Comment 56 for bug 1347305

As indicated in Bug 1084539 after upgrade to TB 31.2 (Win 7 64bits) the lack of contrast between the background color of windows and background color of fields (currently same color) in compose window is the main issue. It make the fields much more difficult to read and edit and therefore are not end-user friendly at all, even after a while of usage. It remain not-intuitive in term of usability.

The address fields background color shall be of different color that the window background color (white would remain most appropriate in a light theme). For constancy, I would expect those field background color to be the same as the body/content field background color (eg: white in a light theme).

The simple fact that developer themselves seems to have difficulties to adjust to the new layout shall have ring a bell that it wasn't an adequate change to make for all. Why to change what's works? Better concentrate on what doesn't...

As a stone to the edifice, you would find in attachment 8507216 a rough mockup proposal that may inspire a better solution as a possible compromise... Basically From and Subject fields appears more separated (thicker lines - same color as window background color) while To,Cc,Bcc scroll down list stand in the middle with addresses lightly separated by thin lines of background windows color... Rounded corner may be optional... just look more smooth... to my opinion... The field shadow may be removed to provide a less bulky aspect and to bring it closer to a "flat design" which seems fashion at the moment but which usually create loss of contrast making things more difficult to distinguish... new version of Android and iOS are good examples...

If you look at Bugzilla, Thunderbird and Firefox layout, most of the editable field by end-users have a white background that clearly contrast with the background color of the window that contain them (eg: url address bar, search field, etc...) this is the most optimized contrast in term of usability. Most of forms on the web (and in software) do use such layout [though some might use a background color for field and white for the background color of windows/table that contain them]. This is a very standard design guideline that works and which is well followed in software development and on the web. Thunderbird should keep it.

As you are at redesigning the layout of compose windows I would also suggest the following additional changes as possible room for improvements:
- Replace the current To/Bcc/Cc separate fields for each email address set by a comma (or semi-colon) list of addresses instead (as usually used in alternative email client software). With a trailing X button for each address to allow deletion/removal or a drop down menu to: delete, copy email address, edit contact, add contact, etc...
- Increase the newly set auto-completion search result display default limit (in To, Cc, Bcc fields) from 5 contacts to the previous value available in TB 24.x (I think it was about twice the amount: 10 contacts) and eventually allow end-users to change this limit within the options.

Those may be created as separate bug if needed.

Hope you would take all those input positively.