libmain: add progress bar with multiple status lines

Add the log-formats `multiline` and `multiline-with-logs` which offer
multiple current active building status lines.

src/libmain/loggers.cc

@@ -17,6 +17,10 @@ LogFormat parseLogFormat(const std::string & logFormatStr) {
         return LogFormat::bar;
     else if (logFormatStr == "bar-with-logs")
         return LogFormat::barWithLogs;
+    else if (logFormatStr == "multiline")
+        return LogFormat::multiline;
+    else if (logFormatStr == "multiline-with-logs")
+        return LogFormat::multilineWithLogs;
     throw Error("option 'log-format' has an invalid value '%s'", logFormatStr);
 }
 
@@ -35,6 +39,17 @@ Logger * makeDefaultLogger() {
         logger->setPrintBuildLogs(true);
         return logger;
     }
+    case LogFormat::multiline: {
+        auto logger = makeProgressBar();
+        logger->setPrintMultiline(true);
+        return logger;
+    }
+    case LogFormat::multilineWithLogs: {
+        auto logger = makeProgressBar();
+        logger->setPrintMultiline(true);
+        logger->setPrintBuildLogs(true);
+        return logger;
+    }
     default:
         abort();
     }

src/libmain/loggers.hh

@@ -11,6 +11,8 @@ enum class LogFormat {
   internalJSON,
   bar,
   barWithLogs,
+  multiline,
+  multilineWithLogs,
 };
 
 void setLogFormat(const std::string & logFormatStr);

src/libmain/progress-bar.cc

@@ -73,6 +73,8 @@ private:
 
         std::map<ActivityType, ActivitiesByType> activitiesByType;
 
+        int lastLines = 1;
+
         uint64_t filesLinked = 0, bytesLinked = 0;
 
         uint64_t corruptedPaths = 0, untrustedPaths = 0;
@@ -89,6 +91,7 @@ private:
     std::condition_variable quitCV, updateCV;
 
     bool printBuildLogs = false;
+    bool printMultiline = false;
     bool isTTY;
 
 public:
@@ -103,7 +106,7 @@ public:
             while (state->active) {
                 if (!state->haveUpdate)
                     state.wait_for(updateCV, nextWakeup);
-                nextWakeup = draw(*state);
+                nextWakeup = draw(*state, {});
                 state.wait_for(quitCV, std::chrono::milliseconds(50));
             }
         });
@@ -165,8 +168,7 @@ public:
     void log(State & state, Verbosity lvl, std::string_view s)
     {
         if (state.active) {
-            writeToStderr("\r\e[K" + filterANSIEscapes(s, !isTTY) + ANSI_NORMAL "\n");
-            draw(state);
+            draw(state, s);
         } else {
             auto s2 = s + ANSI_NORMAL "\n";
             if (!isTTY) s2 = filterANSIEscapes(s2, true);
@@ -354,60 +356,96 @@ public:
         updateCV.notify_one();
     }
 
-    std::chrono::milliseconds draw(State & state)
+    std::chrono::milliseconds draw(State & state, const std::optional<std::string_view> & s)
     {
         auto nextWakeup = A_LONG_TIME;
 
         state.haveUpdate = false;
         if (state.paused || !state.active) return nextWakeup;
 
-        std::string line;
+        auto width = getWindowSize().second;
+        if (width <= 0) {
+            width = std::numeric_limits<decltype(width)>::max();
+        }
 
+        if (printMultiline && state.lastLines) {
+#if defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(__NT__)
+            system("cls");
+#else
+            writeToStderr("\r\033[K\r");
+            for (auto i = 1; i < state.lastLines; i++) {
+                writeToStderr("\033[1A\r\033[K\r"); // \r
+            }
+#endif
+        }
+
+        state.lastLines = 0;
+
+        if (s != std::nullopt)
+            writeToStderr("\r\e[K" + filterANSIEscapes(s.value(), !isTTY) + ANSI_NORMAL "\n");
+
+        std::string line;
         std::string status = getStatus(state);
         if (!status.empty()) {
             line += '[';
             line += status;
             line += "]";
         }
+        if (printMultiline && !line.empty()) {
+            writeToStderr(filterANSIEscapes(line, false, width));
+            state.lastLines++;
+        }
 
         auto now = std::chrono::steady_clock::now();
 
         if (!state.activities.empty()) {
-            if (!status.empty()) line += " ";
-            auto i = state.activities.rbegin();
+            for (auto i = state.activities.begin(); i != state.activities.end(); ++i) {
+                if (!i->visible || (i->s.empty() && i->lastLine.empty())) {
+                    continue;
+                }
 
-            while (i != state.activities.rend()) {
-                if (i->visible && (!i->s.empty() || !i->lastLine.empty())) {
                 /* Don't show activities until some time has
                    passed, to avoid displaying very short
                    activities. */
                 auto delay = std::chrono::milliseconds(10);
-                    if (i->startTime + delay < now)
-                        break;
-                    else
-                        nextWakeup = std::min(nextWakeup, std::chrono::duration_cast<std::chrono::milliseconds>(delay - (now - i->startTime)));
-                }
-                ++i;
+                if (i->startTime + delay >= now) {
+                    nextWakeup = std::min(
+                        nextWakeup,
+                        std::chrono::duration_cast<std::chrono::milliseconds>(
+                            delay - (now - i->startTime)
+                        )
+                    );
                 }
 
-            if (i != state.activities.rend()) {
+                if (!printMultiline) {
                     line += i->s;
+                } else {
+                    line = i->s;
+                }
+
                 if (!i->phase.empty()) {
                     line += " (";
                     line += i->phase;
                     line += ")";
                 }
                 if (!i->lastLine.empty()) {
-                    if (!i->s.empty()) line += ": ";
+                    if (!i->s.empty()) {
+                        line += ": ";
+                    }
                     line += i->lastLine;
                 }
+                if (printMultiline) {
+                    if (state.lastLines)
+                        writeToStderr("\n");
+                    state.lastLines += 1;
+                    writeToStderr(filterANSIEscapes(line, false, width));
+                }
             }
         }
 
-        auto width = getWindowSize().second;
-        if (width <= 0) width = std::numeric_limits<decltype(width)>::max();
-
+        if (!printMultiline) {
             writeToStderr("\r" + filterANSIEscapes(line, false, width) + ANSI_NORMAL + "\e[K");
+        }
 
         return nextWakeup;
     }
@@ -506,9 +544,7 @@ public:
     {
         auto state(state_.lock());
         if (state->active) {
-            std::cerr << "\r\e[K";
-            Logger::writeToStdout(s);
-            draw(*state);
+            draw(*state, s);
         } else {
             Logger::writeToStdout(s);
         }
@@ -521,7 +557,7 @@ public:
         std::cerr << fmt("\r\e[K%s ", msg);
         auto s = trim(readLine(STDIN_FILENO));
         if (s.size() != 1) return {};
-        draw(*state);
+        draw(*state, {});
         return s[0];
     }
 
@@ -529,6 +565,11 @@ public:
     {
         this->printBuildLogs = printBuildLogs;
     }
+
+    void setPrintMultiline(bool printMultiline) override
+    {
+        this->printMultiline = printMultiline;
+    }
 };
 
 Logger * makeProgressBar()

src/libutil/logging.hh

@@ -114,6 +114,9 @@ public:
 
     virtual void setPrintBuildLogs(bool printBuildLogs)
     { }
+
+    virtual void setPrintMultiline(bool printMultiline)
+    { }
 };
 
 /**