Bug 1679751 - Use a shelf packing allocator for the image atlas. r=gw.

Differential Revision: https://phabricator.services.mozilla.com/D98658

gfx/wr/webrender/src/atlas_allocator.rs

@@ -9,6 +9,7 @@ use smallvec::SmallVec;
 
 pub use etagere::AllocatorOptions as ShelfAllocatorOptions;
 pub use etagere::BucketedAtlasAllocator as BucketedShelfAllocator;
+pub use etagere::AtlasAllocator as ShelfAllocator;
 
 /// ID of an allocation within a given allocator.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
@@ -241,3 +242,33 @@ impl AtlasAllocator for BucketedShelfAllocator {
         self.dump_into_svg(Some(&rect.to_i32().cast_unit()), output)
     }
 }
+
+impl AtlasAllocator for ShelfAllocator {
+    type Parameters = ShelfAllocatorOptions;
+
+    fn new(size: i32, options: &Self::Parameters) -> Self {
+        ShelfAllocator::with_options(size2(size, size), options)
+    }
+
+    fn allocate(&mut self, size: DeviceIntSize) -> Option<(AllocId, DeviceIntRect)> {
+        self.allocate(size.to_untyped()).map(|alloc| {
+            (AllocId(alloc.id.serialize()), alloc.rectangle.to_rect().cast_unit())
+        })
+    }
+
+    fn deallocate(&mut self, id: AllocId) {
+        self.deallocate(etagere::AllocId::deserialize(id.0));
+    }
+
+    fn is_empty(&self) -> bool {
+        self.is_empty()
+    }
+
+    fn allocated_space(&self) -> i32 {
+        self.allocated_space()
+    }
+
+    fn dump_into_svg(&self, rect: &Box2D<f32>, output: &mut dyn std::io::Write) -> std::io::Result<()> {
+        self.dump_into_svg(Some(&rect.to_i32().cast_unit()), output)
+    }
+}

gfx/wr/webrender/src/texture_cache.rs

@@ -238,7 +238,7 @@ struct SharedTextures {
     color8_nearest: AllocatorList<SlabAllocator, TextureParameters>,
     alpha8_linear: AllocatorList<SlabAllocator, TextureParameters>,
     alpha16_linear: AllocatorList<SlabAllocator, TextureParameters>,
-    color8_linear: AllocatorList<SlabAllocator, TextureParameters>,
+    color8_linear: AllocatorList<ShelfAllocator, TextureParameters>,
     color8_glyphs: AllocatorList<BucketedShelfAllocator, TextureParameters>,
 }
 
@@ -274,8 +274,10 @@ impl SharedTextures {
             // The primary cache for images, etc.
             color8_linear: AllocatorList::new(
                 2048,
-                SlabAllocatorParameters {
-                    region_size: TEXTURE_REGION_DIMENSIONS,
+                ShelfAllocatorOptions {
+                    num_columns: 2,
+                    alignment: size2(16, 16),
+                    .. ShelfAllocatorOptions::default()
                 },
                 TextureParameters {
                     formats: color_formats.clone(),