.. _guide_resources:

Application resources
=====================

Previous sections in this guide have described how to load images, media and
text documents using pyglet.  Applications also usually have the need to load
other data files: for example, level descriptions in a game, internationalised
strings, and so on.

Programmers are often tempted to load, for example, an image required by their
application with::

    image = pyglet.image.load('logo.png')

This code assumes ``logo.png`` is in the current working directory.
Unfortunately the working directory is not necessarily the same as the
directory containing the application script files.

* Applications started from the command line can start from an arbitrary
  working directory.
* Applications bundled into an egg, Mac OS X package or Windows executable
  may have their resources inside a ZIP file.
* The application might need to change the working directory in order to
  work with the user's files.

A common workaround for this is to construct a path relative to the script
file instead of the working directory::

    import os

    script_dir = os.path.dirname(__file__)
    path = os.path.join(script_dir, 'logo.png')
    image = pyglet.image.load(path)

This, besides being tedious to write, still does not work for resources within
ZIP files, and can be troublesome in projects that span multiple packages.

The :py:mod:`pyglet.resource` module solves this problem elegantly::

    image = pyglet.resource.image('logo.png')

The following sections describe exactly how the resources are located, and how
the behaviour can be customised.

Loading resources
-----------------

Use the :py:mod:`pyglet.resource` module when files shipped with the
application need to be loaded.  For example, instead of writing::

    data_file = open('file.txt')

use::

    data_file = pyglet.resource.file('file.txt')

There are also convenience functions for loading media files for pyglet.  The
following table shows the equivalent resource functions for the standard file
functions.

    .. list-table::
        :header-rows: 1

        * - File function
          - Resource function
          - Type
        * - ``open``
          - :py:func:`pyglet.resource.file`
          - File-like object
        * - :py:func:`pyglet.image.load`
          - :py:func:`pyglet.resource.image`
          - :py:class:`~pyglet.image.Texture` or :py:class:`~pyglet.image.TextureRegion`
        * - :py:func:`pyglet.image.load`
          - :py:func:`pyglet.resource.texture`
          - :py:class:`~pyglet.image.Texture`
        * - :py:func:`pyglet.image.load_animation`
          - :py:func:`pyglet.resource.animation`
          - :py:class:`~pyglet.image.Animation`
        * - :py:func:`pyglet.media.load`
          - :py:func:`pyglet.resource.media`
          - :py:class:`~pyglet.media.Source`
        * - | :py:func:`pyglet.text.load`
            | mimetype = ``text/plain``
          - :py:func:`pyglet.resource.text`
          - :py:class:`~pyglet.text.document.UnformattedDocument`
        * - | :py:func:`pyglet.text.load`
            | mimetype = ``text/html``
          - :py:func:`pyglet.resource.html`
          - :py:class:`~pyglet.text.document.FormattedDocument`
        * - | :py:func:`pyglet.text.load`
            | mimetype = ``text/vnd.pyglet-attributed``
          - :py:func:`pyglet.resource.attributed`
          - :py:class:`~pyglet.text.document.FormattedDocument`
        * - :py:func:`pyglet.font.add_file`
          - :py:func:`pyglet.resource.add_font`
          - ``None``

:py:func:`pyglet.resource.texture` is for loading stand-alone textures.
This can be useful when using the texture for a 3D model, or generally
working with OpenGL directly.

:py:func:`pyglet.resource.image` is optimised for loading sprite-like
images that can have their texture coordinates adjusted.
The resource module attempts to pack small images into larger texture atlases
(explained in :ref:`guide_texture-bins-and-atlases`) for efficient rendering
(which is why the return type of this function can be
:py:class:`~pyglet.image.TextureRegion`).
It is also advisable to use the texture atlas classes directly if you wish
to have different achor points on multiple copies of the same image.
This is because when loading an image more than once, you will actually get
the **same** object back. You can still use the resource module for getting
the image location, and described in the next section.


Resource locations
^^^^^^^^^^^^^^^^^^

Some resource files reference other files by name.  For example, an HTML
document can contain ``<img src="image.png" />`` elements.  In this case your
application needs to locate ``image.png`` relative to the original HTML file.

Use :py:func:`pyglet.resource.location` to get a
:py:class:`~pyglet.resource.Location` object describing the location of an
application resource.  This location might be a file system
directory or a directory within a ZIP file.
The :py:class:`~pyglet.resource.Location` object can directly open files by
name, so your application does not need to distinguish between these cases.

In the following example, a ``thumbnails.txt`` file is assumed to contain a
list of image filenames (one per line), which are then loaded assuming the
image files are located in the same directory as the ``thumbnails.txt`` file::

    thumbnails_file = pyglet.resource.file('thumbnails.txt', 'rt')
    thumbnails_location = pyglet.resource.location('thumbnails.txt')

    for line in thumbnails_file:
        filename = line.strip()
        image_file = thumbnails_location.open(filename)
        image = pyglet.image.load(filename, file=image_file)
        # Do something with `image`...

This code correctly ignores other images with the same filename that might
appear elsewhere on the resource path.

Specifying the resource path
----------------------------

By default, only the script home directory is searched (the directory
containing the ``__main__`` module).
You can set :py:attr:`pyglet.resource.path` to a list of locations to
search in order.  This list is indexed, so after modifying it you will
need to call :py:func:`pyglet.resource.reindex`.

Each item in the path list is either a path relative to the script home, or
the name of a Python module preceded with an "at" symbol (``@``).  For example,
if you would like to package all your resources in a ``res`` directory::

    pyglet.resource.path = ['res']
    pyglet.resource.reindex()

Items on the path are not searched recursively, so if your resource directory
itself has subdirectories, these need to be specified explicitly::

    pyglet.resource.path = ['res', 'res/images', 'res/sounds', 'res/fonts']
    pyglet.resource.reindex()

The entries in the resource path always use forward slash characters as path
separators even when the operating systems using a different character.

Specifying module names makes it easy to group code with its resources.  The
following example uses the directory containing the hypothetical
``gui.skins.default`` for resources::

    pyglet.resource.path = ['@gui.skins.default', '.']
    pyglet.resource.reindex()

Multiple loaders
----------------

A :py:class:`~pyglet.resource.Loader` encapsulates a complete resource path
and cache.  This lets your application cleanly separate resource loading of
different modules.
Loaders are constructed for a given search path, andnexposes the same methods
as the global :py:mod:`pyglet.resource` module functions.

For example, if a module needs to load its own graphics but does not want to
interfere with the rest of the application's resource loading, it would create
its own :py:class:`~pyglet.resource.Loader` with a local search path::

    loader = pyglet.resource.Loader(['@' + __name__])
    image = loader.image('logo.png')

This is particularly suitable for "plugin" modules.

You can also use a :py:class:`~pyglet.resource.Loader` instance to load a set
of resources relative to some user-specified document directory.
The following example creates a loader for a directory specified on the
command line::

    import sys
    home = sys.argv[1]
    loader = pyglet.resource.Loader(script_home=[home])

This is the only way that absolute directories and resources not bundled with
an application should be used with :py:mod:`pyglet.resource`.

Saving user preferences
-----------------------

Because Python applications can be distributed in several ways, including
within ZIP files, it is usually not feasible to save user preferences, high
score lists, and so on within the application directory (or worse, the working
directory).

The :py:func:`pyglet.resource.get_settings_path` function returns a directory
suitable for writing arbitrary user-centric data. The directory used follows
the operating system's convention:

* ``~/.config/ApplicationName/`` on Linux (depends on `XDG_CONFIG_HOME`
  environment variable).
* ``$HOME\Application Settings\ApplicationName`` on Windows
* ``~/Library/Application Support/ApplicationName`` on Mac OS X

The returned directory name is not guaranteed to exist -- it is the
application's responsibility to create it.  The following example opens a high
score list file for a game called "SuperGame" into the settings directory::

    import os

    dir = pyglet.resource.get_settings_path('SuperGame')
    if not os.path.exists(dir):
        os.makedirs(dir)
    filename = os.path.join(dir, 'highscores.txt')
    file = open(filename, 'wt')
