Modify built in `Write` button (attach drop down)

[kenjiuno]

Quick research topic of Dropdown support for default menu entry Write,Reply,Forward, etc. | Topicbox

In TB 68 and prior, this kind of UI mutation has been done by writing add-on with chrome.manifest.

That way is called XUL Overlay (Cross Package Overlays).

However since TB 74 Beta, add-on using XUL Overlay doesn't work any more. Because JavaScript execution context is separated now: Thunderbird privileged context and extension contexts.

TB dev team declares latest TB supports WebExtension (MailExtension) now.

TB still uses XUL. However add-on cannot access XUL directly.

TB dev team allowed us to use WebExtension Experiments in order to access privileged part of Thunderbird including XUL with JavaScript code.

So can we modify builtin Write button by writing WebExtension Experiments?

[kenjiuno]

https://github.com/HiraokaHyperTools/sample-extensions/tree/master/modifyWriteButton sample will replace builtin Write button like following:

At first click [ModifyWriteButton] at top-right, and then click [ReplaceWriteButton] button:

[kenjiuno]

Or you can try replacement of Write button with privileged DevTool:

• Press Ctrl+Shift+I
• Click OK
• Enter Console tab
• Paste and execute script

newToolbarButton = MozXULElement.parseXULToFragment(`
  <toolbarbutton id="button-newmsg"
                 type="menu-button"
                 class="toolbarbutton-1"
                 label="Write"
                 tooltiptext="New message">
    <menupopup is="menupopup">
      <menuitem id="button-newmsg-1"
                label="New message alternative 1"/>
      <menuitem id="button-newmsg-2"
                label="New message alternative 2"/>
      <menuitem id="button-newmsg-3"
                label="New message alternative 3"/>
    </menupopup>

  </toolbarbutton>
`)

newToolbarButton.querySelector("#button-newmsg-1").addEventListener("command", () => { alert("1"); event.stopPropagation(); })
newToolbarButton.querySelector("#button-newmsg-2").addEventListener("command", () => { alert("2") })
newToolbarButton.querySelector("#button-newmsg-3").addEventListener("command", () => { alert("3") })

doc = Services.wm.getMostRecentWindow(null).document

newMsg = doc.getElementById("button-newmsg")
newMsg.parentNode.replaceChild(newToolbarButton, newMsg)

newToolbarButton = doc.getElementById("button-newmsg")
newToolbarButton.addEventListener("command", () => alert("0"))

[kenjiuno]

There are still more issues to be solved in this modifyWriteButton extension...

• [ ] Extend browser.modifyWriteButtonApi.replaceWriteButton() function so that it can do practical actions.
• [ ] The replaced builtin Write button doesn't accept Customization like: moving position, and button removal.
• [ ] Tear down on extension unload (recover initial Write button on shutdown)

[kenjiuno]

Copied from: https://thunderbird.topicbox.com/groups/addons/Ta0d377f7f4d64034-M1af07002daa494534724b7b1/dropdown-support-for-default-menu-entry-write-reply-forward-etc

browser_action

• ref: https://thunderbird-webextensions.readthedocs.io/en/latest/browserAction.html
• sample: https://github.com/thundernest/sample-extensions/tree/master/layout
• screen shot: browser_action

message_display_action

• ref: https://thunderbird-webextensions.readthedocs.io/en/latest/messageDisplayAction.html
• sample: https://github.com/thundernest/sample-extensions/tree/master/messageDisplay
• screen shot: message_display_action

compose_action

• ref: https://thunderbird-webextensions.readthedocs.io/en/latest/composeAction.html
• sample: https://github.com/thundernest/sample-extensions/tree/master/composeBody
• screen shot: compose_action

[kenjiuno]

I have tested the script https://github.com/HiraokaHyperTools/sample-extensions/issues/1#issuecomment-625801050 on TB 68.8.0: