In my web app, the user selects local images via input type='file'. The app has multiple 'brushes' and, for each brush, the user can select a different set of local images to be used as 'paint' by the brush. If possible, I would like to use just one input type='file' and, when a given brush X is the editable brush (only one brush at a time is editable), I'd like to refresh the input so that its Filelist is the editable brush's Filelist, not simply the most recently selected bunch of files. I expect this is not possible. Is that right?
You wouldn't be able to set the FileList on an input control programmatically as that would imply that you could read (or re-upload) files that the user had not just selected manually (security risk.)
Maybe what you could do instead is compromise on the "I would like to use just one input type='file'" part. You could have an array of the input type='file' elements, and then show/hide them depending on which brush is selected. That would give the illusion of showing a different list of selected files in the UI.