1 files changed, 35 insertions, 5 deletions

diff --git a/src/systems/draw.rs b/src/systems/draw.rs
index 1d5ee6b..fd0185e 100644
--- a/src/systems/draw.rs
+++ b/src/systems/draw.rs
@@ -1,4 +1,8 @@
+use std::thread;
+use std::time::{Duration, Instant};
+
 use sdl2::pixels::Color;
+use sdl2::rect::Rect;
 use sdl2::render::WindowCanvas;
 use sdl2::video::{Window, WindowContext};
 use specs::prelude::*;
@@ -6,8 +10,14 @@ use specs::prelude::*;
 use crate::components::{Pos, StaticDrawable};
 use crate::texture_manager::TextureManager;
 
+/// The minimum time in micro a frame should take to limit the number of
+/// frames drawn to the screen. 5000 microseconds for a maximum of 200 frames
+/// per second.
+pub const FRAME_TIME_MIN_US: u64 = (1_000_000. / 200.) as u64;
+
 pub struct SysDraw
 {
+    last_frame_time: Instant,
     canvas:          WindowCanvas,
     texture_manager: TextureManager<WindowContext>,
 }
@@ -25,10 +35,20 @@ impl SysDraw
         let texture_manager = TextureManager::new(canvas.texture_creator());
 
         Self {
+            last_frame_time: Instant::now(),
             canvas,
             texture_manager,
         }
     }
+
+    pub fn delay_for_min_frametime(&mut self)
+    {
+        let frame_duration_us = (Instant::now() - self.last_frame_time).as_micros() as u64;
+        if frame_duration_us < FRAME_TIME_MIN_US {
+            thread::sleep(Duration::from_micros(FRAME_TIME_MIN_US - frame_duration_us));
+        }
+        self.last_frame_time = Instant::now();
+    }
 }
 
 impl<'a> System<'a> for SysDraw
@@ -39,20 +59,30 @@ impl<'a> System<'a> for SysDraw
     {
         self.canvas.clear();
 
-        // XXX: This is so slow.. yaaaawn. Replace with ids and texture manager
-        // lifetime?
-        for (_pos, drawable) in (&pos, &drawable).join() {
+        /* XXX: This is so slow.. yaaaawn. Replace with ids and texture manager
+         * lifetime? */
+        for (pos, drawable) in (&pos, &drawable).join() {
             let texture = self
                 .texture_manager
                 .get(&drawable.texture_name)
                 .expect("Unable to load texture");
 
-            // let texture_info = texture.query();
             self.canvas
-                .copy(&texture, None, None)
+                .copy(
+                    &texture,
+                    Some(drawable.source_rect),
+                    Rect::new(
+                        pos.0.x as i32,
+                        pos.0.y as i32,
+                        drawable.source_rect.width(),
+                        drawable.source_rect.height(),
+                    ),
+                )
                 .expect("Unable to draw texture");
         }
 
+        self.delay_for_min_frametime();
+
         self.canvas.present();
     }
 }