How to create custom Plugins

CMS Plugins are reusable content publishers that can be inserted into django CMS pages (or indeed into any content that uses django CMS placeholders). They enable the publishing of information automatically, without further intervention.

This means that your published web content, whatever it is, is kept up-to-date at all times.

It’s like magic, but quicker.

Unless you’re lucky enough to discover that your needs can be met by the built-in plugins, or by the many available third-party plugins, you’ll have to write your own custom CMS Plugin. Don’t worry though - writing a CMS Plugin is very straightforward.

Why would you need to write a plugin?

A plugin is the most convenient way to integrate content from another Django app into a django CMS page.

For example, suppose you’re developing a site for a record company in django CMS. You might like to have a “Latest releases” box on your site’s home page.

Of course, you could every so often edit that page and update the information. However, a sensible record company will manage its catalogue in Django too, which means Django already knows what this week’s new releases are.

This is an excellent opportunity to make use of that information to make your life easier - all you need to do is create a django CMS plugin that you can insert into your home page, and leave it to do the work of publishing information about the latest releases for you.

Plugins are reusable. Perhaps your record company is producing a series of reissues of seminal Swiss punk records; on your site’s page about the series, you could insert the same plugin, configured a little differently, that will publish information about recent new releases in that series.

Overview

A django CMS plugin is fundamentally composed of three things.

  • a plugin editor, to configure a plugin each time it is deployed
  • a plugin publisher, to do the automated work of deciding what to publish
  • a plugin template, to render the information into a web page

These correspond to the familiar Model-View-Template scheme:

  • the plugin model to store its configuration
  • the plugin view that works out what needs to be displayed
  • the plugin template to render the information

And so to build your plugin, you’ll make it from:

A note about cms.plugin_base.CMSPluginBase

cms.plugin_base.CMSPluginBase is actually a sub-class of django.contrib.admin.ModelAdmin.

Because CMSPluginBase sub-classes ModelAdmin several important ModelAdmin options are also available to CMS plugin developers. These options are often used:

  • exclude
  • fields
  • fieldsets
  • form
  • formfield_overrides
  • inlines
  • radio_fields
  • raw_id_fields
  • readonly_fields

Please note, however, that not all ModelAdmin options are effective in a CMS plugin. In particular, any options that are used exclusively by the ModelAdmin‘s changelist will have no effect. These and other notable options that are ignored by the CMS are:

  • actions
  • actions_on_top
  • actions_on_bottom
  • actions_selection_counter
  • date_hierarchy
  • list_display
  • list_display_links
  • list_editable
  • list_filter
  • list_max_show_all
  • list_per_page
  • ordering
  • paginator
  • preserve_fields
  • save_as
  • save_on_top
  • search_fields
  • show_full_result_count
  • view_on_site

An aside on models and configuration

The plugin model, the sub-class of cms.models.pluginmodel.CMSPlugin, is actually optional.

You could have a plugin that doesn’t need to be configured, because it only ever does one thing.

For example, you could have a plugin that only publishes information about the top-selling record of the past seven days. Obviously, this wouldn’t be very flexible - you wouldn’t be able to use the same plugin for the best-selling release of the last month instead.

Usually, you find that it is useful to be able to configure your plugin, and this will require a model.

The simplest plugin

You may use python manage.py startapp to set up the basic layout for you plugin app (remember to add your plugin to INSTALLED_APPS). Alternatively, just add a file called cms_plugins.py to an existing Django application.

In cms_plugins.py, you place your plugins. For our example, include the following code:

from cms.plugin_base import CMSPluginBase
from cms.plugin_pool import plugin_pool
from cms.models.pluginmodel import CMSPlugin
from django.utils.translation import ugettext_lazy as _

class HelloPlugin(CMSPluginBase):
    model = CMSPlugin
    render_template = "hello_plugin.html"
    cache = False

plugin_pool.register_plugin(HelloPlugin)

Now we’re almost done. All that’s left is to add the template. Add the following into the root template directory in a file called hello_plugin.html:

<h1>Hello {% if request.user.is_authenticated %}{{ request.user.first_name }} {{ request.user.last_name}}{% else %}Guest{% endif %}</h1>

This plugin will now greet the users on your website either by their name if they’re logged in, or as Guest if they’re not.

Now let’s take a closer look at what we did there. The cms_plugins.py files are where you should define your sub-classes of cms.plugin_base.CMSPluginBase, these classes define the different plugins.

There are two required attributes on those classes:

  • model: The model you wish to use for storing information about this plugin. If you do not require any special information, for example configuration, to be stored for your plugins, you can simply use cms.models.pluginmodel.CMSPlugin (we’ll look at that model more closely in a bit). In a normal admin class, you don’t need to supply this information because admin.site.register(Model, Admin) takes care of it, but a plugin is not registered in that way.
  • name: The name of your plugin as displayed in the admin. It is generally good practice to mark this string as translatable using django.utils.translation.ugettext_lazy(), however this is optional. By default the name is a nicer version of the class name.

And one of the following must be defined if render_plugin attribute is True (the default):

  • render_template: The template to render this plugin with.

or

  • get_render_template: A method that returns a template path to render the plugin with.

In addition to those attributes, you can also override the render() method which determines the template context variables that are used to render your plugin. By default, this method only adds instance and placeholder objects to your context, but plugins can override this to include any context that is required.

A number of other methods are available for overriding on your CMSPluginBase sub-classes. See: CMSPluginBase for further details.

Troubleshooting

Since plugin modules are found and loaded by django’s importlib, you might experience errors because the path environment is different at runtime. If your cms_plugins isn’t loaded or accessible, try the following:

$ python manage.py shell
>>> from importlib import import_module
>>> m = import_module("myapp.cms_plugins")
>>> m.some_test_function()

Storing configuration

In many cases, you want to store configuration for your plugin instances. For example, if you have a plugin that shows the latest blog posts, you might want to be able to choose the amount of entries shown. Another example would be a gallery plugin where you want to choose the pictures to show for the plugin.

To do so, you create a Django model by sub-classing cms.models.pluginmodel.CMSPlugin in the models.py of an installed application.

Let’s improve our HelloPlugin from above by making its fallback name for non-authenticated users configurable.

In our models.py we add the following:

from cms.models.pluginmodel import CMSPlugin

from django.db import models

class Hello(CMSPlugin):
    guest_name = models.CharField(max_length=50, default='Guest')

If you followed the Django tutorial, this shouldn’t look too new to you. The only difference to normal models is that you sub-class cms.models.pluginmodel.CMSPlugin rather than django.db.models.Model.

Now we need to change our plugin definition to use this model, so our new cms_plugins.py looks like this:

from cms.plugin_base import CMSPluginBase
from cms.plugin_pool import plugin_pool
from django.utils.translation import ugettext_lazy as _

from .models import Hello

class HelloPlugin(CMSPluginBase):
    model = Hello
    name = _("Hello Plugin")
    render_template = "hello_plugin.html"
    cache = False

    def render(self, context, instance, placeholder):
        context = super(HelloPlugin, self).render(context, instance, placeholder)
        return context

plugin_pool.register_plugin(HelloPlugin)

We changed the model attribute to point to our newly created Hello model and pass the model instance to the context.

As a last step, we have to update our template to make use of this new configuration:

<h1>Hello {% if request.user.is_authenticated %}
  {{ request.user.first_name }} {{ request.user.last_name}}
{% else %}
  {{ instance.guest_name }}
{% endif %}</h1>

The only thing we changed there is that we use the template variable {{ instance.guest_name }} instead of the hard-coded Guest string in the else clause.

Warning

You cannot name your model fields the same as any installed plugins lower- cased model name, due to the implicit one-to-one relation Django uses for sub-classed models. If you use all core plugins, this includes: file, googlemap, link, picture, snippetptr, teaser, twittersearch, twitterrecententries and video.

Additionally, it is recommended that you avoid using page as a model field, as it is declared as a property of cms.models.pluginmodel.CMSPlugin, and your plugin will not work as intended in the administration without further work.

Warning

If you are using Python 2.x and overriding the __unicode__ method of the model file, make sure to return its results as UTF8-string. Otherwise saving an instance of your plugin might fail with the frontend editor showing an <Empty> plugin instance. To return in Unicode use a return statement like return u'{0}'.format(self.guest_name).

Handling Relations

Every time the page with your custom plugin is published the plugin is copied. So if your custom plugin has foreign key (to it, or from it) or many-to-many relations you are responsible for copying those related objects, if required, whenever the CMS copies the plugin - it won’t do it for you automatically.

Every plugin model inherits the empty cms.models.pluginmodel.CMSPlugin.copy_relations() method from the base class, and it’s called when your plugin is copied. So, it’s there for you to adapt to your purposes as required.

Typically, you will want it to copy related objects. To do this you should create a method called copy_relations on your plugin model, that receives the old instance of the plugin as an argument.

You may however decide that the related objects shouldn’t be copied - you may want to leave them alone, for example. Or, you might even want to choose some altogether different relations for it, or to create new ones when it’s copied... it depends on your plugin and the way you want it to work.

If you do want to copy related objects, you’ll need to do this in two slightly different ways, depending on whether your plugin has relations to or from other objects that need to be copied too:

For foreign key relations from other objects

Your plugin may have items with foreign keys to it, which will typically be the case if you set it up so that they are inlines in its admin. So you might have two models, one for the plugin and one for those items:

class ArticlePluginModel(CMSPlugin):
    title = models.CharField(max_length=50)

class AssociatedItem(models.Model):
    plugin = models.ForeignKey(
        ArticlePluginModel,
        related_name="associated_item"
    )

You’ll then need the copy_relations() method on your plugin model to loop over the associated items and copy them, giving the copies foreign keys to the new plugin:

class ArticlePluginModel(CMSPlugin):
    title = models.CharField(max_length=50)

    def copy_relations(self, oldinstance):
        # Before copying related objects from the old instance, the ones
        # on the current one need to be deleted. Otherwise, duplicates may
        # appear on the public version of the page
        self.associated_item.all().delete()

        for associated_item in oldinstance.associated_item.all():
            # instance.pk = None; instance.pk.save() is the slightly odd but
            # standard Django way of copying a saved model instance
            associated_item.pk = None
            associated_item.plugin = self
            associated_item.save()

For many-to-many or foreign key relations to other objects

Let’s assume these are the relevant bits of your plugin:

class ArticlePluginModel(CMSPlugin):
    title = models.CharField(max_length=50)
    sections = models.ManyToManyField(Section)

Now when the plugin gets copied, you want to make sure the sections stay, so it becomes:

class ArticlePluginModel(CMSPlugin):
    title = models.CharField(max_length=50)
    sections = models.ManyToManyField(Section)

    def copy_relations(self, oldinstance):
        self.sections = oldinstance.sections.all()

If your plugins have relational fields of both kinds, you may of course need to use both the copying techniques described above.

Relations between plugins

It is much harder to manage the copying of relations when they are from one plugin to another.

See the GitHub issue copy_relations() does not work for relations between cmsplugins #4143 for more details.

Advanced

Inline Admin

If you want to have the foreign key relation as a inline admin, you can create an admin.StackedInline class and put it in the Plugin to “inlines”. Then you can use the inline admin form for your foreign key references:

class ItemInlineAdmin(admin.StackedInline):
    model = AssociatedItem


class ArticlePlugin(CMSPluginBase):
    model = ArticlePluginModel
    name = _("Article Plugin")
    render_template = "article/index.html"
    inlines = (ItemInlineAdmin,)

    def render(self, context, instance, placeholder):
        context = super(ArticlePlugin, self).render(context, instance, placeholder)
        items = instance.associated_item.all()
        context.update({
            'items': items,
        })
        return context

Plugin form

Since cms.plugin_base.CMSPluginBase extends django.contrib.admin.ModelAdmin, you can customise the form for your plugins just as you would customise your admin interfaces.

The template that the plugin editing mechanism uses is cms/templates/admin/cms/page/plugin/change_form.html. You might need to change this.

If you want to customise this the best way to do it is:

  • create a template of your own that extends cms/templates/admin/cms/page/plugin/change_form.html to provide the functionality you require;
  • provide your cms.plugin_base.CMSPluginBase sub-class with a change_form_template attribute pointing at your new template.

Extending admin/cms/page/plugin/change_form.html ensures that you’ll keep a unified look and functionality across your plugins.

There are various reasons why you might want to do this. For example, you might have a snippet of JavaScript that needs to refer to a template variable), which you’d likely place in {% block extrahead %}, after a {{ block.super }} to inherit the existing items that were in the parent template.

Handling media

If your plugin depends on certain media files, JavaScript or stylesheets, you can include them from your plugin template using django-sekizai. Your CMS templates are always enforced to have the css and js sekizai namespaces, therefore those should be used to include the respective files. For more information about django-sekizai, please refer to the django-sekizai documentation.

Note that sekizai can’t help you with the admin-side plugin templates - what follows is for your plugins’ output templates.

Sekizai style

To fully harness the power of django-sekizai, it is helpful to have a consistent style on how to use it. Here is a set of conventions that should be followed (but don’t necessarily need to be):

  • One bit per addtoblock. Always include one external CSS or JS file per addtoblock or one snippet per addtoblock. This is needed so django-sekizai properly detects duplicate files.
  • External files should be on one line, with no spaces or newlines between the addtoblock tag and the HTML tags.
  • When using embedded javascript or CSS, the HTML tags should be on a newline.

A good example:

{% load sekizai_tags %}

{% addtoblock "js" %}<script type="text/javascript" src="{{ MEDIA_URL }}myplugin/js/myjsfile.js"></script>{% endaddtoblock %}
{% addtoblock "js" %}<script type="text/javascript" src="{{ MEDIA_URL }}myplugin/js/myotherfile.js"></script>{% endaddtoblock %}
{% addtoblock "css" %}<link rel="stylesheet" type="text/css" href="{{ MEDIA_URL }}myplugin/css/astylesheet.css">{% endaddtoblock %}
{% addtoblock "js" %}
<script type="text/javascript">
    $(document).ready(function(){
        doSomething();
    });
</script>
{% endaddtoblock %}

A bad example:

{% load sekizai_tags %}

{% addtoblock "js" %}<script type="text/javascript" src="{{ MEDIA_URL }}myplugin/js/myjsfile.js"></script>
<script type="text/javascript" src="{{ MEDIA_URL }}myplugin/js/myotherfile.js"></script>{% endaddtoblock %}
{% addtoblock "css" %}
    <link rel="stylesheet" type="text/css" href="{{ MEDIA_URL }}myplugin/css/astylesheet.css"></script>
{% endaddtoblock %}
{% addtoblock "js" %}<script type="text/javascript">
    $(document).ready(function(){
        doSomething();
    });
</script>{% endaddtoblock %}

Plugin Context

The plugin has access to the django template context. You can override variables using the with tag.

Example:

{% with 320 as width %}{% placeholder "content" %}{% endwith %}

Plugin Context Processors

Plugin context processors are callables that modify all plugins’ context before rendering. They are enabled using the CMS_PLUGIN_CONTEXT_PROCESSORS setting.

A plugin context processor takes 3 arguments:

  • instance: The instance of the plugin model
  • placeholder: The instance of the placeholder this plugin appears in.
  • context: The context that is in use, including the request.

The return value should be a dictionary containing any variables to be added to the context.

Example:

def add_verbose_name(instance, placeholder, context):
    '''
    This plugin context processor adds the plugin model's verbose_name to context.
    '''
    return {'verbose_name': instance._meta.verbose_name}

Plugin Processors

Plugin processors are callables that modify all plugins’ output after rendering. They are enabled using the CMS_PLUGIN_PROCESSORS setting.

A plugin processor takes 4 arguments:

  • instance: The instance of the plugin model
  • placeholder: The instance of the placeholder this plugin appears in.
  • rendered_content: A string containing the rendered content of the plugin.
  • original_context: The original context for the template used to render the plugin.

Note

Plugin processors are also applied to plugins embedded in Text plugins (and any custom plugin allowing nested plugins). Depending on what your processor does, this might break the output. For example, if your processor wraps the output in a div tag, you might end up having div tags inside of p tags, which is invalid. You can prevent such cases by returning rendered_content unchanged if instance._render_meta.text_enabled is True, which is the case when rendering an embedded plugin.

Example

Suppose you want to wrap each plugin in the main placeholder in a colored box but it would be too complicated to edit each individual plugin’s template:

In your settings.py:

CMS_PLUGIN_PROCESSORS = (
    'yourapp.cms_plugin_processors.wrap_in_colored_box',
)

In your yourapp.cms_plugin_processors.py:

def wrap_in_colored_box(instance, placeholder, rendered_content, original_context):
    '''
    This plugin processor wraps each plugin's output in a colored box if it is in the "main" placeholder.
    '''
    # Plugins not in the main placeholder should remain unchanged
    # Plugins embedded in Text should remain unchanged in order not to break output
    if placeholder.slot != 'main' or (instance._render_meta.text_enabled and instance.parent):
        return rendered_content
    else:
        from django.template import Context, Template
        # For simplicity's sake, construct the template from a string:
        t = Template('<div style="border: 10px {{ border_color }} solid; background: {{ background_color }};">{{ content|safe }}</div>')
        # Prepare that template's context:
        c = Context({
            'content': rendered_content,
            # Some plugin models might allow you to customise the colors,
            # for others, use default colors:
            'background_color': instance.background_color if hasattr(instance, 'background_color') else 'lightyellow',
            'border_color': instance.border_color if hasattr(instance, 'border_color') else 'lightblue',
        })
        # Finally, render the content through that template, and return the output
        return t.render(c)

Nested Plugins

You can nest CMS Plugins in themselves. There’s a few things required to achieve this functionality:

models.py:

class ParentPlugin(CMSPlugin):
    # add your fields here

class ChildPlugin(CMSPlugin):
    # add your fields here

cms_plugins.py:

from .models import ParentPlugin, ChildPlugin

class ParentCMSPlugin(CMSPluginBase):
    render_template = 'parent.html'
    name = 'Parent'
    model = ParentPlugin
    allow_children = True  # This enables the parent plugin to accept child plugins
    # You can also specify a list of plugins that are accepted as children,
    # or leave it away completely to accept all
    # child_classes = ['ChildCMSPlugin']

    def render(self, context, instance, placeholder):
        context = super(ParentCMSPlugin, self).render(context, instance, placeholder)
        return context

plugin_pool.register_plugin(ParentCMSPlugin)


class ChildCMSPlugin(CMSPluginBase):
    render_template = 'child.html'
    name = 'Child'
    model = ChildPlugin
    require_parent = True  # Is it required that this plugin is a child of another plugin?
    # You can also specify a list of plugins that are accepted as parents,
    # or leave it away completely to accept all
    # parent_classes = ['ParentCMSPlugin']

    def render(self, context, instance, placeholder):
        context = super(ChildCMSPlugin, self).render(context, instance, placeholder)
        return context

plugin_pool.register_plugin(ChildCMSPlugin)

parent.html:

{% load cms_tags %}

<div class="plugin parent">
    {% for plugin in instance.child_plugin_instances %}
        {% render_plugin plugin %}
    {% endfor %}
</div>

child.html:

<div class="plugin child">
    {{ instance }}
</div>

Extending context menus of placeholders or plugins

There are three possibilities to extend the context menus of placeholders or plugins.

  • You can either extend a placeholder context menu.
  • You can extend all plugin context menus.
  • You can extend the current plugin context menu.

For this purpose you can overwrite 3 methods on CMSPluginBase.

Example:

class AliasPlugin(CMSPluginBase):
    name = _("Alias")
    allow_children = False
    model = AliasPluginModel
    render_template = "cms/plugins/alias.html"

    def render(self, context, instance, placeholder):
        context = super(AliasPlugin, self).render(context, instance, placeholder)
        if instance.plugin_id:
            plugins = instance.plugin.get_descendants(include_self=True).order_by('placeholder', 'tree_id', 'level',
                                                                                  'position')
            plugins = downcast_plugins(plugins)
            plugins[0].parent_id = None
            plugins = build_plugin_tree(plugins)
            context['plugins'] = plugins
        if instance.alias_placeholder_id:
            content = render_placeholder(instance.alias_placeholder, context)
            print content
            context['content'] = mark_safe(content)
        return context

    def get_extra_global_plugin_menu_items(self, request, plugin):
        return [
            PluginMenuItem(
                _("Create Alias"),
                reverse("admin:cms_create_alias"),
                data={'plugin_id': plugin.pk, 'csrfmiddlewaretoken': get_token(request)},
            )
        ]

    def get_extra_placeholder_menu_items(self, request, placeholder):
        return [
            PluginMenuItem(
                _("Create Alias"),
                reverse("admin:cms_create_alias"),
                data={'placeholder_id': placeholder.pk, 'csrfmiddlewaretoken': get_token(request)},
            )
        ]

    def get_plugin_urls(self):
        urlpatterns = [
            url(r'^create_alias/$', self.create_alias, name='cms_create_alias'),
        ]
        return urlpatterns

    def create_alias(self, request):
        if not request.user.is_staff:
            return HttpResponseForbidden("not enough privileges")
        if not 'plugin_id' in request.POST and not 'placeholder_id' in request.POST:
            return HttpResponseBadRequest("plugin_id or placeholder_id POST parameter missing.")
        plugin = None
        placeholder = None
        if 'plugin_id' in request.POST:
            pk = request.POST['plugin_id']
            try:
                plugin = CMSPlugin.objects.get(pk=pk)
            except CMSPlugin.DoesNotExist:
                return HttpResponseBadRequest("plugin with id %s not found." % pk)
        if 'placeholder_id' in request.POST:
            pk = request.POST['placeholder_id']
            try:
                placeholder = Placeholder.objects.get(pk=pk)
            except Placeholder.DoesNotExist:
                return HttpResponseBadRequest("placeholder with id %s not found." % pk)
            if not placeholder.has_change_permission(request):
                return HttpResponseBadRequest("You do not have enough permission to alias this placeholder.")
        clipboard = request.toolbar.clipboard
        clipboard.cmsplugin_set.all().delete()
        language = request.LANGUAGE_CODE
        if plugin:
            language = plugin.language
        alias = AliasPluginModel(language=language, placeholder=clipboard, plugin_type="AliasPlugin")
        if plugin:
            alias.plugin = plugin
        if placeholder:
            alias.alias_placeholder = placeholder
        alias.save()
        return HttpResponse("ok")

Plugin data migrations

Due to the migration from Django MPTT to django-treebeard in version 3.1, the plugin model is different between the two versions. Schema migrations are not affected as the migration systems (both South and Django) detects the different bases.

Data migrations are a different story, though.

If your data migration does something like:

MyPlugin = apps.get_model('my_app', 'MyPlugin')

for plugin in MyPlugin.objects.all():
    ... do something ...

You may end up with an error like django.db.utils.OperationalError: (1054, "Unknown column 'cms_cmsplugin.level' in 'field list'") because depending on the order the migrations are executed, the historical models may be out of sync with the applied database schema.

To keep compatibility with 3.0 and 3.x you can force the data migration to run before the django CMS migration that creates treebeard fields, by doing this the data migration will always be executed on the “old” database schema and no conflict will exist.

For South migrations add this:

from distutils.version import LooseVersion
import cms
USES_TREEBEARD = LooseVersion(cms.__version__) >= LooseVersion('3.1')

class Migration(DataMigration):

    if USES_TREEBEARD:
        needed_by = [
            ('cms', '0070_auto__add_field_cmsplugin_path__add_field_cmsplugin_depth__add_field_c')
        ]

For Django migrations add this:

from distutils.version import LooseVersion
import cms
USES_TREEBEARD = LooseVersion(cms.__version__) >= LooseVersion('3.1')

class Migration(migrations.Migration):

    if USES_TREEBEARD:
        run_before = [
            ('cms', '0004_auto_20140924_1038')
        ]