servo/components/canvas/canvas_paint_task.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use azure::azure::AzFloat;
use azure::azure_hl::{DrawTarget, SurfaceFormat, BackendType, StrokeOptions, DrawOptions, Pattern};
use azure::azure_hl::{ColorPattern, PathBuilder, JoinStyle, CapStyle, DrawSurfaceOptions, Filter};
use azure::azure_hl::{GradientStop, LinearGradientPattern, RadialGradientPattern, ExtendMode};
use geom::matrix2d::Matrix2D;
use geom::point::Point2D;
use geom::rect::Rect;
use geom::size::Size2D;
use gfx::color;
use util::task::spawn_named;
use util::vec::byte_swap;

use cssparser::RGBA;
use std::borrow::ToOwned;
use std::sync::mpsc::{channel, Sender};

#[derive(Clone)]
pub enum CanvasMsg {
    FillRect(Rect<f32>),
    ClearRect(Rect<f32>),
    StrokeRect(Rect<f32>),
    BeginPath,
    ClosePath,
    Fill,
    Stroke,
    DrawImage(Vec<u8>, Rect<i32>, Rect<i32>, bool),
    DrawImageSelf(Size2D<i32>, Rect<i32>, Rect<i32>, bool),
    MoveTo(Point2D<f32>),
    LineTo(Point2D<f32>),
    QuadraticCurveTo(Point2D<f32>, Point2D<f32>),
    BezierCurveTo(Point2D<f32>, Point2D<f32>, Point2D<f32>),
    Arc(Point2D<f32>, f32, f32, f32, bool),
    SetFillStyle(FillOrStrokeStyle),
    SetStrokeStyle(FillOrStrokeStyle),
    SetTransform(Matrix2D<f32>),
    Recreate(Size2D<i32>),
    SendPixelContents(Sender<Vec<u8>>),
    GetImageData(Rect<i32>, Size2D<i32>, Sender<Vec<u8>>),
    PutImageData(Vec<u8>, Rect<i32>, Option<Rect<i32>>),
    Close,
}

impl<'a> CanvasPaintTask<'a> {
    /// It reads image data from the canvas
    /// canvas_size: The size of the canvas we're reading from
    /// read_rect: The area of the canvas we want to read from
    fn read_pixels(&self, read_rect: Rect<i32>, canvas_size: Size2D<i32>) -> Vec<u8>{
        let canvas_rect = Rect(Point2D(0i32, 0i32), canvas_size);
        let src_read_rect = canvas_rect.intersection(&read_rect).unwrap_or(Rect::zero());

        let mut image_data = Vec::new();
        if src_read_rect.is_empty() || canvas_size.width <= 0 && canvas_size.height <= 0 {
          return image_data;
        }

        let data_surface = self.drawtarget.snapshot().get_data_surface();
        let mut src_data = Vec::new();
        data_surface.with_data(|element| { src_data = element.to_vec(); });
        let stride = data_surface.stride();

        //start offset of the copyable rectangle
        let mut src = (src_read_rect.origin.y * stride + src_read_rect.origin.x * 4) as usize;
        //copy the data to the destination vector
        for _ in 0..src_read_rect.size.height {
            let row = &src_data[src .. src + (4 * src_read_rect.size.width) as usize];
            image_data.push_all(row);
            src += stride as usize;
        }

        image_data
    }

    /// It writes image data to the canvas
    /// source_rect: the area of the image data to be written
    /// dest_rect: The area of the canvas where the imagedata will be copied
    /// smoothing_enabled: if smoothing is applied to the copied pixels
    fn write_pixels(&self, imagedata: &[u8],
                    image_size: Size2D<i32>,
                    source_rect: Rect<i32>,
                    dest_rect: Rect<i32>,
                    smoothing_enabled: bool) {
        // From spec https://html.spec.whatwg.org/multipage/scripting.html#dom-context-2d-drawimage
        // When scaling up, if the imageSmoothingEnabled attribute is set to true, the user agent should attempt
        // to apply a smoothing algorithm to the image data when it is scaled.
        // Otherwise, the image must be rendered using nearest-neighbor interpolation.
        let filter = if smoothing_enabled {
            Filter::Linear
        } else {
            Filter::Point
        };

        let source_surface = self.drawtarget.create_source_surface_from_data(imagedata,
            image_size, image_size.width * 4, SurfaceFormat::B8G8R8A8);

        let draw_surface_options = DrawSurfaceOptions::new(filter, true);
        let draw_options = DrawOptions::new(1.0f64 as AzFloat, 0);

        self.drawtarget.draw_surface(source_surface,
                                     dest_rect.to_azfloat(),
                                     source_rect.to_azfloat(),
                                     draw_surface_options, draw_options);
    }

    /// dirty_rect: original dirty_rect provided by the putImageData call
    /// image_data_rect: the area of the image to be copied
    /// Result: It retuns the modified dirty_rect by the rules described in
    /// the spec https://html.spec.whatwg.org/#dom-context-2d-putimagedata
    fn calculate_dirty_rect(&self,
                            mut dirty_rect: Rect<i32>,
                            image_data_rect: Rect<i32>) -> Rect<i32>{
        // 1) If dirtyWidth is negative,
        // let dirtyX be dirtyX+dirtyWidth,
        // and let dirtyWidth be equal to the absolute magnitude of dirtyWidth.
        if dirty_rect.size.width < 0 {
            dirty_rect.origin.x = dirty_rect.origin.x + dirty_rect.size.width;
            dirty_rect.size.width = -dirty_rect.size.width;
        }

        // 2) If dirtyHeight is negative, let dirtyY be dirtyY+dirtyHeight,
        // and let dirtyHeight be equal to the absolute magnitude of dirtyHeight.
        if dirty_rect.size.height < 0 {
            dirty_rect.origin.y = dirty_rect.origin.y + dirty_rect.size.height;
            dirty_rect.size.height = -dirty_rect.size.height;
        }

        // 3) If dirtyX is negative, let dirtyWidth be dirtyWidth+dirtyX, and let dirtyX be zero.
        if dirty_rect.origin.x < 0 {
            dirty_rect.size.width += dirty_rect.origin.x;
            dirty_rect.origin.x = 0;
        }

        // 3) If dirtyY is negative, let dirtyHeight be dirtyHeight+dirtyY, and let dirtyY be zero.
        if dirty_rect.origin.y < 0 {
            dirty_rect.size.height += dirty_rect.origin.y;
            dirty_rect.origin.y = 0;
        }

        // 4) If dirtyX+dirtyWidth is greater than the width attribute of the imagedata argument,
        // let dirtyWidth be the value of that width attribute, minus the value of dirtyX.
        if dirty_rect.origin.x + dirty_rect.size.width > image_data_rect.size.width {
            dirty_rect.size.width = image_data_rect.size.width - dirty_rect.origin.x;
        }

        // 4) If dirtyY+dirtyHeight is greater than the height attribute of the imagedata argument,
        // let dirtyHeight be the value of that height attribute, minus the value of dirtyY.
        if dirty_rect.origin.y + dirty_rect.size.height > image_data_rect.size.height {
            dirty_rect.size.height = image_data_rect.size.height - dirty_rect.origin.y;
        }

        dirty_rect
    }

    /// It writes an image to the destination canvas
    /// imagedata: Pixel information of the image to be written
    /// source_rect: Area of the source image to be copied
    /// dest_rect: Area of the destination canvas where the pixels will be copied
    /// smoothing_enabled: It determines if smoothing is applied to the image result
    fn write_image(&self, mut imagedata: Vec<u8>,
                   source_rect: Rect<i32>, dest_rect: Rect<i32>, smoothing_enabled: bool) {
        if imagedata.len() == 0 {
            return
        }
        // Image data already contains the portion of the image we want to draw
        // so the source rect corresponds to the whole area of the copied imagedata
        let source_rect = Rect(Point2D(0i32, 0i32), source_rect.size);
        // rgba -> bgra
        byte_swap(imagedata.as_mut_slice());
        self.write_pixels(&imagedata, source_rect.size, source_rect, dest_rect, smoothing_enabled);
    }

}

pub struct CanvasPaintTask<'a> {
    drawtarget: DrawTarget,
    fill_style: Pattern,
    stroke_style: Pattern,
    stroke_opts: StrokeOptions<'a>,
    /// TODO(pcwalton): Support multiple paths.
    path_builder: PathBuilder,
    /// The current 2D transform matrix.
    transform: Matrix2D<f32>,
}

impl<'a> CanvasPaintTask<'a> {
    fn new(size: Size2D<i32>) -> CanvasPaintTask<'a> {
        let draw_target = CanvasPaintTask::create(size);
        let path_builder = draw_target.create_path_builder();
        CanvasPaintTask {
            drawtarget: draw_target,
            fill_style: Pattern::Color(ColorPattern::new(color::black())),
            stroke_style: Pattern::Color(ColorPattern::new(color::black())),
            stroke_opts: StrokeOptions::new(1.0, JoinStyle::MiterOrBevel, CapStyle::Butt, 1.0, &[]),
            path_builder: path_builder,
            transform: Matrix2D::identity(),
        }
    }

    pub fn start(size: Size2D<i32>) -> Sender<CanvasMsg> {
        let (chan, port) = channel::<CanvasMsg>();
        spawn_named("CanvasTask".to_owned(), move || {
            let mut painter = CanvasPaintTask::new(size);

            loop {
                match port.recv().unwrap() {
                    CanvasMsg::FillRect(ref rect) => painter.fill_rect(rect),
                    CanvasMsg::StrokeRect(ref rect) => painter.stroke_rect(rect),
                    CanvasMsg::ClearRect(ref rect) => painter.clear_rect(rect),
                    CanvasMsg::BeginPath => painter.begin_path(),
                    CanvasMsg::ClosePath => painter.close_path(),
                    CanvasMsg::Fill => painter.fill(),
                    CanvasMsg::Stroke => painter.stroke(),
                    CanvasMsg::DrawImage(imagedata, dest_rect, source_rect, smoothing_enabled) => {
                        painter.draw_image(imagedata, dest_rect, source_rect, smoothing_enabled)
                    }
                    CanvasMsg::DrawImageSelf(image_size, dest_rect, source_rect, smoothing_enabled) => {
                        painter.draw_image_self(image_size, dest_rect, source_rect, smoothing_enabled)
                    }
                    CanvasMsg::MoveTo(ref point) => painter.move_to(point),
                    CanvasMsg::LineTo(ref point) => painter.line_to(point),
                    CanvasMsg::QuadraticCurveTo(ref cp, ref pt) => {
                        painter.quadratic_curve_to(cp, pt)
                    }
                    CanvasMsg::BezierCurveTo(ref cp1, ref cp2, ref pt) => {
                        painter.bezier_curve_to(cp1, cp2, pt)
                    }
                    CanvasMsg::Arc(ref center, radius, start, end, ccw) => {
                        painter.arc(center, radius, start, end, ccw)
                    }
                    CanvasMsg::SetFillStyle(style) => painter.set_fill_style(style),
                    CanvasMsg::SetStrokeStyle(style) => painter.set_stroke_style(style),
                    CanvasMsg::SetTransform(ref matrix) => painter.set_transform(matrix),
                    CanvasMsg::Recreate(size) => painter.recreate(size),
                    CanvasMsg::SendPixelContents(chan) => painter.send_pixel_contents(chan),
                    CanvasMsg::GetImageData(dest_rect, canvas_size, chan) => painter.get_image_data(dest_rect, canvas_size, chan),
                    CanvasMsg::PutImageData(imagedata, image_data_rect, dirty_rect)
                        => painter.put_image_data(imagedata, image_data_rect, dirty_rect),
                    CanvasMsg::Close => break,
                }
            }
        });
        chan
    }

    fn fill_rect(&self, rect: &Rect<f32>) {
        let drawopts = DrawOptions::new(1.0, 0);
        self.drawtarget.fill_rect(rect, self.fill_style.to_pattern_ref(), Some(&drawopts));
    }

    fn clear_rect(&self, rect: &Rect<f32>) {
        self.drawtarget.clear_rect(rect);
    }

    fn stroke_rect(&self, rect: &Rect<f32>) {
        let drawopts = DrawOptions::new(1.0, 0);
        match self.stroke_style {
            Pattern::Color(ref color) => {
                self.drawtarget.stroke_rect(rect, color, &self.stroke_opts, &drawopts)
            }
            _ => {
                // TODO(pcwalton)
            }
        };
    }

    fn begin_path(&mut self) {
        self.path_builder = self.drawtarget.create_path_builder()
    }

    fn close_path(&self) {
        self.path_builder.close()
    }

    fn fill(&self) {
        let draw_options = DrawOptions::new(1.0, 0);
        match self.fill_style {
            Pattern::Color(ref color) => {
                self.drawtarget.fill(&self.path_builder.finish(), color, &draw_options);
            }
            _ => {
                // TODO(pcwalton)
            }
        };
    }

    fn stroke(&self) {
        let draw_options = DrawOptions::new(1.0, 0);
        match self.stroke_style {
            Pattern::Color(ref color) => {
                self.drawtarget.stroke(&self.path_builder.finish(),
                                       color, &self.stroke_opts, &draw_options);
            }
            _ => {
                // TODO
            }
        };
    }

    fn draw_image(&self, imagedata: Vec<u8>, dest_rect: Rect<i32>,
                  source_rect: Rect<i32>, smoothing_enabled: bool) {
        self.write_image(imagedata, source_rect, dest_rect, smoothing_enabled);
    }

    fn draw_image_self(&self, image_size: Size2D<i32>,
                       dest_rect: Rect<i32>, source_rect: Rect<i32>,
                       smoothing_enabled: bool) {
        // Reads pixels from source image
        // In this case source and target are the same canvas
        let imagedata = self.read_pixels(source_rect, image_size);
        // Writes on target canvas
        self.write_image(imagedata, source_rect, dest_rect, smoothing_enabled);
    }

    fn move_to(&self, point: &Point2D<AzFloat>) {
        self.path_builder.move_to(*point)
    }

    fn line_to(&self, point: &Point2D<AzFloat>) {
        self.path_builder.line_to(*point)
    }

    fn quadratic_curve_to(&self,
                          cp: &Point2D<AzFloat>,
                          endpoint: &Point2D<AzFloat>) {
        self.path_builder.quadratic_curve_to(cp, endpoint)
    }

    fn bezier_curve_to(&self,
                       cp1: &Point2D<AzFloat>,
                       cp2: &Point2D<AzFloat>,
                       endpoint: &Point2D<AzFloat>) {
        self.path_builder.bezier_curve_to(cp1, cp2, endpoint)
    }

    fn arc(&self,
           center: &Point2D<AzFloat>,
           radius: AzFloat,
           start_angle: AzFloat,
           end_angle: AzFloat,
           ccw: bool) {
        self.path_builder.arc(*center, radius, start_angle, end_angle, ccw)
    }

    fn set_fill_style(&mut self, style: FillOrStrokeStyle) {
        self.fill_style = style.to_azure_pattern(&self.drawtarget)
    }

    fn set_stroke_style(&mut self, style: FillOrStrokeStyle) {
        self.stroke_style = style.to_azure_pattern(&self.drawtarget)
    }

    fn set_transform(&mut self, transform: &Matrix2D<f32>) {
        self.transform = *transform;
        self.drawtarget.set_transform(transform)
    }

    fn create(size: Size2D<i32>) -> DrawTarget {
        DrawTarget::new(BackendType::Skia, size, SurfaceFormat::B8G8R8A8)
    }

    fn recreate(&mut self, size: Size2D<i32>) {
        self.drawtarget = CanvasPaintTask::create(size);
    }

    fn send_pixel_contents(&mut self, chan: Sender<Vec<u8>>) {
        self.drawtarget.snapshot().get_data_surface().with_data(|element| {
            chan.send(element.to_vec()).unwrap();
        })
    }

    fn get_image_data(&self, mut dest_rect: Rect<i32>, canvas_size: Size2D<i32>, chan: Sender<Vec<u8>>) {
        if dest_rect.size.width < 0 {
            dest_rect.size.width = -dest_rect.size.width;
            dest_rect.origin.x -= dest_rect.size.width;
        }
        if dest_rect.size.height < 0 {
            dest_rect.size.height = -dest_rect.size.height;
            dest_rect.origin.y -= dest_rect.size.height;
        }
        if dest_rect.size.width == 0 {
            dest_rect.size.width = 1;
        }
        if dest_rect.size.height == 0 {
            dest_rect.size.height = 1;
        }

        let mut dest_data = self.read_pixels(dest_rect, canvas_size);

        // bgra -> rgba
        byte_swap(dest_data.as_mut_slice());
        chan.send(dest_data).unwrap();
    }

    fn put_image_data(&mut self, mut imagedata: Vec<u8>,
                      image_data_rect: Rect<i32>,
                      dirty_rect: Option<Rect<i32>>) {

        if image_data_rect.size.width <= 0 || image_data_rect.size.height <= 0 {
            return
        }

        assert!(image_data_rect.size.width * image_data_rect.size.height * 4 == imagedata.len() as i32);
        // rgba -> bgra
        byte_swap(imagedata.as_mut_slice());

        let image_rect = Rect(Point2D(0i32, 0i32),
                               Size2D(image_data_rect.size.width, image_data_rect.size.height));

        // Dirty rectangle defines the area of the source image to be copied
        // on the destination canvas
        let source_rect = match dirty_rect {
            Some(dirty_rect) =>
                self.calculate_dirty_rect(dirty_rect, image_data_rect),
            // If no dirty area is provided we consider the whole source image
            // as the area to be copied to the canvas
            None => image_rect,
        };

        // 5) If either dirtyWidth or dirtyHeight is negative or zero,
        // stop without affecting any bitmaps
        if source_rect.size.width <= 0 || source_rect.size.height <= 0 {
            return
        }

        // 6) For all integer values of x and y where dirtyX ≤ x < dirty
        // X+dirtyWidth and dirtyY ≤ y < dirtyY+dirtyHeight, copy the
        // four channels of the pixel with coordinate (x, y) in the imagedata
        // data structure's Canvas Pixel ArrayBuffer to the pixel with coordinate
        // (dx+x, dy+y) in the rendering context's scratch bitmap.
        // It also clips the destination rectangle to the canvas area
        let dest_rect = Rect(
            Point2D(image_data_rect.origin.x + source_rect.origin.x,
                    image_data_rect.origin.y + source_rect.origin.y),
            Size2D(source_rect.size.width, source_rect.size.height));

        self.write_pixels(&imagedata, image_data_rect.size, source_rect, dest_rect, true)
    }
}

#[derive(Clone)]
pub struct CanvasGradientStop {
    pub offset: f64,
    pub color: RGBA,
}

#[derive(Clone)]
pub struct LinearGradientStyle {
    pub x0: f64,
    pub y0: f64,
    pub x1: f64,
    pub y1: f64,
    pub stops: Vec<CanvasGradientStop>
}

impl LinearGradientStyle {
    pub fn new(x0: f64, y0: f64, x1: f64, y1: f64, stops: Vec<CanvasGradientStop>)
        -> LinearGradientStyle {
        LinearGradientStyle {
            x0: x0,
            y0: y0,
            x1: x1,
            y1: y1,
            stops: stops,
        }
    }
}

#[derive(Clone)]
pub struct RadialGradientStyle {
    pub x0: f64,
    pub y0: f64,
    pub r0: f64,
    pub x1: f64,
    pub y1: f64,
    pub r1: f64,
    pub stops: Vec<CanvasGradientStop>
}

impl RadialGradientStyle {
    pub fn new(x0: f64, y0: f64, r0: f64, x1: f64, y1: f64, r1: f64, stops: Vec<CanvasGradientStop>)
        -> RadialGradientStyle {
        RadialGradientStyle {
            x0: x0,
            y0: y0,
            r0: r0,
            x1: x1,
            y1: y1,
            r1: r1,
            stops: stops,
        }
    }
}

#[derive(Clone)]
pub enum FillOrStrokeStyle {
    Color(RGBA),
    LinearGradient(LinearGradientStyle),
    RadialGradient(RadialGradientStyle),
}

impl FillOrStrokeStyle {
    fn to_azure_pattern(&self, drawtarget: &DrawTarget) -> Pattern {
        match *self {
            FillOrStrokeStyle::Color(ref color) => {
                Pattern::Color(ColorPattern::new(color::new(color.red,
                                                            color.green,
                                                            color.blue,
                                                            color.alpha)))
            },
            FillOrStrokeStyle::LinearGradient(ref linear_gradient_style) => {
                let gradient_stops: Vec<GradientStop> = linear_gradient_style.stops.iter().map(|s| {
                    GradientStop {
                        offset: s.offset as AzFloat,
                        color: color::new(s.color.red, s.color.green, s.color.blue, s.color.alpha)
                    }
                }).collect();

                Pattern::LinearGradient(LinearGradientPattern::new(
                    &Point2D(linear_gradient_style.x0 as AzFloat, linear_gradient_style.y0 as AzFloat),
                    &Point2D(linear_gradient_style.x1 as AzFloat, linear_gradient_style.y1 as AzFloat),
                    drawtarget.create_gradient_stops(&gradient_stops, ExtendMode::Clamp),
                    &Matrix2D::identity()))
            },
            FillOrStrokeStyle::RadialGradient(ref radial_gradient_style) => {
                let gradient_stops: Vec<GradientStop> = radial_gradient_style.stops.iter().map(|s| {
                    GradientStop {
                        offset: s.offset as AzFloat,
                        color: color::new(s.color.red, s.color.green, s.color.blue, s.color.alpha)
                    }
                }).collect();

                Pattern::RadialGradient(RadialGradientPattern::new(
                    &Point2D(radial_gradient_style.x0 as AzFloat, radial_gradient_style.y0 as AzFloat),
                    &Point2D(radial_gradient_style.x1 as AzFloat, radial_gradient_style.y1 as AzFloat),
                    radial_gradient_style.r0 as AzFloat, radial_gradient_style.r1 as AzFloat,
                    drawtarget.create_gradient_stops(&gradient_stops, ExtendMode::Clamp),
                    &Matrix2D::identity()))
            }
        }
    }
}

pub trait ToAzFloat {
    fn to_azfloat(&self) -> Rect<AzFloat>;
}

impl ToAzFloat for Rect<i32> {
    fn to_azfloat(&self) -> Rect<AzFloat> {
        Rect(Point2D(self.origin.x as AzFloat, self.origin.y as AzFloat),
             Size2D(self.size.width as AzFloat, self.size.height as AzFloat))
    }
}