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Flatten display list structure

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Instead of producing a tree of stacking contexts, display list
generation now produces a flat list of display items and a tree of
stacking contexts. This will eventually allow display list construction
to produce and modify WebRender vertex buffers directly, removing the
overhead of display list conversion.  This change also moves
layerization of the display list to the paint thread, since it isn't
currently useful for WebRender.

To accomplish this, display list generation now takes three passes of
the flow tree:

        1. Calculation of absolute positions.
        2. Collection of a tree of stacking contexts.
        3. Creation of a list of display items.

After collection of display items, they are sorted based upon the index
of their parent stacking contexts and their position in CSS 2.1
Appendeix E stacking order.

This is a big change, but it actually simplifies display list generation.
This commit is contained in:
Martin Robinson 2016-02-19 10:40:33 -08:00
parent 22ce878edc
commit e7019f2721
27 changed files with 1709 additions and 1861 deletions
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1370
components/gfx/display_list/mod.rs
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97
components/gfx/display_list/optimizer.rs
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/* 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/. */
//! Transforms a display list to produce a visually-equivalent, but cheaper-to-paint, one.
use app_units::Au;
use display_list::{DisplayItem, DisplayList, StackingContext};
use euclid::rect::Rect;
use euclid::{Matrix2D, Matrix4};
use std::collections::linked_list::LinkedList;
use std::sync::Arc;
use util::geometry;
/// Transforms a display list to produce a visually-equivalent, but cheaper-to-paint, one.
pub struct DisplayListOptimizer {
/// The visible rect in page coordinates.
visible_rect: Rect<Au>,
}
impl DisplayListOptimizer {
/// Creates a new display list optimizer object. `visible_rect` specifies the visible rect in
/// page coordinates.
pub fn new(visible_rect: &Rect<f32>) -> DisplayListOptimizer {
DisplayListOptimizer {
visible_rect: geometry::f32_rect_to_au_rect(*visible_rect),
}
}
/// Optimizes the given display list, returning an equivalent, but cheaper-to-paint, one.
pub fn optimize(self, display_list: &DisplayList) -> DisplayList {
let mut result = DisplayList::new();
self.add_in_bounds_display_items(&mut result.background_and_borders,
display_list.background_and_borders.iter());
self.add_in_bounds_display_items(&mut result.block_backgrounds_and_borders,
display_list.block_backgrounds_and_borders.iter());
self.add_in_bounds_display_items(&mut result.floats, display_list.floats.iter());
self.add_in_bounds_display_items(&mut result.content, display_list.content.iter());
self.add_in_bounds_display_items(&mut result.positioned_content,
display_list.positioned_content.iter());
self.add_in_bounds_display_items(&mut result.outlines,
display_list.outlines.iter());
result
}
/// Adds display items that intersect the visible rect to `result_list`.
fn add_in_bounds_display_items<'a, I>(&self,
result_list: &mut LinkedList<DisplayItem>,
display_items: I)
where I: Iterator<Item=&'a DisplayItem> {
for display_item in display_items {
if !self.should_include_display_item(display_item) {
continue;
}
result_list.push_back((*display_item).clone())
}
}
fn should_include_display_item(&self, item: &DisplayItem) -> bool {
if let &DisplayItem::StackingContextClass(ref stacking_context) = item {
return self.should_include_stacking_context(stacking_context);
}
if !self.visible_rect.intersects(&item.bounds()) {
return false;
}
if let Some(base_item) = item.base() {
if !base_item.clip.might_intersect_rect(&self.visible_rect) {
return false;
}
}
true
}
fn should_include_stacking_context(&self, stacking_context: &Arc<StackingContext>) -> bool {
// Transform this stacking context to get it into the same space as
// the parent stacking context.
let origin_x = stacking_context.bounds.origin.x.to_f32_px();
let origin_y = stacking_context.bounds.origin.y.to_f32_px();
let transform = Matrix4::identity().translate(origin_x,
origin_y,
0.0)
.mul(&stacking_context.transform);
let transform_2d = Matrix2D::new(transform.m11, transform.m12,
transform.m21, transform.m22,
transform.m41, transform.m42);
let overflow = geometry::au_rect_to_f32_rect(stacking_context.overflow);
let overflow = transform_2d.transform_rect(&overflow);
let overflow = geometry::f32_rect_to_au_rect(overflow);
self.visible_rect.intersects(&overflow)
}
}