Merge topic 'doc-include-dir-props'

907e422b Help: Explain build/install-tree include dirs in more places (#14946)

1 files changed, 18 insertions, 0 deletions

diff --git a/Help/prop_tgt/INTERFACE_INCLUDE_DIRECTORIES.rst b/Help/prop_tgt/INTERFACE_INCLUDE_DIRECTORIES.rst
index bf4ab46..899e821 100644
--- a/Help/prop_tgt/INTERFACE_INCLUDE_DIRECTORIES.rst
+++ b/Help/prop_tgt/INTERFACE_INCLUDE_DIRECTORIES.rst
@@ -3,6 +3,10 @@ INTERFACE_INCLUDE_DIRECTORIES
 
 List of public include directories for a library.
 
+The :command:`target_include_directories` command populates this property
+with values given to the ``PUBLIC`` and ``INTERFACE`` keywords.  Projects
+may also get and set the property directly.
+
 Targets may populate this property to publish the include directories
 required to compile against the headers for the target.  Consuming
 targets can add entries to their own :prop_tgt:`INCLUDE_DIRECTORIES`
@@ -13,3 +17,17 @@ Contents of ``INTERFACE_INCLUDE_DIRECTORIES`` may use "generator expressions"
 with the syntax ``$<...>``.  See the :manual:`cmake-generator-expressions(7)`
 manual for available expressions.  See the :manual:`cmake-buildsystem(7)`
 manual for more on defining buildsystem properties.
+
+Include directories usage requirements commonly differ between the build-tree
+and the install-tree.  The ``BUILD_INTERFACE`` and ``INSTALL_INTERFACE``
+generator expressions can be used to describe separate usage requirements
+based on the usage location.  Relative paths are allowed within the
+``INSTALL_INTERFACE`` expression and are interpreted relative to the
+installation prefix.  For example:
+
+.. code-block:: cmake
+
+  set_property(TARGET mylib APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include/mylib>
+    $<INSTALL_INTERFACE:include/mylib>  # <prefix>/include/mylib
+    )