I wonder which files are being considered to go through hook_file_download. When this function is triggered, what are conditions ?
(Generally, how I can track myself hooks conditions ?)
I am trying to put some custom created download links (files are not uploaded via drupal, but link to them are defined manually, as described in this issue.)
EDIT: For those searching for hook_file_download related issue, it seems that it is triggered (also) whenever you try to access a valid link to a file in private filesystem.