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@ -73,11 +73,12 @@ the tag.
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| Tag | Permitted Attributes |
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|--------|--------------------------------------------------------------------------------------------------------------------------------------------|
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| `span` | `data-mx-bg-color`, `data-mx-color`, `data-mx-spoiler` (see [spoiler messages](#spoiler-messages)) |
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| `span` | `data-mx-bg-color`, `data-mx-color`, `data-mx-spoiler` (see [spoiler messages](#spoiler-messages)), `data-mx-maths` (see [mathematical messages](#mathematical-messages)) |
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| `a` | `name`, `target`, `href` (provided the value is not relative and has a scheme matching one of: `https`, `http`, `ftp`, `mailto`, `magnet`) |
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| `img` | `width`, `height`, `alt`, `title`, `src` (provided it is a [Matrix Content (`mxc://`) URI](#matrix-content-mxc-uris)) |
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| `ol` | `start` |
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| `code` | `class` (only classes which start with `language-` for syntax highlighting) |
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| `div` | `data-mx-maths` (see [mathematical messages](#mathematical-messages)) |
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Additionally, web clients should ensure that *all* `a` tags get a
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`rel="noopener"` to prevent the target page from referencing the
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@ -385,6 +386,64 @@ An example of a media message with a caption is:
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Clients MUST render the caption alongside the media and SHOULD prefer its
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formatted representation.
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##### Mathematical messages
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{{% added-in v="1.11" %}}
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Users might want to send mathematical notations in their messages.
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To send mathematical notations clients MUST use the `formatted_body` and
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therefore the `org.matrix.custom.html` format, described above. This makes
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mathematical notations valid on any `msgtype` which can support this format
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appropriately.
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Mathematical notations themselves use the `span` or `div` tags, depending
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whether the notation should be presented inline or not. The mathematical
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notation is written in [LaTeX](https://www.latex-project.org/) format using the
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`data-mx-maths` attribute.
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The contents of the tag should be a fallback representation for clients that
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cannot render the LaTeX format. The fallback representation could be, for
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example, an image, or an HTML approximation, or the raw LaTeX source. When using
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an image as a fallback, the sending client should be aware of issues that may
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arise from the receiving client using a different background colour. The `body`
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should include a textual representation of the notation.
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An example of a mathematical notation is:
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```json
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{
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"msgtype": "m.text",
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"format": "org.matrix.custom.html",
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"body": "This is an equation: sin(x)=a/b.",
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"formatted_body": "This is an equation:
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<span data-mx-maths=\"\\sin(x)=\\frac{a}{b}\">
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sin(<i>x</i>)=<sup><i>a</i></sup>/<sub><i>b</i></sub>
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</span>"
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}
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```
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The LaTeX format is poorly defined and has several extensions, so if a client
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encounters syntax that it cannot render, it SHOULD present the fallback
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representation instead. Clients SHOULD, however, aim to support, at minimum, the
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basic [LaTeX2e](https://www.latex-project.org/) maths commands and the
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[TeX](https://tug.org/) maths commands, with the possible exception of commands
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that could be security risks.
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{{% boxes/warning %}}
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In general, LaTeX places a heavy burden on client authors to ensure that it is
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processed safely. Certain commands, such as [those that can create macros](https://katex.org/docs/supported#macros),
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are potentially dangerous. Clients should either decline to process those
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commands, or should take care to ensure that they are handled in safe ways (such
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as by limiting recursion). In general, LaTeX commands should be filtered by
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allowing known-good commands rather than forbidding known-bad commands.
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Therefore, clients should not render mathematics by calling a LaTeX compiler
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without proper sandboxing, as those executables were not written to handle
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untrusted input. Some LaTeX rendering libraries are better suited for that by
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allowing only a subset of LaTeX and enforcing recursion limits.
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{{% /boxes/warning %}}
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#### Server behaviour
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Homeservers SHOULD reject `m.room.message` events which don't have a
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Kévin Commaille
4 weeks ago
committed by