Thunderbird extension: add button in message reader toolbar

Question

I'm trying to add a button in the message reader toolbar :

I successfully added a button in the mail toolbar, using the chrome.manifest and XUL files. I just don't know how to access this particular toolbar. I have tried finiding it using the DOM Inspector, to no avail. My button doesn't appear in the "Customize" box either.

My question is therefore: how can I add a button to this particular toolbar?

Answer 1

After looking some more with the DOM Inspector I finally got it.

The toolbar and toolbox ids are header-view-toolbar and header-view toolbox and the classes are inline-toolbar and inline-toolbox. The CSS class for buttons is msgHeaderView-button. The XUL for adding a button there should look like this:

<toolbarpalette id="header-view-toolbar">
  <toolbarbutton id="my-button"/>
</toolbarpalette>

<toolbarbutton id="my-button"
  label="This is my button!"
  tooltiptext="Click on it!"
  oncommand="MyButton[1]()"
  class="toolbarbutton-1 msgHeaderView-button my-button"
/>