Split color and mask atlases apart

src/lib.rs

@@ -8,19 +8,24 @@ mod text_render;
 pub use error::{PrepareError, RenderError};
 use recently_used::RecentlyUsedMap;
 pub use text_atlas::TextAtlas;
+use text_render::ContentType;
 pub use text_render::TextRenderer;
 
 pub use cosmic_text;
 
-pub(crate) enum GpuCache {
+pub(crate) enum GpuCacheStatus {
-    InAtlas { x: u16, y: u16 },
+    InAtlas {
+        x: u16,
+        y: u16,
+        content_type: ContentType,
+    },
     SkipRasterization,
 }
 
 pub(crate) struct GlyphDetails {
     width: u16,
     height: u16,
-    gpu_cache: GpuCache,
+    gpu_cache: GpuCacheStatus,
     atlas_id: Option<AllocId>,
     top: i16,
     left: i16,
@@ -33,6 +38,7 @@ pub(crate) struct GlyphToRender {
     dim: [u16; 2],
     uv: [u16; 2],
     color: u32,
+    content_type: u32,
 }
 
 /// The screen resolution to use when rendering text.

src/shader.wgsl

@@ -4,12 +4,14 @@ struct VertexInput {
     @location(1) dim: u32,
     @location(2) uv: u32,
     @location(3) color: u32,
+    @location(4) content_type: u32,
 }
 
 struct VertexOutput {
     @builtin(position) position: vec4<f32>,
     @location(0) color: vec4<f32>,
     @location(1) uv: vec2<f32>,
+    @location(2) content_type: u32,
 };
 
 struct Params {
@@ -21,9 +23,12 @@ struct Params {
 var<uniform> params: Params;
 
 @group(0) @binding(1)
-var atlas_texture: texture_2d<f32>;
+var color_atlas_texture: texture_2d<f32>;
 
 @group(0) @binding(2)
+var mask_atlas_texture: texture_2d<f32>;
+
+@group(0) @binding(3)
 var atlas_sampler: sampler;
 
 @vertex
@@ -70,12 +75,37 @@ fn vs_main(in_vert: VertexInput) -> VertexOutput {
         f32((color & 0xff000000u) >> 24u),
     ) / 255.0;
 
-    vert_output.uv = vec2<f32>(uv) / vec2<f32>(textureDimensions(atlas_texture).xy);
+    var dim = vec2<u32>(0);
+    switch in_vert.content_type {
+        case 0u: {
+            dim = textureDimensions(color_atlas_texture);
+            break;
+        }
+        case 1u: {
+            dim = textureDimensions(mask_atlas_texture);
+            break;
+        }
+        default: {}
+    }
+
+    vert_output.content_type = in_vert.content_type;
+
+    vert_output.uv = vec2<f32>(uv) / vec2<f32>(dim);
 
     return vert_output;
 }
 
 @fragment
 fn fs_main(in_frag: VertexOutput) -> @location(0) vec4<f32> {
-    return in_frag.color * textureSample(atlas_texture, atlas_sampler, in_frag.uv);
+    switch in_frag.content_type {
+        case 0u: {
+            return textureSampleLevel(color_atlas_texture, atlas_sampler, in_frag.uv, 0.0);
+        }
+        case 1u: {
+            return in_frag.color * textureSampleLevel(mask_atlas_texture, atlas_sampler, in_frag.uv, 0.0);
+        }
+        default: {
+            return vec4<f32>(0.0);
+        }
+    }
 }

src/text_atlas.rs

@@ -1,37 +1,32 @@
+use crate::{
+    text_render::ContentType, GlyphDetails, GlyphToRender, Params, RecentlyUsedMap, Resolution,
+};
 use cosmic_text::CacheKey;
-use etagere::{size2, BucketedAtlasAllocator};
+use etagere::{size2, Allocation, BucketedAtlasAllocator};
 use std::{borrow::Cow, mem::size_of, num::NonZeroU64, sync::Arc};
 use wgpu::{
-    BindGroup, BindGroupEntry, BindGroupLayoutEntry, BindingResource, BindingType, BlendState,
+    BindGroup, BindGroupDescriptor, BindGroupEntry, BindGroupLayoutEntry, BindingResource,
-    Buffer, BufferBindingType, BufferDescriptor, BufferUsages, ColorTargetState, ColorWrites,
+    BindingType, BlendState, Buffer, BufferBindingType, BufferDescriptor, BufferUsages,
-    Device, Extent3d, FilterMode, FragmentState, MultisampleState, PipelineLayoutDescriptor,
+    ColorTargetState, ColorWrites, Device, Extent3d, FilterMode, FragmentState, MultisampleState,
-    PrimitiveState, Queue, RenderPipeline, RenderPipelineDescriptor, SamplerBindingType,
+    PipelineLayoutDescriptor, PrimitiveState, Queue, RenderPipeline, RenderPipelineDescriptor,
-    SamplerDescriptor, ShaderModuleDescriptor, ShaderSource, ShaderStages, Texture,
+    SamplerBindingType, SamplerDescriptor, ShaderModuleDescriptor, ShaderSource, ShaderStages,
-    TextureDescriptor, TextureDimension, TextureFormat, TextureSampleType, TextureUsages,
+    Texture, TextureDescriptor, TextureDimension, TextureFormat, TextureSampleType, TextureUsages,
-    TextureViewDescriptor, TextureViewDimension, VertexFormat, VertexState,
+    TextureView, TextureViewDescriptor, TextureViewDimension, VertexFormat, VertexState,
 };
 
-use crate::{GlyphDetails, GlyphToRender, Params, RecentlyUsedMap, Resolution};
+pub(crate) struct InnerAtlas {
-
+    pub texture_pending: Vec<u8>,
-pub(crate) const NUM_ATLAS_CHANNELS: usize = 4usize;
+    pub texture: Texture,
-
+    pub texture_view: TextureView,
-/// An atlas containing a cache of rasterized glyphs that can be rendered.
+    pub packer: BucketedAtlasAllocator,
-pub struct TextAtlas {
+    pub width: u32,
-    pub(crate) texture_pending: Vec<u8>,
+    pub height: u32,
-    pub(crate) texture: Texture,
+    pub glyph_cache: RecentlyUsedMap<CacheKey, GlyphDetails>,
-    pub(crate) packer: BucketedAtlasAllocator,
+    pub num_atlas_channels: usize,
-    pub(crate) width: u32,
-    pub(crate) height: u32,
-    pub(crate) glyph_cache: RecentlyUsedMap<CacheKey, GlyphDetails>,
-    pub(crate) params: Params,
-    pub(crate) params_buffer: Buffer,
-    pub(crate) pipeline: Arc<RenderPipeline>,
-    pub(crate) bind_group: Arc<BindGroup>,
 }
 
-impl TextAtlas {
+impl InnerAtlas {
-    /// Creates a new `TextAtlas`.
+    fn new(device: &Device, _queue: &Queue, num_atlas_channels: usize) -> Self {
-    pub fn new(device: &Device, _queue: &Queue, format: TextureFormat) -> Self {
         let max_texture_dimension_2d = device.limits().max_texture_dimension_2d;
         let width = max_texture_dimension_2d;
         let height = max_texture_dimension_2d;
@@ -39,7 +34,7 @@ impl TextAtlas {
         let packer = BucketedAtlasAllocator::new(size2(width as i32, height as i32));
 
         // Create a texture to use for our atlas
-        let texture_pending = vec![0; (width * height) as usize * NUM_ATLAS_CHANNELS];
+        let texture_pending = vec![0; (width * height) as usize * num_atlas_channels];
         let texture = device.create_texture(&TextureDescriptor {
             label: Some("glyphon atlas"),
             size: Extent3d {
@@ -50,10 +45,61 @@ impl TextAtlas {
             mip_level_count: 1,
             sample_count: 1,
             dimension: TextureDimension::D2,
-            format: TextureFormat::Rgba8Unorm,
+            format: match num_atlas_channels {
+                1 => TextureFormat::R8Unorm,
+                4 => TextureFormat::Rgba8Unorm,
+                _ => panic!("unexpected number of channels"),
+            },
             usage: TextureUsages::TEXTURE_BINDING | TextureUsages::COPY_DST,
         });
+
         let texture_view = texture.create_view(&TextureViewDescriptor::default());
+
+        let glyph_cache = RecentlyUsedMap::new();
+
+        Self {
+            texture_pending,
+            texture,
+            texture_view,
+            packer,
+            width,
+            height,
+            glyph_cache,
+            num_atlas_channels,
+        }
+    }
+
+    pub(crate) fn try_allocate(&mut self, width: usize, height: usize) -> Option<Allocation> {
+        let size = size2(width as i32, height as i32);
+
+        loop {
+            let allocation = self.packer.allocate(size);
+            if allocation.is_some() {
+                return allocation;
+            }
+
+            // Try to free least recently used allocation
+            let (key, value) = self.glyph_cache.pop()?;
+            self.packer
+                .deallocate(value.atlas_id.expect("cache corrupt"));
+            self.glyph_cache.remove(&key);
+        }
+    }
+}
+
+/// An atlas containing a cache of rasterized glyphs that can be rendered.
+pub struct TextAtlas {
+    pub(crate) params: Params,
+    pub(crate) params_buffer: Buffer,
+    pub(crate) pipeline: Arc<RenderPipeline>,
+    pub(crate) bind_group: Arc<BindGroup>,
+    pub(crate) color_atlas: InnerAtlas,
+    pub(crate) mask_atlas: InnerAtlas,
+}
+
+impl TextAtlas {
+    /// Creates a new `TextAtlas`.
+    pub fn new(device: &Device, queue: &Queue, format: TextureFormat) -> Self {
         let sampler = device.create_sampler(&SamplerDescriptor {
             label: Some("glyphon sampler"),
             min_filter: FilterMode::Nearest,
@@ -64,8 +110,6 @@ impl TextAtlas {
             ..Default::default()
         });
 
-        let glyph_cache = RecentlyUsedMap::new();
-
         // Create a render pipeline to use for rendering later
         let shader = device.create_shader_module(ShaderModuleDescriptor {
             label: Some("glyphon shader"),
@@ -96,6 +140,11 @@ impl TextAtlas {
                     offset: size_of::<u32>() as u64 * 4,
                     shader_location: 3,
                 },
+                wgpu::VertexAttribute {
+                    format: VertexFormat::Uint32,
+                    offset: size_of::<u32>() as u64 * 5,
+                    shader_location: 4,
+                }
             ],
         }];
 
@@ -123,6 +172,16 @@ impl TextAtlas {
                 },
                 BindGroupLayoutEntry {
                     binding: 2,
+                    visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
+                    ty: BindingType::Texture {
+                        multisampled: false,
+                        view_dimension: TextureViewDimension::D2,
+                        sample_type: TextureSampleType::Float { filterable: true },
+                    },
+                    count: None,
+                },
+                BindGroupLayoutEntry {
+                    binding: 3,
                     visibility: ShaderStages::FRAGMENT,
                     ty: BindingType::Sampler(SamplerBindingType::Filtering),
                     count: None,
@@ -146,7 +205,10 @@ impl TextAtlas {
             mapped_at_creation: false,
         });
 
-        let bind_group = Arc::new(device.create_bind_group(&wgpu::BindGroupDescriptor {
+        let color_atlas = InnerAtlas::new(device, queue, 4);
+        let mask_atlas = InnerAtlas::new(device, queue, 1);
+
+        let bind_group = Arc::new(device.create_bind_group(&BindGroupDescriptor {
             layout: &bind_group_layout,
             entries: &[
                 BindGroupEntry {
@@ -155,10 +217,14 @@ impl TextAtlas {
                 },
                 BindGroupEntry {
                     binding: 1,
-                    resource: BindingResource::TextureView(&texture_view),
+                    resource: BindingResource::TextureView(&color_atlas.texture_view),
                 },
                 BindGroupEntry {
                     binding: 2,
+                    resource: BindingResource::TextureView(&mask_atlas.texture_view),
+                },
+                BindGroupEntry {
+                    binding: 3,
                     resource: BindingResource::Sampler(&sampler),
                 },
             ],
@@ -199,16 +265,38 @@ impl TextAtlas {
         }));
 
         Self {
-            texture_pending,
-            texture,
-            packer,
-            width,
-            height,
-            glyph_cache,
             params,
             params_buffer,
             pipeline,
             bind_group,
+            color_atlas,
+            mask_atlas,
+        }
+    }
+
+    pub(crate) fn contains_cached_glyph(&self, glyph: &CacheKey) -> bool {
+        self.mask_atlas.glyph_cache.contains_key(glyph)
+            || self.color_atlas.glyph_cache.contains_key(glyph)
+    }
+
+    pub(crate) fn glyph(&self, glyph: &CacheKey) -> Option<&GlyphDetails> {
+        self.mask_atlas
+            .glyph_cache
+            .get(glyph)
+            .or_else(|| self.color_atlas.glyph_cache.get(glyph))
+    }
+
+    pub(crate) fn inner_for_content(&self, content_type: ContentType) -> &InnerAtlas {
+        match content_type {
+            ContentType::Color => &self.color_atlas,
+            ContentType::Mask => &self.mask_atlas,
+        }
+    }
+
+    pub(crate) fn inner_for_content_mut(&mut self, content_type: ContentType) -> &mut InnerAtlas {
+        match content_type {
+            ContentType::Color => &mut self.color_atlas,
+            ContentType::Mask => &mut self.mask_atlas,
         }
     }
 }

src/text_render.rs

@@ -1,17 +1,14 @@
+use crate::{
+    GlyphDetails, GlyphToRender, GpuCacheStatus, Params, PrepareError, RenderError, Resolution,
+    TextAtlas, TextOverflow,
+};
 use cosmic_text::{CacheKey, Color, SwashCache, SwashContent};
-use etagere::{size2, Allocation};
-
 use std::{collections::HashSet, iter, mem::size_of, num::NonZeroU32, slice};
 use wgpu::{
     Buffer, BufferDescriptor, BufferUsages, Device, Extent3d, ImageCopyTexture, ImageDataLayout,
     IndexFormat, Origin3d, Queue, RenderPass, TextureAspect, COPY_BUFFER_ALIGNMENT,
 };
 
-use crate::{
-    text_atlas::NUM_ATLAS_CHANNELS, GlyphDetails, GlyphToRender, GpuCache, Params, PrepareError,
-    RenderError, Resolution, TextAtlas, TextOverflow,
-};
-
 /// A text renderer that uses cached glyphs to render text into an existing render pass.
 pub struct TextRenderer {
     vertex_buffer: Buffer,
@@ -87,7 +84,16 @@ impl TextRenderer {
             y_min: usize,
             y_max: usize,
         }
-        let mut upload_bounds = None::<UploadBounds>;
+
+        struct BoundsPerAtlas {
+            color: Option<UploadBounds>,
+            mask: Option<UploadBounds>,
+        }
+
+        let mut upload_bounds_per_atlas = BoundsPerAtlas {
+            color: None,
+            mask: None,
+        };
 
         self.glyphs_in_use.clear();
 
@@ -98,37 +104,33 @@ impl TextRenderer {
                 for glyph in run.glyphs.iter() {
                     self.glyphs_in_use.insert(glyph.cache_key);
 
-                    let already_on_gpu = atlas.glyph_cache.contains_key(&glyph.cache_key);
+                    let already_on_gpu = atlas.contains_cached_glyph(&glyph.cache_key);
 
                     if already_on_gpu {
                         continue;
                     }
 
                     let image = cache.get_image_uncached(glyph.cache_key).unwrap();
-                    let mut bitmap = image.data;
 
-                    match image.content {
+                    let content_type = match image.content {
-                        SwashContent::Color => {}
+                        SwashContent::Color => ContentType::Color,
-                        SwashContent::Mask => {
+                        SwashContent::Mask => ContentType::Mask,
-                            // Technically only one channel is needed, but store the mask only in the alpha channel for now.
-                            bitmap = bitmap
-                                .iter()
-                                .flat_map(|color| iter::repeat(255).take(NUM_ATLAS_CHANNELS - 1).chain(iter::once(*color)))
-                                .collect();
-                        }
                         SwashContent::SubpixelMask => {
                             // Not implemented yet, but don't panic if this happens.
+                            ContentType::Mask
                         }
-                    }
+                    };
 
                     let width = image.placement.width as usize;
                     let height = image.placement.height as usize;
 
                     let should_rasterize = width > 0 && height > 0;
 
-                    let (gpu_cache, atlas_id) = if should_rasterize {
+                    let (gpu_cache, atlas_id, inner) = if should_rasterize {
+                        let inner = atlas.inner_for_content_mut(content_type);
+
                         // Find a position in the packer
-                        let allocation = match try_allocate(atlas, width, height) {
+                        let allocation = match inner.try_allocate(width, height) {
                             Some(a) => a,
                             None => return Err(PrepareError::AtlasFull),
                         };
@@ -138,14 +140,20 @@ impl TextRenderer {
                         for row in 0..height {
                             let y_offset = atlas_min.y as usize;
                             let x_offset =
-                                (y_offset + row) * atlas.width as usize + atlas_min.x as usize;
+                                (y_offset + row) * inner.width as usize + atlas_min.x as usize;
-                            let bitmap_row = &bitmap[row * width * NUM_ATLAS_CHANNELS
+                            let num_atlas_channels = inner.num_atlas_channels;
-                                ..(row + 1) * width * NUM_ATLAS_CHANNELS];
+                            let bitmap_row = &image.data[row * width * num_atlas_channels
-                            atlas.texture_pending[x_offset * NUM_ATLAS_CHANNELS
+                                ..(row + 1) * width * num_atlas_channels];
-                                ..(x_offset + width) * NUM_ATLAS_CHANNELS]
+                            inner.texture_pending[x_offset * num_atlas_channels
+                                ..(x_offset + width) * num_atlas_channels]
                                 .copy_from_slice(bitmap_row);
                         }
 
+                        let upload_bounds = match content_type {
+                            ContentType::Color => &mut upload_bounds_per_atlas.color,
+                            ContentType::Mask => &mut upload_bounds_per_atlas.mask,
+                        };
+
                         match upload_bounds.as_mut() {
                             Some(ub) => {
                                 ub.x_min = ub.x_min.min(atlas_min.x as usize);
@@ -154,7 +162,7 @@ impl TextRenderer {
                                 ub.y_max = ub.y_max.max(atlas_max.y as usize);
                             }
                             None => {
-                                upload_bounds = Some(UploadBounds {
+                                *upload_bounds = Some(UploadBounds {
                                     x_min: atlas_min.x as usize,
                                     x_max: atlas_max.x as usize,
                                     y_min: atlas_min.y as usize,
@@ -164,18 +172,21 @@ impl TextRenderer {
                         }
 
                         (
-                            GpuCache::InAtlas {
+                            GpuCacheStatus::InAtlas {
                                 x: atlas_min.x as u16,
                                 y: atlas_min.y as u16,
+                                content_type,
                             },
                             Some(allocation.id),
+                            inner,
                         )
                     } else {
-                        (GpuCache::SkipRasterization, None)
+                        let inner = &mut atlas.color_atlas;
+                        (GpuCacheStatus::SkipRasterization, None, inner)
                     };
 
-                    if !atlas.glyph_cache.contains_key(&glyph.cache_key) {
+                    if !inner.glyph_cache.contains_key(&glyph.cache_key) {
-                        atlas.glyph_cache.insert(
+                        inner.glyph_cache.insert(
                             glyph.cache_key,
                             GlyphDetails {
                                 width: width as u16,
@@ -191,10 +202,16 @@ impl TextRenderer {
             }
         }
 
-        if let Some(ub) = upload_bounds {
+        for (content_type, bounds) in [
+            (ContentType::Color, upload_bounds_per_atlas.color),
+            (ContentType::Mask, upload_bounds_per_atlas.mask),
+        ] {
+            if let Some(ub) = bounds {
+                let inner = atlas.inner_for_content(content_type);
+                let num_atlas_channels = inner.num_atlas_channels;
                 queue.write_texture(
                     ImageCopyTexture {
-                    texture: &atlas.texture,
+                        texture: &inner.texture,
                         mip_level: 0,
                         origin: Origin3d {
                             x: ub.x_min as u32,
@@ -203,12 +220,12 @@ impl TextRenderer {
                         },
                         aspect: TextureAspect::All,
                     },
-                &atlas.texture_pending
+                    &inner.texture_pending
-                    [ub.y_min * atlas.width as usize + ub.x_min * NUM_ATLAS_CHANNELS..],
+                        [ub.y_min * inner.width as usize + ub.x_min * num_atlas_channels..],
                     ImageDataLayout {
                         offset: 0,
-                    bytes_per_row: NonZeroU32::new(atlas.width * NUM_ATLAS_CHANNELS as u32),
+                        bytes_per_row: NonZeroU32::new(inner.width * num_atlas_channels as u32),
-                    rows_per_image: NonZeroU32::new(atlas.height),
+                        rows_per_image: NonZeroU32::new(inner.height),
                     },
                     Extent3d {
                         width: (ub.x_max - ub.x_min) as u32,
@@ -217,6 +234,7 @@ impl TextRenderer {
                     },
                 );
             }
+        }
 
         let mut glyph_vertices: Vec<GlyphToRender> = Vec::new();
         let mut glyph_indices: Vec<u32> = Vec::new();
@@ -239,14 +257,14 @@ impl TextRenderer {
                         None => default_color,
                     };
 
-                    let details = atlas.glyph_cache.get(&glyph.cache_key).unwrap();
+                    let details = atlas.glyph(&glyph.cache_key).unwrap();
 
                     let mut x = glyph.x_int + details.left as i32;
                     let mut y = line_y + glyph.y_int - details.top as i32;
 
-                    let (mut atlas_x, mut atlas_y) = match details.gpu_cache {
+                    let (mut atlas_x, mut atlas_y, content_type) = match details.gpu_cache {
-                        GpuCache::InAtlas { x, y } => (x, y),
+                        GpuCacheStatus::InAtlas { x, y, content_type } => (x, y, content_type),
-                        GpuCache::SkipRasterization => continue,
+                        GpuCacheStatus::SkipRasterization => continue,
                     };
 
                     let mut width = details.width as i32;
@@ -303,6 +321,7 @@ impl TextRenderer {
                             dim: [width as u16, height as u16],
                             uv: [atlas_x, atlas_y],
                             color: color.0,
+                            content_type: content_type as u32,
                         })
                         .take(4),
                     );
@@ -394,7 +413,7 @@ impl TextRenderer {
         {
             // Validate that glyphs haven't been evicted from cache since `prepare`
             for glyph in self.glyphs_in_use.iter() {
-                if !atlas.glyph_cache.contains_key(glyph) {
+                if !atlas.contains_cached_glyph(glyph) {
                     return Err(RenderError::RemovedFromAtlas);
                 }
             }
@@ -415,22 +434,11 @@ impl TextRenderer {
     }
 }
 
-fn try_allocate(atlas: &mut TextAtlas, width: usize, height: usize) -> Option<Allocation> {
+#[repr(u32)]
-    let size = size2(width as i32, height as i32);
+#[derive(Clone, Copy, Eq, PartialEq)]
-
+pub(crate) enum ContentType {
-    loop {
+    Color = 0,
-        let allocation = atlas.packer.allocate(size);
+    Mask = 1,
-        if allocation.is_some() {
-            return allocation;
-        }
-
-        // Try to free least recently used allocation
-        let (key, value) = atlas.glyph_cache.pop()?;
-        atlas
-            .packer
-            .deallocate(value.atlas_id.expect("cache corrupt"));
-        atlas.glyph_cache.remove(&key);
-    }
 }
 
 fn next_copy_buffer_size(size: u64) -> u64 {