Proposed investigation: responsive video assets

[KaliedaRik]

Responsive video is now A Thing - see the article by Scott Jehl detailing Responsive HTML Video (and how to use it) for more details.

Currently SC can display responsive images - specifically <img> elements which include a srcset attribute. When the page loads and selects an image of to display in the element, and when the browser width changes, triggering the upload of a different image file to display, SC will do the work to adapt to that change with minimal disruption to the canvas element output.

We need to investigate whether SC will have to perform similar work for responsive videos in similar circumstances.

[KaliedaRik]

July 2024 update:

Can confirm that this functionality works in Chrome, Safari, Firefox.

The functionality is that the browser will select the most appropriately sized video during page load. Once the selected video has loaded, it remains "sticky" for the rest of the page's life, regardless of any changes to the browser viewport dimensions the user/device may make while the page is live.

This functionality differs from responsive image functionality, where:

• Safari selects the most appropriately sized image on page load, which then remains "sticky" for the rest of the page's life
• Chrome will update to the next appropriately sized image if the user increases browser viewport (width) while viewing the page, but the latest image remains "sticky" when the viewport shrinks
• Firefox will update to the most appropriately sized image as the user changes browser viewport (width) regardless of the direction of change

Consideration

SC includes functionality to handle changes in an image's source file, in response to browser behaviour when the user/device changes the browser's viewport size.

However for responsive video, the functionality seems to be that only one file gets selected on page load and does not change thereafter. SC already handles dimensional issues during initial video loading.

Thus, I don't think we need to do any further work to accommodate responsive video in SC. If devs include a responsive video, they will need to remember to use relative (String%) values for copyDimension attributes to avoid unfortunate display issues.

Closing as Won't fix