try to calculate character width

NixOS · Dec 15, 2024 · 5c98449 · 5c98449
1 parent 6a23803
commit 5c98449
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Showing 3 changed files with 80 additions and 24 deletions.
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
@@ -17,6 +17,19 @@
 
 let
   inherit (lib) fileset;
+  widecharwidth = stdenv.mkDerivation {
+    name = "widecharwidth";
+    dontUnpack = true;
+    dontStrip = true;
+    installPhase = ''
+      mkdir -p $out/include
+      cp $src $out/include/widechar_width.h
+    '';
+    src = builtins.fetchurl {
+      url = "https://raw.githubusercontent.com/ridiculousfish/widecharwidth/533e50efb0b9b122a08f2273337dbf6b44b03cc7/widechar_width.h";
+      sha256 = "sha256:1kcqj74i788byz9gp4qz34j4q44jvgpkr9m3gnhvkalrz4cvv2jh";
+    };
+  };
 in
 
 mkMesonLibrary (finalAttrs: {
@@ -38,6 +51,10 @@ mkMesonLibrary (finalAttrs: {
     (fileset.fileFilter (file: file.hasExt "hh") ./.)
   ];
 
+  nativeBuildInputs = [
+    widecharwidth
+  ];
+
   buildInputs = [
     brotli
     libsodium
@@ -65,6 +82,7 @@ mkMesonLibrary (finalAttrs: {
   mesonFlags = [
     (lib.mesonEnable "cpuid" stdenv.hostPlatform.isx86_64)
   ];
+  NIX_CFLAGS_COMPILE = "-I${widecharwidth}/include";
 
   env = {
     # Needed for Meson to find Boost.

diff --git a/src/libutil/terminal.cc b/src/libutil/terminal.cc
@@ -11,6 +11,58 @@
 # include <sys/ioctl.h>
 #endif
 #include <unistd.h>
+#include <widechar_width.h>
+
+namespace {
+
+inline std::pair<int, size_t> charWidthUTF8Helper(std::string_view s, bool printableASCII = false)
+{
+    size_t bytes = 1;
+    uint32_t ch = 0;
+    uint32_t max = 1U << 7;
+    if ((s[0] & 0x80) == 0) {
+        if (printableASCII) {
+            return {bytes, bytes}; // assume printable ASCII character
+        } else {
+            ch = s[0];
+        }
+    } else if ((s[0] & 0xe0) == 0xc0) {
+        ch = s[0] & 0x1f;
+        bytes = 2;
+        max = 1U << 11;
+    } else if ((s[0] & 0xf0) == 0xe0) {
+        ch = s[0] & 0x0f;
+        bytes = 3;
+        max = 1U << 16;
+    } else if ((s[0] & 0xf8) == 0xf0) {
+        ch = s[0] & 0x07;
+        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 +124,18 @@ 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()}, true);
+            w += chWidth;
+            auto n = i + bytes;
+            if (w <= (size_t) width) {
+                t += {i, n};
+            }
+            i = n;
         }
     }
-
     return t;
 }
 
-
 //////////////////////////////////////////////////////////////////////
 
 static Sync<std::pair<unsigned short, unsigned short>> windowSize{{0, 0}};