servo/src/components/gfx/render_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/. */

//! The task that handles all rendering/painting.

use buffer_map::BufferMap;
use display_list::DisplayList;
use font_context::{FontContext, FontContextInfo};
use render_context::RenderContext;

use azure::azure_hl::{B8G8R8A8, Color, DrawTarget, StolenGLResources};
use azure::AzFloat;
use geom::matrix2d::Matrix2D;
use geom::rect::Rect;
use geom::size::Size2D;
use layers::platform::surface::{NativePaintingGraphicsContext, NativeSurface};
use layers::platform::surface::{NativeSurfaceMethods};
use layers;
use servo_msg::compositor_msg::{Epoch, IdleRenderState, LayerBuffer};
use servo_msg::compositor_msg::{LayerBufferSet, LayerId, LayerMetadata, RenderListener};
use servo_msg::compositor_msg::{RenderingRenderState, ScrollPolicy};
use servo_msg::constellation_msg::{ConstellationChan, PipelineId, RendererReadyMsg};
use servo_msg::constellation_msg::{Failure, FailureMsg};
use servo_msg::platform::surface::NativeSurfaceAzureMethods;
use servo_util::opts::Opts;
use servo_util::smallvec::{SmallVec, SmallVec1};
use servo_util::time::{ProfilerChan, profile};
use servo_util::time;
use servo_util::task::send_on_failure;

use std::comm::{Chan, Port};
use std::task;
use sync::Arc;

/// Information about a layer that layout sends to the painting task.
pub struct RenderLayer {
    /// A per-pipeline ID describing this layer that should be stable across reflows.
    id: LayerId,
    /// The display list describing the contents of this layer.
    display_list: Arc<DisplayList>,
    /// The position of the layer in pixels.
    position: Rect<uint>,
    /// The color of the background in this layer. Used for unrendered content.
    background_color: Color,
    /// The scrolling policy of this layer.
    scroll_policy: ScrollPolicy,
}

pub enum Msg {
    RenderMsg(SmallVec1<RenderLayer>),
    ReRenderMsg(~[BufferRequest], f32, LayerId, Epoch),
    UnusedBufferMsg(~[~LayerBuffer]),
    PaintPermissionGranted,
    PaintPermissionRevoked,
    ExitMsg(Option<Chan<()>>),
}

/// A request from the compositor to the renderer for tiles that need to be (re)displayed.
#[deriving(Clone)]
pub struct BufferRequest {
    // The rect in pixels that will be drawn to the screen
    screen_rect: Rect<uint>,
    
    // The rect in page coordinates that this tile represents
    page_rect: Rect<f32>,
}

pub fn BufferRequest(screen_rect: Rect<uint>, page_rect: Rect<f32>) -> BufferRequest {
    BufferRequest {
        screen_rect: screen_rect,
        page_rect: page_rect,
    }
}

// FIXME(#2005, pcwalton): This should be a newtype struct.
pub struct RenderChan {
    chan: Chan<Msg>,
}

impl Clone for RenderChan {
    fn clone(&self) -> RenderChan {
        RenderChan {
            chan: self.chan.clone(),
        }
    }
}

impl RenderChan {
    pub fn new() -> (Port<Msg>, RenderChan) {
        let (port, chan) = Chan::new();
        let render_chan = RenderChan {
            chan: chan,
        };
        (port, render_chan)
    }

    pub fn send(&self, msg: Msg) {
        assert!(self.try_send(msg), "RenderChan.send: render port closed")
    }

    pub fn try_send(&self, msg: Msg) -> bool {
        self.chan.try_send(msg)
    }
}

/// If we're using GPU rendering, this provides the metadata needed to create a GL context that
/// is compatible with that of the main thread.
enum GraphicsContext {
    CpuGraphicsContext,
    GpuGraphicsContext,
}

pub struct RenderTask<C> {
    id: PipelineId,
    port: Port<Msg>,
    compositor: C,
    constellation_chan: ConstellationChan,
    font_ctx: ~FontContext,
    opts: Opts,

    /// A channel to the profiler.
    profiler_chan: ProfilerChan,

    /// The graphics context to use.
    graphics_context: GraphicsContext,

    /// The native graphics context.
    native_graphics_context: Option<NativePaintingGraphicsContext>,

    /// The layers to be rendered.
    render_layers: SmallVec1<RenderLayer>,

    /// Permission to send paint messages to the compositor
    paint_permission: bool,

    /// A counter for epoch messages
    epoch: Epoch,

    /// A data structure to store unused LayerBuffers
    buffer_map: BufferMap<~LayerBuffer>,
}

// If we implement this as a function, we get borrowck errors from borrowing
// the whole RenderTask struct.
macro_rules! native_graphics_context(
    ($task:expr) => (
        $task.native_graphics_context.as_ref().expect("Need a graphics context to do rendering")
    )
)

fn initialize_layers<C:RenderListener>(
                     compositor: &mut C,
                     pipeline_id: PipelineId,
                     epoch: Epoch,
                     render_layers: &[RenderLayer]) {
    let metadata = render_layers.iter().map(|render_layer| {
        LayerMetadata {
            id: render_layer.id,
            position: render_layer.position,
            background_color: render_layer.background_color,
            scroll_policy: render_layer.scroll_policy,
        }
    }).collect();
    compositor.initialize_layers_for_pipeline(pipeline_id, metadata, epoch);
}

impl<C: RenderListener + Send> RenderTask<C> {
    pub fn create(id: PipelineId,
                  port: Port<Msg>,
                  compositor: C,
                  constellation_chan: ConstellationChan,
                  failure_msg: Failure,
                  opts: Opts,
                  profiler_chan: ProfilerChan,
                  shutdown_chan: Chan<()>) {
        let mut builder = task::task().named("RenderTask");
        let ConstellationChan(c) = constellation_chan.clone();
        send_on_failure(&mut builder, FailureMsg(failure_msg), c);
        builder.spawn(proc() {

            { // Ensures RenderTask and graphics context are destroyed before shutdown msg
                let native_graphics_context = compositor.get_graphics_metadata().map(
                    |md| NativePaintingGraphicsContext::from_metadata(&md));
                let cpu_painting = opts.cpu_painting;

                // FIXME: rust/#5967
                let mut render_task = RenderTask {
                    id: id,
                    port: port,
                    compositor: compositor,
                    constellation_chan: constellation_chan,
                    font_ctx: ~FontContext::new(FontContextInfo {
                        backend: opts.render_backend.clone(),
                        needs_font_list: false,
                        profiler_chan: profiler_chan.clone(),
                    }),
                    opts: opts,
                    profiler_chan: profiler_chan,

                    graphics_context: if cpu_painting {
                        CpuGraphicsContext
                    } else {
                        GpuGraphicsContext
                    },

                    native_graphics_context: native_graphics_context,

                    render_layers: SmallVec1::new(),

                    paint_permission: false,
                    epoch: Epoch(0),
                    buffer_map: BufferMap::new(10000000),
                };

                render_task.start();

                // Destroy all the buffers.
                match render_task.native_graphics_context.as_ref() {
                    Some(ctx) => render_task.buffer_map.clear(ctx),
                    None => (),
                }
            }

            debug!("render_task: shutdown_chan send");
            shutdown_chan.send(());
        });
    }

    fn start(&mut self) {
        debug!("render_task: beginning rendering loop");

        loop {
            match self.port.recv() {
                RenderMsg(render_layers) => {
                    self.epoch.next();
                    self.render_layers = render_layers;

                    if !self.paint_permission {
                        debug!("render_task: render ready msg");
                        let ConstellationChan(ref mut c) = self.constellation_chan;
                        c.send(RendererReadyMsg(self.id));
                        continue;
                    }

                    initialize_layers(&mut self.compositor,
                                      self.id,
                                      self.epoch,
                                      self.render_layers.as_slice());
                }
                ReRenderMsg(tiles, scale, layer_id, epoch) => {
                    if self.epoch == epoch {
                        self.render(tiles, scale, layer_id);
                    } else {
                        debug!("renderer epoch mismatch: {:?} != {:?}", self.epoch, epoch);
                    }
                }
                UnusedBufferMsg(unused_buffers) => {
                    // move_rev_iter is more efficient
                    for buffer in unused_buffers.move_rev_iter() {
                        self.buffer_map.insert(native_graphics_context!(self), buffer);
                    }
                }
                PaintPermissionGranted => {
                    self.paint_permission = true;

                    // Here we assume that the main layer—the layer responsible for the page size—
                    // is the first layer. This is a pretty fragile assumption. It will be fixed
                    // once we use the layers-based scrolling infrastructure for all scrolling.
                    if self.render_layers.len() > 1 {
                        self.epoch.next();
                        initialize_layers(&mut self.compositor,
                                          self.id,
                                          self.epoch,
                                          self.render_layers.as_slice());
                    }
                }
                PaintPermissionRevoked => {
                    self.paint_permission = false;
                }
                ExitMsg(response_ch) => {
                    debug!("render_task: exitmsg response send");
                    response_ch.map(|ch| ch.send(()));
                    break;
                }
            }
        }
    }

    /// Renders one layer and sends the tiles back to the layer.
    ///
    /// FIXME(pcwalton): We will probably want to eventually send all layers belonging to a page in
    /// one transaction, to avoid the user seeing inconsistent states.
    fn render(&mut self, tiles: ~[BufferRequest], scale: f32, layer_id: LayerId) {
        time::profile(time::RenderingCategory, self.profiler_chan.clone(), || {
            // FIXME: Try not to create a new array here.
            let mut new_buffers = ~[];

            // Find the appropriate render layer.
            let render_layer = match self.render_layers.iter().find(|layer| layer.id == layer_id) {
                Some(render_layer) => render_layer,
                None => return,
            };

            self.compositor.set_render_state(RenderingRenderState);

            // Divide up the layer into tiles.
            for tile in tiles.iter() {
                let width = tile.screen_rect.size.width;
                let height = tile.screen_rect.size.height;

                let size = Size2D(width as i32, height as i32);
                let draw_target = match self.graphics_context {
                    CpuGraphicsContext => {
                        DrawTarget::new(self.opts.render_backend, size, B8G8R8A8)
                    }
                    GpuGraphicsContext => {
                        // FIXME(pcwalton): Cache the components of draw targets
                        // (texture color buffer, renderbuffers) instead of recreating them.
                        let draw_target =
                            DrawTarget::new_with_fbo(self.opts.render_backend,
                                                     native_graphics_context!(self),
                                                     size,
                                                     B8G8R8A8);
                        draw_target.make_current();
                        draw_target
                    }
                };

                {
                    // Build the render context.
                    let mut ctx = RenderContext {
                        draw_target: &draw_target,
                        font_ctx: &mut self.font_ctx,
                        opts: &self.opts,
                        page_rect: tile.page_rect,
                        screen_rect: tile.screen_rect,
                    };

                    // Apply the translation to render the tile we want.
                    let matrix: Matrix2D<AzFloat> = Matrix2D::identity();
                    let matrix = matrix.scale(scale as AzFloat, scale as AzFloat);
                    let matrix = matrix.translate(-(tile.page_rect.origin.x) as AzFloat,
                                                  -(tile.page_rect.origin.y) as AzFloat);
                    let matrix = matrix.translate(-(render_layer.position.origin.x as AzFloat),
                                                  -(render_layer.position.origin.y as AzFloat));

                    ctx.draw_target.set_transform(&matrix);

                    // Clear the buffer.
                    ctx.clear();

                    // Draw the display list.
                    profile(time::RenderingDrawingCategory, self.profiler_chan.clone(), || {
                        render_layer.display_list.get().draw_into_context(&mut ctx);
                        ctx.draw_target.flush();
                    });
                }

                // Extract the texture from the draw target and place it into its slot in the
                // buffer. If using CPU rendering, upload it first.
                //
                // FIXME(pcwalton): We should supply the texture and native surface *to* the
                // draw target in GPU rendering mode, so that it doesn't have to recreate it.
                let buffer = match self.graphics_context {
                    CpuGraphicsContext => {
                        let buffer = match self.buffer_map.find(tile.screen_rect.size) {
                            Some(buffer) => {
                                let mut buffer = buffer;
                                buffer.rect = tile.page_rect;
                                buffer.screen_pos = tile.screen_rect;
                                buffer.resolution = scale;
                                buffer.native_surface.mark_wont_leak();
                                buffer
                            }
                            None => {
                                // Create an empty native surface. We mark it as not leaking
                                // in case it dies in transit to the compositor task.
                                let mut native_surface: NativeSurface =
                                    layers::platform::surface::NativeSurfaceMethods::new(
                                        native_graphics_context!(self),
                                        Size2D(width as i32, height as i32),
                                        width as i32 * 4);
                                native_surface.mark_wont_leak();

                                ~LayerBuffer {
                                    native_surface: native_surface,
                                    rect: tile.page_rect,
                                    screen_pos: tile.screen_rect,
                                    resolution: scale,
                                    stride: (width * 4) as uint
                                }
                            }
                        };

                        draw_target.snapshot().get_data_surface().with_data(|data| {
                            buffer.native_surface.upload(native_graphics_context!(self), data);
                            debug!("RENDERER uploading to native surface {:d}",
                                   buffer.native_surface.get_id() as int);
                        });

                        buffer
                    }
                    GpuGraphicsContext => {
                        draw_target.make_current();
                        let StolenGLResources {
                            surface: native_surface
                        } = draw_target.steal_gl_resources().unwrap();

                        // We mark the native surface as not leaking in case the surfaces
                        // die on their way to the compositor task.
                        let mut native_surface: NativeSurface =
                            NativeSurfaceAzureMethods::from_azure_surface(native_surface);
                        native_surface.mark_wont_leak();

                        ~LayerBuffer {
                            native_surface: native_surface,
                            rect: tile.page_rect,
                            screen_pos: tile.screen_rect,
                            resolution: scale,
                            stride: (width * 4) as uint
                        }
                    }
                };

                new_buffers.push(buffer);
            }

            let layer_buffer_set = ~LayerBufferSet {
                buffers: new_buffers,
            };

            debug!("render_task: returning surface");
            if self.paint_permission {
                self.compositor.paint(self.id, render_layer.id, layer_buffer_set, self.epoch);
            } else {
                debug!("render_task: RendererReadyMsg send");
                let ConstellationChan(ref mut c) = self.constellation_chan;
                c.send(RendererReadyMsg(self.id));
            }
            self.compositor.set_render_state(IdleRenderState);
        })
    }
}