Merge pull request #2422 from deepbluev7/master

MSC2422: Allow color on font tag

proposals/2422-allow-color-attribute-on-font-tag.md

@@ -0,0 +1,39 @@
+# MSC2422: Allow `color` as attribute for `<font>` in messages
+
+Currently the spec recommends that you to use `data-mx-color` instead of the standard
+`color` html attribute for the `<font>` tag. This is probably done to make it
+consistent with `<span>`, where you may not want to allow a generic style tag for.
+
+On the other hand the /rainbow command on almost every client just uses the
+`color` attribute of the `<font>` tag. While some clients support
+`data-mx-color` (i.e. Riot Web), most clients don't. Most clients support
+rendering `color` however.
+
+It would probably be for the best to allow or even prefer `color` on the
+`<font>` tag.
+
+## Proposal
+
+Add the `color` attribute to the allowed attributes of `<font>` in section
+13.2.1.7. No changes to the allowable values from the HTML spec are made here.
+
+## Potential issues
+
+- We now have a redundant attribute in the spec. While it matches what the
+    clients currently do, it may be better to fix each client instead.
+- Clients may not sanitize the color attribute and will let other color values
+    through, increasing compatibility issues again.
+- Clients may never support the data-mx-* attributes now.
+- Old messages could loose their color
+- This proposal doesn't touch span at all, maybe it should?
+
+## Alternatives
+
+- fix the clients  
+  -> This currently seems not feasible. Multiple clients started using color first (i.e. RiotX, Gomuks) and if it isn't spelled out explicitly in the spec, this will probably continue.
+- remove the `data-mx-color` and `data-mx-bg-color` attributes entirely, leaving us just with `color` for `<font>`  
+  -> This would break old messages and can be done independently of this proposal at a later date, if it is deemed useful.
+- Add a section to tell the clients to prefer `color` over `mx-data-color`  
+  -> I don't really know, why mx-data-* was chosen, but I assume there was a reason, so I don't want to change that.
+- Spec an entirely different format for messages (that would probably not make this proposal obsolete)  
+  -> This wouldn't fix the issue, where some client may choose to remove the color tag, since it is discouraged in the spec. Migration would probably also take a while, so this proposal is a quick solution, that doesn't prevent other solutions at a later date.