try to calculate character width

NixOS · Dec 17, 2024 · e28764d · e28764d
1 parent 6a23803
commit e28764d
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Showing 4 changed files with 74 additions and 24 deletions.
diff --git a/packaging/dependencies.nix b/packaging/dependencies.nix
@@ -199,6 +199,22 @@ scope: {
     meta.platforms = lib.platforms.all;
   });
 
+  widecharwidth = stdenv.mkDerivation {
+    name = "widecharwidth";
+    dontConfigure = true;
+    dontBuild = true;
+    installPhase = ''
+      mkdir -p $out/include
+      cp $src/widechar_width.h $out/include
+    '';
+    src = pkgs.fetchFromGitHub {
+      owner = "ridiculousfish";
+      repo = "widecharwidth";
+      rev = "533e50efb0b9b122a08f2273337dbf6b44b03cc7";
+      hash = "sha256-Vy1jCv0wqV/4sNCQIYGKiHq5A8QGE6Q+1v8k3Cn6sJ4=";
+    };
+  };
+
   inherit resolvePath filesetToSource;
 
   mkMesonDerivation =

diff --git a/src/libutil/meson.build b/src/libutil/meson.build
@@ -108,6 +108,9 @@ deps_private += cpuid
 nlohmann_json = dependency('nlohmann_json', version : '>= 3.9')
 deps_public += nlohmann_json
 
+cxx = meson.get_compiler('cpp')
+cxx.has_header('widechar_width.h', required : true)
+
 config_h = configure_file(
   configuration : configdata,
   output : 'config-util.hh',

diff --git a/src/libutil/package.nix b/src/libutil/package.nix
@@ -9,6 +9,7 @@
 , libsodium
 , nlohmann_json
 , openssl
+, widecharwidth
 
 # Configuration Options
 
@@ -42,6 +43,7 @@ mkMesonLibrary (finalAttrs: {
     brotli
     libsodium
     openssl
+    widecharwidth
   ] ++ lib.optional stdenv.hostPlatform.isx86_64 libcpuid
   ;
 

diff --git a/src/libutil/terminal.cc b/src/libutil/terminal.cc
@@ -11,6 +11,53 @@
 # include <sys/ioctl.h>
 #endif
 #include <unistd.h>
+#include <widechar_width.h>
+
+namespace {
+
+inline std::pair<int, size_t> charWidthUTF8Helper(std::string_view s)
+{
+    size_t bytes = 1;
+    uint32_t ch = s[0];
+    uint32_t max = 1U << 7;
+    if ((ch & 0x80U) == 0U) {
+    } else if ((ch & 0xe0U) == 0xc0U) {
+        ch &= 0x1fU;
+        bytes = 2;
+        max = 1U << 11;
+    } else if ((ch & 0xf0U) == 0xe0U) {
+        ch &= 0x0fU;
+        bytes = 3;
+        max = 1U << 16;
+    } else if ((ch & 0xf8U) == 0xf0U) {
+        ch &= 0x07U;
+        bytes = 4;
+        max = 0x110000U;
+    } else {
+        return {bytes, bytes}; // invalid UTF-8 start byte
+    }
+    size_t len = s.size();
+    for (size_t i = 1; i < bytes; i++) {
+        if (i < len && (s[i] & 0x80)) {
+            ch = (ch << 6) | (s[i] & 0x3f);
+        } else {
+            return {i, i}; // invalid UTF-8 encoding; assume one character per byte
+        }
+    }
+    int width = bytes; // in case of overlong encoding
+    if (ch < max) {
+        width = widechar_wcwidth(ch);
+        if (width == widechar_ambiguous) {
+            width = 1; // just a guess...
+        } else if (width == widechar_widened_in_9) {
+            width = 2;
+        }
+        width = std::max(width, 0);
+    }
+    return {width, bytes};
+}
+
+}
 
 namespace nix {
 
@@ -72,35 +119,17 @@ std::string filterANSIEscapes(std::string_view s, bool filterAll, unsigned int w
             i++;
 
         else {
-            w++;
-            // Copy one UTF-8 character.
-            if ((*i & 0xe0) == 0xc0) {
-                t += *i++;
-                if (i != s.end() && ((*i & 0xc0) == 0x80)) t += *i++;
-            } else if ((*i & 0xf0) == 0xe0) {
-                t += *i++;
-                if (i != s.end() && ((*i & 0xc0) == 0x80)) {
-                    t += *i++;
-                    if (i != s.end() && ((*i & 0xc0) == 0x80)) t += *i++;
-                }
-            } else if ((*i & 0xf8) == 0xf0) {
-                t += *i++;
-                if (i != s.end() && ((*i & 0xc0) == 0x80)) {
-                    t += *i++;
-                    if (i != s.end() && ((*i & 0xc0) == 0x80)) {
-                        t += *i++;
-                        if (i != s.end() && ((*i & 0xc0) == 0x80)) t += *i++;
-                    }
-                }
-            } else
-                t += *i++;
+            auto [chWidth, bytes] = charWidthUTF8Helper({i, s.end()});
+            w += chWidth;
+            if (w <= (size_t) width) {
+                t += {i, i + bytes};
+            }
+            i += bytes;
         }
     }
-
     return t;
 }
 
-
 //////////////////////////////////////////////////////////////////////
 
 static Sync<std::pair<unsigned short, unsigned short>> windowSize{{0, 0}};