Thank you for the detailed investigation.
Let’s start by clarifying how the extension works.
Save Selection: Add-on saves the selection (and appends to previously saved) to its own storage and repeats the process every time a new text is saved.
This function does not save to memory and it has nothing to do with Clipboard at all or dom.event.clipboardevents.enabled
.
There is no limit on how many times you can save text to Text MultiCopy (except the built-in JSON limit of 5m which a a lot of text).
Copy Saved to clipboard: Add-on gets the previously saved data from its storage, pastes it to the clipboard and clears the storage.
Web Extension API does not have a dedicated Clipboard API. Add-ons have to use Web API by injecting a script to the current page and process the paste to clipboard from within that page. There is no other way.
Firefox limits injecting script into some pages like internal pages or AMO and some other 14 domains.
I have written a work-around for this limitation in my other add-ons and will add it to Text MultiCopy in the next upgrade.
As you have mentioned (I have not tested it), above setting may interfere with clipboard events from the page but that is not something that is expected to be set to false. If it does interfere then doing so will break any WE with clipboard functionality.
I will do some test to see how dom.event.clipboardevents.enabled
actually affects the add-on.
The lag should not relate to the function of the add-on as add-on will save data normally regardless on the dom.event.clipboardevents.enabled
which only comes into effect on pasting to clipboard.
Pasting in Texarea also should not be affected either way.