more accurate timing

@@ -30,8 +30,11 @@ pub trait Canvas {
     fn init_events(&self);
     fn start_events(&self, tx :mpsc::Sender<i32>);
 
+    fn width(&self) -> u16;
+    fn height(&self) -> u16;
+
     fn clear(&mut self);
-    fn draw(&mut self, c :&dyn Drawable, ofs :Coordinate);
+    fn draw(&mut self, c :&dyn Drawable, ofs :Coordinate, color :u32);
     fn show(&self);
 }
 
@@ -225,7 +228,9 @@ impl Drawable for Polygon {
                 }
                 let mut j = a.line(&i);
                 let     l = j.len();
-                r.append(&mut j[1..l-1].to_vec());
+                if l > 1 {
+                    r.append(&mut j[1..l-1].to_vec());
+                }
                 Coordinates(r)
             },
         }

@@ -24,8 +24,8 @@ use std::fmt::Display;
 use std::num::TryFromIntError;
 use std::ops::{Add,Sub,Neg,Mul,Div};
 use std::sync::mpsc;
-use std::time;
 use std::thread;
+use std::time::{Duration, Instant};
 
 use fractional::continuous::Continuous;
 use fractional::easel::{ Coordinate, Coordinates, Drawable, Line, Polyline
@@ -340,37 +340,149 @@ fn main() {
 
     let (tx, rx) = mpsc::channel();
 
-    let i = Vector(Fractional(  0,1), Fractional(-35,1), Fractional(0,1));
-    let j = Vector(Fractional( 30,1), Fractional( 17,1), Fractional(0,1));
-    let k = Vector(Fractional(-30,1), Fractional( 17,1), Fractional(0,1));
-
-    fn to_i32(x :Fractional) -> i32 {
-        let Fractional(n, d) = x;
-        (n / d + if (n % d).abs() < (n / 2).abs() { 0 } else { 1 }) as i32
+    // TODO I ran into overflow issues using fractionals so for now
+    // use floating point values.
+    // https://rechneronline.de/pi/tetrahedron.php
+    // yi = a / 12 * √6
+    // yc = a / 4 * √6
+    // zi = √3 / 6 * a
+    // zc = √3 / 3 * a
+    let yi = 60.0 / 12.0 * 6.0.sqrt().unwrap();
+    let yc = 60.0 /  4.0 * 6.0.sqrt().unwrap();
+    let zi = 3.0.sqrt().unwrap() / 6.0 * 60.0;
+    let zc = 3.0.sqrt().unwrap() / 3.0 * 60.0;
+
+    let i = Vector(  0.0,  yc, 0.0);
+    let j = Vector(-30.0, -yi, -zi);
+    let k = Vector( 30.0, -yi, -zi);
+    let l = Vector(  0.0, -yi,  zc);
+
+    let cf1 = Vector(-30.0,  30.0, -30.0);
+    let cf2 = Vector(-30.0, -30.0, -30.0);
+    let cf3 = Vector( 30.0, -30.0, -30.0);
+    let cf4 = Vector( 30.0,  30.0, -30.0);
+
+    let cb1 = Vector(-30.0,  30.0,  30.0);
+    let cb2 = Vector(-30.0, -30.0,  30.0);
+    let cb3 = Vector( 30.0, -30.0,  30.0);
+    let cb4 = Vector( 30.0,  30.0,  30.0);
+
+    fn to_screen(c: &dyn Canvas, v :Vector<f64>) -> Coordinate {
+        // TODO .. these are in fact constants that should be stored once
+        // somewhere… Rust doesn't let me make this static here.
+        // In a way they are part of the canvas and they should change as the
+        // canvas is changing…
+        let fovx :f64 = 1.0 / <f64 as Trig>::tan(50);
+        let fovy :f64 = c.width() as f64 / c.height() as f64 * fovx;
+
+        let xs = ( v.x() / v.z() * fovx * c.width() as f64 ).round() as i32
+                 + c.width() as i32 / 2;
+        let ys = ( -v.y() / v.z() * fovy * c.height() as f64 ).round() as i32
+                 + c.height() as i32 / 2;
+
+        Coordinate(xs, ys)
     }
 
     canvas.start_events(tx);
 
+    let     start = Instant::now();
+    let     step  = Duration::from_millis(25);
+    let mut last  = Instant::now();
     thread::spawn(move || {
-        let mut deg :i32 = 0;
-        loop {
-            let rot :TMatrix<Fractional> = rotate_z(deg) * rotate_x(-deg);
+        //const DWC :f64 = 10.0;
 
-            let Vector(ix, iy, _) = rot.apply(&i);
-            let Vector(jx, jy, _) = rot.apply(&j);
-            let Vector(kx, ky, _) = rot.apply(&k);
+        loop {
+            let deg = ((start.elapsed() / 20).as_millis() % 360) as i32;
+            let rot1 :TMatrix<f64> = rotate_z(deg)
+                                   * rotate_x(-deg*2)
+                                   * translate(Vector(0.0, 0.0, 150.0));
+
+            let rot2 :TMatrix<f64> = rotate_z(deg)
+                                   * rotate_y(-deg*2)
+                                   * translate(Vector(0.0, 0.0, 150.0));
+
+            let ia = rot1.apply(&i);
+            let ja = rot1.apply(&j);
+            let ka = rot1.apply(&k);
+            let la = rot1.apply(&l);
+
+            let cf1a = rot2.apply(&cf1);
+            let cf2a = rot2.apply(&cf2);
+            let cf3a = rot2.apply(&cf3);
+            let cf4a = rot2.apply(&cf4);
+
+            let cb1a = rot2.apply(&cb1);
+            let cb2a = rot2.apply(&cb2);
+            let cb3a = rot2.apply(&cb3);
+            let cb4a = rot2.apply(&cb4);
+
+            let pg1 = Polygon(Coordinates(vec!( to_screen(&canvas, ja)
+                                              , to_screen(&canvas, ka)
+                                              , to_screen(&canvas, la) )));
+            let pg2 = Polygon(Coordinates(vec!( to_screen(&canvas, ja)
+                                              , to_screen(&canvas, ia)
+                                              , to_screen(&canvas, ka) )));
+            let pg3 = Polygon(Coordinates(vec!( to_screen(&canvas, la)
+                                              , to_screen(&canvas, ia)
+                                              , to_screen(&canvas, ja) )));
+            let pg4 = Polygon(Coordinates(vec!( to_screen(&canvas, ka)
+                                              , to_screen(&canvas, ia)
+                                              , to_screen(&canvas, la) )));
+
+            // front: cf1 cf2 cf3 cf4
+            let cf = Polygon(Coordinates(vec!( to_screen(&canvas, cf1a)
+                                             , to_screen(&canvas, cf2a)
+                                             , to_screen(&canvas, cf3a)
+                                             , to_screen(&canvas, cf4a) )));
+            // back: cb4 cb3 cb2 cb1
+            let cb = Polygon(Coordinates(vec!( to_screen(&canvas, cb4a)
+                                             , to_screen(&canvas, cb3a)
+                                             , to_screen(&canvas, cb2a)
+                                             , to_screen(&canvas, cb1a) )));
+            // top: cf2 cb2 cb3 cf3
+            let ct = Polygon(Coordinates(vec!( to_screen(&canvas, cf2a)
+                                             , to_screen(&canvas, cb2a)
+                                             , to_screen(&canvas, cb3a)
+                                             , to_screen(&canvas, cf3a) )));
+            // bottom: cf1 cf4 cb4 cb1
+            let co = Polygon(Coordinates(vec!( to_screen(&canvas, cf1a)
+                                             , to_screen(&canvas, cf4a)
+                                             , to_screen(&canvas, cb4a)
+                                             , to_screen(&canvas, cb1a) )));
+            // left: cf1 cb1 cb2 cf2
+            let cl = Polygon(Coordinates(vec!( to_screen(&canvas, cf1a)
+                                             , to_screen(&canvas, cb1a)
+                                             , to_screen(&canvas, cb2a)
+                                             , to_screen(&canvas, cf2a) )));
+            // right: cf3 cb3 cb4 cf4
+            let cr = Polygon(Coordinates(vec!( to_screen(&canvas, cf3a)
+                                             , to_screen(&canvas, cb3a)
+                                             , to_screen(&canvas, cb4a)
+                                             , to_screen(&canvas, cf4a) )));
 
-            let pg = Polygon(
-                Coordinates(vec!( Coordinate(to_i32(ix), to_i32(iy))
-                                , Coordinate(to_i32(jx), to_i32(jy))
-                                , Coordinate(to_i32(kx), to_i32(ky)) )));
             canvas.clear();
-            canvas.draw(&pg, Coordinate(75,75));
+            canvas.draw(&pg1, Coordinate(0,0), 0xFFFF00);
+            canvas.draw(&pg2, Coordinate(0,0), 0xFFFF00);
+            canvas.draw(&pg3, Coordinate(0,0), 0xFFFF00);
+            canvas.draw(&pg4, Coordinate(0,0), 0xFFFF00);
+            canvas.draw( &cf, Coordinate(0,0), 0x0000FF);
+            canvas.draw( &cb, Coordinate(0,0), 0x0000FF);
+            canvas.draw( &ct, Coordinate(0,0), 0x0000FF);
+            canvas.draw( &co, Coordinate(0,0), 0x0000FF);
+            canvas.draw( &cl, Coordinate(0,0), 0x0000FF);
+            canvas.draw( &cr, Coordinate(0,0), 0x0000FF);
             canvas.show();
 
-            deg = (deg + 1) % 360;
+            let passed = Instant::now() - last;
+            let f      = (passed.as_nanos() / step.as_nanos()) as u32;
+
+            if f > 1 {
+                println!("!!! Detected frame drop");
+            }
 
-            thread::sleep(time::Duration::from_millis(5));
+            last = last + step*(f + 1);
+            println!("Sleep for: {:?}", last - Instant::now());
+            thread::sleep(last - Instant::now());
         }
     });
 

@@ -207,6 +207,14 @@ impl<'a> Canvas for XcbCanvas<'a> {
         });
     }
 
+    fn width(&self) -> u16 {
+        self.width
+    }
+
+    fn height(&self) -> u16 {
+        self.height
+    }
+
     fn clear(&mut self) {
         unsafe {
             let ptr = self.shm.as_mut_ptr();
@@ -215,13 +223,13 @@ impl<'a> Canvas for XcbCanvas<'a> {
         }
     }
 
-    fn draw(&mut self, d :&dyn Drawable, ofs :Coordinate) {
+    fn draw(&mut self, d :&dyn Drawable, ofs :Coordinate, color: u32) {
         let Coordinates(c)         = d.plot();
         let Coordinate(xofs, yofs) = ofs;
 
         for Coordinate(x, y) in c {
             let idx :usize = ((y+yofs)*(self.width as i32)+x+xofs) as usize;
-            self.shm[idx] = 0xFFFFFF;
+            self.shm[idx] = color;
         }
     }