time i64
-	last_tick  i64
+	gg        &gg.Context = unsafe { nil }
+	score     int
+	best      HighScore
+	snake     []Vec
+	dir       Vec
+	dir_queue datatypes.Queue[Vec]
+	food      Vec
+	last_tick i64
 }
 
 // utility
 fn (mut app App) reset_game() {
 	app.score = 0
 	app.snake = [
-		Pos{3, 8},
-		Pos{2, 8},
-		Pos{1, 8},
-		Pos{0, 8},
+		Vec{3, 8},
+		Vec{2, 8},
+		Vec{1, 8},
+		Vec{0, 8},
 	]
-	app.dir = .right
-	app.last_dir = app.dir
-	app.food = Pos{10, 8}
-	app.start_time = time.ticks()
+	app.dir = Vec{1, 0}
+	app.dir_queue = datatypes.Queue[Vec]{}
+	app.food = Vec{10, 8}
 	app.last_tick = time.ticks()
 }
 
@@ -79,7 +69,7 @@ fn (mut app App) move_food() {
 	for {
 		x := rand.intn(game_size) or { 0 }
 		y := rand.intn(game_size) or { 0 }
-		app.food = Pos{x, y}
+		app.food = Vec{x, y}
 
 		if app.food !in app.snake {
 			return
@@ -89,81 +79,65 @@ fn (mut app App) move_food() {
 
 // events
 fn on_keydown(key gg.KeyCode, mod gg.Modifier, mut app App) {
-	match key {
+	dir := match key {
 		.w, .up {
-			if app.last_dir != .down {
-				app.dir = .up
-			}
+			Vec{0, -1}
 		}
 		.s, .down {
-			if app.last_dir != .up {
-				app.dir = .down
-			}
+			Vec{0, 1}
 		}
 		.a, .left {
-			if app.last_dir != .right {
-				app.dir = .left
-			}
+			Vec{-1, 0}
 		}
 		.d, .right {
-			if app.last_dir != .left {
-				app.dir = .right
-			}
+			Vec{1, 0}
+		}
+		else {
+			return
 		}
-		else {}
 	}
+	app.dir_queue.push(dir)
 }
 
 fn on_frame(mut app App) {
+	// check if snake bit itself
+	if app.snake[0] in app.snake[1..] {
+		app.reset_game()
+	}
+
+	// check if snake hit a wall
+	if app.snake[0].x < 0 || app.snake[0].x >= game_size || app.snake[0].y < 0
+		|| app.snake[0].y >= game_size {
+		app.reset_game()
+	}
+
+	progress := f32_min(1, f32(time.ticks() - app.last_tick) / f32(tick_rate_ms))
 	app.gg.begin()
 
-	now := time.ticks()
+	// draw food
+	app.gg.draw_rect_filled(tile_size * app.food.x, tile_size * app.food.y + top_height,
+		tile_size, tile_size, gx.red)
 
-	if now - app.last_tick >= tick_rate_ms {
-		app.last_tick = now
-
-		// finding delta direction
-		delta_dir := match app.dir {
-			.up { Pos{0, -1} }
-			.down { Pos{0, 1} }
-			.left { Pos{-1, 0} }
-			.right { Pos{1, 0} }
-		}
-
-		// "snaking" along
-		mut prev := app.snake[0]
-		app.snake[0] = app.snake[0] + delta_dir
-
-		for i in 1 .. app.snake.len {
-			tmp := app.snake[i]
-			app.snake[i] = prev
-			prev = tmp
-		}
-
-		// adding last segment
-		if app.snake[0] == app.food {
-			app.move_food()
-			app.score++
-			if app.score > app.best {
-				app.best = app.score
-				app.best.save()
-			}
-			app.snake << app.snake.last() + app.snake.last() - app.snake[app.snake.len - 2]
-		}
-
-		app.last_dir = app.dir
-	}
-	// drawing snake
-	for pos in app.snake {
+	// draw snake
+	for pos in app.snake[..app.snake.len - 1] {
 		app.gg.draw_rect_filled(tile_size * pos.x, tile_size * pos.y + top_height, tile_size,
 			tile_size, gx.blue)
 	}
 
-	// drawing food
-	app.gg.draw_rect_filled(tile_size * app.food.x, tile_size * app.food.y + top_height,
-		tile_size, tile_size, gx.red)
+	// draw partial head
+	head := app.snake[0]
+	app.gg.draw_rect_filled(int(tile_size * (head.x + app.dir.x * progress)),
+		int(tile_size * (head.y + app.dir.y * progress)) + top_height, tile_size, tile_size,
+		gx.blue)
 
-	// drawing top
+	// draw partial tail
+	tail := app.snake.last()
+	tail_dir := app.snake[app.snake.len - 2] - tail
+	app.gg.draw_rect_filled(int(tile_size * (tail.x + tail_dir.x * progress)),
+		int(tile_size * (tail.y + tail_dir.y * progress)) + top_height, tile_size, tile_size,
+		gx.blue)
+
+	// draw score bar
 	app.gg.draw_rect_filled(0, 0, canvas_size, top_height, gx.black)
 	app.gg.draw_text(150, top_height / 2, 'Score: ${app.score}', gx.TextCfg{
 		color: gx.white
@@ -178,14 +152,35 @@ fn on_frame(mut app App) {
 		size: 65
 	})
 
-	// checking if snake bit itself
-	if app.snake[0] in app.snake[1..] {
-		app.reset_game()
-	}
-	// checking if snake hit a wall
-	if app.snake[0].x < 0 || app.snake[0].x >= game_size || app.snake[0].y < 0
-		|| app.snake[0].y >= game_size {
-		app.reset_game()
+	if progress == 1 {
+		// "snake" along
+		mut prev := app.snake[0]
+		app.snake[0] = app.snake[0] + app.dir
+
+		for i in 1 .. app.snake.len {
+			tmp := app.snake[i]
+			app.snake[i] = prev
+			prev = tmp
+		}
+
+		// add tail segment if food has been eaten
+		if app.snake[0] == app.food {
+			app.score++
+			if app.score > app.best {
+				app.best = app.score
+				app.best.save()
+			}
+			app.snake << app.snake.last() + app.snake.last() - app.snake[app.snake.len - 2]
+			app.move_food()
+		}
+
+		if dir := app.dir_queue.pop() {
+			if dir.x != -app.dir.x || dir.y != -app.dir.y {
+				app.dir = dir
+			}
+		}
+
+		app.last_tick = time.ticks()
 	}
 
 	app.gg.end()