From cb86cd2bcd8ea96f842142b1b98906fe21cf56dc Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Tue, 15 Sep 2020 08:55:35 +0200
Subject: [PATCH] fix: regression in quantity::op<<() for the case of
 std::setw() fixed

---
 src/include/units/bits/unit_text.h | 10 ++++++++++
 src/include/units/quantity.h       | 11 +++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/include/units/bits/unit_text.h b/src/include/units/bits/unit_text.h
index f10ab0ff..95421d51 100644
--- a/src/include/units/bits/unit_text.h
+++ b/src/include/units/bits/unit_text.h
@@ -178,4 +178,14 @@ constexpr auto unit_text()
   }
 }
 
+template<typename CharT, class Traits, typename D, typename U, typename Rep>
+void to_stream(std::basic_ostream<CharT, Traits>& os, const quantity<D, U, Rep>& q)
+{
+  os << q.count();
+  constexpr auto symbol = detail::unit_text<D, U>();
+  if constexpr (symbol.standard().size()) {
+    os << " " << symbol.standard();
+  }
+}
+
 }  // namespace units::detail
diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index 57b84410..72e53405 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -334,11 +334,14 @@ public:
   template<class CharT, class Traits>
   friend std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const quantity& q)
   {
-    os << q.count();
-    constexpr auto symbol = detail::unit_text<D, U>();
-    if constexpr (symbol.standard().size()) {
-      os << " " << symbol.standard();
+    if(os.width()) {
+      // std::setw() applies to the whole quantity output so it has to be first put into std::string
+      std::basic_ostringstream<CharT, Traits> s;
+      detail::to_stream(s, q);
+      return os << s.str();
     }
+
+    detail::to_stream(os, q);
     return os;
   }
 };