Support multi viewport rendering with reusable text atlas

src/shader.wgsl

@@ -23,13 +23,13 @@ struct Params {
 @group(0) @binding(0)
 var<uniform> params: Params;
 
-@group(0) @binding(1)
+@group(1) @binding(0)
 var color_atlas_texture: texture_2d<f32>;
 
-@group(0) @binding(2)
+@group(1) @binding(1)
 var mask_atlas_texture: texture_2d<f32>;
 
-@group(0) @binding(3)
+@group(1) @binding(2)
 var atlas_sampler: sampler;
 
 fn srgb_to_linear(c: f32) -> f32 {

src/text_atlas.rs

@@ -1,20 +1,20 @@
 use crate::{
     text_render::ContentType, CacheKey, FontSystem, GlyphDetails, GlyphToRender, GpuCacheStatus,
-    Params, Resolution, SwashCache,
+    Params, SwashCache,
 };
 use etagere::{size2, Allocation, BucketedAtlasAllocator};
 use lru::LruCache;
 use std::{borrow::Cow, collections::HashSet, mem::size_of, num::NonZeroU64, sync::Arc};
 use wgpu::{
     BindGroup, BindGroupDescriptor, BindGroupEntry, BindGroupLayout, BindGroupLayoutEntry,
-    BindingResource, BindingType, BlendState, Buffer, BufferBindingType, BufferDescriptor,
-    BufferUsages, ColorTargetState, ColorWrites, DepthStencilState, Device, Extent3d, FilterMode,
-    FragmentState, ImageCopyTexture, ImageDataLayout, MultisampleState, Origin3d, PipelineLayout,
-    PipelineLayoutDescriptor, PrimitiveState, Queue, RenderPipeline, RenderPipelineDescriptor,
-    Sampler, SamplerBindingType, SamplerDescriptor, ShaderModule, ShaderModuleDescriptor,
-    ShaderSource, ShaderStages, Texture, TextureAspect, TextureDescriptor, TextureDimension,
-    TextureFormat, TextureSampleType, TextureUsages, TextureView, TextureViewDescriptor,
-    TextureViewDimension, VertexFormat, VertexState,
+    BindingResource, BindingType, BlendState, BufferBindingType, ColorTargetState, ColorWrites,
+    DepthStencilState, Device, Extent3d, FilterMode, FragmentState, ImageCopyTexture,
+    ImageDataLayout, MultisampleState, Origin3d, PipelineLayout, PipelineLayoutDescriptor,
+    PrimitiveState, Queue, RenderPipeline, RenderPipelineDescriptor, Sampler, SamplerBindingType,
+    SamplerDescriptor, ShaderModule, ShaderModuleDescriptor, ShaderSource, ShaderStages, Texture,
+    TextureAspect, TextureDescriptor, TextureDimension, TextureFormat, TextureSampleType,
+    TextureUsages, TextureView, TextureViewDescriptor, TextureViewDimension, VertexFormat,
+    VertexState,
 };
 
 #[allow(dead_code)]
@@ -255,15 +255,14 @@ pub enum ColorMode {
 
 /// 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) cached_pipelines: Vec<(
         MultisampleState,
         Option<DepthStencilState>,
         Arc<RenderPipeline>,
     )>,
     pub(crate) bind_group: Arc<BindGroup>,
     pub(crate) bind_group_layout: BindGroupLayout,
+    pub(crate) text_render_bind_group_layout: BindGroupLayout,
     pub(crate) sampler: Sampler,
     pub(crate) color_atlas: InnerAtlas,
     pub(crate) mask_atlas: InnerAtlas,
@@ -340,9 +339,9 @@ impl TextAtlas {
             ],
         }];
 
-        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
-            entries: &[
-                BindGroupLayoutEntry {
+        let text_render_bind_group_layout =
+            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+                entries: &[BindGroupLayoutEntry {
                     binding: 0,
                     visibility: ShaderStages::VERTEX,
                     ty: BindingType::Buffer {
@@ -351,9 +350,14 @@ impl TextAtlas {
                         min_binding_size: NonZeroU64::new(size_of::<Params>() as u64),
                     },
                     count: None,
-                },
+                }],
+                label: Some("glyphon text render bind group layout"),
+            });
+
+        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+            entries: &[
                 BindGroupLayoutEntry {
-                    binding: 1,
+                    binding: 0,
                     visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
                     ty: BindingType::Texture {
                         multisampled: false,
@@ -363,7 +367,7 @@ impl TextAtlas {
                     count: None,
                 },
                 BindGroupLayoutEntry {
-                    binding: 2,
+                    binding: 1,
                     visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
                     ty: BindingType::Texture {
                         multisampled: false,
@@ -373,28 +377,13 @@ impl TextAtlas {
                     count: None,
                 },
                 BindGroupLayoutEntry {
-                    binding: 3,
+                    binding: 2,
                     visibility: ShaderStages::FRAGMENT,
                     ty: BindingType::Sampler(SamplerBindingType::Filtering),
                     count: None,
                 },
             ],
-            label: Some("glyphon bind group layout"),
-        });
-
-        let params = Params {
-            screen_resolution: Resolution {
-                width: 0,
-                height: 0,
-            },
-            _pad: [0, 0],
-        };
-
-        let params_buffer = device.create_buffer(&BufferDescriptor {
-            label: Some("glyphon params"),
-            size: size_of::<Params>() as u64,
-            usage: BufferUsages::UNIFORM | BufferUsages::COPY_DST,
-            mapped_at_creation: false,
+            label: Some("glyphon text atlas bind group layout"),
         });
 
         let color_atlas = InnerAtlas::new(
@@ -414,34 +403,29 @@ impl TextAtlas {
             entries: &[
                 BindGroupEntry {
                     binding: 0,
-                    resource: params_buffer.as_entire_binding(),
-                },
-                BindGroupEntry {
-                    binding: 1,
                     resource: BindingResource::TextureView(&color_atlas.texture_view),
                 },
                 BindGroupEntry {
-                    binding: 2,
+                    binding: 1,
                     resource: BindingResource::TextureView(&mask_atlas.texture_view),
                 },
                 BindGroupEntry {
-                    binding: 3,
+                    binding: 2,
                     resource: BindingResource::Sampler(&sampler),
                 },
             ],
-            label: Some("glyphon bind group"),
+            label: Some("glyphon text atlas bind group"),
         }));
 
         let pipeline_layout = device.create_pipeline_layout(&PipelineLayoutDescriptor {
             label: None,
-            bind_group_layouts: &[&bind_group_layout],
+            bind_group_layouts: &[&text_render_bind_group_layout, &bind_group_layout],
             push_constant_ranges: &[],
         });
 
         Self {
-            params,
-            params_buffer,
             cached_pipelines: Vec::new(),
+            text_render_bind_group_layout,
             bind_group,
             bind_group_layout,
             sampler,
@@ -540,18 +524,14 @@ impl TextAtlas {
             entries: &[
                 BindGroupEntry {
                     binding: 0,
-                    resource: self.params_buffer.as_entire_binding(),
-                },
-                BindGroupEntry {
-                    binding: 1,
                     resource: BindingResource::TextureView(&self.color_atlas.texture_view),
                 },
                 BindGroupEntry {
-                    binding: 2,
+                    binding: 1,
                     resource: BindingResource::TextureView(&self.mask_atlas.texture_view),
                 },
                 BindGroupEntry {
-                    binding: 3,
+                    binding: 2,
                     resource: BindingResource::Sampler(&self.sampler),
                 },
             ],

src/text_render.rs

@@ -4,20 +4,22 @@ use crate::{
 };
 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,
-    TextureAspect, COPY_BUFFER_ALIGNMENT,
+    BindGroupDescriptor, BindGroupEntry, Buffer, BufferDescriptor, BufferUsages, DepthStencilState,
+    Device, Extent3d, ImageCopyTexture, ImageDataLayout, IndexFormat, MultisampleState, Origin3d,
+    Queue, RenderPass, RenderPipeline, TextureAspect, COPY_BUFFER_ALIGNMENT,
 };
 
 /// A text renderer that uses cached glyphs to render text into an existing render pass.
 pub struct TextRenderer {
+    params: Params,
+    params_buffer: Buffer,
     vertex_buffer: Buffer,
     vertex_buffer_size: u64,
     index_buffer: Buffer,
     index_buffer_size: u64,
     vertices_to_render: u32,
-    screen_resolution: Resolution,
     pipeline: Arc<RenderPipeline>,
+    bind_group: wgpu::BindGroup,
 }
 
 impl TextRenderer {
@@ -46,17 +48,40 @@ impl TextRenderer {
 
         let pipeline = atlas.get_or_create_pipeline(device, multisample, depth_stencil);
 
+        let params = Params {
+            screen_resolution: Resolution {
+                width: 0,
+                height: 0,
+            },
+            _pad: [0, 0],
+        };
+
+        let params_buffer = device.create_buffer(&BufferDescriptor {
+            label: Some("glyphon params"),
+            size: size_of::<Params>() as u64,
+            usage: BufferUsages::UNIFORM | BufferUsages::COPY_DST,
+            mapped_at_creation: false,
+        });
+
+        let bind_group = device.create_bind_group(&BindGroupDescriptor {
+            layout: &atlas.text_render_bind_group_layout,
+            entries: &[BindGroupEntry {
+                binding: 0,
+                resource: params_buffer.as_entire_binding(),
+            }],
+            label: Some("glyphon text render bind group"),
+        });
+
         Self {
+            params,
+            params_buffer,
             vertex_buffer,
             vertex_buffer_size,
             index_buffer,
             index_buffer_size,
             vertices_to_render: 0,
-            screen_resolution: Resolution {
-                width: 0,
-                height: 0,
-            },
             pipeline,
+            bind_group,
         }
     }
 
@@ -72,15 +97,11 @@ impl TextRenderer {
         cache: &mut SwashCache,
         mut metadata_to_depth: impl FnMut(usize) -> f32,
     ) -> Result<(), PrepareError> {
-        self.screen_resolution = screen_resolution;
-
-        let atlas_current_resolution = { atlas.params.screen_resolution };
-
-        if screen_resolution != atlas_current_resolution {
-            atlas.params.screen_resolution = screen_resolution;
-            queue.write_buffer(&atlas.params_buffer, 0, unsafe {
+        if self.params.screen_resolution != screen_resolution {
+            self.params.screen_resolution = screen_resolution;
+            queue.write_buffer(&self.params_buffer, 0, unsafe {
                 slice::from_raw_parts(
-                    &atlas.params as *const Params as *const u8,
+                    &self.params as *const Params as *const u8,
                     size_of::<Params>(),
                 )
             });
@@ -394,15 +415,9 @@ impl TextRenderer {
             return Ok(());
         }
 
-        {
-            // Validate that screen resolution hasn't changed since `prepare`
-            if self.screen_resolution != atlas.params.screen_resolution {
-                return Err(RenderError::ScreenResolutionChanged);
-            }
-        }
-
         pass.set_pipeline(&self.pipeline);
-        pass.set_bind_group(0, &atlas.bind_group, &[]);
+        pass.set_bind_group(0, &self.bind_group, &[]);
+        pass.set_bind_group(1, &atlas.bind_group, &[]);
         pass.set_vertex_buffer(0, self.vertex_buffer.slice(..));
         pass.set_index_buffer(self.index_buffer.slice(..), IndexFormat::Uint32);
         pass.draw_indexed(0..self.vertices_to_render, 0, 0..1);