Refactor animations (#5)

- `SpriteRef` impls `Animation`, `Sprite` does not
- Animation duration and delta time now lives on the struct that handles the animation "state machine"
- Tweak the player animation to 100ms frame duration (was 50ms)

simple-invaders/src/lib.rs

@@ -8,7 +8,7 @@ use std::time::Duration;
 
 pub use controls::{Controls, Direction};
 use loader::{load_assets, Assets};
-use sprites::{blit, Drawable, Frame, Sprite, SpriteRef};
+use sprites::{blit, Animation, Frame, Sprite, SpriteRef};
 
 mod controls;
 mod loader;
@@ -35,8 +35,7 @@ pub struct World {
     score: u32,
     assets: Assets,
     screen: Vec<u8>,
-    timing: Duration,
-    frame_count: usize,
+    dt: Duration,
 }
 
 /// A tiny position vector
@@ -124,7 +123,7 @@ impl World {
             bounds: Bounds::default(),
         };
         let player = Player {
-            sprite: SpriteRef::new(&assets, Player1),
+            sprite: SpriteRef::new(&assets, Player1, Duration::from_millis(100)),
             pos: Point::new(80, 216),
             last_update: 0,
         };
@@ -148,8 +147,7 @@ impl World {
             score: 0,
             assets,
             screen,
-            timing: Duration::default(),
-            frame_count: 0,
+            dt: Duration::default(),
         }
     }
 
@@ -163,17 +161,16 @@ impl World {
         let one_frame = Duration::new(0, 16_666_667);
 
         // Advance the timer by the delta time
-        self.timing += dt;
+        self.dt += dt;
 
         // Step the invaders one by one
-        while self.timing >= one_frame {
-            self.frame_count += 1;
-            self.timing -= one_frame;
+        while self.dt >= one_frame {
+            self.dt -= one_frame;
             self.step_invaders();
         }
 
         // Handle player movement and animation
-        self.step_player(controls);
+        self.step_player(controls, dt);
 
         // TODO: Handle lasers and bullets
         // Movements can be multiplied by the delta-time frame count, instead of looping
@@ -216,34 +213,25 @@ impl World {
         // TODO: Move the invader
 
         // Animate the invader
-        invader.sprite.animate(&self.assets);
+        invader.sprite.step_frame(&self.assets);
     }
 
-    fn step_player(&mut self, controls: &Controls) {
-        let animate_player = match controls.direction {
+    fn step_player(&mut self, controls: &Controls, dt: Duration) {
+        match controls.direction {
             Direction::Left => {
                 if self.player.pos.x > 0 {
                     self.player.pos.x -= 1;
-                    true
-                } else {
-                    false
+                    self.player.sprite.animate(&self.assets, dt);
                 }
             }
 
             Direction::Right => {
                 if self.player.pos.x < 224 - 16 {
                     self.player.pos.x += 1;
-                    true
-                } else {
-                    false
+                    self.player.sprite.animate(&self.assets, dt);
                 }
             }
-            _ => false,
-        };
-
-        if animate_player && self.frame_count - self.player.last_update >= 3 {
-            self.player.last_update = self.frame_count;
-            self.player.sprite.animate(&self.assets);
+            _ => (),
         }
     }
 
@@ -331,7 +319,7 @@ fn make_invader_grid(assets: &Assets) -> Vec<Vec<Option<Invader>>> {
             (0..COLS)
                 .map(|x| {
                     Some(Invader {
-                        sprite: SpriteRef::new(assets, Blipjoy1),
+                        sprite: SpriteRef::new(assets, Blipjoy1, Duration::default()),
                         pos: START + BLIPJOY_OFFSET + Point::new(x, y) * GRID,
                         score: 10,
                     })
@@ -342,7 +330,7 @@ fn make_invader_grid(assets: &Assets) -> Vec<Vec<Option<Invader>>> {
             (0..COLS)
                 .map(|x| {
                     Some(Invader {
-                        sprite: SpriteRef::new(assets, Ferris1),
+                        sprite: SpriteRef::new(assets, Ferris1, Duration::default()),
                         pos: START + FERRIS_OFFSET + Point::new(x, y) * GRID,
                         score: 10,
                     })
@@ -353,7 +341,7 @@ fn make_invader_grid(assets: &Assets) -> Vec<Vec<Option<Invader>>> {
             (0..COLS)
                 .map(|x| {
                     Some(Invader {
-                        sprite: SpriteRef::new(assets, Cthulhu1),
+                        sprite: SpriteRef::new(assets, Cthulhu1, Duration::default()),
                         pos: START + CTHULHU_OFFSET + Point::new(x, y) * GRID,
                         score: 10,
                     })

simple-invaders/src/sprites.rs

@@ -1,4 +1,5 @@
 use std::rc::Rc;
+use std::time::Duration;
 
 use crate::loader::Assets;
 use crate::{Point, SCREEN_WIDTH};
@@ -26,13 +27,15 @@ pub(crate) enum Frame {
     // Laser2,
 }
 
-/// Sprites can be drawn and animated.
+/// Sprites can be drawn and procedurally generated.
+///
+/// A `Sprite` owns its pixel data, and cannot be animated. Use a `SpriteRef` if you need
+/// animations.
 #[derive(Debug)]
 pub(crate) struct Sprite {
     width: usize,
     height: usize,
     pixels: Vec<u8>,
-    frame: Frame,
 }
 
 /// SpriteRefs can be drawn and animated.
@@ -44,6 +47,8 @@ pub(crate) struct SpriteRef {
     height: usize,
     pixels: Rc<Vec<u8>>,
     frame: Frame,
+    duration: Duration,
+    dt: Duration,
 }
 
 /// Drawables can be blitted to the pixel buffer and animated.
@@ -51,15 +56,43 @@ pub(crate) trait Drawable {
     fn width(&self) -> usize;
     fn height(&self) -> usize;
     fn pixels(&self) -> &[u8];
-    fn update_pixels(&mut self, pixels: Rc<Vec<u8>>);
-    fn frame(&self) -> &Frame;
-    fn update_frame(&mut self, frame: Frame);
+}
 
-    fn animate(&mut self, assets: &Assets) {
+pub(crate) trait Animation {
+    fn animate(&mut self, assets: &Assets, dt: Duration);
+}
+
+impl Sprite {
+    pub(crate) fn new(assets: &Assets, frame: Frame) -> Sprite {
+        let (width, height, pixels) = assets.sprites().get(&frame).unwrap();
+
+        Sprite {
+            width: *width,
+            height: *height,
+            pixels: pixels.to_vec(),
+        }
+    }
+}
+
+impl SpriteRef {
+    pub(crate) fn new(assets: &Assets, frame: Frame, duration: Duration) -> SpriteRef {
+        let (width, height, pixels) = assets.sprites().get(&frame).unwrap();
+
+        SpriteRef {
+            width: *width,
+            height: *height,
+            pixels: pixels.clone(),
+            frame,
+            duration,
+            dt: Duration::default(),
+        }
+    }
+
+    pub(crate) fn step_frame(&mut self, assets: &Assets) {
         use Frame::*;
 
         let assets = assets.sprites();
-        let (pixels, frame) = match self.frame() {
+        let (pixels, frame) = match self.frame {
             Blipjoy1 => (assets.get(&Blipjoy2).unwrap().2.clone(), Blipjoy2),
             Blipjoy2 => (assets.get(&Blipjoy1).unwrap().2.clone(), Blipjoy1),
 
@@ -78,34 +111,8 @@ pub(crate) trait Drawable {
             // Laser2 => (assets.get(&Laser1).unwrap().2.clone(), Laser1),
         };
 
-        self.update_pixels(pixels);
-        self.update_frame(frame);
-    }
-}
-
-impl Sprite {
-    pub(crate) fn new(assets: &Assets, frame: Frame) -> Sprite {
-        let (width, height, pixels) = assets.sprites().get(&frame).unwrap();
-
-        Sprite {
-            width: *width,
-            height: *height,
-            pixels: pixels.to_vec(),
-            frame,
-        }
-    }
-}
-
-impl SpriteRef {
-    pub(crate) fn new(assets: &Assets, frame: Frame) -> SpriteRef {
-        let (width, height, pixels) = assets.sprites().get(&frame).unwrap();
-
-        SpriteRef {
-            width: *width,
-            height: *height,
-            pixels: pixels.clone(),
-            frame,
-        }
+        self.pixels = pixels;
+        self.frame = frame;
     }
 }
 
@@ -121,18 +128,6 @@ impl Drawable for Sprite {
     fn pixels(&self) -> &[u8] {
         &self.pixels
     }
-
-    fn update_pixels(&mut self, pixels: Rc<Vec<u8>>) {
-        self.pixels = pixels.to_vec();
-    }
-
-    fn frame(&self) -> &Frame {
-        &self.frame
-    }
-
-    fn update_frame(&mut self, frame: Frame) {
-        self.frame = frame;
-    }
 }
 
 impl Drawable for SpriteRef {
@@ -147,17 +142,20 @@ impl Drawable for SpriteRef {
     fn pixels(&self) -> &[u8] {
         &self.pixels
     }
-
-    fn update_pixels(&mut self, pixels: Rc<Vec<u8>>) {
-        self.pixels = pixels;
 }
 
-    fn frame(&self) -> &Frame {
-        &self.frame
-    }
+impl Animation for SpriteRef {
+    fn animate(&mut self, assets: &Assets, dt: Duration) {
+        if self.duration.subsec_nanos() == 0 {
+            self.step_frame(assets);
+        } else {
+            self.dt += dt;
 
-    fn update_frame(&mut self, frame: Frame) {
-        self.frame = frame;
+            while self.dt >= self.duration {
+                self.dt -= self.duration;
+                self.step_frame(assets);
+            }
+        }
     }
 }