Snap sprites to pixel grid in Renderer

Previously, we were doing so in the `SpriteCache` but that would cause
floating point errors that caused glyphs to sometimes be positioned
midway through a pixel.

gpui/src/platform/mac/renderer.rs

@@ -293,11 +293,13 @@ impl Renderer {
                 glyph.origin,
                 scene.scale_factor(),
             ) {
+                // Snap sprite to pixel grid.
+                let origin = (glyph.origin * scene.scale_factor()).floor() + sprite.offset.to_f32();
                 sprites_by_atlas
                     .entry(sprite.atlas_id)
                     .or_insert_with(Vec::new)
                     .push(shaders::GPUISprite {
-                        origin: (glyph.origin * scene.scale_factor() + sprite.offset).to_float2(),
+                        origin: origin.to_float2(),
                         size: sprite.size.to_float2(),
                         atlas_origin: sprite.atlas_origin.to_float2(),
                         color: glyph.color.to_uchar4(),

gpui/src/platform/mac/sprite_cache.rs

@@ -23,7 +23,7 @@ struct GlyphDescriptor {
 pub struct GlyphSprite {
     pub atlas_id: usize,
     pub atlas_origin: Vector2I,
-    pub offset: Vector2F,
+    pub offset: Vector2I,
     pub size: Vector2I,
 }
 
@@ -109,13 +109,10 @@ impl SpriteCache {
                         bounds
                     });
 
-                // Snap sprite to pixel grid.
-                let offset = glyph_bounds.origin().to_f32()
-                    - vec2f(target_position.x().fract(), target_position.y().fract());
                 Some(GlyphSprite {
                     atlas_id: atlasses.len() - 1,
                     atlas_origin: atlas_bounds.origin(),
-                    offset,
+                    offset: glyph_bounds.origin(),
                     size: glyph_bounds.size(),
                 })
             })