1 files changed, 20 insertions, 0 deletions
diff --git a/src/libmain/progress-bar.cc b/src/libmain/progress-bar.cc
index 28bb14863..e36bc0b01 100644
--- a/src/libmain/progress-bar.cc
+++ b/src/libmain/progress-bar.cc
@@ -13,6 +13,11 @@
 
 namespace nix {
 
+// 100 years ought to be enough for anyone (yet sufficiently smaller than max() to not cause signed integer overflow).
+constexpr const auto A_LONG_TIME = std::chrono::duration_cast<std::chrono::milliseconds>(
+    100 * 365 * std::chrono::seconds(86400)
+);
+
 using namespace std::literals::chrono_literals;
 
 static std::string_view getS(const std::vector<Logger::Field> & fields, size_t n)
@@ -36,6 +41,21 @@ static std::string_view storePathToName(std::string_view path)
     return i == std::string::npos ? base.substr(0, 0) : base.substr(i + 1);
 }
 
+ProgressBar::ProgressBar(bool isTTY)
+    : isTTY(isTTY)
+{
+    state_.lock()->active = isTTY;
+    updateThread = std::thread([&]() {
+        auto state(state_.lock());
+        auto nextWakeup = A_LONG_TIME;
+        while (state->active) {
+            if (!state->haveUpdate)
+                state.wait_for(updateCV, nextWakeup);
+            nextWakeup = draw(*state, {});
+            state.wait_for(quitCV, std::chrono::milliseconds(50));
+        }
+    });
+}
 
 ProgressBar::~ProgressBar()
 {