Comment 4 for bug 1480427

Reviewed: https://review.openstack.org/277220
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=c9de52d6bb31ccd41afd9183c9345606d28f415f
Submitter: Jenkins
Branch: master

commit c9de52d6bb31ccd41afd9183c9345606d28f415f
Author: Diana Whitten <email address hidden>
Date: Sat Jan 30 09:42:15 2016 -0700

    Dynamic Themes

    Horizon themes are now configurable at a user level, through the use
    of cookies. The themes that can be set are configurable at a
    deployment level through settings.py. Horizon can be configured to
    run with multiple themes, and allow users to choose which themes
    they wish to run.

    Django Compressor:
    In order to support dynamic themes, each theme configuration must
    be pre-compiled through the Django compressor. By making use of its
    built in COMPRESS_OFFLINE_CONTEXT, we now return a generator to
    create each of the theme's necessary offline contexts.

    Templates:
    Horizon themes allowed template overrides via their 'templates'
    subfolder. In order to maintain this parity, a custom theme template
    loader was created. It is run before the other loads, and simply
    looks for a Django template in the current theme (cookie driven)
    before diverting to the previous template loaders.

    Static Files:
    Horizon themes allowed static overrides of the images in
    'dashboard/img' folder. A template tag, 'themable_asset' was created
    to maintain this parity. Any asset that is wished to be made themable,
    given that it is located in Horizon's 'static/dashboard' folder, can
    now be made ot be themable. By making this a template tag, this
    gives the developers more granular control over what branders can
    customize.

    Angular and Plugins:
    By far, the trickiest part of this task, Angular and Plugins are
    dynamic in the files that they 'discover'. SCSS is not flexible in
    this manner at ALL. SCSS disallows the importation of a variable
    name. To get around this, themes.scss was created as a Django
    template. This template is the top level import file for all styles
    within Horizon, and therefore, allows ALL the scss files to share a
    common namespace and thus, can use shared variables as well as extend
    shared styles.

    Other:
    This change is fundamental, in that it changes the method by which
    Horizon ingests its SCSS files. Many problems existing in the
    previous implementation, in an effort to make Horizon flexible, its
    SCSS was made very inflexible. This patch corrects those problems.

    Change-Id: Ic48b4b5c1d1a41f1e01a8d52784c9d38d192c8f1
    Implements: blueprint horizon-dynamic-theme
    Closes-Bug: #1480427