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D++ (DPP)
C++ Discord API Bot Library
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D++ (DPP)
C++ Discord API Bot Library
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This page lists the coding style we stick to when maintaining the D++ library. If you are submitting a pull request or other code contribution to the library, you should stick to the styles listed below. If something is not covered here, ask on the official Discord server!
All class, variable/member, function and method names should use snake_case, similar to the style of the C++ standard library.
Enums and their values should be snake_case as with class, function and method names. You do not need to use enum class, so make sure that enum values are prefixed with a prefix to make them unique and grouped within the IDE, e.g. ll_debug, ll_trace, etc.
This covers your standard Curly Braces (commonly known as squiggly brackets), and lists.
Curly Braces should be on the same line as the keyword, for example:
This applies to functions, while statements, if statements, lambdas, nearly anything that uses curly braces with statements!
Lists should have a space after the comma in parameter lists, and after opening brackets and before closing brackets except when calling a function, for example:
When using the dot notation repeatedly (For example, creating an embed.), you should start each .function() on a new line, as such:
Indentation should always be tab characters. It is up to you how wide you set tab characters in your editor for your personal tastes. All code blocks delimited within curly braces should be indented neatly and uniformly.
Constants and macros should be all UPPERCASE with SNAKE_CASE to separate words. Macros should not have any unexpected side effects.
All comments should be in doxygen format (similar to javadoc). Please see existing class definitions for an example. You should use doxygen style comments in a class definition inside a header file, and can use any other comment types within the .cpp file. Be liberal with comments, especially if your code makes any assumptions!
To prevent typos, a GitHub-Action checks the documentation. If it fails for a word that was falsely flagged, you can add them to .cspell.json.
If you export a class which is to be accessible to users, be sure to prefix it with the DPP_EXPORT macro, for example:
The DPP_EXPORT macro ensures that on certain platforms (notably Windows) the symbol is exported to be available to the library user.
It is a design philosophy of D++ that everything possible in a class should be public, unless the user really does not need it (you should consider justifying in comments why) or user adjustment of the variable could badly break the functioning of the library. Avoid the use of accessors for setting/getting values in a class, except for bit fields, where you should provide accessors for setting and getting individual bits (for example, see user.h), or in the event you want to provide a "fluent" interface. The exception to this is where you want to provide a logic validation of a field, for example if you have a string field with a minimum and maximum length, you can provide a setter the user can optionally use which will validate their input.
All exceptions thrown should derive from dpp::exception (see dpp/exception.h) - when validating string lengths, a string which is too long should be truncated using dpp::utility::utf8substr and any strings that are too short should throw a dpp::length_exception.
Keep levels of inheritance low. If you need to inherit more than 3 levels deep, it is probable that the design could be simplified. Remember that at scale, there can be tens of millions of certain classes and each level of virtual nesting adds to the vtable of that object's instance in RAM.
Where Discord provides boolean flags, if the user is expected to store many of the objects in RAM, or in cache, you should pack all these booleans into bit fields (see user.h and channel.h for examples). In the event that the object is transient, such as an interaction or a message, packing the data into bit fields is counter intuitive. Remember that you should provide specific accessors for bit field values!
Where you are making use of an external dependency such as opus or libssl, do not place references to the types/structs, or the header files of these external libraries within the header files of D++. Doing so adds that library as a public dependency to the project (which is bad!). Instead make an opaque class, and/or forward-declare the structs (for examples see sslclient.h and discordvoiceclient.h).
Where Discord provides a name in PascalCase we should stick as closely to that name as possible but convert it to snake_case. For example, GuildMember would become guild_member.
Do not introduce platform specific (e.g. Windows only) code or libc functions. If you really must use these functions safely wrap them e.g. in #ifdef _WIN32 and provide a cross-platform alternative so that it works for everyone.
The code must work with the C++17 standard, unless, for an optional feature that can be enabled and that uses a more recent standard (e.g. Coroutines).
If a value will only hold values up to 255, use uint8_t. If a value cannot hold over 65536, use uint16_t. These types can help use a lot less RAM at scale.
Where possible, if you are adding methods to a class you should consider fluent design. Fluent design is the use of class methods that return a reference to self (via return *this), so that you can chain object method calls together (in the way dpp::message and dpp::embed do). For example:
This would allow the user to do this:
All types for the library should be within the dpp namespace. There are a couple of additional namespaces, e.g. dpp::utility for static standalone helper functions and helper classes, and dpp::events for internal websocket event handlers.
All pull requests ("PRs") should be submitted against the dev branch in GitHub.
It’s good to have descriptive commit messages, or PR titles so that other contributors can understand about your commit or the PR Created. Commits must be prefixed with a type, which consists of a noun, feat, fix, etc., followed by a colon and a space. Other commit types can be breaking, docs, refactor, deprecate, perf, test, chore, and misc. Read conventional commits for more information on how we like to format commit messages.
All PRs must pass the GitHub Actions tests before being allowed to be merged. This is to ensure that no code committed into the project fails to compile on any of our officially supported platforms or architectures.
All code contributed to D++ must be submitted under agreement of the Linux Foundation Developer Certificate of Origin. This is a simple agreement which protects you and us from any potential legal issues: