[Evolution] User point of view on the attachment bar?

[Milan Crha <mcrha redhat com>]

        Hello,
there is an ongoing effort to port Evolution to use WebKit2
(WebKitGTK4), instead of the old WebKit1 (WebKitGTK3). The WebKit1 is
not actively maintained by upstream, thus has many issues. The upstream
focuses on the WebKit2 development, which makes perfect sense. By the
port of the Evolution to the WebKit2 it'll receive more fresh software,
the same as it'll use the maintained version. It'll also get more up-
to-date editor code, which we hope will fix some of the issues
currently seen in the Evolution. It's a win-win state.

As the WebKit2 is conceptually different, very different, the port is
not just about linking against a newer library version, but requires
conceptual changes also in the Evolution.

This email is a plea for an opinion on the attachment bar issue from
the user point of view.

The attachment bar is currently (3.20.x-) located between the message
headers and the message body. It says how many attachments the message
has and one can expand it and look on all of them (Icon View/List
View), eventually can operate with them, including Save/Open/drag&drop.
If there is a message attachment, which has its own attachments, then
it has shown its own attachment bar on the appropriate place. Maybe
this ASCII-drawing of the message preview will help:

   From: user example com
   To: user example com
   Subject: Message with attachments

   [>] 2 Attachments (13,0 KB) [ Save All ]           <-- the attachment bar, collapsed  <--

   Message body is here, with the text from the sender

   [Attachment 1 is here][v]   attachment description
   [Attachment 2 is here][v]   attachment description

The attachment bar is a native Gtk+ widget, inserted in the middle of
an HTML code. The WebKit1 allowed this, but the WebKit2 doesn't, thus
we should deal with it in some way.

I looked on Thunderbird (45.0), how it deals with the attachments, and
they show the attachment bar at the bottom of the preview, but in a
non-scrollable area, thus the attachment bar always uses part of the
view, which could be otherwise used by the message body. They also add
into the attachment bar all attachments, thus also attachments of the
attached messages.

I tend to do it the same as they do. Their attachment bar is not that
tall (collapsed), but seeing constant changes in the gtk+ theme, there
is no guarantee that the attachment bar in the Evolution couldn't use
"larger" part of the preview panel height in the future (like when the
gap around the buttons will be made bigger for whatever reason in the
gtk+ theme).

The problem is that I do not see any other option currently. Everything
else we thought of (like splitting the message preview into multiple
WebKit views and pasting native widgets between WebKit views) would
lead to a very complex code in the Evolution, which would easily break
(by some change in either gtk+ or WebKitGTK+, I'm pretty sure even due
to unrelated changes in either of them). I do not want to come too much
into detail with all the issues spotted, unless explicitly asked to.

Maybe the attachment bar could be made hide-able, for users whom do not
use it and prefer to operate on the attachments below the message, thus
adding it to View->Preview->Attachment Bar, eventually
View->Layout->Attachment Bar, though the Attachment Bar is tight to the
Preview itself, thus it makes more sense there.

Also to mention, the attachment buttons, those below the message, allow
drag&drop too. This functionality will be removed in the WebKit2. The
reason is the same as with the attachment bar, it used to be a native
Gtk+ widget, inserted in the middle of the HTML code, which we cannot
do in the WebKit2. The Expand/Collapse and the popup menu will be
preserved.

Does this change sound sane, from the user point of view?
Do you use the attachment bar at all?
Any other opinion?

        Thanks and bye,
        Milan