From 175e80ff47a187540f2e9170d530cff0d9c30ee2 Mon Sep 17 00:00:00 2001
From: phi hu <humdrum00001010@gmail.com>
Date: Fri, 26 Jun 2026 18:20:01 +0900
Subject: [PATCH] perf: cache FontMgr + system font enumeration thread-locally
 in SkiaLayerRenderer::new
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SkiaLayerRenderer::new() called FontMgr::default() + collect_system_families()
(enumerating every installed font family) on every page. Measured ~8.4 ms/call on
macOS — ~15-21% of a page's raster time, and ~3.6 s of pure repeated enumeration on
a 426-page export. The system font set is process/thread stable, so compute it once
in a thread_local and clone (FontMgr = refcount bump, families = small HashSet clone,
~3 us) into each new().

Font-matching inputs are unchanged, so render output is byte-identical (verified:
p13/p9 PNG md5 match baseline). new() drops 8390 us -> 3.0 us. Native-skia render
path only (no wasm/NIF impact). 48 skia tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 src/renderer/skia/renderer.rs | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/renderer/skia/renderer.rs b/src/renderer/skia/renderer.rs
index 1b7f66819..0c3e0b3b7 100644
--- a/src/renderer/skia/renderer.rs
+++ b/src/renderer/skia/renderer.rs
@@ -284,13 +284,23 @@ pub struct SkiaLayerRenderer {
 
 impl SkiaLayerRenderer {
     pub fn new() -> Self {
-        let font_mgr = FontMgr::default();
-        let system_families = collect_system_families(&font_mgr);
-        Self {
-            font_mgr,
-            custom_typefaces: HashMap::new(),
-            system_families,
+        // [perf] FontMgr::default() + collect_system_families() (시스템 폰트 family 전수
+        // 열거) 는 페이지당 ~8ms 가 드는데, 프로세스(스레드) 내에서 불변이다. 매 렌더마다
+        // 재열거하지 않도록 thread-local 로 1회만 계산하고, 이후 new() 는 캐시를 복제
+        // (FontMgr = refcount bump, families = HashSet clone ~수십 µs) 해 재사용한다.
+        // 폰트 매칭 입력이 동일하므로 렌더 출력은 바이트 단위로 불변이다.
+        thread_local! {
+            static SKIA_FONT_BASE: (FontMgr, SystemFontFamilies) = {
+                let font_mgr = FontMgr::default();
+                let system_families = collect_system_families(&font_mgr);
+                (font_mgr, system_families)
+            };
         }
+        SKIA_FONT_BASE.with(|(font_mgr, system_families)| Self {
+            font_mgr: font_mgr.clone(),
+            custom_typefaces: HashMap::new(),
+            system_families: system_families.clone(),
+        })
     }
 
     /// 사용자 지정 폰트 디렉토리 (ttfs 등) 의 폰트를 로드하여 Skia 가 직접 사용 가능하게 한다.