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novelWriter/docs/source/tech_technical.rst
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2021-01-10 18:30:58 +01:00

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.. _a_tech:
*********************
Technical Information
*********************
This section contains details of how novelWriter stores and handles the project data.
How Project Data is Stored
==========================
All novelWriter files are written with utf-8 encoding. Since Python automatically converts Unix
line endings to Windows line endings on Windows systems, novelWriter does not make any adaptations
to the formatting on Windows systems. This is handled entirely by the Python standard library.
Python also handles this fairly well when working on the same files on both Windows and Unix-based
operating systems.
Main Project File
-----------------
The project itself requires a dedicated folder for storing its files where novelWriter will create
its own "file system" where the folder and file hierarchy is described in a project XML file. This
is the main project file in the project's root folder with the name ``nwProject.nwx``. This file
also contains all the meta data required for the project, and a number of related project settings.
If this file is lost or corrupted, the structure of the project is lost, although not the text
itself. It is important to keep this file backed up, either through the built-in backup tool, or
your own backup solution.
.. tip::
The novelWriter project folder is structured so that it can easily be added to a version control
system like git. If so, you may want to add a `.gitignore` file to exclude files with the
extensions `.json` as JSON files are used to cache the index and various run-time settings and
are generally large files that change often. You'd also want to exclude the ``cache`` folder.
The project XML file is indent-formatted, suitable for diff tools and version control since most of
the file will stay static, although a timesetamp is set in the meta section on line 2 each time the
file is saved, and various meta data entries are incremented on each save.
Project Documents
-----------------
The project documents are saved in a folder in the main project folder named ``content``. Each
document has a file handle taken from the first 13 characters of a SHA256 hash of the system time
when the document was first created. The documents are saved with a filename assembled from this
hash and the file extension ``.nwd``.
If you wish to find the physical location of a document in the project, you can either look it up
in the project XML file, select :guilabel:`Show File Details` from the :guilabel:`Document` menu
when having the document open, or look in the ``ToC.txt`` file in the root of the project folder.
The ``ToC.txt`` file has a list of all documents in the project and where they are saved.
The reason for this cryptic file naming is to avoid issues with file naming conventions and
restrictions on different operating systems, and also to have a file name that does not depend on
what the user names the document within the project, or changes it to. The file meta data in the
project tree is mainly saved in the project XML file, although some basic meta data is added to the
header of each document file.
Each document file contains a plain text version of the text from the editor. The file can in
principle be edited in any text editor, and is suitable for diffing and version control if so
desired. Just make sure the file remains in utf-8 encoding, otherwise unicode chatracters may
become mangled when the file is opened in novelWriter again.
The first lines of the file may contain some meta data starting with the characters ``%%~``. These
lines are mainly there to restore some information if it is lost from the project file, and the
information may be helpful if you do open the file in an external editor as it contains the
document label and the document class and layout. The lines can be deleted without any consequences
to the rest of the content of the file, and will be added back the next time the document is saved
in novelWriter.
The File Saving Process
-----------------------
When saving the project file, or any of the documents, the data is first saved to a temporary file.
If successful, the old data file is removed, and the temporary file becomes the new file. This
ensures that the previously saved data is only replaced when the new data has been successfully
saved to the storage medium.
For the project XML file, a ``.bak`` file is in addition kept, which will always contain the
previous version of the file, although when auto-save is enabled, they may have the same content.
If the opening of a project file fails, novelWriter will automatically try to open the ``.bak``
file instead.