Proposal: agree on a unified `sidebar_action` API for mv3

[carlosjeurissen]

Since sidebar_action is not implemented in Chromium we have the opportunity to still define what it should look like in mv3.

In mv2, this has been implemented by Mozilla Firefox, Opera and Naver Whale. Yet they are different across browsers. See:
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/sidebar_action
https://developers.whale.naver.com/api/extensions/sidebarAction/
https://dev.opera.com/extensions/sidebar-action-api/

One of the differences is the support of sidebar_action next to another action in Firefox and Opera, but not in Naver Whale. Another is the lack of open_at_install in Opera. And Firefox uses default_panel while Naver Whale uses default_page.

Going forward, we can define a merged API covering the aspects in each of these browsers. Have a meeting about it in which we invite both Opera, Naver Whale and potentially Vivaldi (they have non-extension web panels) to discuss directions and come to an agreement.

[aam1r]

Hi there,

We recently shipped a new feature in our Chrome Extension leveraging the Side Panel API.

Initially, we were confused by the fact that this functionality seemed exclusive to Chrome Extensions. Our searches, such as "side panel Firefox," didn't yield the expected results. However, after discovering this issue, we realized that similar capabilities exist in other browsers but under different names.

Given this context, I'm curious if there are any plans to standardize the terminology used across different browsers for this feature. Harmonizing the nomenclature could bring several benefits:

• Discoverability: Enhanced discoverability of the API which could lead to broader adoption. Our team's experience is a testament to the challenges posed by inconsistent naming.
• Simpler Documentation: Simplified cross-browser documentation comparison, enabling developers to quickly understand what's supported in each browser.
• Better DX: Easier comparison of API functionalities for Sidebars, making development and planning easier.

Thank you