Implementing Inline Mode in Telegram Bots
Inline mode is a feature of sending messages "via bots". When a bot supports the inline mode, a user can access it from any chat to send a message generated by the bot. The inline mode works even in chats where the bot does not participate.
For example, this allows bot users to quickly search for videos or music and instantly send it.
A user starts the inline mode by entering bot username and a space. They may add a text query afterwards if needed; the query can contain up to 256 characters. Then, the menu of results appears. The user clicks on a result to send the message.
A developer can enable inline mode in BotFather, as well as select a placeholder (the default is "Search...")
Group admins may forbid everyone or selected users sending inline messages. In the official Telegram apps, this group member restriction is united with the restriction to send stickers and GIFs.
Result layout
The results may form a grid (which looks well in case of pictures) or a vertical list (which looks good in case of text).
Two layouts may be combined, but apparently this works correctly only in Telegram Desktop (while other official apps show such results in a list.)
Combination screenshot
Inline feedback
Inline feedback is updates arriving when a user chooses an inline result and sends a message. You will not receive them unless you explicitly turn on this setting in BotFather.
Although the purpose of the inline feedback feature is collecting statistics, bot developers sometimes use it to edit messages after they are sent. This comes handy when the bot should load only the selected result rather then all of them. For example, a music search bot may add a song to a sent message and not load all songs during the search.
Here is a trick: a bot may edit a sent inline message only if it contains inline buttons. (Otherwise, the inline feedback update does not include the message ID.)