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This commit is contained in:
Simon Sapin 2020-01-13 23:13:43 +01:00
parent c72f7894aa
commit cac32867ba
1 changed files with 24 additions and 19 deletions
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43
components/layout_2020/display_list.rs
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@ -299,23 +299,6 @@ impl<'a> BuilderForBoxFragment<'a> {
intrinsic: IntrinsicSizes,
key: wr::ImageKey,
) {
// Our job here would be easier if WebRender’s `RepeatingImageDisplayItem`
// was “infinitely” repeating in all directions (clipped at `clip_rect`)
// and contained a `units::LayoutPoint` that determines the position of an arbitrary tile.
//
// Instead, it contains a `bounds` rectangle and:
//
// * The tiling is clipped to the intersection of `clip_rect` and `bounds`
// * The origin (top-left corner) of `bounds` is the position
// of the “first” (top-left-most) tile.
//
// However the background clipping area may be larger than the positionning area,
// so that first time may not be the one at position (0, 0).
// So we compute `bounds` such that:
//
// * Its bottom-right is the bottom-right of `clip_rect`
// * Its top-left is the top-left of the top-left-most tile that intersects with `clip_rect`
use style::computed_values::background_clip::single_value::T as Clip;
use style::computed_values::background_origin::single_value::T as Origin;
use style::values::computed::background::BackgroundSize as Size;
@ -416,7 +399,6 @@ impl<'a> BuilderForBoxFragment<'a> {
}
/// Abstract over the horizontal or vertical dimension
/// Returns `(bounds_origin, bounds_size)`
/// Coordinates (0, 0) for the purpose of this function are the positioning area’s origin.
fn layout_1d(
tile_size: &mut f32,
@ -437,9 +419,12 @@ impl<'a> BuilderForBoxFragment<'a> {
.px();
// https://drafts.csswg.org/css-backgrounds/#background-repeat
if let Repeat::Space = repeat {
// The most entire tiles we can fit
let tile_count = (positioning_area_size / *tile_size).floor();
if tile_count >= 2.0 {
position = 0.0;
// Make the outsides of the first and last of that many tiles
// touch the edges of the positioning area:
let total_space = positioning_area_size - *tile_size * tile_count;
let spaces_count = tile_count - 1.0;
*tile_spacing = total_space / spaces_count;
@ -448,14 +433,34 @@ impl<'a> BuilderForBoxFragment<'a> {
}
}
match repeat {
Repeat::NoRepeat => (false, position, *tile_size),
Repeat::Repeat | Repeat::Round | Repeat::Space => {
// WebRender’s `RepeatingImageDisplayItem` contains a `bounds` rectangle and:
//
// * The tiling is clipped to the intersection of `clip_rect` and `bounds`
// * The origin (top-left corner) of `bounds` is the position
// of the “first” (top-left-most) tile.
//
// In the general case that first tile is not the one that is positioned by
// `background-position`.
// We want it to be the top-left-most tile that intersects with `clip_rect`.
// We find it by offsetting by a whole number of strides,
// then compute `bounds` such that:
//
// * Its bottom-right is the bottom-right of `clip_rect`
// * Its top-left is the top-left of first tile.
let tile_stride = *tile_size + *tile_spacing;
let offset = position - clipping_area_origin;
let bounds_origin = position - tile_stride * (offset / tile_stride).ceil();
let bounds_size = clipping_area_size - bounds_origin - clipping_area_origin;
(true, bounds_origin, bounds_size)
},
Repeat::NoRepeat => {
// `RepeatingImageDisplayItem` always repeats in both dimension.
// When we want only one of the dimensions to repeat,
// we use the `bounds` rectangle to clip the tiling to one tile
// in that dimension.
(false, position, *tile_size)
},
}
}