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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
//! Cutouts patterns act a mask on top of already rendered content.
//!
//! Their main purpose is to "punch a hole" in the current layer so that
//! an underlay layer can be seen through it.
//! The clip chain controls the shape of the mask. When rendering the
//! cutout, opaque white means pixels will be fully masked, transparent
//! black means pixels will be shown, and values in between represent
//! different levels of transparency.
use api::{ColorF, units::*};
use crate::pattern::{Pattern, PatternBuilder, PatternBuilderContext, PatternBuilderState};
use crate::renderer::BlendMode;
pub struct Cutout;
impl PatternBuilder for Cutout {
fn build(
&self,
_sub_rect: Option<DeviceRect>,
_offset: LayoutVector2D,
_ctx: &PatternBuilderContext,
_state: &mut PatternBuilderState,
) -> Pattern {
Pattern::color(ColorF::WHITE)
.with_blend_mode(BlendMode::PremultipliedDestOut)
}
}
// TODO: Cutouts are applied to the destination layer entirely in the alpha
// pass, the fully masked segments could be drawn in the opaque pass.
// TODO: Currently, complex masks for cutouts are drawn into intermediate
// surfaces using the same logic as regular patterns. They could be drawn
// directly into the the destination layer.