Update Function editor section (with Project functions functionality - …

…qgis#9293)

docs/user_manual/expressions/expression.rst

@@ -335,12 +335,17 @@ particular needs that would not be covered by the predefined functions.
 To create a new function:
 
 #. Press the |symbologyAdd| :sup:`New File` button.
-#. Enter a name to use in the form that pops up and press :guilabel:`OK`.
+#. Select where to store the new function. You can choose to save it either in a
+   :guilabel:`Function file` or in :guilabel:`Project functions`.
+
+   * If you select :guilabel:`Function file`, you need to enter a name for the Python :file:`.py` file,
+     which is based on a QGIS template file and is stored in the :file:`/python/expressions` folder
+     under the active :ref:`user profile <user_profiles>` directory.
+
+   * If you select :guilabel:`Project functions`, the new function is stored in the project file.
+
+   A new item is added in the left panel of the :guilabel:`Function Editor` tab.
 
-   A new item of the name you provide is added in the left panel of the
-   :guilabel:`Function Editor` tab; this is a Python :file:`.py` file based on
-   QGIS template file and stored in the :file:`/python/expressions` folder
-   under the active :ref:`user profile <user_profiles>` directory.
 #. The right panel displays the content of the file: a python script template.
    Update the code and its help according to your needs.
 #. Press the |start| :guilabel:`Save and Load Functions` button.
@@ -352,20 +357,27 @@ To create a new function:
    Functions` button to make them available in the file, hence in any expression
    tab.
 
-Custom Python functions are stored under the user profile directory, meaning that at
-each QGIS startup, it will auto load all the functions defined with the current user
-profile. Be aware that new functions are only saved in the :file:`/python/expressions`
-folder and not in the project file.
-If you share a project that uses one of your custom functions you will need to also
-share the :file:`.py` file in the :file:`/python/expressions` folder.
+Custom Python functions stored as Function files are stored under the user profile
+directory, meaning that at each QGIS startup, it will auto load all the functions
+defined with the current user profile. Be aware that for sharing Python functions stored
+in Function files you need to share the :file:`.py` file in the :file:`/python/expressions` folder.
+
+On the other hand, custom Python functions stored as Project functions can be easily
+shared by sharing the project file where they were saved. When opening a project
+with project functions, QGIS can load or ignore them depending on whether
+:ref:`embedded Python code is enabled <load_project_code>` in General settings.
 
 To delete a custom function:
 
 #. Enable the :guilabel:`Function Editor` tab
 #. Select the function in the list
 #. Press the |symbologyRemove| :sup:`Remove selected function`. The function is
-   removed from the list and the corresponding ``.py`` file deleted from
-   the user profile folder.
+   removed from the list and, depending on the storage, the corresponding ``.py``
+   file is deleted from the user profile folder, or the Python functions are removed
+   from the project file.
+
+When a project file with Project functions is closed, the corresponding Project
+functions are unloaded and are no longer available in the QGIS session.
 
 **Example**
 

docs/user_manual/introduction/qgis_configuration.rst

@@ -132,8 +132,12 @@ displayed at the bottom of the frame.
   version of QGIS`. You can always open projects created with older version of
   QGIS but once the project is saved, trying to open with older release may fail
   because of features not available in that version.
-* :guilabel:`Enable macros` |selectString|. This option was created to handle
-  macros that are written to perform an action on project events. You can
+
+.. _load_project_code:
+
+* :guilabel:`Enable project's embedded Python code` |selectString|. This option
+  handles execution of macros that are written to perform an action on project
+  events, as well as custom Python functions to be used as expressions. You can
   choose between 'Never', 'Ask', 'For this session only' and
   'Always (not recommended)'.
 * :guilabel:`Default paths`: defines whether paths to files and layers used