4 files changed, 596 insertions, 0 deletions

diff --git a/src/app.rs b/src/app.rs
new file mode 100644
index 0000000..84d884f
--- /dev/null
+++ b/src/app.rs
@@ -0,0 +1,447 @@
+use crate::undo::{ModifyRecord, OpKind, Operation, UndoStack};
+
+use sdl2::{
+    event::Event,
+    keyboard::Keycode,
+    mouse::MouseButton,
+    pixels::Color,
+    rect::{Point, Rect},
+    render::Canvas,
+    video::Window,
+    Sdl,
+};
+
+use crate::consts::{BLACK, GRID_COLOR, WHITE};
+
+pub struct AppState<'ctx> {
+    start: Point,
+    width: u32,
+    height: u32,
+    data: Vec<bool>,
+    zoom: u8,
+    brush_size: u8,
+    grid: Grid,
+    context: &'ctx Sdl,
+    canvas: Canvas<Window>,
+    last_point: Option<Point>,
+    active_color: bool,
+    undo_stack: UndoStack<Operation>,
+    current_operation: Operation,
+}
+
+struct Grid {
+    enabled: bool,
+    color: Color,
+}
+
+impl Grid {
+    fn new() -> Self {
+        Self {
+            enabled: true,
+            color: GRID_COLOR,
+        }
+    }
+}
+
+// private actions on appstate
+impl<'ctx> AppState<'ctx> {
+    fn pan<P: Into<Point>>(&mut self, direction: P) {
+        self.start += direction.into();
+    }
+
+    fn bounds(&self) -> (Point, Point) {
+        let x_min = self.start.x();
+        let y_min = self.start.y();
+        let x_max = self.start.x() + (self.width * self.zoom as u32) as i32;
+        let y_max = self.start.y() + (self.height * self.zoom as u32) as i32;
+        return (
+            Point::new(x_min, y_min),
+            Point::new(x_max as i32, y_max as i32),
+        );
+    }
+
+    fn change_active_color(&mut self) {
+        self.active_color = !self.active_color;
+    }
+
+    fn idx_at_coord<P: Into<Point>>(&self, p: P) -> Option<(u32, u32)> {
+        let p: Point = p.into();
+        if self.within_canvas(p) {
+            // convert p relative to start of drawing area
+            let rel_p = p - self.start;
+            // reduce p based on zoom and cell size
+            let (sx, sy) = (rel_p.x() / self.zoom as i32, rel_p.y() / self.zoom as i32);
+            return Some((sx as u32, sy as u32));
+        } else {
+            None
+        }
+    }
+
+    fn within_canvas<P: Into<Point>>(&self, p: P) -> bool {
+        let p: Point = p.into();
+        let (mini, maxi) = self.bounds();
+        p.x() < maxi.x() && p.y() < maxi.y() && p.x() >= mini.x() && p.y() >= mini.y()
+    }
+
+    fn within_grid<P: Into<Point>>(&self, p: P) -> bool {
+        let p = p.into();
+        let (x, y) = (p.x(), p.y());
+        x >= 0 && x < self.width as i32 && y >= 0 && y < self.height as i32
+    }
+
+    fn set_at<P: Into<Point>>(&mut self, p: P, val: bool) -> Result<ModifyRecord, ()> {
+        let p: Point = p.into();
+        if let Some((x, y)) = self.idx_at_coord(p) {
+            let old_val = self.data[(y * self.width + x) as usize];
+            self.data[(y * self.width + x) as usize] = val;
+            return Ok(ModifyRecord::new((x as i32, y as i32), old_val, val));
+        }
+        return Err(());
+    }
+
+    fn set_with_absolute<P: Into<Point>>(&mut self, p: P, val: bool) -> Result<ModifyRecord, ()> {
+        let p: Point = p.into();
+        let (x, y) = (p.x(), p.y());
+        if self.within_grid(p) {
+            let idx = y as u32 * self.width + x as u32;
+            let old_val = self.data[idx as usize];
+            self.data[idx as usize] = val;
+            return Ok(ModifyRecord::new((x as i32, y as i32), old_val, val));
+        }
+        return Err(());
+    }
+
+    fn toggle_grid(&mut self) {
+        self.grid.enabled = !self.grid.enabled;
+    }
+
+    fn paint_point<P: Into<Point>>(
+        &mut self,
+        center: P,
+        val: bool,
+    ) -> Result<Vec<ModifyRecord>, ()> {
+        let radius = self.brush_size;
+        if radius == 1 {
+            return Ok(self.set_at(center, val).map(|x| vec![x])?);
+        } else {
+            if let Some(center_on_grid) = self.idx_at_coord(center) {
+                // center_on_grid is now a coordinate on the drawing grid
+                let (x0, y0) = (center_on_grid.0 as i64, center_on_grid.1 as i64);
+                let (mut dx, mut dy, mut err) = (radius as i64, 0i64, 1 - radius as i64);
+                let mut circle = vec![];
+                let mut old_vals = vec![];
+                while dx >= dy {
+                    circle.push((x0 + dx, y0 + dy));
+                    circle.push((x0 - dx, y0 + dy));
+                    circle.push((x0 + dx, y0 - dy));
+                    circle.push((x0 - dx, y0 - dy));
+                    circle.push((x0 + dy, y0 + dx));
+                    circle.push((x0 - dy, y0 + dx));
+                    circle.push((x0 + dy, y0 - dx));
+                    circle.push((x0 - dy, y0 - dx));
+                    dy = dy + 1;
+                    if err < 0 {
+                        err = err + 2 * dy + 1;
+                    } else {
+                        dx -= 1;
+                        err += 2 * (dy - dx) + 1;
+                    }
+                }
+                // circle's insides
+                for x in 0..radius as i64 {
+                    for y in 0..radius as i64 {
+                        if x.pow(2) + y.pow(2) < (radius as i64).pow(2) {
+                            circle.push((x0 + x, y0 + y));
+                            circle.push((x0 - x, y0 + y));
+                            circle.push((x0 + x, y0 - y));
+                            circle.push((x0 - x, y0 - y));
+                        }
+                    }
+                }
+                dbg!(&circle);
+                for (x, y) in circle {
+                    if self.within_grid((x as i32, y as i32)) {
+                        let idx = y as u32 * self.width + x as u32;
+                        old_vals.push(ModifyRecord::new(
+                            (x as i32, y as i32),
+                            self.data[idx as usize],
+                            val,
+                        ));
+                        self.data[idx as usize] = val;
+                    }
+                }
+                return Ok(old_vals);
+            }
+        }
+        return Err(());
+    }
+
+    fn draw_line<P: Into<Point>>(&mut self, to: P) {
+        let to = to.into();
+        let from = self.last_point.unwrap_or(to.into());
+    }
+
+    fn apply_operation(&mut self, op: Operation, op_kind: OpKind) -> Result<(), ()> {
+        for ModifyRecord {
+            point,
+            old_val,
+            val,
+        } in op.into_iter()
+        {
+            self.set_with_absolute(
+                point,
+                match op_kind {
+                    OpKind::Undo => old_val,
+                    OpKind::Redo => val,
+                },
+            )?;
+        }
+        Ok(())
+    }
+
+    fn zoom_in(&mut self, p: (i32, i32)) {
+        // attempt to center around cursor
+        if let Some(p) = self.idx_at_coord(p) {
+            let (x1, y1) = (p.0 * (self.zoom as u32), p.1 * (self.zoom as u32));
+            let (x2, y2) = (p.0 * (1 + self.zoom as u32), p.1 * (1 + self.zoom as u32));
+            let diffx = x2 as i32 - x1 as i32;
+            let diffy = y2 as i32 - y1 as i32;
+            self.start = self.start - Point::from((diffx, diffy));
+        }
+        self.zoom += 1;
+    }
+
+    fn increase_brush_size(&mut self) {
+        self.brush_size += 1;
+    }
+
+    fn descrease_brush_size(&mut self) {
+        if self.brush_size > 1 {
+            self.brush_size -= 1;
+        }
+    }
+
+    fn zoom_out(&mut self, p: (i32, i32)) {
+        if self.zoom > 1 {
+            // attempt to center around cursor
+            if let Some(p) = self.idx_at_coord(p) {
+                let (x1, y1) = (p.0 * (self.zoom as u32), p.1 * (self.zoom as u32));
+                let (x2, y2) = (p.0 * (self.zoom as u32 - 1), p.1 * (self.zoom as u32 - 1));
+                let diffx = x2 as i32 - x1 as i32;
+                let diffy = y2 as i32 - y1 as i32;
+                self.start = self.start - Point::from((diffx, diffy));
+            }
+            self.zoom -= 1;
+        }
+    }
+
+    fn draw_grid(&mut self) {
+        let cs = self.zoom as u32;
+        let canvas = &mut self.canvas;
+        canvas.set_draw_color(self.grid.color);
+        for i in 0..=self.width {
+            let x = (i * cs) as i32;
+            let y = (self.height * cs) as i32;
+            let start = self.start + Point::new(x, 0);
+            let end = self.start + Point::new(x, y);
+            canvas.draw_line(start, end).unwrap();
+        }
+        for j in 0..=self.height {
+            let x = (self.width * cs) as i32;
+            let y = (j * cs) as i32;
+            let start = self.start + Point::new(0, y);
+            let end = self.start + Point::new(x, y);
+            canvas.draw_line(start, end).unwrap();
+        }
+    }
+
+    fn draw(&mut self) {
+        let cs = self.zoom as u32;
+        if self.grid.enabled {
+            self.draw_grid();
+        }
+        let canvas = &mut self.canvas;
+        for (idx, val) in self.data.iter().enumerate() {
+            if *val {
+                let idx = idx as i32;
+                let (x, y) = (idx % self.width as i32, idx / self.height as i32);
+                canvas.set_draw_color(WHITE);
+                canvas
+                    .fill_rect(Rect::new(
+                        // start drawing 1 pixel after the grid line
+                        x * cs as i32 + self.start.x() + 1,
+                        y * cs as i32 + self.start.y() + 1,
+                        // stop drawing 1 pixel before the grid line
+                        cs - 1,
+                        cs - 1,
+                    ))
+                    .unwrap();
+            }
+        }
+    }
+
+    fn modify<F>(&mut self, func: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        func(self);
+        self.canvas.set_draw_color(Color::RGB(0, 0, 0));
+        self.canvas.clear();
+        self.canvas.set_draw_color(Color::RGB(64, 64, 64));
+        self.draw();
+        self.canvas.present();
+    }
+}
+
+// publicly available functions on appstate
+impl<'ctx> AppState<'ctx> {
+    pub fn init(width: u32, height: u32, context: &'ctx Sdl) -> Self {
+        let video_subsystem = context.video().unwrap();
+
+        let window = video_subsystem
+            .window("Pixel editor", 200, 200)
+            .position_centered()
+            .opengl()
+            .build()
+            .map_err(|e| e.to_string())
+            .unwrap();
+
+        let canvas = window
+            .into_canvas()
+            .build()
+            .map_err(|e| e.to_string())
+            .unwrap();
+
+        let data = vec![false; (width * height) as usize];
+        Self {
+            start: Point::new(60, 60),
+            width,
+            height,
+            data,
+            zoom: 5,
+            brush_size: 1,
+            grid: Grid::new(),
+            canvas,
+            context,
+            last_point: None,
+            active_color: true,
+            undo_stack: UndoStack::new(),
+            current_operation: Vec::new(),
+        }
+    }
+
+    pub fn run(&mut self) {
+        self.canvas.set_draw_color(BLACK);
+        self.canvas.clear();
+        self.draw();
+        self.canvas.present();
+
+        let mut event_pump = self.context.event_pump().unwrap();
+
+        'running: loop {
+            let mouse = event_pump.mouse_state();
+            for event in event_pump.poll_iter() {
+                match event {
+                    Event::KeyDown {
+                        keycode: Some(k), ..
+                    } => {
+                        match k {
+                            // pan
+                            Keycode::W => self.modify(|e| e.pan((0, 10))),
+                            Keycode::A => self.modify(|e| e.pan((10, 0))),
+                            Keycode::S => self.modify(|e| e.pan((0, -10))),
+                            Keycode::D => self.modify(|e| e.pan((-10, 0))),
+                            // zoom
+                            Keycode::C => {
+                                let cursor = (mouse.x(), mouse.y());
+                                self.modify(|e| e.zoom_in(cursor));
+                            }
+                            Keycode::Z => {
+                                let cursor = (mouse.x(), mouse.y());
+                                self.modify(|e| e.zoom_out(cursor));
+                            }
+                            // brush ops
+                            Keycode::Q => self.modify(|e| e.descrease_brush_size()),
+                            Keycode::E => self.modify(|e| e.increase_brush_size()),
+                            // flip color
+                            Keycode::X => self.modify(|e| e.change_active_color()),
+                            // toggle grid
+                            Keycode::Tab => self.modify(|e| e.toggle_grid()),
+                            // exit
+                            Keycode::Escape => break 'running,
+                            // undo & redo
+                            Keycode::U => self.modify(|e| {
+                                if let Some(op) = e.undo_stack.undo() {
+                                    e.apply_operation(op, OpKind::Undo);
+                                }
+                            }),
+                            Keycode::R => self.modify(|e| {
+                                if let Some(op) = e.undo_stack.redo() {
+                                    e.apply_operation(op, OpKind::Redo);
+                                }
+                            }),
+                            _ => (),
+                        }
+                    }
+                    // start of operation
+                    Event::MouseButtonDown {
+                        x, y, mouse_btn, ..
+                    } => {
+                        self.modify(|e| {
+                            let pt = (x, y);
+                            e.last_point = Some(pt.into());
+                            let val = match mouse_btn {
+                                MouseButton::Right => !e.active_color,
+                                _ => e.active_color,
+                            };
+                            if let Ok(o) = e.paint_point(pt, val) {
+                                e.current_operation.extend(o);
+                            }
+                        });
+                    }
+                    // click and drag
+                    Event::MouseMotion {
+                        x, y, mousestate, ..
+                    } => {
+                        let is_left = mousestate.is_mouse_button_pressed(MouseButton::Left);
+                        let is_right = mousestate.is_mouse_button_pressed(MouseButton::Right);
+                        if is_left {
+                            self.modify(|e| {
+                                let pt = (x, y);
+                                let val = e.active_color;
+                                if let Ok(o) = e.paint_point(pt, val) {
+                                    e.current_operation.extend(o);
+                                }
+                            });
+                        } else if is_right {
+                            self.modify(|e| {
+                                let pt = (x, y);
+                                let val = !e.active_color;
+                                if let Ok(o) = e.paint_point(pt, val) {
+                                    e.current_operation.extend(o);
+                                }
+                            });
+                        }
+                    }
+                    // end of operation
+                    Event::MouseButtonUp { .. } => self.modify(|e| {
+                        dbg!(&e.current_operation.len());
+                        let op = e
+                            .current_operation
+                            .drain(..)
+                            .filter(|v| !v.old_val == v.val)
+                            .collect::<Vec<_>>();
+                        e.undo_stack.push(op);
+                        dbg!(&e.undo_stack);
+                    }),
+                    Event::Quit { .. } => {
+                        break 'running;
+                    }
+                    _ => {
+                        self.modify(|_| ());
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/consts.rs b/src/consts.rs
new file mode 100644
index 0000000..b5cea43
--- /dev/null
+++ b/src/consts.rs
@@ -0,0 +1,6 @@
+use sdl2::pixels::Color;
+
+pub const GRID_COLOR: Color = Color::RGB(64, 64, 64);
+pub const WHITE: Color = Color::RGB(255, 255, 255);
+pub const BLACK: Color = Color::RGB(0, 0, 0);
+
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..bf89508
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,10 @@
+mod app;
+mod consts;
+mod undo;
+
+use app::AppState;
+
+pub fn main() {
+    let sdl_context = sdl2::init().unwrap();
+    AppState::init(100, 100, &sdl_context).run();
+}
diff --git a/src/undo.rs b/src/undo.rs
new file mode 100644
index 0000000..2249fe7
--- /dev/null
+++ b/src/undo.rs
@@ -0,0 +1,133 @@
+#[derive(Copy, Clone, Debug)]
+pub struct ModifyRecord {
+    pub point: (i32, i32),
+    pub old_val: bool,
+    pub val: bool,
+}
+
+impl ModifyRecord {
+    pub fn new(point: (i32, i32), old_val: bool, val: bool) -> Self {
+        ModifyRecord {
+            point,
+            old_val,
+            val,
+        }
+    }
+}
+
+pub enum OpKind {
+    Undo,
+    Redo,
+}
+
+pub type Operation = Vec<ModifyRecord>;
+
+#[derive(Debug)]
+pub struct UndoStack<T> {
+    operations: Vec<T>,
+    position: Option<u32>,
+}
+
+impl<T> UndoStack<T>
+where
+    T: Clone,
+{
+    pub fn new() -> Self {
+        Self {
+            operations: Vec::with_capacity(64),
+            position: None,
+        }
+    }
+
+    pub fn push(&mut self, op: T) {
+        if let Some(p) = self.position {
+            // remove all operations past the newly pushed operation
+            for _ in 1 + (p as usize)..self.operations.len() {
+                self.operations.pop();
+            }
+            // advance position
+            self.position = Some(p + 1);
+            // add new operation
+            self.operations.push(op);
+        } else {
+            // empty ops list or undone till start of stack
+            // remove all operations past the newly pushed operation
+            self.operations.clear();
+            // advance position
+            self.position = Some(0);
+            // add new operation
+            self.operations.push(op);
+        }
+    }
+
+    pub fn undo(&mut self) -> Option<T> {
+        if let Some(p) = self.position {
+            self.position = p.checked_sub(1);
+            // we want to return a clone and not a reference because push deletes the item
+            return Some(self.operations[p as usize].clone());
+        }
+        return None;
+    }
+
+    pub fn redo(&mut self) -> Option<T> {
+        if let Some(p) = self.position {
+            if p < self.operations.len() as u32 - 1 {
+                self.position = Some(p + 1);
+                return Some(self.operations[1 + p as usize].clone());
+            }
+        } else if !self.operations.is_empty() {
+            self.position = Some(0);
+            return Some(self.operations[0].clone());
+        }
+        return None;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn setup() -> UndoStack<u32> {
+        let mut stack = UndoStack::new();
+        stack.push(10);
+        stack.push(5);
+        stack.push(2);
+        stack
+    }
+
+    #[test]
+    fn undo_works() {
+        let mut stack = setup();
+        assert_eq!(stack.undo(), Some(2));
+        assert_eq!(stack.undo(), Some(5));
+        assert_eq!(stack.undo(), Some(10));
+    }
+    #[test]
+    fn redo_works() {
+        let mut stack = setup();
+        stack.undo();
+        stack.undo();
+        stack.undo();
+        assert_eq!(stack.redo(), Some(10));
+        assert_eq!(stack.redo(), Some(5));
+        assert_eq!(stack.redo(), Some(2));
+    }
+
+    #[test]
+    fn undo_push_redo() {
+        let mut stack = setup();
+        stack.undo();
+        stack.push(16);
+        assert_eq!(stack.redo(), None);
+        assert_eq!(stack.undo(), Some(16));
+    }
+
+    #[test]
+    fn stack_identity() {
+        let mut stack = setup();
+        stack.undo();
+        stack.redo();
+        stack.undo();
+        assert_eq!(stack.operations, setup().operations);
+    }
+}