Email notifs need to include proper placeholder avatars

[ara4n]

i.e. server-side render of initial-on-background color

[t3chguy]

/me watches this issue for use in riot-static also

[MadLittleMods]

Current state of room avatar placeholders in emails:

Room for improvement here:

• Groups and users without avatars get a "placeholder" avatar which is just a coloured circle. This doesn't seem to correspond to the colour of the circle seen in element
• That circle doesn't have the letter like it does in element

-- @DMRobertson, matrix-org/synapse#1546 (comment)

[DMRobertson]

(should this be in synapse rather than element-meta?)

[t3chguy]

The synapse repo has a history of rejecting enhancement requests they do not internally deem beneficial to the repository, which may require more context from the Element Product team to push them through, so they live here until a team picks them up and drives them

(edited to clarify the wording)

[DMRobertson]

Oh I see: the point is that the circle's colour doesn't match that which Element uses. (I thought the complaint was "no text at all")

[DMRobertson]

At the moment these circles are plain <img>s, see https://github.com/matrix-org/synapse/blob/c356b4bf422430cd5769c9bf90756fca2efd8451/synapse/res/templates/room.html#L6-L14

I'm not sure how easy it is to render text atop the images.

A block-display element with border-radius set would be ideal for drawing a circle, but it's not clear how well-supported border-radius is in email clients.