Bugzilla

I finally got some time to look into this and it seems that the flutter's layouting logic is forcing Firefox to resize the popup to 0px width.

I don't know flutter enough to quickly determine which part of flutter may be triggering that, but as a confirmation that is actually the case I tweaked the minimal test extension linked in comment 4 with the following few changes:

- created a new `"popup.html"` resource packages in the same extension, this html document includes:
  - an `iframe` with a `src` set to `"index.html"` (which is the flutter demo app that is meant to be rendered in the popup)
  - a style tag with some CSS rules that ensure that the iframe will occupy all the space available in the popup.html document (to make the content of the frame to look like it is actually part of the top level container page)
- in manifest.json, changed the `browser_action`'s `default_popup` to be set to `"popup.html"` instead of `"index.html"`

And that did render the flutter demo app as expected (and the demo app does also work as expected).
While running into the iframe, it does not matter if flutter's layouting logic is setting the width to 0px, that would only have effect on the iframe and so the browserAction popup will still use the default browserAction popup size, and so the bug isn't triggered. 

If I try to load that `"index.html"` into a tab, then the flutter demo app is rendered as expected without any change, that confirms that the bug is triggered for the browserAction popup because Firefox is reactive to flutter setting width to 0px on the browserAction popup window (on the contrary Firefox wouldn't to anything if the same is done when the exact same extension page is loaded in a tab).

I finally got some time to look into this and it seems that the flutter's layouting logic is forcing Firefox to resize the popup to 0px width.

I don't know flutter internal enough to quickly determine which part of flutter may be triggering that, but as a confirmation that is actually the case I tweaked the minimal test extension linked in comment 4 with the following few changes:

- created a new `"popup.html"` resource packages in the same extension, this html document includes:
  - an `iframe` with a `src` set to `"index.html"` (which is the flutter demo app that is meant to be rendered in the popup)
  - a style tag with some CSS rules that ensure that the iframe will occupy all the space available in the popup.html document (to make the content of the frame to look like it is actually part of the top level container page)
- in manifest.json, changed the `browser_action`'s `default_popup` to be set to `"popup.html"` instead of `"index.html"`

And that did render the flutter demo app as expected (and the demo app does also work as expected).
While running into the iframe, it does not matter if flutter's layouting logic is setting the width to 0px, that would only have effect on the iframe and so the browserAction popup will still use the default browserAction popup size, and so the bug isn't triggered. 

If I try to load that `"index.html"` into a tab, then the flutter demo app is rendered as expected without any change, that confirms that the bug is triggered for the browserAction popup because Firefox is reactive to flutter setting width to 0px on the browserAction popup window (on the contrary Firefox wouldn't to anything if the same is done when the exact same extension page is loaded in a tab).