From a8da209ee5d0fe44b9d704b9fc7812e4a96c1888 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Fri, 1 May 2020 09:24:15 +0200
Subject: Flameshot.Internal.Process: monoidify Callbacks

---
 src/Flameshot/Internal/Process.hs | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/src/Flameshot/Internal/Process.hs b/src/Flameshot/Internal/Process.hs
index 47220a3..e38a145 100644
--- a/src/Flameshot/Internal/Process.hs
+++ b/src/Flameshot/Internal/Process.hs
@@ -36,6 +36,40 @@ data Callbacks = Callbacks
     , onStart :: Pid -> IO ()
     }
 
+instance Semigroup Callbacks where
+  a <> b =
+      Callbacks
+        { onOutLine = \pid s -> do
+          onOutLine a pid s
+          onOutLine b pid s
+
+        , onErrLine = \pid s -> do
+          onErrLine a pid s
+          onErrLine b pid s
+
+        , onError = \pid err -> do
+          onError a pid err
+          onError b pid err
+
+        , onExit = \pid status -> do
+          onExit a pid status
+          onExit b pid status
+
+        , onStart = \pid -> do
+          onStart a pid
+          onStart b pid
+        }
+
+instance Monoid Callbacks where
+  mempty =
+    Callbacks
+      { onOutLine = \_pid _s -> return ()
+      , onErrLine = \_pid _s -> return ()
+      , onError = \_pid _err -> return ()
+      , onExit = \_pid _status -> return ()
+      , onStart = \_pid -> return ()
+      }
+
 run :: FilePath
      -> [String]
      -> Maybe FilePath
-- 
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