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Bug 1589319 - Add some picture caching documentation. r=gw

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Differential Revision: https://phabricator.services.mozilla.com/D49566

--HG--
extra : moz-landing-system : lando
This commit is contained in:
Nicolas Silva 2019-10-18 08:46:45 +00:00
parent cd34415e10
commit cee2912fd6
1 changed files with 57 additions and 10 deletions
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67
gfx/wr/webrender/src/picture.rs
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@ -2,6 +2,63 @@
* 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/. */
//! A picture represents a dynamically rendered image.
//!
//! # Overview
//!
//! Pictures consists of:
//!
//! - A number of primitives that are drawn onto the picture.
//! - A composite operation describing how to composite this
//! picture into its parent.
//! - A configuration describing how to draw the primitives on
//! this picture (e.g. in screen space or local space).
//!
//! The tree of pictures are generated during scene building.
//!
//! Depending on their composite operations pictures can be rendered into
//! intermediate targets or folded into their parent picture.
//!
//! ## Picture caching
//!
//! Pictures can be cached to reduce the amount of rasterization happening per
//! frame.
//!
//! When picture caching is enabled, the scene is cut into a small number of slices,
//! typically:
//!
//! - content slice
//! - UI slice
//! - background UI slice which is hidden by the other two slices most of the time.
//!
//! Each of these slice is made up of fixed-size large tiles of 2048x512 pixels
//! (or 128x128 for the UI slice).
//!
//! Tiles can be either cached rasterized content into a texture or "clear tiles"
//! that contain only a solid color rectangle rendered directly during the composite
//! pass.
//!
//! ## Invalidation
//!
//! Each tile keeps track of the elements that affect it, which can be:
//!
//! - primitives
//! - clips
//! - image keys
//! - opacity bindings
//! - transforms
//!
//! These dependency lists are built each frame and compared to the previous frame to
//! see if the tile changed.
//!
//! The tile's primitive dependency information is organized in a quadtree, each node
//! storing an index buffer of tile primitive dependencies.
//!
//! The union of the invalidated leaves of each quadtree produces a per-tile dirty rect
//! which defines the scissor rect used when replaying the tile's drawing commands and
//! can be used for partial present.
//!
use api::{MixBlendMode, PipelineId, PremultipliedColorF, FilterPrimitiveKind};
use api::{PropertyBinding, PropertyBindingId, FilterPrimitive, FontRenderMode};
use api::{DebugFlags, RasterSpace, ImageKey, ColorF, PrimitiveFlags};
@ -40,16 +97,6 @@ use crate::texture_cache::TextureCacheHandle;
use crate::util::{TransformedRectKind, MatrixHelpers, MaxRect, scale_factors, VecHelper};
use crate::filterdata::{FilterDataHandle};
/*
A picture represents a dynamically rendered image. It consists of:
* A number of primitives that are drawn onto the picture.
* A composite operation describing how to composite this
picture into its parent.
* A configuration describing how to draw the primitives on
this picture (e.g. in screen space or local space).
*/
/// Specify whether a surface allows subpixel AA text rendering.
#[derive(Debug, Copy, Clone, PartialEq)]
pub enum SubpixelMode {