This PR adds a new "Add to Scene" dropdown menu for adding elements to
the current scene, and a new Media Library dialog for importing and/or
adding Storyteller Engine assets (characters, scenes, animations, etc.)
associated with the user's Storyteller.ai account.
The scope of this PR is limited to the UI — actual asset importing
behavior, and adding elements other than primitive shapes to the current
scene, will be implemented in follow-up PRs.
### Technical Details
In order to facilitate these changes, a new "overlay" abstraction has
been added to `@storyteller/studio-ui` (loosely modeled after
[`@angular/cdk/overlay`](https://material.angular.io/cdk/overlay/overview))
for managing DOM elements which should render in a self-contained
stacking context "above" the rest of the application.
Two new base UI components — `<sts-menu>` and `<sts-dialog>`
— have also been added to make use of this overlay system, but
it's worth noting that these new components have not yet been
exhaustively tested or thoroughly fleshed out, so they may require
significant changes in order to accommodate future use cases or address
unforeseen bugs.
### Testing
The Media Library makes some API calls which will run into CORS errors
in a normal browser. This can be bypassed by running Chrome with the
following command-line flags:
```
--disable-web-security --ignore-certificate-errors --user-data-dir=path/to/some/temporary/directory
```
Verify all of the following:
* The "Add to Scene" menu opens and closes as expected
* The primitive-shape menu items (Cube, Sphere, etc.) add the
corresponding elements to the scene
* The "Media Library..." menu item correctly opens the Media Library
dialog
* The Media Library's search bar and category filters work as expected
* A single asset can be selected by clicking on it
* Multiple assets can be selected by holding the "Ctrl" or "Cmd" key
* The selection can be cleared by clicking in an empty space in the
results grid
* An "Add to Scene" button appears if (and only if) one or more assets
are selected
* The Media Library dialog can be closed by:
- Clicking the "X" in the upper right-hand corner
- Pressing the "Esc" key
- Clicking anywhere outside of the dialog boundaries
Additionally, ensure that the Media Library dialog handles all of the
following situations gracefully:
* User is not logged in to fakeyou.com
* User is logged in but does not have any engine-compatible assets
uploaded (this can be tested by selecting any of the categories from the
sidebar, since the database has not yet been migrated to use the new
`media_file_class` field, so all of those categories should currently
yield an empty list)
* User is logged in and there are engine-compatible assets to list (this
can be tested by pressing the "Save" button in the main application
toolbar to save the current scene to your account, and selecting the
"Home" entry from the Media Library sidebar)
Danny McGee