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Implement growing logic for TextAtlas

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The `TextAtlas` will have an initial size of `256` (we could make this
configurable) and `try_allocate` will keep track of the glyphs in use
in the current frame, returning `None` when the LRU glyph is in use.

In that case, `TextRenderer::prepare` will return
`PrepareError::AtlasFull` with the `ContentType` of the atlas that is
full. The user of the library can then call `TextAtlas::grow` with the
provided `ContentType` to obtain a bigger atlas (by `256`).

A `TextAtlas::grow` call clears the whole atlas and, as a result, all of
the `prepare` calls need to be repeated in a frame until they all
succeed. Overall, the atlas will rarely need to grow and so the calls
will not need to be repated often.

Finally, the user needs to call `TextAtlas::trim` at the end of the
frame. This allows us to clear the glyphs in use collection in the atlas. Maybe
there is a better way to model this in an API that forces the user to
trim the atlas (e.g. make `trim` return a new type and changing `prepare` and `render` to take that type instead).
This commit is contained in:
Héctor Ramón Jiménez 2023-02-08 23:08:37 +01:00 • committed by Josh Groves
parent d20643702f
commit a74ce29c1a
5 changed files with 159 additions and 59 deletions
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55
src/text_render.rs
View file

@ -1,8 +1,8 @@
use crate::{
CacheKey, FontSystem, GlyphDetails, GlyphToRender, GpuCacheStatus, Params, PrepareError,
RenderError, Resolution, SwashCache, SwashContent, TextArea, TextAtlas,
FontSystem, GlyphDetails, GlyphToRender, GpuCacheStatus, Params, PrepareError, RenderError,
Resolution, SwashCache, SwashContent, TextArea, TextAtlas,
};
use std::{collections::HashSet, iter, mem::size_of, slice, sync::Arc};
use std::{iter, mem::size_of, slice, sync::Arc};
use wgpu::{
Buffer, BufferDescriptor, BufferUsages, DepthStencilState, Device, Extent3d, ImageCopyTexture,
ImageDataLayout, IndexFormat, MultisampleState, Origin3d, Queue, RenderPass, RenderPipeline,
@ -16,7 +16,6 @@ pub struct TextRenderer {
index_buffer: Buffer,
index_buffer_size: u64,
vertices_to_render: u32,
glyphs_in_use: HashSet<CacheKey>,
screen_resolution: Resolution,
pipeline: Arc<RenderPipeline>,
}
@ -53,7 +52,6 @@ impl TextRenderer {
index_buffer,
index_buffer_size,
vertices_to_render: 0,
glyphs_in_use: HashSet::new(),
screen_resolution: Resolution {
width: 0,
height: 0,
@ -88,20 +86,16 @@ impl TextRenderer {
});
}
self.glyphs_in_use.clear();
for text_area in text_areas.iter() {
for run in text_area.buffer.layout_runs() {
for glyph in run.glyphs.iter() {
self.glyphs_in_use.insert(glyph.cache_key);
if atlas.mask_atlas.glyph_cache.contains(&glyph.cache_key) {
atlas.mask_atlas.glyph_cache.promote(&glyph.cache_key);
atlas.mask_atlas.promote(glyph.cache_key);
continue;
}
if atlas.color_atlas.glyph_cache.contains(&glyph.cache_key) {
atlas.color_atlas.glyph_cache.promote(&glyph.cache_key);
atlas.color_atlas.promote(glyph.cache_key);
continue;
}
@ -129,7 +123,9 @@ impl TextRenderer {
// Find a position in the packer
let allocation = match inner.try_allocate(width, height) {
Some(a) => a,
None => return Err(PrepareError::AtlasFull),
None => {
return Err(PrepareError::AtlasFull(content_type));
}
};
let atlas_min = allocation.rectangle.min;
@ -171,19 +167,17 @@ impl TextRenderer {
(GpuCacheStatus::SkipRasterization, None, inner)
};
if !inner.glyph_cache.contains(&glyph.cache_key) {
inner.glyph_cache.put(
glyph.cache_key,
GlyphDetails {
width: width as u16,
height: height as u16,
gpu_cache,
atlas_id,
top: image.placement.top as i16,
left: image.placement.left as i16,
},
);
}
inner.put(
glyph.cache_key,
GlyphDetails {
width: width as u16,
height: height as u16,
gpu_cache,
atlas_id,
top: image.placement.top as i16,
left: image.placement.left as i16,
},
);
}
}
}
@ -383,13 +377,6 @@ impl TextRenderer {
}
{
// Validate that glyphs haven't been evicted from cache since `prepare`
for glyph in self.glyphs_in_use.iter() {
if !atlas.contains_cached_glyph(glyph) {
return Err(RenderError::RemovedFromAtlas);
}
}
// Validate that screen resolution hasn't changed since `prepare`
if self.screen_resolution != atlas.params.screen_resolution {
return Err(RenderError::ScreenResolutionChanged);
@ -407,8 +394,8 @@ impl TextRenderer {
}
#[repr(u32)]
#[derive(Clone, Copy, Eq, PartialEq)]
pub(crate) enum ContentType {
#[derive(Debug, Clone, Copy, Eq, PartialEq)]
pub enum ContentType {
Color = 0,
Mask = 1,
}