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Use a scratch buffer to reduce allocations

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This commit adds a new ShapeBuffer type, which contains some buffers tha
are commonly re-created during the shaping process. New APIs are added
that take this structure, and old APIs are turned into wrappers around
the new API.

The goal is to reduce the number of per-layout allocations that happen
in a typical layout call.
This commit is contained in:
John Nunley 2023-07-18 19:18:56 -07:00 • committed by John Nunley
parent d7214b5417
commit 64e469718b
4 changed files with 265 additions and 66 deletions
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34
src/buffer_line.rs
View file

@ -1,7 +1,7 @@
#[cfg(not(feature = "std"))]
use alloc::{string::String, vec::Vec};
use crate::{Align, AttrsList, FontSystem, LayoutLine, ShapeLine, Shaping, Wrap};
use crate::{Align, AttrsList, FontSystem, LayoutLine, ShapeBuffer, ShapeLine, Shaping, Wrap};
/// A line (or paragraph) of text that is shaped and laid out
#[derive(Debug)]
@ -169,8 +169,18 @@ impl BufferLine {
/// Shape line, will cache results
pub fn shape(&mut self, font_system: &mut FontSystem) -> &ShapeLine {
self.shape_in_buffer(&mut ShapeBuffer::default(), font_system)
}
/// Shape a line using a pre-existing shape buffer.
pub fn shape_in_buffer(
&mut self,
scratch: &mut ShapeBuffer,
font_system: &mut FontSystem,
) -> &ShapeLine {
if self.shape_opt.is_none() {
self.shape_opt = Some(ShapeLine::new(
self.shape_opt = Some(ShapeLine::new_in_buffer(
scratch,
font_system,
&self.text,
&self.attrs_list,
@ -204,6 +214,26 @@ impl BufferLine {
self.layout_opt.as_ref().expect("layout not found")
}
/// Layout a line using a pre-existing shape buffer.
pub fn layout_in_buffer(
&mut self,
scratch: &mut ShapeBuffer,
font_system: &mut FontSystem,
font_size: f32,
width: f32,
wrap: Wrap,
) -> &[LayoutLine] {
if self.layout_opt.is_none() {
self.wrap = wrap;
let align = self.align;
let shape = self.shape_in_buffer(scratch, font_system);
let mut layout = Vec::with_capacity(1);
shape.layout_to_buffer(scratch, font_size, width, wrap, align, &mut layout);
self.layout_opt = Some(layout);
}
self.layout_opt.as_ref().expect("layout not found")
}
/// Get line layout cache
pub fn layout_opt(&self) -> &Option<Vec<LayoutLine>> {
&self.layout_opt