Implement Sprite Instancing

Sprites with the same texture will now be rendered with one draw call.

Author: zicklag

crates/bevy_utils/src/slab.rs

@@ -11,6 +11,14 @@ pub struct SlabKey<V> {
     marker: PhantomData<V>,
 }
 
+impl<V> PartialEq<SlabKey<V>> for SlabKey<V> {
+    fn eq(&self, other: &SlabKey<V>) -> bool {
+        self.index == other.index
+    }
+}
+
+impl<V> Eq for SlabKey<V> {}
+
 impl<V> Copy for SlabKey<V> {}
 
 impl<V> Clone for SlabKey<V> {

pipelined/bevy_sprite2/src/lib.rs

@@ -34,7 +34,8 @@ impl Plugin for SpritePlugin {
             .add_system_to_stage(RenderStage::Prepare, render::prepare_sprites)
             .add_system_to_stage(RenderStage::Queue, queue_sprites)
             .init_resource::<SpriteShaders>()
-            .init_resource::<SpriteMeta>();
+            .init_resource::<SpriteMeta>()
+            .init_resource::<ExtractedSprites>();
         let draw_sprite = DrawSprite::new(&mut render_app.world);
         render_app
             .world