attachment_tool.coffee

buttonHTML = """<button type="button" class="attach" data-action="x-attach">Attach Files</button>"""
fileInputHTML = """<input type="file" multiple>"""

$(Trix.config.toolbar.content).find(".button_group.block_tools").append(buttonHTML)

$(document).on "trix-action-invoke", ($event) ->
  if $event.originalEvent.actionName is "x-attach"
    editorElement = $event.target
    editorElement.focus()

    $fileInput = $(fileInputHTML)
    $fileInput.on "change", ->
      for file in @files
        editorElement.editor.insertFile(file)

    $fileInput.click()