The git history, but it can be challenging and obscure to outsiders and non-technical people.

With the introduction of this blog made with bashblog, we hope to make all the progress more visible and easier of following :)

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Not talking neither about ImageEncoder nor VideoEncoder this time, but rather about StoreRemoteMedia and Embed.

StoreRemoteMedia fetches remote files when they are Linked in a note. I.e., when the major mimetype isn't text. It usually fetches and attempts to generate a thumb, if there are no encoders, it drops.

Embed attempts to generate a page preview from opengraph and oembed. I.e., acts when the major mimetype is text.

We've changed so much with GNU social v3 that, regarding SRM there was no possible port, just a full rewrite. The code of both plugins became much easier of understanding and compact, while promoting the same functionality with more stability.

It's always important to start with the original code as that allows us to review past decisions and understand all the corner cases.

Sadly, what motivated us to re-design the attachment system was the non-considered corner cases.

Key commits:

• 32ad5dbd74 - [ENTITY] Split Attachment in various new entities
• c381e58d33 - [ENTITY] Refactor RemoteURL entities to Link

The reasoning leading to these entities and structure is detailed in our wiki.

Some relevant observations:

• Link is now part of GNU social Data Representation terms. It represents any remote URL being shared in a note.
• There's only one fixed directory for GSFiles.

Its controller handles upload, update and removal.

Important change from v2: Avatars are now regular attachments.

GNU social now has its documentation available in https://docs.gnusocial.rocks/. It features four different books. It is automatically generated from the source using mdBook.

Only the development book is in an elaborated state, the other books are holding for more ready code.

Two of them are updates from existing documentation:

• The User one is adapted from the existing GNU social documentation for users that was provided in v2.
• The Administrator one is adapted from the "Unofficial GNU social docs" by Thomask who asked us to make it official.

And two of them are new:

• The Developer is both intended to guide third-party plugin developers and to make it easier of contributing to the code.
• The Designer is the most recent of the four and came from a necessity of keeping some standardization between templates and ensuring the same principles are kept in mind when designing new themes.

Together with the documentation we've introduced a wiki. Its purpose is to walk-through decisions, convention, terminology. It's where we document the reasoning the dev team went through before implementing more sophisticated functionalities.

Finally, when the documentation doesn't explain, and to ensure the whole code is properly tested, we have the tests. And the coverage is available here.

File Storage in GNU social is used for avatars, for notes containing attachments, and for notes containing links (in which case is an Embed preview). Notes can be created by local users or fetched from remote actors. Filehash is used to reduce file duplication.

When a user shares a Link that uses OpenGraph tags or has an OEmbed provider, the Embed plugin generates a preview for it that may contain a thumbnail.

When a user shares a Link to an image, the StoreRemoteMedia plugin can fetch the file and make it available as an attachment, and will generate a thumbnail.

When an image, video, or other file type is uploaded or retrieved, an Attachment entity is created. When a thumbnail is requested, one is generated.

There are three relevant plugins for attachment handling:

• ImageEncoder: Allows to compress, validate, rescale, and sanitize images using VIPS.
• VideoEncoder: Allows to compress, validate, rescale, and sanitize videos using FFMpeg.
• FileQuota: Ensures a user stays under the file quota.

How is the code organised?

There are various entities related to attachment, and thumbnail handling. The main ones are:

• Attachment
• AttachmentThumbnail

The plugins are able to act by means of the Events system, as elaborated in the documentation.