MoganLab · da-liii · May 19, 2026 · May 14, 2026 · May 15, 2026
diff --git a/devel/0126.md b/devel/0126.md
@@ -0,0 +1,53 @@
+# [0126] 优化 smart_font 字体加载性能
+
+## 1 相关文档
+- [dddd.md](dddd.md) - 任务文档模板
+
+## 2 任务相关的代码文件
+- `src/Graphics/Fonts/smart_font.cpp`
+- `src/Graphics/Fonts/smart_font.hpp`
+- `tests/Graphics/Fonts/smart_font_test.cpp`
+
+## 3 如何测试
+
+### 3.1 确定性测试（单元测试）
+```bash
+xmake b smart_font_test
+xmake r smart_font_test
+```
+
+### 3.2 非确定性测试（文档验证）
+```bash
+# 构建并运行字体相关测试，确保所有用例通过
+xmake b smart_font_test && xmake r smart_font_test
+```
+
+## 4 如何提交
+
+提交前执行以下最少步骤：
+
+```bash
+xmake b smart_font_test
+xmake r smart_font_test
+```
+
+## 5 What
+
+通过缓存避免 smart_font 字体加载过程中的重复函数调用，优化性能。
+
+1. 添加 `maybe_initialize_font` 辅助函数，避免对已初始化的子字体重复调用 `initialize_font`
+2. 在构造函数中缓存 `trimmed_tokenize(family, ",")` 结果（`family_tokens`），避免 `resolve(string c)` 和 `is_italic_prime` 中重复分割字符串
+3. 在构造函数中缓存 `logical_font` 结果（`given_font`），避免 `resolve(c, fam, attempt)` 中重复计算
+4. 缓存 `is_italic_prime` 的结果，避免对同一字体的斜体引号判断重复计算
+5. 新增 `test_performance` 和 `test_math_performance` 回归测试
+
+## 6 Why
+
+在字体加载过程中，通过添加日志发现很多函数会被重复调用。例如解析数学模式下 24 个希腊字母时，`initialize_font` 被调用了 21 次，虽然大部分调用的子字体已经初始化过。`trimmed_tokenize(family, ",")` 和 `logical_font` 也在每次 `resolve` 时被重复计算，造成不必要的性能开销。
+
+## 7 How
+
+- `maybe_initialize_font(int nr)`：在调用 `initialize_font` 前检查 `fn[nr]` 是否已初始化，只有未初始化时才执行实际的字体创建逻辑
+- `family_tokens`：在 `smart_font_rep` 构造函数中将 `trimmed_tokenize(family, ",")` 结果保存为成员变量，供 `resolve(string c)` 和 `is_italic_prime` 直接使用
+- `given_font`：在构造函数中将 `logical_font(family, variant, series, rshape)` 结果保存为成员变量，供 `resolve(c, fam, attempt)` 中的 `is_wanted` 调用直接使用
+- `is_italic_prime` 缓存：添加 `italic_prime_cached` 和 `italic_prime_result` 成员变量，首次计算后缓存结果
diff --git a/src/Graphics/Fonts/smart_font.cpp b/src/Graphics/Fonts/smart_font.cpp
@@ -625,14 +625,17 @@ smart_font_rep::smart_font_rep (string name, font base_fn, font err_fn,
   fn[SUBFONT_MAIN] = adjust_subfont (base_fn);
   fn[SUBFONT_ERROR]= adjust_subfont (err_fn);
   this->copy_math_pars (base_fn);
+  family_tokens      = trimmed_tokenize (family, ",");
+  given_font         = logical_font (family, variant, series, rshape);
+  italic_prime_cached= false;
   if (shape == "mathitalic" || shape == "mathupright" || shape == "mathshape") {
     if (is_math_family (mfam)) {
       rshape= "right";
       if (shape == "mathupright") this->copy_math_pars (base_fn);
       else {
         tree key= tuple ("math", mfam, variant, series, rshape);
         int  nr = sm->add_font (key, REWRITE_MATH);
-        initialize_font (nr);
+        maybe_initialize_font (nr);
         this->copy_math_pars (fn[nr]);
         fn[SUBFONT_MAIN]= fn[nr];
       }
@@ -645,7 +648,7 @@ smart_font_rep::smart_font_rep (string name, font base_fn, font err_fn,
       if (math_kind == 2) this->copy_math_pars (base_fn);
       else {
         italic_nr= sm->add_font (tuple ("fast-italic"), REWRITE_NONE);
-        initialize_font (italic_nr);
+        maybe_initialize_font (italic_nr);
         this->copy_math_pars (fn[italic_nr]);
       }
       (void) sm->add_font (tuple ("special"), REWRITE_SPECIAL);
@@ -836,7 +839,7 @@ smart_font_rep::advance (string s, int& pos, string& r, int& nr) {
         }
 
         if (count == 1 && nr != -1 && fn_index == nr) {
-          if (N (fn) <= nr || is_nil (fn[nr])) initialize_font (nr);
+          maybe_initialize_font (nr);
           if (!fn[nr]->supports (s (start, end))) break;
           pos= end;
         }
@@ -851,7 +854,7 @@ smart_font_rep::advance (string s, int& pos, string& r, int& nr) {
     }
     r= s (start, pos);
     if (nr < 0) return;
-    if (N (fn) <= nr || is_nil (fn[nr])) initialize_font (nr);
+    maybe_initialize_font (nr);
     if (sm->fn_rewr[nr] != REWRITE_NONE) r= rewrite (r, sm->fn_rewr[nr]);
   }
   if (DEBUG_VERBOSE) {
@@ -911,10 +914,9 @@ smart_font_rep::resolve (string c, string fam, int attempt) {
   }
   array<string> a= trimmed_tokenize (fam, "=");
   if (N (a) >= 2) {
-    array<string> given= logical_font (family, variant, series, rshape);
-    fam                = a[1];
-    array<string> b    = tokenize (a[0], " ");
-    bool          ok   = is_wanted (c, fam, b, given);
+    fam             = a[1];
+    array<string> b = tokenize (a[0], " ");
+    bool          ok= is_wanted (c, fam, b, given_font);
     if (!ok) {
       return -1;
     }
@@ -930,7 +932,7 @@ smart_font_rep::resolve (string c, string fam, int attempt) {
       if (cfn->supports (c)) {
         tree key= tuple ("subfont", fam);
         int  nr = sm->add_font (key, REWRITE_NONE);
-        initialize_font (nr);
+        maybe_initialize_font (nr);
         return sm->add_char (key, c);
       }
     }
@@ -957,41 +959,41 @@ smart_font_rep::resolve (string c, string fam, int attempt) {
       if (cfn->supports (c) || c == "<#200B>") {
         tree key= tuple (fam, variant, series, rshape, "1");
         int  nr = sm->add_font (key, REWRITE_NONE);
-        initialize_font (nr);
+        maybe_initialize_font (nr);
         return sm->add_char (key, c);
       }
     }
 
     if (fam == "roman" && range == "greek") {
       tree key= tuple ("greek", fam, variant, series, rshape);
       int  nr = sm->add_font (key, REWRITE_NONE);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       return sm->add_char (key, c);
     }
     if (fam == "roman" && range == "latin") {
       tree key= tuple ("latin", fam, variant, series, rshape);
       int  nr = sm->add_font (key, REWRITE_NONE);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       return sm->add_char (key, c);
     }
     if (is_math_family (fam)) {
       tree key= tuple ("math", fam, variant, series, rshape);
       int  nr = sm->add_font (key, REWRITE_MATH);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       if (fn[nr]->supports (rewrite (c, REWRITE_MATH)))
         return sm->add_char (key, c);
     }
     if ((fam == "roman" || fam == "cyrillic") && N (c) > 1) {
       tree key= tuple ("cyrillic", fam, variant, series, rshape);
       int  nr = sm->add_font (key, REWRITE_CYRILLIC);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       if (fn[nr]->supports (rewrite (c, REWRITE_CYRILLIC)))
         return sm->add_char (key, c);
     }
     if (c == "<#3000>") {
       tree key= tuple ("ignore");
       int  nr = sm->add_font (key, REWRITE_IGNORE);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       return sm->add_char (key, c);
     }
     if (N (c) == 7 && starts (c, "<bbb-") && !occurs ("TeX Gyre", mfam)) {
@@ -1009,14 +1011,14 @@ smart_font_rep::resolve (string c, string fam, int attempt) {
         vw               = max (vw, 0.25 * lw);
         tree key         = tuple ("poor-bbb", as_string (hw), as_string (vw));
         int  nr          = sm->add_font (key, REWRITE_POOR_BBB);
-        initialize_font (nr);
+        maybe_initialize_font (nr);
         return sm->add_char (key, c);
       }
     }
     if (starts (c, "<it-") && ends (c, ">")) {
       tree key= tuple ("it");
       int  nr = sm->add_font (key, REWRITE_ITALIC);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       return sm->add_char (key, c);
     }
     if (fam == mfam && !is_italic_font (mfam)) {
@@ -1025,7 +1027,7 @@ smart_font_rep::resolve (string c, string fam, int attempt) {
         if (virtually_defined (c, emu_names[i])) {
           tree key= tuple ("emulate", emu_names[i]);
           int  nr = sm->add_font (key, REWRITE_NONE);
-          initialize_font (nr);
+          maybe_initialize_font (nr);
           if (fn[nr]->supports (c)) return sm->add_char (key, c);
         }
     }
@@ -1045,7 +1047,7 @@ smart_font_rep::resolve (string c, string fam, int attempt) {
     if (cfn->supports (c) || c == "<#200B>") {
       tree key= tuple (fam, v, series, rshape, as_string (a));
       int  nr = sm->add_font (key, REWRITE_NONE);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       return sm->add_char (key, c);
     }
   }
@@ -1056,12 +1058,18 @@ smart_font_rep::resolve (string c, string fam, int attempt) {
 bool
 smart_font_rep::is_italic_prime (string c) {
   if (c != "'" && c != "`") return false;
-  array<string> a= trimmed_tokenize (family, ",");
-  string        s= "<#2B9>";
+  if (italic_prime_cached) return italic_prime_result;
+  string s= "<#2B9>";
   if (c == "`") s= "<backprime>";
-  for (int i= 0; i < N (a); i++)
-    if (resolve (s, a[i], 1) >= 0) return false;
-  return true;
+  bool result= true;
+  for (int i= 0; i < N (family_tokens); i++)
+    if (resolve (s, family_tokens[i], 1) >= 0) {
+      result= false;
+      break;
+    }
+  italic_prime_cached= true;
+  italic_prime_result= result;
+  return result;
 }
 
 extern bool has_poor_rubber;
@@ -1079,7 +1087,7 @@ smart_font_rep::resolve_rubber (string c, string fam, int attempt) {
   if (goal == "." || goal == "<nobracket>") {
     tree key= tuple ("ignore");
     int  nr = sm->add_font (key, REWRITE_IGNORE);
-    initialize_font (nr);
+    maybe_initialize_font (nr);
     return sm->add_char (key, c);
   }
   if (has_poor_rubber) {
@@ -1101,7 +1109,7 @@ smart_font_rep::resolve_rubber (string c, string fam, int attempt) {
   if (bnr >= 0 && bnr < N (fn) && !is_nil (fn[bnr])) {
     tree key= tuple ("rubber", as_string (bnr));
     int  nr = sm->add_font (key, REWRITE_NONE);
-    initialize_font (nr);
+    maybe_initialize_font (nr);
     // cout << fn[nr]->res_name << " supports " << c << "? "
     //      << fn[nr]->supports (c) << LF;
     if (fn[nr]->supports (c)) return sm->add_char (key, c);
@@ -1138,7 +1146,7 @@ smart_font_rep::resolve (string c) {
     debug_fonts << "Main subfont of " << cork_to_utf8 (c) << " is "
                 << fn[SUBFONT_MAIN]->res_name << LF;
   }
-  array<string> a= trimmed_tokenize (family, ",");
+  array<string> a= family_tokens;
 
   // Special handling for emoji characters - bypass font-family restrictions
   string range= get_unicode_range (c);
@@ -1167,7 +1175,7 @@ smart_font_rep::resolve (string c) {
         if (!is_nil (cfn) && cfn->supports (c)) {
           tree key= tuple ("emoji-font", parts[1]);
           int  nr = sm->add_font (key, REWRITE_NONE);
-          initialize_font (nr);
+          maybe_initialize_font (nr);
           return sm->add_char (key, c);
         }
       }
@@ -1179,22 +1187,22 @@ smart_font_rep::resolve (string c) {
     if (upc != "" && fn[SUBFONT_MAIN]->supports (upc)) {
       tree key= tuple ("up");
       int  nr = sm->add_font (key, REWRITE_UPRIGHT);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       return sm->add_char (key, c);
     }
     string ugc= substitute_upright_greek (c);
     if (ugc != "" && fn[SUBFONT_MAIN]->supports (ugc)) {
       tree key= tuple ("upright-greek");
       int  nr = sm->add_font (key, REWRITE_UPRIGHT_GREEK);
-      initialize_font (nr);
+      maybe_initialize_font (nr);
       return sm->add_char (key, c);
     }
     if (is_greek (c) && use_italic_greek (a) && shape != "mathupright") {
       string gc= substitute_italic_greek (c);
       if (gc != "" && fn[SUBFONT_MAIN]->supports (gc)) {
         tree key= tuple ("italic-greek");
         int  nr = sm->add_font (key, REWRITE_ITALIC_GREEK);
-        initialize_font (nr);
+        maybe_initialize_font (nr);
         return sm->add_char (key, c);
       }
       // cout << "Found " << c << " in greek\n";
@@ -1371,7 +1379,7 @@ smart_font_rep::initialize_font (int nr) {
     fn[nr]   = poor_bbb_font (sfn, pw, ph, 1.5 * pw);
   }
   else if (a[0] == "rubber" && N (a) == 2 && is_int (a[1])) {
-    initialize_font (as_int (a[1]));
+    maybe_initialize_font (as_int (a[1]));
     fn[nr]= adjust_subfont (rubber_font (fn[as_int (a[1])]));
     // fn[nr]= adjust_subfont (rubber_unicode_font (fn[as_int (a[1])]));
   }
@@ -1388,6 +1396,11 @@ smart_font_rep::initialize_font (int nr) {
   }
 }
 
+void
+smart_font_rep::maybe_initialize_font (int nr) {
+  if (N (fn) <= nr || is_nil (fn[nr])) initialize_font (nr);
+}
+
 static int
 get_ex (string family, string variant, string series, string shape,
         int attempt) {

diff --git a/src/Graphics/Fonts/smart_font.hpp b/src/Graphics/Fonts/smart_font.hpp
@@ -99,8 +99,12 @@ struct smart_font_rep : font_rep {
   int    math_kind;
   int    italic_nr;
 
-  array<font> fn;
-  smart_map   sm;
+  array<font>   fn;
+  smart_map     sm;
+  array<string> family_tokens;
+  array<string> given_font;
+  bool          italic_prime_cached;
+  bool          italic_prime_result;
 
   smart_font_rep (string name, font base_fn, font err_fn, string family,
                   string variant, string series, string shape, double sz,
@@ -117,6 +121,7 @@ struct smart_font_rep : font_rep {
   int  resolve_rubber (string c, string fam, int attempt);
   int  resolve (string c);
   void initialize_font (int nr);
+  void maybe_initialize_font (int nr);
   int  adjusted_dpi (string fam, string var, string ser, string sh, int att);
 
   font make_rubber_font (font base) override;

diff --git a/tests/Graphics/Fonts/smart_font_test.cpp b/tests/Graphics/Fonts/smart_font_test.cpp
@@ -38,6 +38,8 @@ private slots:
   void test_get_right_slope ();
   void test_latin_modern_math_italic_greek ();
   void test_cursor_position_iii ();
+  void test_performance ();
+  void test_math_performance ();
 };
 
 void
@@ -161,5 +163,30 @@ TestSmartFont::test_cursor_position_iii () {
   STACK_DELETE_ARRAY (xpos);
 }
 
+void
+TestSmartFont::test_performance () {
+  font fn= smart_font ("sys-chinese", "rm", "medium", "right", 10, 600);
+
+  // Trigger a lot of character resolutions with repeated characters
+  string long_text= "The quick brown fox jumps over the lazy dog. "
+                    "The quick brown fox jumps over the lazy dog. "
+                    "The quick brown fox jumps over the lazy dog.";
+  metric ex;
+  fn->get_extents (long_text, ex);
+}
+
+void
+TestSmartFont::test_math_performance () {
+  font fn=
+      smart_font ("Latin Modern Math", "rm", "medium", "mathitalic", 10, 600);
+
+  // Trigger math character resolutions
+  string math_text= "<alpha><beta><gamma><delta><epsilon><zeta><eta><theta>"
+                    "<iota><kappa><lambda><mu><nu><xi><omicron><pi><rho><sigma>"
+                    "<tau><upsilon><phi><chi><psi><omega>";
+  metric ex;
+  fn->get_extents (math_text, ex);
+}
+
 QTEST_MAIN (TestSmartFont)
 #include "smart_font_test.moc"