Support for placeholderCanvas and accompanyingCanvas

[glenrobson]

UV version:

 [email protected]

I'm submitting a:

• bug report
• feature request => please use the user stories repo
• support request => Please do not submit support requests here, use stackoverflow

Current behavior:
Currently when viewing a manifest with a placeholderCanvas or a accompanyingCanvas the UV ignores these properties and shows the main content.

Expected behavior:
For the placeholderCanvas example it should show the placeholder image while the video is loading.

For the accompanyingCanvas it should play the music while the images are shown.

Steps to reproduce:

• placeholderCanvas: https://uv.netlify.app/#?c=&m=&s=&cv=&manifest=https%3A%2F%2Fpreview.iiif.io%2Fcookbook%2F0013-placeholderCanvas%2Frecipe%2F0013-placeholderCanvas%2Fmanifest.json

• accompanyingCanvas: https://uv.netlify.app/#?c=&m=&s=&cv=&manifest=https%3A%2F%2Fpreview.iiif.io%2Fcookbook%2F0014-accompanyingCanvas%2Frecipe%2F0014-accompanyingcanvas%2Fmanifest.json&xywh=-2467%2C-268%2C8429%2C5358

Related code:

Looks to be related to here:

universalviewer/src/lib/manifold.js

Line 764 in 2a08b8a

Helper.prototype.getPosterCanvas = function () {

Other information:
This is part of the IIIF Cookbook work and relevant recipes are:

• placeholderCanvas
• accompanyingCanvas

[stephenwf]

Relates to: IIIF-Commons/manifesto#52

[LlGC-szw]

All issues will be triaged for further investigation or closure by the 28 September 2023. If your issue is still relevant and would like for it be investigated further please comment by 14 September 2023.

[triplingual]

Still relevant, yes.
The recipes have been published to the public cookbook since the original issue was filed and are now best viewed at

• Load a Preview Image Before the Main Content a.k.a. placeholderCanvas
• Audio Presentation with Accompanying Image a.k.a. accompanyingCanvas

How UV presents the manifests

• placeholderCanvas, UV v3
• placeholderCanvas, UV v4
• accompanyingCanvas, UV v3
• accompanyingCanvas, UV v4

For comparison, here are 2 viewers that implement placeholderCanvas:

• Ramp
• Clover

And one of those that implements accompanyingCanvas: Clover