blitty 0.2.0

Display list based rendering engine with support for automatic damage based painting.
Documentation 
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use embedded_graphics::{
    pixelcolor::{PixelColor, Rgb888, BinaryColor},
    prelude::*,
    primitives::{Rectangle, PrimitiveStyleBuilder},

};

use core::cmp::{min, max};

use super::*;

impl From<Rgb> for Rgb888 {
    fn from(value: Rgb) -> Self {
        Rgb888::new(value.r, value.g, value.b)
    }
}

impl From<Rgb> for BinaryColor {
    fn from(value: Rgb) -> Self {

        if value.r.saturating_add(value.b).saturating_add(value.g) > 0 {
            BinaryColor::On
        } else {
            BinaryColor::Off
        }
    }
}

pub struct EmbeddedRender<'a, D: DrawTarget<Color = C>, C: PixelColor> {
    width: u32,
    height: u32,
    display: &'a mut D,
    chunk_width: u32,
    chunk_height: u32,
    clip: BoundingBox,
}

impl<'a, D: DrawTarget<Color = C>, C: PixelColor> EmbeddedRender<'a, D, C> {
    pub fn new(display: &'a mut D, chunk_width: u32, chunk_height: u32) -> Self {
        let bounds = display.bounding_box();
        let clip = BoundingBox::new(0, 0, chunk_width, chunk_height);
        EmbeddedRender {
            width: bounds.size.width , //BUG: why is this safe?
            height: bounds.size.height, //BUG: why is this safe?,
            display,
            chunk_width,
            chunk_height,
            clip,
        }
    }

    pub fn get_display(&self) -> &D {
        &self.display
    }

    pub fn get_display_mut(&mut self) -> &mut D {
        &mut self.display
    }
}

impl<'a, D: DrawTarget<Color = C>, C: PixelColor> Renderer for EmbeddedRender<'a, D, C> 
    where C: From<Rgb> {
    fn width(&self) -> u32 {
        self.width
    }

    fn height(&self) -> u32 {
        self.height
    }

    fn chunk_size(&self) -> (u32, u32) {
        (self.chunk_width, self.chunk_height)
    }

    // Set the current chunk by the top left x and y offset in pixels.
    fn set_chunk(&mut self, x: u32, y: u32) -> Result<(), RendererError> {
        if (x % self.chunk_width != 0) || (y % self.chunk_height != 0) {
            return Err(RendererError::InvalidChunkOffset{x, y})
        }

        self.clip = BoundingBox{
            x1: x,
            y1: y,
            x2: x + self.chunk_width,
            y2: y + self.chunk_height,
        };

        Ok(())
    }

    fn draw(&mut self, command: &Command) -> Result<(), RendererError> {
        use CommandType::*;

        let clip = self.clip;
        match command.flavor {
            Null => Ok(()),
            Rect(rgb) => {


                let x1 = max(command.bounds.x1, clip.x1);
                let y1 = max(command.bounds.y1, clip.y1);
                let x2 = min(command.bounds.x2, clip.x2);
                let y2 = min(command.bounds.y2, clip.y2);

                let width = (x2 - x1) as u32; // BUG is this safe
                let height = (y2 - y1) as u32; // Bug is this safe
                let x = x1 as i32; // Bug is this safe
                let y = y1 as i32; // Bug is this safe

                let color = rgb.into();

                let line_style = PrimitiveStyleBuilder::new()
                    .fill_color(color)
                    .build();

                Rectangle::new(Point::new(x, y), Size::new(width, height))
                    .into_styled(line_style)
                    .draw(self.display)
                    .map_err(|_e| RendererError::BackingError)?;
                
                Ok(())
            }
        }
    }

    fn clear(&mut self) -> Result<(), RendererError> {
        let clip = self.clip;
        let top_left = Point::new(clip.x1 as i32, clip.y1 as i32);
        let size = Size::new((clip.x2 - clip.x1) as u32, (clip.y2 - clip.y1) as u32);
        let area = Rectangle::new(top_left, size);
        let mut clipped = self.display.clipped(&area);
        let clear_color = Rgb::new(0, 0, 0).into();
        clipped.clear(clear_color)
        .map_err(|_e| RendererError::BackingError)?;

        Ok(())
    }

    async fn flush(&mut self) -> Result<(), RendererError> {
        // This is a noop in this implementation
        Ok(())
    }
}