CoreMedia Studio Manual, Version 7.5.45-10
Chapter 7. Customizing CoreMedia Studio | 7.1. Studio Plugins

The way to easily customize and extend CoreMedia Studio is by using plugins. The Studio module in the CoreMedia Blueprint workspace demonstrates the usage of the plugin mechanism, and defines several plugins for Studio.

Caution

Note that a Studio plugin is not to be confused with an Ext JS component plugin. The former is an application-level construct; Studio plugins are designed to aggregate various extensions (custom UI elements and their functional code, together with the required UI elements to trigger the respective functionality). The latter means a per-component plugin and is purely an Ext JS mechanism. This section deals with Studio plugins; Ext JS plugins are described in Section 5.1.3, “Component Plugins”. In this manual, the terms Studio plugin and component plugin are used, respectively, to avoid ambiguity.

Examples for CoreMedia Studio extension points that plugins may hook into are:

A plugin for CoreMedia Studio usually has the following structure:

Figure 7.1. plugin structure

The example above depicts the layout of a typical Studio module in the CoreMedia Blueprint workspace. All plugins contain a pom.xml file that defines the dependencies of the plugin. The actual source code goes into a subdirectory named joo. The resources subfolder contains some bootstrapping code to register the plugin with CoreMedia Studio, and it may also contain additional static resources such as images or CSS files.

The module blueprint-components, for example, has a main package com.coremedia.blueprint.studio and holds two resource bundles, and an EXML file declaring the plugin and its applicable rules and configuration.

It is recommended to put the source of your plugin into a custom package. This package is reflected in the folder structure below joo. The package name for the example above is com.coremedia.blueprint.studio as it is CoreMedia Blueprint's main Studio plugin.

Each plugin is described in an EXML file (in this example, this is BlueprintStudioPlugin.exml). This file declares the plugin's rule definitions (that is the various Studio extension points that this plugin hook into) and configuration options. Typically, that EXML file is sufficient for a plugin declaration.

However, if you want to run arbitrary ActionScript code as part of your plugin's initialization phase, you can also introduce an ActionScript base class. In this case, you need to declare that base class in your main EXML file, make your base class extend StudioPlugin, and then override the init() method in your base class.

The Main Class

The main class of a plugin can either be defined as ActionScript code or as EXML. In the example in Figure 7.1, “plugin structure” the main class is BlueprintStudioPlugin as EXML. For your own plugins, it is recommended to use a name schema like <your plugin name>StudioPlugin.

The main class for a plugin must implement the interface com.coremedia.cms.editor.sdk.EditorPlugin. The interface defines only one init() method that receives a context object implementing IEditorContext as its only parameter, which is supposed to be used to configure CoreMedia Studio.

In ActionScript, you can simply implement the interface in your source code. In EXML, on the other hand, you cannot implement interfaces. Therefore, Studio provides a base EXML element to inherit from, namely <editor:studioPlugin>. The corresponding ActionScript class com.coremedia.cms.editor.configuration.StudioPlugin not only implements the IEditorContext interface, it also delegates the init() call to all Studio plugins specified in its configurations config option.

The IEditorContext instance handed in to the init() method can be used for the following purposes:

Note that a Studio plugin's init() method is allowed to perform asynchronous calls, which is essential if it needs server-side information (access user, groups, Content, and so on) during initialization. CoreMedia Studio waits for the plugin to handle all callbacks, only then the next plugin (if any) is initialized and eventually, CoreMedia Studio is started. However, you cannot use window.setTimeout() or window.setInterval() in Studio plugin initialization code!

Plugin Rules

The other essential part of a CoreMedia Studio plugin is the plugin rules it declares in its <ui:rules> element. Plugin rules are applied to components whenever they are created, which allows you to modify behavior of standard CoreMedia Studio components with component plugins. The BlueprintStudio plugin, for example, declares rules that add buttons to the favorites toolbar and to the preview panel's toolbar.

The studio plugin file consists of one "rules" element that contains component elements. The components can be either identified by their global id or by namespace and xtype. For the latter case, you need to declare the required namespace(s) in the <exml> tag of the Plugin file. You can read a Studio plugin rule like this: "Whenever a component of the given xtype is built, add the following component plugin(s)."

You can use predefined Ext JS component plugins to modify framework components. The BlueprintStudioPlugin plugin, for example, uses the addItemsPlugin to add buttons to the favorites toolbar.

In the BlueprintFormsStudioPlugin, custom forms for the various Blueprint-defined document types are added by using the addTabbedDocumentFormsPlugin (which is a component plugin).

Warning

While in simple cases, the items to add can be specified directly inline in the Studio plugin EXML file, this is generally discouraged. The reason is that the Studio plugin class is instantiated as a singleton, and all EXML elements that represent objects that are not components or plugins, most prominently Actions, are instantiated immediately, too. This means that Actions are instantiated (too) early, and that a plugin rule may be applied several times with the same Action instance, leading to unexpected results. The best practice is to move the whole component plugin to a separate EXML file and reference this new plugin subclass from the Studio plugin rule. Since the new plugin is referenced by its ptype, a new plugin instance and thus a new Action instance is created for each application of the plugin rule as expected.

The Ext JS plugins of any component are executed in a defined order:

If that specification does not unambiguously decide the order of two plugins, plugins registered earlier are executed earlier. To make sure that a certain module's Studio plugins are registered after another module's Studio plugin, the former module must declare a Maven dependency on the latter module. This way, the Studio plugins run and register in a defined order.

For your own Studio plugin, you might want to use the file from the CoreMedia Project workspace as a starting point. The name of the Studio plugin file should reflect the functionality of the plugin, for example <My-plugin-Name>StudioPlugin.exml for better readability.

The following example shows how a button can be added to the actions toolbar on the right side of the work area:

<editor:studioPlugin>
  <ui:rules>
    ...
    <editor:actionsToolbar>
      <plugins>
        <my:addActionsToolbarItemsPlugin/>
      </plugins>
    </editor:actionsToolbar>
    ...
  </ui:rules>
</editor:studioPlugin>

Because it is embedded in the element <editor:actionsToolbar> in the above declaration, your custom plugin <my:addActionsToolbarItemsPlugin> will be added to all instances of the ActionsToolbar class (which uses the actionsToolbar configuration class).

Your custom plugin is defined in a separate EXML file AddActionsToolbarItemsPlugin.exml that configures an <addItemsPlugin> to add a separator and a button with a custom action to the ActionsToolbar at index 5:

<exml:plugin xmlns...>
  <ui:addItemsPlugin index="5">
    <ui:items>
      <tbseparator/>
      <button>
        <baseAction>
          <my:myAction .../>
        </baseAction>
      </button>
    </ui:items>
  </ui:addItemsPlugin>
</exml:plugin>

While you can insert a component at a fixed position as shown above, it might also make sense to add the component after or before another component with a certain (global) ID, itemId, or xtype. To that end, the addItemsPlugin allows you to specify pattern objects so that new items are added before or after the represented objects. If the component you want to use as an "anchor component" is not a direct child of the component you plug into, you can set the recursive attribute in your rules declaration to true.

When the component you want to modify is located inside a container that is also a public API extension point, you might have to access that container's API to provide context for your customizations. A typical use case for this is that you want to add a button to a toolbar that is nested below a container, but you need to apply your plugin rule to the container (and not the toolbar), because you need to access some API of that Container to configure the items to add (for example, access to the current selection managed by that container), or because the toolbar is reused by other containers, and you want your button to only appear in one specific context. Some Studio components define public API interfaces for accessing the run-time component instance, for example <editor:collectionView> creates a component that is documented to implement the public API interface ICollectionView (package com.coremedia.cms.editor.sdk.collectionview).

To express such nested extension point plugin rules, there is the plugin <ui:nestedRulesPlugin>. Its usage is similar to CoreMedia Studio plugin rules, namely is must contain an element <ui:rules> that again contains nested plugin rules. A nested plugin rule consists of the element of the sub-component to locate with an optional itemId, which in turn contains a <plugins> element with the plugins to add to that component. Typical plugins to use here are addItemsPlugin, removeItemsPlugin, and replaceItemsPlugin, all located in namespace exml:com.coremedia.ui.config.

For example, assume that to every LinkList property field, you want to add a custom action that needs access to the current selection of content items in the LinkList given as a config option contentValueExpression of type ValueExpression. Like in the example above, you have to add a custom plugin to a CoreMedia Studio extension point in your CoreMedia Studio plugin EXML file:

<editor:studioPlugin>
  <ui:rules>
    ...
    <editor:linkListPropertyField>
      <plugins>
        <my:customizeLinkListPropertyFieldPlugin/>
      </plugins>
    </editor:linkListPropertyField>
    ...
  </ui:rules>
</editor:studioPlugin>

Now, in your plugin CustomizeLinkListPropertyFieldPlugin.exml, instead of using <ui:addItemsPlugin> directly, you apply <ui:nestedRulesPlugin> to locate the toolbar you want to customize. Still, the component you plug into is a LinkList property field, and when your custom plugin is instantiated, that component is instantiated, too, and handed in as the config option component. It is good practice to assign the LinkList property field component as well as its initial configuration (when needed) to typed local EXML variables to avoid repeating longish expressions and type casts in inline code.

<exml:plugin
        xmlns:exml="http://www.jangaroo.net/exml/0.8"
        xmlns="exml:ext.config"
        xmlns:ui="exml:com.coremedia.ui.config"
        xmlns:editor="exml:com.coremedia.cms.editor.sdk.config"
        xmlns:my="exml:...">

  <exml:import class="com.coremedia.cms.editor.sdk.premular.fields.LinkListPropertyField"/>
  <exml:import class="com.coremedia.cms.editor.sdk.config.linkListPropertyField"/>

  <exml:var name="myLinkListPropertyField"
            type="LinkListPropertyField"
            value="{LinkListPropertyField(config.component)}"/>

  <exml:var name="linkListPropertyFieldConfig"
            type="linkListPropertyField"
            value="{linkListPropertyField(
                      config.component.initialConfig)}"/>

  <ui:nestedRulesPlugin>
    <ui:rules>
      <editor:linkListPropertyFieldToolbar>
        <plugins>
          <ui:addItemsPlugin>
            <ui:items>
              <tbseparator/>
              <ui:iconButton>
                <baseAction>
                  <my:myAction
                    contentValueExpression=
                      "{myLinkListPropertyField
                        .getSelectedValuesExpression()}"
                    forceReadOnlyValueExpression=
                      "{linkListPropertyFieldConfig
                        .forceReadOnlyValueExpression}"/>
                </baseAction>
              </ui:iconButton>
            </ui:items>
            <ui:before>
              <component
                itemId="{linkListPropertyFieldToolbar
                         .LINK_LIST_SEP_FIRST_ITEM_ID}"/>
            </ui:before>
          </ui:addItemsPlugin>
        </plugins>
      </editor:linkListPropertyFieldToolbar>
    </ui:rules>
  </ui:nestedRulesPlugin>
</exml:plugin>

Note how the above code makes use of the xtype / EXML element linkListPropertyFieldToolbar to locate the toolbar inside the linkListPropertyField, as well as to use an ..._ITEM_ID constant from that config class to specify the new items' location.

As another example, assume you want to create your own component inheriting from <editor:linkListPropertyField>. You want to reuse the default toolbar that the standard link list component defines, but you want to add one additional button to that toolbar. In a very similar fashion to the example above concerning CoreMedia Studio plugins, you can then write your custom component's EXML file like this:

<exml:component xmlns...>
  <exml:cfg name="additionalToolbarItems" type="Array"/>
  <editor:linkListPropertyField>
    <plugins mode="append">
      <ui:nestedRulesPlugin>
        <ui:rules>
          <editor:linkListPropertyFieldToolbar>
            <plugins>
              <ui:addItemsPlugin
                items="{config.additionalToolbarItems}"/>
            </plugins>
          </editor:linkListPropertyFieldToolbar>
        </ui:rules>
      </ui:nestedRulesPlugin>
    </plugins>
  </editor:linkListPropertyField>
</exml:component>

Note that when you inherit from a component and use the <plugins> element to declare the plugins you want to apply to this component, you overwrite the plugins definition of the component you inherit from. That means that all the plugins that the super component defines would not be used in your custom component. To avoid that, you have to set the mode attribute of the plugins element to either append or prepend, which will then add your custom plugin definitions to the end of the super component's declarations, or insert them at the beginning, respectively.

You might also want to remove certain components from their containers. In that case, you can add the removeItemsPlugin to the container component and remove items, again identifying them by pattern objects that can specify id, item id, or xtype.

In order the replace an existing component, you can use the replaceItemsPlugin. For this plugin, you specify one or more replacement components in the items property. Each item must specify an id or an item id and replaces the existing component with exactly that id or item id.

Finally, a custom CoreMedia Studio plugin needs to be registered with the Studio application. This is done in a JavaScript file in the resources folder. In the example, this file is called blueprint-components.module.js. It is recommended that you choose a name following the schema <put your plugin name here>.module.js. The purpose of this file is to add the fully qualified main plugin class to the list of Studio plugins. For your own plugin, you need to change the third and fourth lines of the following example accordingly:

joo.loadModule('${project.groupId}', '${project.artifactId}');
coremediaEditorPlugins.push({
  name:"My Plugin",
  mainClass:"com.my.company.MyStudioPlugin"
});

If your plugin should only be active for a certain group of users, you can add a requiredGroup property to the plugin descriptor. The plugin will only be loaded if the user is a member of the given group.

The object pushed onto the array coremediaEditorPlugins may use the attributes defined by the class EditorPluginDescriptor, especially name and mainClass as shown above. In addition, the name of a group may be specified using the attribute requiredGroup, restricting access to the plugin to members of that group.

You can also implement group specific and own conditions using the onlyIf plugin. Find further information in the ASDoc of com/coremedia/cms/editor/sdk/config/onlyIf.

To recapitulate, this is a brief overview of the configuration chain:

Load external resources

If you want to load external resources like style sheets or JavaScript files into Studio, you can load them with the module JS files mentioned above. Loading a JavaScript file works as follows:

joo.loadScript('<path to JavaScript file
relative to the web application root>');

Adding the following line loads a style sheet into Studio:

joo.loadStyleSheet('<path to CSS-file
relative to the web application root>');

See the CoreMedia Blueprint's main Studio plugin bootstrap code in blueprint-components.module.js for an example on how to load custom style sheets.