matrix-spec-proposals/content/client-server-api/modules/stickers.md

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Sticker Messages

This module allows users to send sticker messages in to rooms or direct messaging sessions.

Sticker messages are specialised image messages that are displayed without controls (e.g. no "download" link, or light-box view on click, as would be displayed for for m.image events).

Sticker messages are intended to provide simple "reaction" events in the message timeline. The matrix client should provide some mechanism to display the sticker "body" e.g. as a tooltip on hover, or in a modal when the sticker image is clicked.

Events

Sticker events are received as a single m.sticker event in the timeline section of a room, in a /sync.

{{% event event="m.sticker" %}}

Client behaviour

Clients supporting this message type should display the image content from the event URL directly in the timeline.

A thumbnail image should be provided in the info object. This is largely intended as a fallback for clients that do not fully support the m.sticker event type. In most cases it is fine to set the thumbnail URL to the same URL as the main event content.

It is recommended that sticker image content should be 512x512 pixels in size or smaller. The dimensions of the image file should be twice the intended display size specified in the info object in order to assist rendering sharp images on higher DPI screens.