Add examples for output capture (fixes #691)

2 files changed, 13 insertions, 1 deletions

diff --git a/include/qpdf/QPDFLogger.hh b/include/qpdf/QPDFLogger.hh
index 54ab7efe..655da668 100644
--- a/include/qpdf/QPDFLogger.hh
+++ b/include/qpdf/QPDFLogger.hh
@@ -56,6 +56,10 @@ class QPDFLogger
     // error -- standard error
     // save -- undefined unless set
     //
+    // "info" is used for diagnostic messages, verbose messages, and
+    // progress messages. "warn" is used for warnings. "error" is used
+    // for errors. "save" is used for saving output -- see below.
+    //
     // On deletion, finish() is called for the standard output and
     // standard error pipelines, which flushes output. If you supply
     // any custom pipelines, you must call finish() on them yourself.
@@ -64,6 +68,13 @@ class QPDFLogger
     //
     // NOTES ABOUT THE SAVE PIPELINE
     //
+    // The save pipeline is used by QPDFJob when some kind of binary
+    // output is being saved. This includes saving attachments and
+    // stream data and also includes when the output file is standard
+    // output. If you want to grab that output, you can call setSave.
+    // See examples/qpdfjob-save-attachment.cc and
+    // examples/qpdfjob-c-save-attachment.c.
+    //
     // You should never set the save pipeline to the same destination
     // as something else. Doing so will corrupt your save output. If
     // you want to save to standard output, use the method
diff --git a/include/qpdf/qpdflogger-c.h b/include/qpdf/qpdflogger-c.h
index 9d31f79c..10ab5bb0 100644
--- a/include/qpdf/qpdflogger-c.h
+++ b/include/qpdf/qpdflogger-c.h
@@ -25,7 +25,8 @@
 
 /*
  * This file provides a C API for QPDFLogger. See QPDFLogger.hh for
- * information about the logger.
+ * information about the logger and
+ * examples/qpdfjob-c-save-attachment.c for an example.
  */
 
 #include <qpdf/DLL.h>