split easel into multiple files

-//
-// This is an abstraction over a drawing environment.
-// Future note: z-Buffer is described here:
-// https://www.scratchapixel.com/lessons/3d-basic-rendering/rasterization-practical-implementation/perspective-correct-interpolation-vertex-attributes
-//
-// Georg Hopp <georg@steffers.org>
-//
-// Copyright © 2019 Georg Hopp
-//
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
-//
-use std::cmp;
-use std::fmt::{Formatter, Debug, Display, Result};
-use std::ops::{Add, Sub, Div};
-use std::sync::mpsc;
-
-pub trait Easel {
-    //fn canvas(&mut self, width :u16, height :u16) -> Option<&dyn Canvas>;
-}
-
-pub trait Canvas<T> {
-    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<T>, ofs :Coordinate<T>, color :u32);
-    fn put_text(&self, ofs :Coordinate<T>, s :&str);
-    fn set_pixel(&mut self, c :Coordinate<T>, color :u32);
-    fn show(&self);
-}
-
-pub trait Drawable<T> {
-    fn plot(&self) -> Coordinates<T>;
-}
-
-pub trait Fillable<T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Copy + From<i32> {
-    fn fill(&self, canvas :&mut dyn Canvas<T>, color :u32);
-}
-
-#[derive(Debug, Clone, Copy)]
-pub struct Coordinate<T>(pub i32, pub i32, pub T);
-
-#[derive(Debug, Clone)]
-pub struct Coordinates<T>(pub Vec<Coordinate<T>>);
-
-#[derive(Debug, Clone, Copy)]
-pub struct LineIterator<T> where T: Debug {
-               a :Option<Coordinate<T>>
-    ,          b :Coordinate<T>
-    ,         dx :i32
-    ,         dy :i32
-    ,         dz :T
-    ,         sx :i32
-    ,         sy :i32
-    ,        err :i32
-    , only_edges :bool
-}
-
-impl<T> Iterator for LineIterator<T>
-where T: Add<Output = T> + Debug + Copy + From<i32> {
-    type Item = Coordinate<T>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        match self.a {
-            None    => None,
-            Some(a) => {
-                let Coordinate(ax, ay, az) = a;
-                let Coordinate(bx, by,  _) = self.b;
-
-                if ax != bx || ay != by {
-                    match (2 * self.err >= self.dy, 2 * self.err <= self.dx ) {
-                        (true, false) => {
-                            let r    = self.a;
-                            self.a   = Some(Coordinate( ax + self.sx
-                                                      , ay
-                                                      , az + self.dz ));
-                            self.err = self.err + self.dy;
-                            if self.only_edges { self.next() } else { r }
-                        },
-                        (false, true) => {
-                            let r    = self.a;
-                            self.a   = Some(Coordinate( ax
-                                                      , ay + self.sy
-                                                      , az + self.dz ));
-                            self.err = self.err + self.dx;
-                            r
-                        },
-                        _             => {
-                            let r    = self.a;
-                            self.a   = Some(Coordinate( ax + self.sx
-                                                      , ay + self.sy
-                                                      , az + self.dz ));
-                            self.err = self.err + self.dx + self.dy;
-                            r
-                        },
-                    }
-                } else {
-                    self.a = None;
-                    Some(self.b)
-                }
-            }
-        }
-    }
-}
-
-impl<T> Coordinate<T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Clone + Copy + From<i32> {
-    fn iter(self, b :&Self, only_edges :bool) -> LineIterator<T> {
-        let Coordinate(ax, ay, az) = self;
-        let Coordinate(bx, by, bz) = *b;
-
-        let dx = (bx - ax).abs();
-        let dy = -(by - ay).abs();
-
-        LineIterator {    a: Some(self)
-                     ,    b: *b
-                     ,   dx: dx
-                     ,   dy: dy
-                     ,   dz: (bz - az) / cmp::max(dx, -dy).into()
-                     ,   sx: if ax < bx { 1 } else { -1 }
-                     ,   sy: if ay < by { 1 } else { -1 }
-                     , err: dx + dy
-                     , only_edges: only_edges
-        }
-    }
-
-    fn line_iter(self, b :&Self) -> LineIterator<T> {
-        self.iter(b, false)
-    }
-
-    fn line(self, b :&Self) -> Vec<Self> {
-        self.line_iter(b).collect()
-    }
-
-    fn edge_iter(self, b :&Self) -> LineIterator<T> {
-        self.iter(b, true)
-    }
-
-    fn edge(self, b :&Self) -> Vec<Self> {
-        self.edge_iter(b).collect()
-    }
-
-    fn face(edges :&[Self]) -> Vec<Self> {
-        edges.to_vec()
-    }
-}
-
-impl<T> Display for Coordinate<T> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        write!(f, "<{},{}>", self.0, self.1)
-    }
-}
-
-impl<T> Display for Coordinates<T> where T: Copy {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        let Coordinates(is) = self;
-
-        let c = match is[..] {
-            []  => String::from(""),
-            [a] => format!("{}", a),
-            _   => {
-                let mut a = format!("{}", is[0]);
-                for i in is[1..].iter() {
-                    a = a + &format!(",{}", i);
-                }
-                a
-            }
-        };
-
-        write!(f, "Coordinates[{}]", c)
-    }
-}
-
-
-#[derive(Debug, Clone, Copy)]
-pub struct Point<T>(pub Coordinate<T>);
-
-impl<T> Drawable<T> for Point<T> where T: Copy {
-    fn plot(&self) -> Coordinates<T> {
-        let Point(c) = *self;
-        Coordinates(vec!(c))
-    }
-}
-
-impl<T> Display for Point<T> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        let Point(p) = self;
-        write!(f, "Point[{}]", p)
-    }
-}
-
-#[derive(Debug, Clone, Copy)]
-pub struct Line<T>(pub Coordinate<T>, pub Coordinate<T>);
-
-impl<T> Drawable<T> for Line<T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Clone + Copy + From<i32> {
-    fn plot(&self) -> Coordinates<T> {
-        let Line(a, b) = *self;
-        Coordinates(a.line(&b))
-    }
-}
-
-impl<T> Display for Line<T> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        let Line(a, b) = self;
-        write!(f, "Line[{},{}]", a, b)
-    }
-}
-
-#[derive(Debug, Clone)]
-pub struct Polyline<T>(pub Coordinates<T>);
-
-impl<T> Drawable<T> for Polyline<T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Clone + Copy + From<i32> {
-    fn plot(&self) -> Coordinates<T> {
-        let Polyline(Coordinates(cs)) = self;
-
-        match cs[..] {
-            []     => Coordinates(Vec::<Coordinate<T>>::new()),
-            [a]    => Coordinates(vec!(a)),
-            [a, b] => Coordinates(a.line(&b)),
-            _      => {
-                let (a, b) = (cs[0], cs[1]);
-                let mut r = a.line(&b);
-                let mut i = b;
-                for j in cs[2..].iter() {
-                    r.append(&mut i.line(j)[1..].to_vec());
-                    i = *j;
-                }
-                Coordinates(r)
-            },
-        }
-    }
-}
-
-impl<T> Display for Polyline<T> where T: Copy {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        let Polyline(a) = self;
-        write!(f, "PLine[{}]", a)
-    }
-}
-
-#[derive(Debug, Clone, Copy)]
-enum Direction { Left, Right }
-
-#[derive(Debug, Clone)]
-pub struct Polygon<T>(pub Coordinates<T>);
-
-#[derive(Debug, Clone)]
-enum VertexIteratorMode { Vertex, Edge }
-#[derive(Debug, Clone)]
-pub struct VertexIterator<'a,T> where T: Debug {
-    p         :&'a Polygon<T>,
-    top       :usize,
-    current   :Option<usize>,
-    edge      :Option<LineIterator<T>>,
-    mode      :VertexIteratorMode,
-    direction :Direction,
-}
-
-impl<'a,T> VertexIterator<'a,T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Copy + From<i32> {
-    fn edge(p :&'a Polygon<T>, direction :Direction) -> Self {
-        let top  = p.vert_min(direction);
-        let next = p.next_y(top, direction);
-        let edge = match next {
-            None       => None,
-            Some(next) => Some(p.vertex(top).edge_iter(&p.vertex(next))),
-        };
-
-        VertexIterator { p:         p
-                       , top:       top
-                       , current:   next
-                       , edge:      edge
-                       , mode:      VertexIteratorMode::Edge
-                       , direction: direction }
-    }
-
-    fn vertex(p :&'a Polygon<T>, direction :Direction) -> Self {
-        let top  = p.vert_min(direction);
-        let next = p.next_y(top, direction);
-
-        VertexIterator { p:         p
-                       , top:       top
-                       , current:   next
-                       , edge:      None
-                       , mode:      VertexIteratorMode::Vertex
-                       , direction: direction }
-    }
-
-    // if this yields "None" we are finished.
-    fn next_edge(&mut self) -> Option<LineIterator<T>> {
-        let current  = self.current?;
-        let next     = self.p.next_y(current, self.direction)?;
-        let mut edge = self.p.vertex(current).edge_iter(&self.p.vertex(next));
-
-        match edge.next() {
-            // It should be impossible that a new edge iterator has no values
-            // at all… anyway, just in case I handle it here.
-            None    => self.next_edge(),
-            Some(_) => {
-                self.current = Some(next);
-                self.edge    = Some(edge);
-                self.edge
-            },
-        }
-    }
-}
-
-impl<'a,T> Iterator for VertexIterator<'a,T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Copy + From<i32> {
-    type Item = Coordinate<T>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        match self.mode {
-            VertexIteratorMode::Edge => {
-                // if for whatever reason edge is "None" finish this iterator.
-                let next = self.edge.as_mut()?.next();
-
-                match next {
-                    Some(_) => next,
-                    None    => {
-                        self.next_edge()?;
-                        self.next()
-                    },
-                }
-            },
-            VertexIteratorMode::Vertex => {
-                let current  = self.current?;
-                self.current = self.p.next_y(current, self.direction);
-                Some(self.p.vertex(current))
-            },
-        }
-    }
-}
-
-impl<T> Polygon<T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Copy + Debug + From<i32> {
-    #[inline]
-    fn vertex(&self, v :usize) -> Coordinate<T> {
-        let Polygon(Coordinates(cs)) = self;
-        cs[v]
-    }
-
-    fn vert_min<'a>(&'a self, d :Direction) -> usize {
-        let Polygon(Coordinates(cs)) = self;
-
-        type ICoord<'a,T> = (usize, &'a Coordinate<T>);
-
-        // TODO I guess the problem here is that it does not account for the
-        //      same y vertex on the beggining and the end. So i guess correct
-        //      would be finding the first one and then dependings on the
-        //      given direction either search left or right for same y's.
-        let fold = |acc :Option<ICoord<'a,T>>, x :ICoord<'a,T>|
-            match acc {
-                None    => Some(x),
-                Some(a) => {
-                    let Coordinate(_, ay, _) = a.1;
-                    let Coordinate(_, xy, _) = x.1;
-                    if xy < ay {Some(x)} else {Some(a)}
-                },
-            };
-
-        let mut  min = cs.iter().enumerate().fold(None, fold).unwrap().0;
-        let mut next = self.step(min, d);
-
-        while self.vertex(min).1 == self.vertex(next).1 {
-            min = next;
-            next = self.step(min, d);
-        }
-
-        min
-    }
-
-    fn left_edge(&self) -> VertexIterator<T> {
-        VertexIterator::edge(self, Direction::Left)
-    }
-
-    fn right_edge(&self) -> VertexIterator<T> {
-        VertexIterator::edge(self, Direction::Right)
-    }
-
-    fn left_vertices(&self) -> VertexIterator<T> {
-        VertexIterator::vertex(self, Direction::Left)
-    }
-
-    fn right_vertices(&self) -> VertexIterator<T> {
-        VertexIterator::vertex(self, Direction::Right)
-    }
-
-    fn left(&self, v :usize) -> usize {
-        let Polygon(Coordinates(cs)) = self;
-
-        match v {
-            0 => cs.len() - 1,
-            _ => v - 1,
-        }
-    }
-
-    fn right(&self, v :usize) -> usize {
-        let Polygon(Coordinates(cs)) = self;
-
-        (v + 1) % cs.len()
-    }
-
-    fn step(&self, v :usize, d :Direction) -> usize {
-        match d {
-            Direction::Left  => self.left(v),
-            Direction::Right => self.right(v),
-        }
-    }
-
-    fn next_y(&self, c :usize, d :Direction) -> Option<usize> {
-        fn inner<T>( p :&Polygon<T>
-                   , c :usize
-                   , n :usize
-                   , d :Direction) -> Option<usize>
-        where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-               + Copy + Debug + From<i32> {
-            if c == n {
-                None
-            } else {
-                let Coordinate(_, cy, _) = p.vertex(c);
-                let Coordinate(_, ny, _) = p.vertex(n);
-
-                if ny < cy { None } else { Some(n) }
-            }
-        }
-
-        inner(self, c, self.step(c, d), d)
-    }
-
-    pub fn debug(&self) {
-        let mut left  = self.left_vertices();
-        let mut right = self.right_vertices();
-
-        if left.find(|l| right.find(|r| l.0 == r.0).is_some()).is_some() {
-            let left  :Vec<Coordinate<T>> = self.left_vertices().collect();
-            let right :Vec<Coordinate<T>> = self.right_vertices().collect();
-
-            println!("===");
-            println!("==  poly : {:?}", self);
-            println!("==  ltop : {:?}", self.vert_min(Direction::Left));
-            println!("==  rtop : {:?}", self.vert_min(Direction::Right));
-            println!("==  left : {:?}", left);
-            println!("== right : {:?}", right);
-            println!("===");
-        }
-    }
-}
-
-impl<T> Drawable<T> for Polygon<T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Clone + Copy + From<i32> {
-    fn plot(&self) -> Coordinates<T> {
-        let Polygon(Coordinates(cs)) = self;
-
-        match cs[..] {
-            []     => Coordinates(Vec::<Coordinate<T>>::new()),
-            [a]    => Coordinates(vec!(a)),
-            [a, b] => Coordinates(a.line(&b)),
-            _      => {
-                let (a, b) = (cs[0], cs[1]);
-                let mut r = a.line(&b);
-                let mut i = b;
-                for j in cs[2..].iter() {
-                    r.append(&mut i.line(j)[1..].to_vec());
-                    i = *j;
-                }
-                let mut j = a.line(&i);
-                let     l = j.len();
-                if l > 1 {
-                    r.append(&mut j[1..l-1].to_vec());
-                }
-                Coordinates(r)
-            },
-        }
-    }
-}
-
-impl<T> Fillable<T> for Polygon<T>
-where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
-       + Debug + Clone + Copy + From<i32> {
-    fn fill(&self, canvas :&mut dyn Canvas<T>, color :u32) {
-        let scanlines = self.left_edge().zip(self.right_edge());
-
-        for l in scanlines.flat_map(|(l, r)| l.line_iter(&r)) {
-            canvas.set_pixel(l, color);
-        }
-    }
-}
-
-impl<T> Display for Polygon<T> where T: Copy {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        let Polygon(a) = self;
-        write!(f, "Poly[{}]", a)
-    }
-}

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use std::fmt::{Debug, Display, Formatter, Result};
+use std::ops::{Add, Div, Sub};
+use std::sync::mpsc;
+
+use super::drawable::Drawable;
+use super::line_iterator::LineIterator;
+
+// A 2D drawing surface.
+pub trait Canvas<T> {
+    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<T>, color :u32);
+    fn set_pixel(&mut self, c :Vertex<T>, color :u32);
+    fn put_text(&self, ofs :Vertex<T>, s :&str);
+    fn show(&self);
+}
+
+// A Vertex is a position on a 2D drawing surface along other stuff
+// that needs to iterate between those coordinates.
+#[derive(Debug, Clone, Copy)]
+pub struct Vertex<T>{  x :i32   // canvas x coordinate
+                    ,  y :i32   // canvas y coordinate
+                    , zr :T   } // z reciprocal from 3D projection.
+
+pub type Vertices<T> = Vec<Vertex<T>>;
+
+impl<T> Vertex<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Clone + Copy + From<i32> {
+    pub fn new(x :i32, y :i32, zr :T) -> Self {
+        Vertex{x, y, zr}
+    }
+
+    #[inline]
+    pub fn as_tuple(&self) -> (i32, i32, T) {
+        (self.x, self.y, self.zr)
+    }
+
+    #[inline]
+    pub fn same_x(&self, b :&Self) -> bool {
+        self.x == b.x
+    }
+
+    #[inline]
+    pub fn same_y(&self, b :&Self) -> bool {
+        self.y == b.y
+    }
+
+    #[inline]
+    pub fn same_position(&self, b :&Self) -> bool {
+        self.same_x(b) && self.same_y(b)
+    }
+
+    fn iter(self, b :Self, only_edges :bool) -> LineIterator<T> {
+        LineIterator::new(self, b, only_edges)
+    }
+
+    pub fn line_iter(self, b :Self) -> LineIterator<T> {
+        self.iter(b, false)
+    }
+
+    pub fn line(self, b :Self) -> Vec<Self> {
+        self.line_iter(b).collect()
+    }
+
+    pub fn edge_iter(self, b :Self) -> LineIterator<T> {
+        self.iter(b, true)
+    }
+
+    fn edge(self, b :Self) -> Vec<Self> {
+        self.edge_iter(b).collect()
+    }
+
+    fn face(edges :&[Self]) -> Vec<Self> {
+        edges.to_vec()
+    }
+}
+
+impl<T> Display for Vertex<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        write!(f, "<{},{}>", self.x, self.y)
+    }
+}
+
+impl<T> Add for Vertex<T> where T: Add<Output=T> {
+    type Output = Self;
+
+    fn add(self, other :Self) -> Vertex<T> {
+        Vertex{  x: self.x  + other.x
+              ,  y: self.y  + other.y
+              , zr: self.zr + other.zr }
+    }
+}

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use super::canvas::Vertices;
+
+pub trait Drawable<T> {
+    fn plot(&self) -> Vertices<T>;
+}

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use std::fmt::Debug;
+use std::ops::{Add, Div, Sub};
+
+use super::canvas::Canvas;
+
+pub trait Fillable<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Copy + From<i32> {
+    fn fill(&self, canvas :&mut dyn Canvas<T>, color :u32);
+}

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use std::fmt::{Debug, Display, Formatter, Result};
+use std::ops::{Add, Div, Sub};
+
+use super::canvas::{Vertex, Vertices};
+use super::drawable::Drawable;
+
+#[derive(Debug, Clone, Copy)]
+pub struct Line<T>(pub Vertex<T>, pub Vertex<T>);
+
+impl<T> Drawable<T> for Line<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Clone + Copy + From<i32> {
+    fn plot(&self) -> Vertices<T> {
+        let Line(a, b) = *self;
+        a.line(b)
+    }
+}
+
+impl<T> Display for Line<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        let Line(a, b) = self;
+        write!(f, "Line[{},{}]", a, b)
+    }
+}

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use std::cmp::max;
+use std::fmt::Debug;
+use std::ops::{Add, Div, Sub};
+
+use super::canvas::Vertex;
+
+#[derive(Debug, Clone, Copy)]
+pub struct LineIterator<T> where T: Debug {
+          a :Option<Vertex<T>>
+    ,     b :Vertex<T>
+    ,    dx :i32
+    ,    dy :i32
+    ,  incx :Vertex<T>
+    ,  incy :Vertex<T>
+    , incxy :Vertex<T>
+    ,   err :i32
+    , edges :bool
+}
+
+impl<T> LineIterator<T>
+where T: Add<Output=T> + Div<Output=T> + Sub<Output=T>
+       + Debug + Clone + Copy + From<i32> {
+    pub fn new(a :Vertex<T>, b :Vertex<T>, edges :bool) -> LineIterator<T> {
+        let (ax, ay, azr) = a.as_tuple();
+        let (bx, by, bzr) = b.as_tuple();
+
+        let dx = (bx - ax).abs();
+        let dy = -(by - ay).abs();
+        let dz = (bzr - azr) / max(dx, -dy).into();
+
+        let sx = if ax < bx { 1 } else { -1 };
+        let sy = if ay < by { 1 } else { -1 };
+
+        LineIterator { a:     Some(a)
+                     , b:     b
+                     , dx:    dx
+                     , dy:    dy
+                     , incx:  Vertex::new(      sx, 0.into(), dz)
+                     , incy:  Vertex::new(0.into(),       sy, dz)
+                     , incxy: Vertex::new(      sx,       sy, dz)
+                     , err:   dx + dy
+                     , edges: edges }
+    }
+}
+
+impl<T> Iterator for LineIterator<T>
+where T: Add<Output=T> + Div<Output=T> + Sub<Output=T>
+       + Debug + Copy + From<i32> {
+    type Item = Vertex<T>;
+
+    // Bresenham based line iteration.
+    fn next(&mut self) -> Option<Self::Item> {
+        if ! self.a?.same_position(&self.b) {
+            let ret = self.a;
+            let inc = match (2*self.err >= self.dy, 2*self.err <= self.dx ) {
+                (true, false) => ( self.incx,         self.dy, self.edges),
+                (false, true) => ( self.incy,         self.dx, false),
+                _             => (self.incxy, self.dx+self.dy, false),
+            };
+
+            self.a   = Some(self.a? + inc.0);
+            self.err = self.err + inc.1;
+            if inc.2 { self.next() } else { ret }
+        } else {
+            self.a = None;
+            Some(self.b)
+        }
+    }
+}

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+pub trait Easel {
+}
+
+// Trait to implement for a concrete canvas as well as struct for canvas
+// coordinates (which also includes z reciprocal)
+pub mod canvas;
+
+// Traits that new drawing primitives must implement to be drawn on a canvas.
+pub mod drawable;
+pub mod fillable;
+
+// Drawing primitives
+pub mod line;
+pub mod point;
+pub mod polygon;
+pub mod polyline;
+
+// Helper iterators to find all positions a primitive needs to draw.
+mod line_iterator;
+mod vertex_iterator;

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use std::fmt::{Display, Formatter, Result};
+
+use super::canvas::{Vertex, Vertices};
+use super::drawable::Drawable;
+
+#[derive(Debug, Clone, Copy)]
+pub struct Point<T>(pub Vertex<T>);
+
+impl<T> Drawable<T> for Point<T> where T: Copy {
+    fn plot(&self) -> Vertices<T> {
+        let Point(c) = *self;
+        vec!(c)
+    }
+}
+
+impl<T> Display for Point<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        let Point(p) = self;
+        write!(f, "Point[{}]", p)
+    }
+}

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use std::fmt::Debug;
+use std::ops::{Add, Div, Sub};
+
+use super::canvas::{Canvas, Vertex, Vertices};
+use super::drawable::Drawable;
+use super::fillable::Fillable;
+use super::vertex_iterator::{Direction, VertexIterator};
+
+#[derive(Debug, Clone)]
+pub struct Polygon<T>(pub Vertices<T>);
+
+impl<T> Polygon<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Copy + Debug + From<i32> {
+    #[inline]
+    pub fn vertex(&self, v :usize) -> Vertex<T> {
+        let Polygon(cs) = self;
+        cs[v]
+    }
+
+    pub fn vert_min<'a>(&'a self, d :Direction) -> usize {
+        let Polygon(cs) = self;
+
+        type ICoord<'a, T> = (usize, &'a Vertex<T>);
+
+        let fold = |acc :Option<ICoord<'a,T>>, x :ICoord<'a, T>|
+                   match acc {
+                       None    => Some(x),
+                       Some(a) => {
+                           let (_, ay, _) = a.1.as_tuple();
+                           let (_, xy, _) = x.1.as_tuple();
+                           if xy < ay {Some(x)} else {Some(a)}
+                       },
+                   };
+
+        let mut  min = cs.iter().enumerate().fold(None, fold).unwrap().0;
+        let mut next = self.step(min, d);
+
+        while self.vertex(min).same_y(&self.vertex(next)) {
+            min  = next;
+            next = self.step(min, d);
+        }
+
+        min
+    }
+
+    fn left_edge(&self) -> VertexIterator<T> {
+        VertexIterator::edge(self, Direction::Left)
+    }
+
+    fn right_edge(&self) -> VertexIterator<T> {
+        VertexIterator::edge(self, Direction::Right)
+    }
+
+    fn left_vertices(&self) -> VertexIterator<T> {
+        VertexIterator::line(self, Direction::Left)
+    }
+
+    fn right_vertices(&self) -> VertexIterator<T> {
+        VertexIterator::line(self, Direction::Right)
+    }
+
+    fn left(&self, v :usize) -> usize {
+        let Polygon(cs) = self;
+
+        match v {
+            0 => cs.len() - 1,
+            _ => v - 1,
+        }
+    }
+
+    fn right(&self, v :usize) -> usize {
+        let Polygon(cs) = self;
+
+        (v + 1) % cs.len()
+    }
+
+    fn step(&self, v :usize, d :Direction) -> usize {
+        match d {
+            Direction::Left  => self.left(v),
+            Direction::Right => self.right(v),
+        }
+    }
+
+    pub fn next_y(&self, c :usize, d :Direction) -> Option<usize> {
+        fn inner<T>( p :&Polygon<T>
+                   , c :usize
+                   , n :usize
+                   , d :Direction) -> Option<usize>
+        where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+               + Copy + Debug + From<i32> {
+            if c == n {
+                None
+            } else {
+                let (_, cy, _) = p.vertex(c).as_tuple();
+                let (_, ny, _) = p.vertex(n).as_tuple();
+
+                if ny < cy { None } else { Some(n) }
+            }
+        }
+
+        inner(self, c, self.step(c, d), d)
+    }
+}
+
+impl<T> Drawable<T> for Polygon<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Clone + Copy + From<i32> {
+    fn plot(&self) -> Vertices<T> {
+        let Polygon(cs) = self;
+
+        match cs[..] {
+            []     => Vec::<Vertex<T>>::new(),
+            [a]    => vec!(a),
+            [a, b] => a.line(b),
+            _      => {
+                let (a, b) = (cs[0], cs[1]);
+                let mut r = a.line(b);
+                let mut i = b;
+                for j in cs[2..].iter() {
+                    r.append(&mut i.line(*j)[1..].to_vec());
+                    i = *j;
+                }
+                let mut j = a.line(i);
+                let     l = j.len();
+                if l > 1 {
+                    r.append(&mut j[1..l-1].to_vec());
+                }
+                r
+            },
+        }
+    }
+}
+
+impl<T> Fillable<T> for Polygon<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Clone + Copy + From<i32> {
+    fn fill(&self, canvas :&mut dyn Canvas<T>, color :u32) {
+        let scanlines = self.left_edge().zip(self.right_edge());
+        let  vertices = |(l, r) :(Vertex<T>, Vertex<T>)| l.line_iter(r);
+
+        for p in scanlines.flat_map(vertices) {
+            canvas.set_pixel(p, color);
+        }
+    }
+}
+
+/*
+impl<T> Display for Polygon<T> where T: Copy {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        let Polygon(a) = self;
+        write!(f, "Poly[{}]", a)
+    }
+}
+*/

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+use std::fmt::Debug;
+use std::ops::{Add, Div, Sub};
+
+use super::canvas::{Vertex, Vertices};
+use super::drawable::Drawable;
+
+#[derive(Debug, Clone)]
+pub struct Polyline<T>(pub Vertices<T>);
+
+impl<T> Drawable<T> for Polyline<T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Clone + Copy + From<i32> {
+    fn plot(&self) -> Vertices<T> {
+        let Polyline(cs) = self;
+
+        match cs[..] {
+            []     => Vec::<Vertex<T>>::new(),
+            [a]    => vec!(a),
+            [a, b] => a.line(b),
+            _      => {
+                let (a, b) = (cs[0], cs[1]);
+                let mut r = a.line(b);
+                let mut i = b;
+                for j in cs[2..].iter() {
+                    r.append(&mut i.line(*j)[1..].to_vec());
+                    i = *j;
+                }
+                r
+            },
+        }
+    }
+}
+/*
+impl<T> Display for Polyline<T> where T: Copy {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        let Polyline(a) = self;
+        write!(f, "PLine[{}]", a)
+    }
+}
+*/

+//
+// …
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+use std::fmt::Debug;
+use std::ops::{Add, Sub, Div};
+
+use super::line_iterator::LineIterator;
+use super::canvas::Vertex;
+use super::polygon::Polygon;
+
+#[derive(Debug, Clone, Copy)]
+pub enum Direction {
+    Left,
+    Right,
+}
+
+#[derive(Debug, Clone)]
+enum VertexIteratorMode {
+    Line,
+    Edge
+}
+
+#[derive(Debug, Clone)]
+pub struct VertexIterator<'a, T> where T: Debug {
+    p         :&'a Polygon<T>,
+    top       :usize,
+    current   :Option<usize>,
+    edge      :Option<LineIterator<T>>,
+    mode      :VertexIteratorMode,
+    direction :Direction,
+}
+
+impl<'a, T> VertexIterator<'a, T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Copy + From<i32> {
+    pub fn line(p :&'a Polygon<T>, direction :Direction) -> Self {
+        let top  = p.vert_min(direction);
+        let next = p.next_y(top, direction);
+
+        VertexIterator { p:         p
+                       , top:       top
+                       , current:   next
+                       , edge:      None
+                       , mode:      VertexIteratorMode::Line
+                       , direction: direction }
+    }
+
+    pub fn edge(p :&'a Polygon<T>, direction :Direction) -> Self {
+        let mut vi = Self::line(p, direction);
+
+        vi.mode = VertexIteratorMode::Edge;
+        vi.edge = match vi.current {
+            None       => None,
+            Some(next) => Some(p.vertex(vi.top).edge_iter(p.vertex(next))),
+        };
+
+        vi
+    }
+
+    // if this yields "None" we are finished.
+    fn next_edge(&mut self) -> Option<LineIterator<T>> {
+        let current  = self.current?;
+        let next     = self.p.next_y(current, self.direction)?;
+        let mut edge = self.p.vertex(current).edge_iter(self.p.vertex(next));
+
+        match edge.next() {
+            // It should be impossible that a new edge iterator has no values
+            // at all… anyway, just in case I handle it here.
+            None    => self.next_edge(),
+            Some(_) => {
+                self.current = Some(next);
+                self.edge    = Some(edge);
+                self.edge
+            },
+        }
+    }
+}
+
+impl<'a,T> Iterator for VertexIterator<'a,T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Debug + Copy + From<i32> {
+    type Item = Vertex<T>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match self.mode {
+            VertexIteratorMode::Edge => {
+                // if for whatever reason edge is "None" finish this iterator.
+                let next = self.edge.as_mut()?.next();
+
+                match next {
+                    Some(_) => next,
+                    None    => {
+                        self.next_edge()?;
+                        self.next()
+                    },
+                }
+            },
+            VertexIteratorMode::Line => {
+                let current  = self.current?;
+                self.current = self.p.next_y(current, self.direction);
+                Some(self.p.vertex(current))
+            },
+        }
+    }
+}

@@ -22,7 +22,8 @@ use std::convert::{From, Into};
 use std::ops::{Add,Sub,Neg,Mul,Div};
 use std::fmt::Debug;
 
-use crate::easel::{Canvas, Coordinate, Coordinates, Polygon};
+use crate::easel::canvas::{Canvas, Vertex};
+use crate::easel::polygon::Polygon;
 use crate::transform::{TMatrix, Transformable};
 use crate::trigonometry::Trig;
 use crate::vector::Vector;
@@ -251,20 +252,15 @@ where T: Add<Output = T> + Sub<Output = T> + Neg<Output = T>
         let f2 :T = 2.into();
         let ch    = a / (f2 * T::sqrt(f2).unwrap());
 
-        let ps = vec!( Point::new(-ch, -ch,  ch)    // A
-                     , Point::new(-ch,  ch, -ch)    // C
-                     , Point::new( ch, -ch, -ch)    // E
-                     , Point::new( ch,  ch,  ch) ); // G
+        let ps = vec!( Point::new(-ch, -ch,  ch)
+                     , Point::new(-ch,  ch, -ch)
+                     , Point::new( ch, -ch, -ch)
+                     , Point::new( ch,  ch,  ch) );
 
-        // bottom: 1, 2, 3
         let fs = vec!( Face::new(vec!(2, 1, 0), &ps) // bottom
                      , Face::new(vec!(3, 2, 0), &ps)
                      , Face::new(vec!(0, 1, 3), &ps)
                      , Face::new(vec!(1, 2, 3), &ps) );
-        //let fs = vec!( Face::new(vec!(0, 1, 2), &ps) // bottom
-        //             , Face::new(vec!(0, 2, 3), &ps)
-        //             , Face::new(vec!(3, 1, 0), &ps)
-        //             , Face::new(vec!(3, 2, 1), &ps) );
 
         Polyeder{ points: ps, faces: fs }
     }
@@ -335,15 +331,15 @@ where T: Add<Output = T> + Sub<Output = T> + Neg<Output = T>
         // Helper to create a Polygon from Coordinates…
         // TODO probably there needs to be a Polygon constructor for this.
         fn polygon<I, T>(c :I) -> Polygon<T>
-        where I: Iterator<Item = Coordinate<T>> {
-            Polygon(Coordinates(c.collect()))
+        where I: Iterator<Item = Vertex<T>> {
+            Polygon(c.collect())
         }
 
         // this one does the projection... as the projection was the last
         // matrix we do not need to do it here.
         let to_coord = |p :&usize| {
             let Point(v, _) = camera.project(self.points[*p]);
-            Coordinate(T::round(&v.x()), T::round(&v.y()), v.z() - 1.into())
+            Vertex::new(T::round(&v.x()), T::round(&v.y()), v.z() - 1.into())
         };
         let to_poly  = |f :&Face<T>| {
                        let     pg    = polygon(f.corners.iter().map(to_coord));

+//
+// easel3d is a library that provides basic math for 3D transformation and
+// projection as well as a simple software resterizer.
+//
+// All of them implemented as generics so that they work with f64 and other
+// suitable types.
+//
+// This is mainly the result of my learning rust experiments. So it is
+// very likely not optimal and improvements and suggestions are welcome.
+//
+// The rasterization part, called easel consists of two traits (easel and
+// canvas) where the one is cuttently empty because I found no methods that
+// I currently need. And the other needs to be implemented to get a
+// concrete rasterizer. After that one can use all of the other types there.
+//
+// Georg Hopp <georg@steffers.org>
+//
+// Copyright © 2019 Georg Hopp
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
 extern crate lazy_static;
 
 pub type Error = &'static str;
@@ -11,253 +43,3 @@ pub mod geometry;
 mod utils;
 
 use vector::Vector;
-use easel::{Canvas, Coordinate, Drawable, Fillable};
-use geometry::{Camera, DirectLight, Polyeder, Primitives};
-use transform::{TMatrix};
-
-use std::fmt::{Display, Formatter, Result};
-use std::sync::mpsc;
-use std::time::Instant;
-use wasm_bindgen::prelude::*;
-
-// When the `wee_alloc` feature is enabled, use `wee_alloc` as the global
-// allocator.
-#[cfg(feature = "wee_alloc")]
-#[global_allocator]
-static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
-
-#[wasm_bindgen]
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub struct Color(u8, u8, u8, u8);
-
-#[wasm_bindgen]
-pub struct View3d { width       :u16
-                  , height      :u16
-                  , size        :usize
-                  , degree      :i32
-                  //, start       :Instant
-                  , tetrahedron :Polyeder<f64>
-                  , cube        :Polyeder<f64>
-                  , camera      :Option<Camera<f64>>
-                  , light       :DirectLight<f64>
-                  , zbuf        :Vec<f64>
-                  , image       :Vec<Color>
-}
-
-#[wasm_bindgen]
-impl View3d {
-    pub fn new(width :u16, height :u16) -> Self {
-        let size = width as usize * height as usize;
-        let light_vector = Vector(0.0, 0.0, 1.0);
-
-        let mut view3d = Self { width:       width
-                              , height:      height
-                              , size:        size
-                              , degree:      0
-                              //, start:       Instant::now()
-                              , tetrahedron: Polyeder::tetrahedron(100.0)
-                              , cube:        Polyeder::cube(56.25)
-                              , camera:      None
-                              , light:       DirectLight::new(light_vector)
-                              , zbuf:        vec!(0.0; size)
-                              , image:       vec!(Color(0, 0, 0, 0xFF); size)
-        };
-
-        view3d.camera = Some(Camera::<f64>::new(&view3d, 45));
-        view3d
-    }
-
-    pub fn width(&self) -> u16 {
-        self.width
-    }
-
-    pub fn height(&self) -> u16 {
-        self.height
-    }
-
-    pub fn update(&mut self) {
-        //let deg = ((self.start.elapsed() / 25).as_millis() % 360) as i32;
-        let  t = TMatrix::translate(Vector(0.0, 0.0, 150.0));
-        let rz = TMatrix::rotate_z(self.degree);
-        let rx = TMatrix::rotate_x(-self.degree*2);
-        let ry = TMatrix::rotate_y(-self.degree*2);
-
-        let rot1 = TMatrix::combine(vec!(rz, rx, t));
-        let rot2 = TMatrix::combine(vec!(rz, ry, t));
-
-        let objects = vec!( (self.tetrahedron.transform(&rot1), 0xFFFF00)
-                          , (       self.cube.transform(&rot2), 0x0000FF) );
-
-        self.degree = (self.degree + 1) % 360;
-
-        self.clear();
-
-        match self.camera {
-            None         => {},
-            Some(camera) => {
-                for (o, color) in objects {
-                    for (pg, c) in o.project(&camera, &self.light, color) {
-                        (&pg).fill(self, c);
-                    }
-                }
-            },
-        }
-    }
-
-    pub fn image(&self) -> *const Color {
-        self.image.as_ptr()
-    }
-}
-
-impl Canvas<f64> for View3d {
-    fn width(&self) -> u16 {
-        self.width
-    }
-
-    fn height(&self) -> u16 {
-        self.height
-    }
-
-    fn clear(&mut self) {
-        self.zbuf  = vec!(0.0; self.size);
-        self.image = vec!(Color(0, 0, 0, 0xFF); self.size);
-    }
-
-    fn set_pixel(&mut self, c :Coordinate<f64>, color :u32) {
-        let Coordinate(x, y, zr) = c;
-        let idx :usize = (y * (self.width as i32) + x) as usize;
-
-        let r = ((color >> 16) & 0xFF) as u8;
-        let g = ((color >>  8) & 0xFF) as u8;
-        let b = (        color & 0xFF) as u8;
-
-        if self.zbuf[idx] < zr {
-            self.zbuf[idx]  = zr;
-            self.image[idx] = Color(r, g, b, 0xFF);
-        }
-    }
-
-    // Empty implementations for now… mostly not needed because it is
-    // done from JavaScript…
-    fn init_events(&self) {}
-    fn start_events(&self, _ :mpsc::Sender<i32>) {}
-    fn draw( &mut self, _ :&dyn Drawable<f64>, _ :Coordinate<f64>, _ :u32 ) {}
-    fn put_text(&self, _ :Coordinate<f64>, _ :&str) {}
-    fn show(&self) {}
-}
-
-#[wasm_bindgen]
-#[repr(u8)]
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-pub enum Cell {
-    Dead  = 0,
-    Alive = 1,
-}
-
-#[wasm_bindgen]
-pub struct Universe {
-    width  :u32,
-    height :u32,
-    cells  :Vec<Cell>,
-}
-
-#[wasm_bindgen]
-impl Universe {
-    pub fn new() -> Universe {
-        let width  = 64;
-        let height = 64;
-
-        let init_cells = |i :u32| {
-            if i % 2 == 0 || i % 7 == 0 { Cell::Alive } else { Cell::Dead }
-        };
-
-        let cells = (0..width * height).map(init_cells).collect();
-
-        Universe {
-            width:  width,
-            height: height,
-            cells:  cells,
-        }
-    }
-
-    pub fn width(&self) -> u32 {
-        self.width
-    }
-
-    pub fn height(&self) -> u32 {
-        self.height
-    }
-
-    pub fn cells(&self) -> *const Cell {
-        self.cells.as_ptr()
-    }
-
-    pub fn render(&self) -> String {
-        self.to_string()
-    }
-
-    pub fn tick(&mut self) {
-        let mut next = self.cells.clone();
-
-        for row in 0..self.height {
-            for col in 0..self.width {
-                let idx            = self.get_index(row, col);
-                let cell           = self.cells[idx];
-                let live_neighbors = self.live_neighbor_count(row, col);
-
-                // Game of life rules....
-                let next_cell = match (cell, live_neighbors) {
-                    (Cell::Alive, 2) |
-                    (Cell::Alive, 3) => Cell::Alive,
-                    (Cell::Alive, _) => Cell::Dead,
-                    ( Cell::Dead, 3) => Cell::Alive,
-                    (  otherwise, _) => otherwise,
-                };
-
-                next[idx] = next_cell;
-            }
-        }
-
-        self.cells = next;
-    }
-
-    fn get_index(&self, row :u32, col :u32) -> usize {
-        (row * self.width + col) as usize
-    }
-
-    fn live_neighbor_count(&self, row :u32, col :u32) -> u8 {
-        let mut count = 0;
-
-        for delta_row in [self.height - 1, 0, 1].iter().cloned() {
-            for delta_col in [self.width - 1, 0, 1].iter().cloned() {
-                if delta_row == 0 && delta_col == 0 {
-                    continue;
-                }
-
-                let neighbor_row = (row + delta_row) % self.height;
-                let neighbor_col = (col + delta_col) % self.width;
-                let idx = self.get_index(neighbor_row, neighbor_col);
-                count += self.cells[idx] as u8;
-            }
-        }
-
-        count
-    }
-}
-
-impl Display for Universe {
-    fn fmt(&self, f :&mut Formatter) -> Result {
-        for line in self.cells.as_slice().chunks(self.width as usize) {
-            for &cell in line {
-                let symbol = match cell {
-                    Cell::Dead  => ' ',
-                    Cell::Alive => '*',
-                };
-                write!(f, "{}", symbol)?;
-            }
-            write!(f, "\n")?;
-        }
-
-        Ok(())
-    }
-}

-pub fn set_panic_hook() {
-    // When the `console_error_panic_hook` feature is enabled, we can call the
-    // `set_panic_hook` function at least once during initialization, and then
-    // we will get better error messages if our code ever panics.
-    //
-    // For more details see
-    // https://github.com/rustwasm/console_error_panic_hook#readme
-    #[cfg(feature = "console_error_panic_hook")]
-    console_error_panic_hook::set_once();
-}