Revert recent anti-aliasing improvements (#24289)

This reverts commit 31fa414422.
This reverts commit b9e0aae49f.

`lyon` commit revert:

![image](https://github.com/user-attachments/assets/0243f61c-0713-416d-b8db-47372e04abaa)

`MSAA` commit revert:

![image](https://github.com/user-attachments/assets/b1a4a9fe-0192-47ef-be6f-52e03c025724)

cc @huacnlee , @\as-cii had decided to revert this PR due to a selection
right corner rendering bug.
Not sure what to propose for a fix from my side

Release Notes:

- N/A

crates/gpui/src/platform/mac/metal_atlas.rs

@@ -13,14 +13,13 @@ use std::borrow::Cow;
 pub(crate) struct MetalAtlas(Mutex<MetalAtlasState>);
 
 impl MetalAtlas {
-    pub(crate) fn new(device: Device, path_sample_count: u32) -> Self {
+    pub(crate) fn new(device: Device) -> Self {
         MetalAtlas(Mutex::new(MetalAtlasState {
             device: AssertSend(device),
             monochrome_textures: Default::default(),
             polychrome_textures: Default::default(),
             path_textures: Default::default(),
             tiles_by_key: Default::default(),
-            path_sample_count,
         }))
     }
 
@@ -28,10 +27,6 @@ impl MetalAtlas {
         self.0.lock().texture(id).metal_texture.clone()
     }
 
-    pub(crate) fn msaa_texture(&self, id: AtlasTextureId) -> Option<metal::Texture> {
-        self.0.lock().texture(id).msaa_texture.clone()
-    }
-
     pub(crate) fn allocate(
         &self,
         size: Size<DevicePixels>,
@@ -59,7 +54,6 @@ struct MetalAtlasState {
     polychrome_textures: AtlasTextureList<MetalAtlasTexture>,
     path_textures: AtlasTextureList<MetalAtlasTexture>,
     tiles_by_key: FxHashMap<AtlasKey, AtlasTile>,
-    path_sample_count: u32,
 }
 
 impl PlatformAtlas for MetalAtlas {
@@ -182,18 +176,6 @@ impl MetalAtlasState {
         texture_descriptor.set_usage(usage);
         let metal_texture = self.device.new_texture(&texture_descriptor);
 
-        // We currently only enable MSAA for path textures.
-        let msaa_texture = if self.path_sample_count > 1 && kind == AtlasTextureKind::Path {
-            let mut descriptor = texture_descriptor.clone();
-            descriptor.set_texture_type(metal::MTLTextureType::D2Multisample);
-            descriptor.set_storage_mode(metal::MTLStorageMode::Private);
-            descriptor.set_sample_count(self.path_sample_count as _);
-            let msaa_texture = self.device.new_texture(&descriptor);
-            Some(msaa_texture)
-        } else {
-            None
-        };
-
         let texture_list = match kind {
             AtlasTextureKind::Monochrome => &mut self.monochrome_textures,
             AtlasTextureKind::Polychrome => &mut self.polychrome_textures,
@@ -209,7 +191,6 @@ impl MetalAtlasState {
             },
             allocator: etagere::BucketedAtlasAllocator::new(size.into()),
             metal_texture: AssertSend(metal_texture),
-            msaa_texture: AssertSend(msaa_texture),
             live_atlas_keys: 0,
         };
 
@@ -236,7 +217,6 @@ struct MetalAtlasTexture {
     id: AtlasTextureId,
     allocator: BucketedAtlasAllocator,
     metal_texture: AssertSend<metal::Texture>,
-    msaa_texture: AssertSend<Option<metal::Texture>>,
     live_atlas_keys: u32,
 }
 

crates/gpui/src/platform/mac/metal_renderer.rs

@@ -28,9 +28,6 @@ pub(crate) type PointF = crate::Point<f32>;
 const SHADERS_METALLIB: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/shaders.metallib"));
 #[cfg(feature = "runtime_shaders")]
 const SHADERS_SOURCE_FILE: &str = include_str!(concat!(env!("OUT_DIR"), "/stitched_shaders.metal"));
-// Use 4x MSAA, all devices support it.
-// https://developer.apple.com/documentation/metal/mtldevice/1433355-supportstexturesamplecount
-const PATH_SAMPLE_COUNT: u32 = 4;
 
 pub type Context = Arc<Mutex<InstanceBufferPool>>;
 pub type Renderer = MetalRenderer;
@@ -173,7 +170,6 @@ impl MetalRenderer {
             "path_rasterization_vertex",
             "path_rasterization_fragment",
             MTLPixelFormat::R16Float,
-            PATH_SAMPLE_COUNT,
         );
         let path_sprites_pipeline_state = build_pipeline_state(
             &device,
@@ -233,7 +229,7 @@ impl MetalRenderer {
         );
 
         let command_queue = device.new_command_queue();
-        let sprite_atlas = Arc::new(MetalAtlas::new(device.clone(), PATH_SAMPLE_COUNT));
+        let sprite_atlas = Arc::new(MetalAtlas::new(device.clone()));
         let core_video_texture_cache =
             unsafe { CVMetalTextureCache::new(device.as_ptr()).unwrap() };
 
@@ -535,20 +531,10 @@ impl MetalRenderer {
                 .unwrap();
 
             let texture = self.sprite_atlas.metal_texture(texture_id);
-            let msaa_texture = self.sprite_atlas.msaa_texture(texture_id);
-
-            if let Some(msaa_texture) = msaa_texture {
-                color_attachment.set_texture(Some(&msaa_texture));
-                color_attachment.set_resolve_texture(Some(&texture));
-                color_attachment.set_load_action(metal::MTLLoadAction::Clear);
-                color_attachment.set_store_action(metal::MTLStoreAction::MultisampleResolve);
-            } else {
-                color_attachment.set_texture(Some(&texture));
-                color_attachment.set_load_action(metal::MTLLoadAction::Clear);
-                color_attachment.set_store_action(metal::MTLStoreAction::Store);
-            }
+            color_attachment.set_texture(Some(&texture));
+            color_attachment.set_load_action(metal::MTLLoadAction::Clear);
+            color_attachment.set_store_action(metal::MTLStoreAction::Store);
             color_attachment.set_clear_color(metal::MTLClearColor::new(0., 0., 0., 1.));
-
             let command_encoder = command_buffer.new_render_command_encoder(render_pass_descriptor);
             command_encoder.set_render_pipeline_state(&self.paths_rasterization_pipeline_state);
             command_encoder.set_vertex_buffer(
@@ -1174,7 +1160,6 @@ fn build_path_rasterization_pipeline_state(
     vertex_fn_name: &str,
     fragment_fn_name: &str,
     pixel_format: metal::MTLPixelFormat,
-    path_sample_count: u32,
 ) -> metal::RenderPipelineState {
     let vertex_fn = library
         .get_function(vertex_fn_name, None)
@@ -1187,10 +1172,6 @@ fn build_path_rasterization_pipeline_state(
     descriptor.set_label(label);
     descriptor.set_vertex_function(Some(vertex_fn.as_ref()));
     descriptor.set_fragment_function(Some(fragment_fn.as_ref()));
-    if path_sample_count > 1 {
-        descriptor.set_raster_sample_count(path_sample_count as _);
-        descriptor.set_alpha_to_coverage_enabled(true);
-    }
     let color_attachment = descriptor.color_attachments().object_at(0).unwrap();
     color_attachment.set_pixel_format(pixel_format);
     color_attachment.set_blending_enabled(true);