5 files changed, 53 insertions, 71 deletions
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 5be7ce60dab9..9f669f7e4645 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -3428,7 +3428,7 @@ void DerivationGoal::flushLine()
     else {
         if (settings.verboseBuild &&
             (settings.printRepeatedBuilds || curRound == 1))
-            printError(filterANSIEscapes(currentLogLine, true));
+            printError(currentLogLine);
         else {
             logTail.push_back(currentLogLine);
             if (logTail.size() > settings.logLines) logTail.pop_front();
diff --git a/src/libutil/logging.cc b/src/libutil/logging.cc
index 6924e0080475..27a631a37d10 100644
--- a/src/libutil/logging.cc
+++ b/src/libutil/logging.cc
@@ -44,7 +44,7 @@ public:
             prefix = std::string("<") + c + ">";
         }
 
-        writeToStderr(prefix + (tty ? fs.s : filterANSIEscapes(fs.s)) + "\n");
+        writeToStderr(prefix + filterANSIEscapes(fs.s) + "\n");
     }
 
     void startActivity(ActivityId act, Verbosity lvl, ActivityType type,
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 272997397794..f7a12d21b244 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1178,36 +1178,51 @@ void ignoreException()
 }
 
 
-string filterANSIEscapes(const string & s, bool nixOnly)
-{
-    string t, r;
-    enum { stTop, stEscape, stCSI } state = stTop;
-    for (auto c : s) {
-        if (state == stTop) {
-            if (c == '\e') {
-                state = stEscape;
-                r = c;
-            } else
-                t += c;
-        } else if (state == stEscape) {
-            r += c;
-            if (c == '[')
-                state = stCSI;
-            else {
-                t += r;
-                state = stTop;
+std::string filterANSIEscapes(const std::string & s, unsigned int width)
+{
+    std::string t, e;
+    size_t w = 0;
+    auto i = s.begin();
+
+    while (w < (size_t) width && i != s.end()) {
+
+        if (*i == '\e') {
+            std::string e;
+            e += *i++;
+            char last = 0;
+
+            if (i != s.end() && *i == '[') {
+                e += *i++;
+                // eat parameter bytes
+                while (i != s.end() && *i >= 0x30 && *i <= 0x3f) e += *i++;
+                // eat intermediate bytes
+                while (i != s.end() && *i >= 0x20 && *i <= 0x2f) e += *i++;
+                // eat final byte
+                if (i != s.end() && *i >= 0x40 && *i <= 0x7e) e += last = *i++;
+            } else {
+                if (i != s.end() && *i >= 0x40 && *i <= 0x5f) e += *i++;
             }
-        } else {
-            r += c;
-            if (c >= 0x40 && c <= 0x7e) {
-                if (nixOnly && (c != 'p' && c != 'q' && c != 's' && c != 'a' && c != 'b'))
-                    t += r;
-                state = stTop;
-                r.clear();
+
+            if (last == 'm')
+                t += e;
+        }
+
+        else if (*i == '\t') {
+            i++; t += ' '; w++;
+            while (w < (size_t) width && w % 8) {
+                t += ' '; w++;
             }
         }
+
+        else if (*i == '\r')
+            // do nothing for now
+            ;
+
+        else {
+            t += *i++; w++;
+        }
     }
-    t += r;
+
     return t;
 }
 
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 75eb9751524e..47e02bc898a6 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -388,10 +388,12 @@ void ignoreException();
 #define ANSI_BLUE "\e[34;1m"
 
 
-/* Filter out ANSI escape codes from the given string. If ‘nixOnly’ is
-   set, only filter escape codes generated by Nixpkgs' stdenv (used to
-   denote nesting etc.). */
-string filterANSIEscapes(const string & s, bool nixOnly = false);
+/* Truncate a string to 'width' printable characters. Certain ANSI
+   escape sequences (such as colour setting) are copied but not
+   included in the character count. Other ANSI escape sequences are
+   filtered. Also, tabs are expanded to spaces. */
+std::string filterANSIEscapes(const std::string & s,
+    unsigned int width = std::numeric_limits<unsigned int>::max());
 
 
 /* Base64 encoding/decoding. */
diff --git a/src/nix/progress-bar.cc b/src/nix/progress-bar.cc
index 252d12c5d37f..e6553c06f4ae 100644
--- a/src/nix/progress-bar.cc
+++ b/src/nix/progress-bar.cc
@@ -23,44 +23,6 @@ static uint64_t getI(const std::vector<Logger::Field> & fields, size_t n)
     return fields[n].i;
 }
 
-/* Truncate a string to 'width' printable characters. ANSI escape
-   sequences are copied but not included in the character count. Also,
-   tabs are expanded to spaces. */
-static std::string ansiTruncate(const std::string & s, int width)
-{
-    if (width <= 0) return s;
-
-    std::string t;
-    size_t w = 0;
-    auto i = s.begin();
-
-    while (w < (size_t) width && i != s.end()) {
-        if (*i == '\e') {
-            t += *i++;
-            if (i != s.end() && *i == '[') {
-                t += *i++;
-                while (i != s.end() && (*i < 0x40 || *i > 0x7e)) {
-                    t += *i++;
-                }
-                if (i != s.end()) t += *i++;
-            }
-        }
-
-        else if (*i == '\t') {
-            t += ' '; w++;
-            while (w < (size_t) width && w & 8) {
-                t += ' '; w++;
-            }
-        }
-
-        else {
-            t += *i++; w++;
-        }
-    }
-
-    return t;
-}
-
 class ProgressBar : public Logger
 {
 private:
@@ -343,7 +305,10 @@ public:
             }
         }
 
-        writeToStderr("\r" + ansiTruncate(line, getWindowSize().second) + "\e[K");
+        auto width = getWindowSize().second;
+        if (width <= 0) std::numeric_limits<decltype(width)>::max();
+
+        writeToStderr("\r" + filterANSIEscapes(line, width) + "\e[K");
     }
 
     std::string getStatus(State & state)