| [Commands](./modules/commands.md) | Adds named commands, scoped to a context, to the CommandsManager | `setToolActive()`, `nextSeries()` |
| [Panel](./modules/panel.md) | Adds left or right hand side panels | `<ThumbnailList />`, `<MeasurementsTable />` |
| [SOPClassHandler](./modules/sop-class-handler.md) | Determines how retrieved study data is split into "DisplaySets" | `getDisplaySetFromSeries()` |
| [Toolbar](./modules/toolbar.md) | Adds buttons or custom components to the toolbar | Toolbar button, nested buttons, custom |
| [Viewport](./modules/viewport.md) | Adds a component responsible for rendering a "DisplaySet" | `<CornerstoneViewport />`, `<DicomPdfViewport />` |
<spanstyle={{"textAlign":'center','fontStyle':'italic'}}>Tbl. Module types with abridged descriptions and examples. Each module links to a dedicated documentation page.</span>
### Contexts
The `@ohif/viewer` tracks "active contexts" that extensions can use to scope
their functionality. Some example contexts being:
- Route: `ROUTE:VIEWER`, `ROUTE:STUDY_LIST`
- Active Viewport: `ACTIVE_VIEWPORT:CORNERSTONE`, `ACTIVE_VIEWPORT:VTK`
An extension module can use these to say "Only show this Toolbar Button if the
active viewport is a Cornerstone viewport." This helps us use the appropriate UI
and behaviors depending on the current contexts.
For example, if we have hotkey that "rotates the active viewport", each Viewport
module that supports this behavior can add a command with the same name, scoped
to the appropriate context. When the `command` is fired, the "active contexts"
are used to determine the appropriate implementation of the rotate behavior.
## Consuming Extensions
We consume extensions, via the `ExtensionManager`, in our `@ohif/viewer`
project.
```js
const extensionManager = new ExtensionManager({
commandsManager,
servicesManager,
hotkeysManager
});
// prettier-ignore
extensionManager.registerExtensions([ /** **/ ]);
```
The `@ohif/viewer` project handles data fetching, basic routing, wires up UI
services, and is the home to the more bespoke application logic that doesn't
make as much sense to make reusable.
Long-term, replacing the `@ohif/viewer` application and consuming extensions
(and the `ExtensionManager`) in your own project is the ideal path for
applications requiring a high degree of customization that can't be achieved
with current theming, configuration, extension, and services support.
If you're not sure how to achieve your goals with the extensibility available
today, create a GitHub issue!
### `ExtensionManager`
The `ExtensionManager` is a class made available to us via the `@ohif/core`
project (platform/core). Our application instantiates a single instance of it,
and provides a `ServicesManager` and `CommandsManager` along with the
application's configuration through the appConfig key (optional).
```js
const commandsManager = new CommandsManager();
const servicesManager = new ServicesManager();
const extensionManager = new ExtensionManager({
commandsManager,
servicesManager,
appConfig,
});
```
The `ExtensionManager` only has a few public members:
-`registerExtension` - Registers a single extension
-`registerExtensions` - Registers an array of extensions
-`modules` - An object containing registered extensions by `MODULE_TYPE`
During registration, lifecycle hooks and modules have access to the extension's
config, the application's config and `ExtensionManager`'s `ServicesManager` and
`CommandsManager` instances.
Our `@ohif/viewer` uses the `modules` member to access registered extensions at
appropriate places in our application.
## Maintained Extensions
A small number of powerful extensions for popular use cases are maintained by
OHIF. They're co-located in the [`OHIF/Viewers`][viewers-repo] repository, in
the top level [`extensions/`][ext-source] directory.
A viewport powered by <code>cornerstone.js</code>. Adds support for 2D DICOM rendering and manipulation, as well as support for the tools features in <ahref="https://tools.cornerstonejs.org/examples/"><code>cornerstone-tools</code></a>. Also adds "CINE Dialog" to the Toolbar.
Renders text and HTML content for <ahref="https://github.com/OHIF/Viewers/blob/master/extensions/dicom-html/src/OHIFDicomHtmlSopClassHandler.js#L4-L12">specific SopClassUIDs</a>.
Renders PDFs for a <ahref="https://github.com/OHIF/Viewers/blob/master/extensions/dicom-pdf/src/OHIFDicomPDFSopClassHandler.js#L4-L6">specific SopClassUID</a>.
Renders Microscopy images for a <ahref="https://github.com/OHIF/Viewers/blob/master/extensions/dicom-microscopy/src/DicomMicroscopySopClassHandler.js#L5-L7">specific SopClassUID</a>.
Renders segmentation images for a <ahref="https://github.com/OHIF/Viewers/blob/master/extensions/dicom-segmentation/src/OHIFDicomSegSopClassHandler.js#L5-L7">specific SopClassUID</a>.
