Help: Document HEADER_FILE_ONLY use case

Describe how to get sources into IDE project files.

1 files changed, 15 insertions, 0 deletions

diff --git a/Help/prop_sf/HEADER_FILE_ONLY.rst b/Help/prop_sf/HEADER_FILE_ONLY.rst
index b4fb2db..71d62ae 100644
--- a/Help/prop_sf/HEADER_FILE_ONLY.rst
+++ b/Help/prop_sf/HEADER_FILE_ONLY.rst
@@ -7,3 +7,18 @@ A property on a source file that indicates if the source file is a
 header file with no associated implementation.  This is set
 automatically based on the file extension and is used by CMake to
 determine if certain dependency information should be computed.
+
+By setting this property to ``ON``, you can disable compilation of
+the given source file, even if it should be compiled because it is
+part of the library's/executable's sources.
+
+This is useful if you have some source files which you somehow
+pre-process, and then add these pre-processed sources via
+:command:`add_library` or :command:`add_executable`. Normally, in IDE,
+there would be no reference of the original sources, only of these
+pre-processed sources. So by setting this property for all the original
+source files to ``ON``, and then either calling :command:`add_library`
+or :command:`add_executable` while passing both the pre-processed
+sources and the original sources, or by using :command:`target_sources`
+to add original source files will do exactly what would one expect, i.e.
+the original source files would be visible in IDE, and will not be built.