Merge pull request opengisch#28 from opengisch/sd-card

Sd card and favorite directories explanation

en/project-management/project-selection.rst

@@ -12,21 +12,29 @@ Inside these directories, only subdirectories and files with the ".qgs" extensio
 
 QField requires the project file to be physically on the device, so it is not possible to use providers that work with remote files (e.g. Google Drive). On the other hand you can use apps like `syncthing <https://syncthing.net/>`_ or `nextcloud <https://nextcloud.com/>`_ (or dropbox and probably many others) that allow you tho physically sync the file to your device.
 
+Favorite directories
+--------------------
+In the first screen of the file selector, there is a section showing the favorite directories. To add a directory to the favorites, long click in the file selector on the directory name. To remove an entry from the favorites, long click on the entry in the favorites list. 
+
 External SD card
 ----------------
-The file selector only shows the application-specific directory on an external SD card, as it is the only directory for which the app has write access. The directory is the following:
+The file selector shows the root of the SD card labeled as "read-only" and the application-specific directory separated from the rest of the SD card, as it is the only directory for which the app has write access. The directory is the following:
 
-.. code-block:: none
+.. code-block::
 
     /Android/data/ch.opengis.qfield/files
 
+.. note::
+
+    Technically, this is due to the fact that Android intents ACTION_OPEN_DOCUMENT and ACTION_OPEN_DOCUMENT_TREE, work and grant read-write access on the content of the returning URI, not on the real linked file. This limitation which makes sense for how Android is structured but currently it is unusable with QField as QField needs to access the real file with a real path.
+
 Warning!
 --------
 By storing data in this folder, you risk losing data.
 The application-specific directory (`/Android/data/ch.opengis.qfield/`) will be deleted by the system if you uninstall QField from your Android device. This is important if you keep the data in the External sd card.
 
 How to turn external SD card into internal storage
---------
+--------------------------------------------------
 Starting from Android 6.0, you can use the SD card as internal storage for your Android phone. A feature called Adoptable Storage allows the Android OS to format an external storage media as a permanent internal storage. The data on the adopted SD card is encrypted and it can’t be mounted on another device.
 
 **Please be sure you start with an empty SD card. It needs to be empty because when the card is converted to "Internal" storage, it will be formatted (wiped).**
@@ -36,6 +44,7 @@ Starting from Android 6.0, you can use the SD card as internal storage for your
 3. Now select “Format as internal”, and then “Erase & Format”.
 4. Your SD Card will now be formatted as internal storage.
 5. Reboot your phone.
+
 If you don't reboot the phone, many things may not work correctly, so make sure you do.
 
 It might be possible that the Adoptable Storage feature is not present on your device even if it is running Android 6.0 and above. The device manufacturer may have disabled the feature. However, command-line methods exist which allow you to force a device to adopt a storage.