Introduce `canvas::Cache` grouping

Caches with the same `Group` will share their text
atlas!

2 files changed, 65 insertions, 22 deletions

diff --git a/wgpu/src/geometry.rs b/wgpu/src/geometry.rs
index 60967082..f6213e1d 100644
--- a/wgpu/src/geometry.rs
+++ b/wgpu/src/geometry.rs
@@ -3,6 +3,7 @@ use crate::core::text::LineHeight;
 use crate::core::{
     Pixels, Point, Radians, Rectangle, Size, Transformation, Vector,
 };
+use crate::graphics::cache::{self, Cached};
 use crate::graphics::color;
 use crate::graphics::geometry::fill::{self, Fill};
 use crate::graphics::geometry::{
@@ -10,7 +11,7 @@ use crate::graphics::geometry::{
 };
 use crate::graphics::gradient::{self, Gradient};
 use crate::graphics::mesh::{self, Mesh};
-use crate::graphics::{self, Cached, Text};
+use crate::graphics::{self, Text};
 use crate::text;
 use crate::triangle;
 
@@ -38,7 +39,11 @@ impl Cached for Geometry {
         Geometry::Cached(cache.clone())
     }
 
-    fn cache(self, previous: Option<Self::Cache>) -> Self::Cache {
+    fn cache(
+        self,
+        group: cache::Group,
+        previous: Option<Self::Cache>,
+    ) -> Self::Cache {
         match self {
             Self::Live { meshes, text } => {
                 if let Some(mut previous) = previous {
@@ -51,14 +56,14 @@ impl Cached for Geometry {
                     if let Some(cache) = &mut previous.text {
                         cache.update(text);
                     } else {
-                        previous.text = text::Cache::new(text);
+                        previous.text = text::Cache::new(group, text);
                     }
 
                     previous
                 } else {
                     Cache {
                         meshes: triangle::Cache::new(meshes),
-                        text: text::Cache::new(text),
+                        text: text::Cache::new(group, text),
                     }
                 }
             }
diff --git a/wgpu/src/text.rs b/wgpu/src/text.rs
index 38712660..5806863c 100644
--- a/wgpu/src/text.rs
+++ b/wgpu/src/text.rs
@@ -1,7 +1,8 @@
 use crate::core::alignment;
 use crate::core::{Rectangle, Size, Transformation};
+use crate::graphics::cache;
 use crate::graphics::color;
-use crate::graphics::text::cache::{self, Cache as BufferCache};
+use crate::graphics::text::cache::{self as text_cache, Cache as BufferCache};
 use crate::graphics::text::{font_system, to_color, Editor, Paragraph};
 
 use rustc_hash::FxHashMap;
@@ -35,6 +36,7 @@ pub enum Item {
 #[derive(Debug, Clone)]
 pub struct Cache {
     id: Id,
+    group: cache::Group,
     text: Rc<[Text]>,
     version: usize,
 }
@@ -43,7 +45,7 @@ pub struct Cache {
 pub struct Id(u64);
 
 impl Cache {
-    pub fn new(text: Vec<Text>) -> Option<Self> {
+    pub fn new(group: cache::Group, text: Vec<Text>) -> Option<Self> {
         static NEXT_ID: AtomicU64 = AtomicU64::new(0);
 
         if text.is_empty() {
@@ -52,6 +54,7 @@ impl Cache {
 
         Some(Self {
             id: Id(NEXT_ID.fetch_add(1, atomic::Ordering::Relaxed)),
+            group,
             text: Rc::from(text),
             version: 0,
         })
@@ -65,29 +68,39 @@ impl Cache {
 
 struct Upload {
     renderer: glyphon::TextRenderer,
-    atlas: glyphon::TextAtlas,
     buffer_cache: BufferCache,
     transformation: Transformation,
     version: usize,
     text: rc::Weak<[Text]>,
+    _atlas: rc::Weak<()>,
 }
 
 #[derive(Default)]
 pub struct Storage {
+    groups: FxHashMap<cache::Group, Group>,
     uploads: FxHashMap<Id, Upload>,
 }
 
+struct Group {
+    atlas: glyphon::TextAtlas,
+    previous_uploads: usize,
+    handle: Rc<()>,
+}
+
 impl Storage {
     pub fn new() -> Self {
         Self::default()
     }
 
-    fn get(&self, cache: &Cache) -> Option<&Upload> {
+    fn get(&self, cache: &Cache) -> Option<(&glyphon::TextAtlas, &Upload)> {
         if cache.text.is_empty() {
             return None;
         }
 
-        self.uploads.get(&cache.id)
+        self.groups
+            .get(&cache.group)
+            .map(|group| &group.atlas)
+            .zip(self.uploads.get(&cache.id))
     }
 
     fn prepare(
@@ -101,6 +114,20 @@ impl Storage {
         bounds: Rectangle,
         target_size: Size<u32>,
     ) {
+        let group_count = self.groups.len();
+
+        let group = self.groups.entry(cache.group).or_insert_with(|| {
+            log::info!("New text atlas created (total: {})", group_count + 1);
+
+            Group {
+                atlas: glyphon::TextAtlas::with_color_mode(
+                    device, queue, format, COLOR_MODE,
+                ),
+                previous_uploads: 0,
+                handle: Rc::new(()),
+            }
+        });
+
         match self.uploads.entry(cache.id) {
             hash_map::Entry::Occupied(entry) => {
                 let upload = entry.into_mut();
@@ -114,7 +141,7 @@ impl Storage {
                         queue,
                         encoder,
                         &mut upload.renderer,
-                        &mut upload.atlas,
+                        &mut group.atlas,
                         &mut upload.buffer_cache,
                         &cache.text,
                         bounds,
@@ -127,16 +154,11 @@ impl Storage {
                     upload.transformation = new_transformation;
 
                     upload.buffer_cache.trim();
-                    upload.atlas.trim();
                 }
             }
             hash_map::Entry::Vacant(entry) => {
-                let mut atlas = glyphon::TextAtlas::with_color_mode(
-                    device, queue, format, COLOR_MODE,
-                );
-
                 let mut renderer = glyphon::TextRenderer::new(
-                    &mut atlas,
+                    &mut group.atlas,
                     device,
                     wgpu::MultisampleState::default(),
                     None,
@@ -149,7 +171,7 @@ impl Storage {
                     queue,
                     encoder,
                     &mut renderer,
-                    &mut atlas,
+                    &mut group.atlas,
                     &mut buffer_cache,
                     &cache.text,
                     bounds,
@@ -159,11 +181,11 @@ impl Storage {
 
                 let _ = entry.insert(Upload {
                     renderer,
-                    atlas,
                     buffer_cache,
                     transformation: new_transformation,
                     version: 0,
                     text: Rc::downgrade(&cache.text),
+                    _atlas: Rc::downgrade(&group.handle),
                 });
 
                 log::info!(
@@ -178,6 +200,22 @@ impl Storage {
     pub fn trim(&mut self) {
         self.uploads
             .retain(|_id, upload| upload.text.strong_count() > 0);
+
+        self.groups.retain(|_id, group| {
+            let uploads_alive = Rc::weak_count(&group.handle);
+
+            if uploads_alive == 0 {
+                return false;
+            }
+
+            if uploads_alive < group.previous_uploads {
+                group.atlas.trim();
+            }
+
+            group.previous_uploads = uploads_alive;
+
+            true
+        });
     }
 }
 
@@ -306,10 +344,10 @@ impl Pipeline {
                     layer_count += 1;
                 }
                 Item::Cached { cache, .. } => {
-                    if let Some(upload) = storage.get(cache) {
+                    if let Some((atlas, upload)) = storage.get(cache) {
                         upload
                             .renderer
-                            .render(&upload.atlas, render_pass)
+                            .render(atlas, render_pass)
                             .expect("Render cached text");
                     }
                 }
@@ -345,7 +383,7 @@ fn prepare(
     enum Allocation {
         Paragraph(Paragraph),
         Editor(Editor),
-        Cache(cache::KeyHash),
+        Cache(text_cache::KeyHash),
         Raw(Arc<glyphon::Buffer>),
     }
 
@@ -369,7 +407,7 @@ fn prepare(
             } => {
                 let (key, _) = buffer_cache.allocate(
                     font_system,
-                    cache::Key {
+                    text_cache::Key {
                         content,
                         size: f32::from(*size),
                         line_height: f32::from(*line_height),