whitelist mxc:// URLs in img tags in html msgs

[ara4n]

for parity with web so that custom emoji etc work

[anoadragon453]

On ponies.im we have started implementing custom emoji, and yes our iOS users cannot participate.

Web:

iOS:

[manuroe]

One example of such event can be found at
https://riot.im/develop/#/room/#riot-ios:matrix.org/$15365682994513Vtcfe:maunium.net

  "content": {
    "body": "text\n![image](mxc://maunium.net/LVIVUOpCxwnIKabeYaQuXApF)\ntext",
    "msgtype": "m.text",
    "formatted_body": "text<br /><img src=\"mxc://maunium.net/LVIVUOpCxwnIKabeYaQuXApF\" alt=\"image\" /><br />text",
    "format": "org.matrix.custom.html"
  },

[manuroe]

Need some investigations.
Rendering html things is limited in the app. A full support like will require to display a web view in each cell of the table view. This may kill the app performance.

[arychj]

How is this still unresolved after five years? This seems like basic functionality; these are Matrix resources the app should be able to display them.

Web is giving this:

{
  ...
  "content": {
    "body": "test: ",
    "msgtype": "m.text",
    "format": "org.matrix.custom.html",
    "formatted_body": "test: <img src=\"mxc://example.org/jEdZNvMYXbWhYxEWjuEUdidL\"/>"
  },
  ...
}

While iOS is giving this:

{
  ...
  "content" : {
    "body" : "test: ",
    "msgtype" : "m.text",
    "format" : "org.matrix.custom.html",
    "formatted_body" : "test: <img src=\"mxc:\/\/example.org\/jEdZNvMYXbWhYxEWjuEUdidL\"\/>"
  },
  ...
}

We're trying to adopt Matrix as alternative to Slack, but without the ability for our apps to include images in formatted messages we're going to have to look for an alternative solution.