rename get_rect to to_rect, and there is scrolling!

src/camera.rs

@@ -2,23 +2,45 @@ use sdl2::rect::Rect;
 
 
 pub struct Camera {
-    pub x: i32,
-    pub y: i32,
-    pub w: i32,
-    pub h: i32
+    x: i32,
+    y: i32,
+    w: i32,
+    h: i32,
+    bounding: Rect
 }
 
 impl Camera {
-    pub fn new(x: i32, y: i32, w: i32, h: i32) -> Camera {
+    pub fn new(x: i32, y: i32, w: i32, h: i32, bounding: Rect) -> Camera {
         Camera {
             x: x,
             y: y,
             w: w,
-            h: h
+            h: h,
+            bounding: bounding
         }
     }
 
-    pub fn get_rect(&self) -> Rect {
+    pub fn center(&mut self, object: &Rect) {
+        let mut x = (object.x + object.w / 2) - (self.w / 2);
+        let mut y = (object.y + object.h / 2) - (self.h / 2);
+
+        if x < self.bounding.x {
+            x = self.bounding.x;
+        } else if x + self.w > self.bounding.w {
+            x = self.bounding.w - self.w;
+        }
+
+        if y < self.bounding.y {
+            y = self.bounding.y;
+        } else if y + self.h > self.bounding.h {
+            y = self.bounding.h - self.h;
+        }
+
+        self.x = x;
+        self.y = y;
+    }
+
+    pub fn to_rect(&self) -> Rect {
         Rect::new(self.x, self.y, self.w, self.h)
     }
 }

src/main.rs

@@ -48,17 +48,16 @@ fn main() {
         Err(err) => panic!("failed to create renderer: {}", err)
     };
 
-    let mut camera = Camera::new(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
     let mut layer = Layer::new(120, 20, TILE_WIDTH, TILE_HEIGHT, Tile::Empty);
 
-    camera.x = 16;
-
     let colors = vec![Color::RGB(0, 0, 255), Color::RGB(0, 128, 255)];
 
     for x in range(0, 120) {
         layer.set_tile(x, 14, Tile::Floor(colors[(x % 2) as uint]));
     }
 
+    let mut camera = Camera::new(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT, layer.to_rect());
+
     let mut player = Player::new(290.0, 390.0);
 
     let mut current : uint;
@@ -110,12 +109,12 @@ fn main() {
         while lag >= MS_PER_UPDATE {
             player.update();
 
-            layer.for_each_intersecting(&player.get_rect(), |tile: &Tile, position: &Rect| {
+            layer.for_each_intersecting(&player.to_rect(), |tile: &Tile, position: &Rect| {
                 match *tile {
                     Tile::Empty => (),
                     Tile::Floor(_) => {
-                        if position.has_intersection(&player.get_rect()) {
-                            match position.intersection(&player.get_rect()) {
+                        if position.has_intersection(&player.to_rect()) {
+                            match position.intersection(&player.to_rect()) {
                                 Some(intersect) => {
                                     if intersect.w >= intersect.h {
                                         if player.velocity.y < 0.0 {
@@ -146,7 +145,7 @@ fn main() {
 
             player.on_ground = false;
 
-            let mut ground = player.get_rect();
+            let mut ground = player.to_rect();
 
             ground.y += ground.h;
             ground.h = 1;
@@ -162,23 +161,30 @@ fn main() {
                 }
             });
 
+            camera.center(&player.to_rect());
+
             lag -= MS_PER_UPDATE;
         }
 
         let _ = renderer.set_draw_color(Color::RGB(0, 0, 0));
         let _ = renderer.clear();
 
-        layer.for_each_intersecting(&camera.get_rect(), |tile: &Tile, position: &Rect| {
+        layer.for_each_intersecting(&camera.to_rect(), |tile: &Tile, position: &Rect| {
+            let object = camera_relative_rect(&camera.to_rect(), position);
+
             match *tile {
                 Tile::Empty => (),
-                Tile::Floor(c) => {
-                    let _ = renderer.set_draw_color(c);
-                    let _ = renderer.fill_rect(position);
+                Tile::Floor(color) => {
+                    let _ = renderer.set_draw_color(color);
+                    let _ = renderer.fill_rect(&object);
                 }
             }
         });
 
-        player.render(&renderer);
+        let player_rect = camera_relative_rect(&camera.to_rect(), &player.to_rect());
+
+        let _ = renderer.set_draw_color(Color::RGB(0, 255, 0));
+        let _ = renderer.fill_rect(&player_rect);
 
         renderer.present();
 
@@ -187,3 +193,7 @@ fn main() {
 
     sdl2::quit();
 }
+
+fn camera_relative_rect(camera: &Rect, other: &Rect) -> Rect {
+    Rect::new(other.x - camera.x, other.y - camera.y, other.w, other.h)
+}

src/player.rs

@@ -35,12 +35,7 @@ impl Player {
         self.position.y += self.velocity.y;
     }
 
-    pub fn render(&self, renderer: &Renderer) {
-        let _ = renderer.set_draw_color(Color::RGB(0, 255, 0));
-        let _ = renderer.fill_rect(&self.get_rect());
-    }
-
-    pub fn get_rect(&self) -> Rect {
+    pub fn to_rect(&self) -> Rect {
         Rect::new(self.position.x as i32 - 16, self.position.y as i32 - 16, 32, 32)
     }
 }

src/tile.rs

@@ -62,4 +62,8 @@ impl<T> Layer<T> where T: Clone {
             }
         }
     }
+
+    pub fn to_rect(&self) -> Rect {
+        Rect::new(0, 0, self.width * self.tile_width, self.height * self.tile_height)
+    }
 }