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diff --git a/doc/doxygen/scripts/filter b/doc/doxygen/scripts/filter
index 65fbcaf5eca5e864fd4702a975a0335cb9daa4dd..682eac5638265a045f2cb3be4dd3afe68b5309f6 100755 (executable)
--- a/doc/doxygen/scripts/filter
+++ b/doc/doxygen/scripts/filter
@@ -140,6 +140,14 @@ while (<>)
     #         multiple lines
     ########################################################
 
+    # NOTE: The doxygen documentation says that "the filter must not
+    # add or remove lines; it is applied before the code is scanned,
+    # but not when the output code is generated. If lines are added or
+    # removed, the anchors will not be placed correctly."
+    #
+    # In other words, filters below can munch multiple lines, but they
+    # must print the result on as many lines as they were on before.
+
 
     # Finally output the last line of what has been substituted
     print;