# Contributing Feedback and contributions are very welcome! Here's help on how to make contributions, divided into the following sections: The quick-read part: * general information, * vulnerability reporting, * documentation. The long-read part: * code changes, * how to check proposed changes before submitting them, * reuse of other libraries, frameworks etc. ## General information For specific proposals, please provide them as [pull requests](https://github.com/quotient-im/libQuotient/pulls) or [issues](https://github.com/quotient-im/libQuotient/issues) For general discussion, feel free to use our Matrix room: [#quotient:matrix.org](https://matrix.to/#/#quotient:matrix.org). If you're new to the project (or FLOSS in general), [issues tagged as easy](https://github.com/quotient-im/libQuotient/labels/easy) are smaller tasks that don't require much knowledge about the project. You are welcome aboard! ### Pull requests and different branches recommended Pull requests are preferred, since they are specific. See the GitHub Help [articles about pull requests](https://help.github.com/articles/using-pull-requests/) to learn how to deal with them. We recommend creating different branches for different (logical) changes, and creating a pull request when you're done into the master branch. See the GitHub documentation on [creating branches](https://help.github.com/articles/creating-and-deleting-branches-within-your-repository/) and [using pull requests](https://help.github.com/articles/using-pull-requests/). ### How we handle proposals We use GitHub to track all changes via its [issue tracker](https://github.com/quotient-im/libQuotient/issues) and [pull requests](https://github.com/quotient-im/libQuotient/pulls). Specific changes are proposed using those mechanisms. Issues are assigned to an individual who works on it and then marks it complete. If there are questions or objections, the conversation area of that issue or pull request is used to resolve it. ### License Unless a contributor explicitly specifies otherwise, we assume contributors to agree that all contributed code is released either under *LGPL v2.1 or later*. This is more than just [LGPL v2.1 libQuotient now uses](./COPYING) because the project plans to switch to LGPL v3 for library code in the near future. Any components proposed for reuse should have a license that permits releasing a derivative work under *LGPL v3 or later* (that includes licenses permitting *LGPL v2.1 or later* but not *LGPL v2.1 only*). In any case, the component should be redistributable under a license from [the list approved by OSI](https://opensource.org/licenses), no exceptions. We use [SPDX](https://spdx.dev) conventions for copyright statements. Please follow them when making a sizable contribution: add your name and year to the top of the file. New files should begin with the following preamble: ```cpp // SPDX-FileCopyrightText: 2021 Your Name // SPDX-License-Identifier: LGPL-2.1-or-later ``` ## Vulnerability reporting (security issues) - see [SECURITY.md](./SECURITY.md) ## Documentation changes Most of the documentation is in Markdown format. All Markdown files use the .md filename extension. Any help on fixing/extending these is more than welcome. Where reasonable, limit yourself to Markdown that will be accepted by different markdown processors (e.g., what is specified by CommonMark or the original Markdown). In practice, as long as libQuotient is hosted at GitHub, [GFM (GitHub-flavoured Markdown)](https://help.github.com/articles/github-flavored-markdown/) is used to show those files in a browser, so it's fine to use its extensions. In particular, you can mark code snippets with the programming language used; blank lines separate paragraphs, newlines inside a paragraph do *not* force a line break. Beware - this is *not* the same markdown algorithm used by GitHub when it renders issue or pull comments; in those cases [newlines in paragraph-like content are considered as real line breaks](https://help.github.com/articles/writing-on-github/); unfortunately this other algorithm is *also* called GitHub-flavoured markdown. (Yes, it'd be better if there were different names for different things.) In your markdown, please don't use tab characters and avoid "bare" URLs. In a hyperlink, the link text and URL should be on the same line. While historically we didn't care about the line length in markdown texts (and more often than not put the whole paragraph into one line), this is subject to change anytime soon, with 80-character limit _recommendation_ (which is softer than the limit for C/C++ code) imposed on everything _except hyperlinks_ (because wrapping hyperlinks breaks the rendering). Do not use trailing two spaces for line breaks, since these cannot be seen and may be silently removed by some tools. If, for whatever reason, a blank line is not an option, use <br /> (an HTML break). ## End of TL;DR If you don't plan/have substantial contributions, you can stop reading here. Further sections are for those who's going to actively hack on the library code. ## Code changes The code should strive to be DRY (don't repeat yourself), clear, and obviously correct (i.e. buildable). Some technical debt is inevitable, just don't bankrupt us with it. Refactoring is welcome. ### Code style and formatting As of Quotient 0.6, the C++ standard for newly written code is C++17, with a few restrictions, notably: * standard library's _deduction guides_ cannot be used to lighten up syntax in template instantiation, i.e. you have to still write `std::array { 1, 2 }` instead of `std::array { 1, 2 }` or use helpers like `std::make_pair` - once we move over to the later Apple toolchain, this will be no more necessary. * enumerators and slots cannot have `[[attributes]]` because moc of Qt 5.9 chokes on them. This will be lifted when we move on to Qt 5.12 for the oldest supported version. * things from `std::filesystem` cannot be used until we push the oldest required g++/libc to version 8. The code style is defined by `.clang-format`, and in general, all C++ files should follow it. Files with minor deviations from the defined style are still accepted in PRs; however, unless explicitly marked with `// clang-format off` and `// clang-format on`, these deviations will be rectified any commit soon after. Additional considerations: * 4-space indents, no tabs, no trailing spaces, no last empty lines. If you spot the code abusing these - thank you for fixing it. * Prefer keeping lines within 80 characters. Slight overflows are ok only if that helps readability. * Please don't make "hypocritical structs" with protected or private members. In general, `struct` is used to denote a plain-old-data structure, rather than data+behaviour. If you need access control or are adding yet another non-trivial (construction, assignment) member function to a `struct`, just make it a `class` instead. * For newly created classes, keep to [the rule of 3/5/0](http://en.cppreference.com/w/cpp/language/rule_of_three) - make sure to read about the rule of zero if you haven't before, it's not what you might think it is. * Qt containers are generally preferred to STL containers; however, there are notable exceptions, and libQuotient already uses them: * `std::array` and `std::deque` have no direct counterparts in Qt. * Because of COW semantics, Qt containers cannot hold uncopyable classes. Classes without a default constructor are a problem too. Examples of that are `SyncRoomData` and `EventsArray<>`. Use STL containers for those but see the next point and also consider if you can supply a reasonable copy/default constructor. * STL containers can be freely used in code internal to a translation unit (i.e., in a certain .cpp file) _as long as that is not exposed in the API_. It's ok to use, e.g., `std::vector` instead of `QVector` to tighten up code where you don't need COW, or when dealing with uncopyable data structures (see the previous point). However, exposing STL containers in the API is not encouraged (except where absolutely necessary, e.g. we use `std::deque` for a timeline). Exposing STL containers or iterators in API intended for usage by QML code (e.g. in `Q_PROPERTY`) is unlikely to work and therefore unlikely to be accepted into `master`. * Prefer using `std::unique_ptr<>` over `QScopedPointer<>` as it gives stronger guarantees. Earlier revisions of this text recommended using `QScopedPointer<>` because Qt Creator's debugger UI had a display helper for it; it now has helpers for both. * Use `QVector` instead of `QList` where possible - see the [great article by Marc Mutz on Qt containers](https://marcmutz.wordpress.com/effective-qt/containers/) for details. ### API conventions Calls, data structures and other symbols not intended for use by clients should _not_ be exposed in (public) .h files, unless they are necessary to declare other public symbols. In particular, this involves private members (functions, typedefs, or variables) in public classes; use pimpl idiom to hide implementation details as much as possible. `_impl` namespace is reserved for definitions that should not be used by clients and are not covered by API guarantees. Note: As of now, all header files of libQuotient are considered public; this may change eventually. ### Comments Whenever you add a new call to the library API that you expect to be used from client code, you must supply a proper doc-comment along with the call. Doxygen style is preferred; but Javadoc is acceptable too. Some parts are not documented at all; adding doc-comments to them is highly encouraged. Use `\brief` for the summary, and follow with details after an empty doc-comment line. For in-code comments, the advice is as follows: * Don't restate what's happening in the code unless it's not really obvious. We assume the readers to have at least some command of C++ and Qt. If your code is not obvious, consider making it clearer itself before commenting. * Both C++ and Qt still come with their arcane features and dark corners, and we don't want to limit anybody who feels they have a case for variable templates, raw literals, or use `std::as_const` to avoid container detachment. Use your experience to figure what might be less well-known to readers and comment such cases (references to web pages, Quotient wiki etc. are very much ok, the previous bullet notwithstanding). * Make sure to document not so much "what" but more "why" certain code is done the way it is. In the worst case, the logic of the code can be reverse-engineered; but you can almost never reverse-engineer the line of reasoning and the pitfalls avoided. ### Automated tests There's no testing framework as of now; either Catch or Qt Test or both will be used eventually. The `tests/` directory contains a command-line program, quotest, used for automated functional testing. Any significant addition to the library API should be accompanied by a respective test in quotest. To add a test you should: - Add a new test to the `TestSuite` class (technically, each test is a private slot and there are two macros, `TEST_DECL()` and `TEST_IMPL()`, that conceal passing the testing handle in `thisTest` variable to the test method). - Add test logic to the slot, using `FINISH_TEST` macro to assert the test outcome and complete the test (`FINISH_TEST` contains `return`). ALL (even failing) branches should conclude with a `FINISH_TEST` (or `FAIL_TEST` that is a shortcut for a failing `FINISH_TEST`) invocation, unless you intend to have a "DID NOT FINISH" message in the logs in certain conditions. The `TestManager` class sets up some basic test fixture to help you with testing; notably, the tests can rely on having an initialised `Room` object for the test room in `targetRoom` member variable. PRs to introduce a proper testing framework are very welcome (make sure to migrate tests from quotest though). Note that tests can go async, which is the biggest hurdle for Qt Test adoption. ### Security, privacy, and performance Pay attention to security, and work *with*, not against, the usual security hardening practices (however few in C++). `char *` and similar unchecked C-style read/write arrays are forbidden - use Qt containers or at the very least `std::array<>` instead. Where you see fit (usually with data structures), try to use smart pointers, especially `std::unique_ptr<>` or `QScopedPointer` instead of bare pointers. When dealing with `QObject`s, use the parent-child ownership semantics exercised by Qt (this is preferred to using smart pointers). If you find a particular use case where the strict semantic of unique pointers doesn't help and a shared pointer is necessary, feel free to step up with the working code and it will be considered for inclusion. Exercise the [principle of least privilege](https://en.wikipedia.org/wiki/Principle_of_least_privilege) where reasonable and appropriate. Prefer less-coupled cohesive code. Protect private information, in particular passwords and email addresses. Absolutely _don't_ spill around this information in logs, and only display those in UI where really needed. Do not forget about local access to data (in particular, be very careful when storing something in temporary files, let alone permanent configuration or state). Avoid mechanisms that could be used for tracking where possible (we do need to verify people are logged in but that's pretty much it), and ensure that third parties can't use interactions for tracking. Matrix protocols evolve towards decoupling the personally identifiable information from user activity entirely - follow this trend. We want the software to have decent performance for users even on weaker machines. At the same time we keep libQuotient single-threaded as much as possible, to keep the code simple. That means being cautious about operation complexity (read about big-O notation if you need a kickstart on the topic). This especially refers to operations on the whole timeline and the list of users - each of these can have tens of thousands of elements so even operations with linear complexity, if heavy enough (with I/O or complex processing), can produce noticeable GUI freezing or stuttering. When you don't see a way to reduce algorithmic complexity, embed occasional `processEvents()` invocations in heavy loops (see `Connection::saveState()` to get the idea). Having said that, there's always a trade-off between various attributes; in particular, readability and maintainability of the code is more important than squeezing every bit out of that clumsy algorithm. Beware of premature optimization and profile the code before before diving into hardcore tweaking that might not give the benefits you think it would. Speaking of profiling logs (see README.md on how to turn them on) - if you expect some code to take considerable (more than 10k "simple operations") time you might want to setup a `QElapsedTimer` and drop the elapsed time into logs under `PROFILER` logging category (see the existing code for examples - `room.cpp` has quite a few). In order to reduce small timespan logging spam, `PROFILER` log lines are usually guarded by a check that the timer counted some considerable time (200 microseconds by default, 20 microseconds for tighter parts). It's possible to override this limit library-wide by passing the new value (in microseconds) in `PROFILER_LOG_USECS` definition to the compiler; I don't think anybody ever used this facility. If you used it, and are reading this text - let me (`@kitsune`) know. ### Generated C++ code for CS API The code in `lib/csapi`, `lib/identity` and `lib/application-service`, although it resides in Git, is actually generated from the official Swagger/OpenAPI definition files. If you're unhappy with something in there and want to improve the code, you have to understand the way these files are produced and setup some additional tooling. The shortest possible procedure resembling the below text can be found in .travis.yml (our CI configuration actually regenerates those files upon every build). As described below, there is also a handy build target for CMake. #### Why generate the code at all? Because otherwise we have to do monkey business of writing boilerplate code, with the same patterns, types etc., literally, for every single API endpoint, and one of libQuotient authors got fed up with it at some point in time. By then about 15 job classes were written; the entire API is about 100 endpoints and counting. Besides, the existing jobs had to be updated according to changes in CS API that have been, and will keep, coming. Other considerations can be found in [this talk about API description languages](https://youtu.be/W5TmRozH-rg) that also briefly touches on GTAD. #### Prerequisites for CS API code generation 1. Get the source code of GTAD and its dependencies, e.g. using the command: `git clone --recursive https://github.com/KitsuneRal/gtad.git` 2. Build GTAD: in the source code directory, do `cmake . && cmake --build .` (you might need to pass `-DCMAKE_PREFIX_PATH=`, similar to libQuotient itself). 3. Get the Matrix CS API definitions that are included in a matrix-doc repo. You can `git clone https://github.com/matrix-org/matrix-doc.git`, the official repo; it's recommended though to instead `git clone https://github.com/quotient-im/matrix-doc.git` - this repo closely follows the official one, with an additional guarantee that you can always generate working Quotient code from its HEAD commit. And of course you can use your own repository if you need to change the API definition. 4. If you plan to submit a PR or just would like the generated code to be properly formatted, you should either ensure you have clang-format (version 6 at least) in your PATH or pass the _absolute_ path to it by adding `-DCLANG_FORMAT=` to the CMake invocation below. #### Generating CS API contents 1. Pass additional configuration to CMake when configuring libQuotient: `-DMATRIX_DOC_PATH= -DGTAD_PATH=`. If everything's right, these two CMake variables will be mentioned in CMake output and will trigger configuration of an additional build target, see the next step. 2. Generate the code: `cmake --build --target update-api`; if you use CMake with GNU Make, you can just do `make update-api` instead. Building this target will create (overwriting without warning) `.h` and `.cpp` files in `lib/csapi`, `lib/identity`, `lib/application-service` for all YAML files it can find in `matrix-doc/api/client-server` and other files in `matrix-doc/api` these depend on. 3. Re-run CMake so that the build system knows about new files, if there are any (this step is unnecessary if you use CMake 3.12 or later). #### Changing generated code See the more detailed description of what GTAD is and how it works in the documentation on GTAD in its source repo. Only parts specific for libQuotient are described here. GTAD uses the following three kinds of sources: 1. OpenAPI files. Each file is treated as a separate source (if you worked with swagger-codegen - you do _not_ need to have a single file for the whole API). 2. A configuration file, in our case it's `gtad/gtad.yaml` - this one is common for all OpenAPI files GTAD is invoked on. 3. Source code template files: `gtad/*.mustache` - are also common. The Mustache files have a templated (not in C++ sense) definition of a network job, deriving from BaseJob; if necessary, data structure definitions used by this job are put before the job class. Bigger Mustache files look a bit hideous for a newcomer; and the only known highlighter that can handle the combination of Mustache (originally a web templating language) and C++ is provided in CLion IDE. Fortunately, all our Mustache files are reasonably concise and well-formatted these days. To simplify things some reusable Mustache blocks are defined in `gtad.yaml` - see its `mustache:` section. Adventurous souls that would like to figure what's going on in these files should speak up in the Quotient room - I (Kitsune) will be very glad to help you out. The types map in `gtad.yaml` is the central switchboard when it comes to matching OpenAPI types with C++ (and Qt) ones. It uses the following type attributes aside from pretty obvious "imports:": * `avoidCopy` - this attribute defines whether a const ref should be used instead of a value. For basic types like int this is obviously unnecessary; but compound types like `QVector` should rather be taken by reference when possible. * `moveOnly` - some types are not copyable at all and must be moved instead (an obvious example is anything "tainted" with a member of type `std::unique_ptr<>`). The template will use `T&&` instead of `T` or `const T&` to pass such types around. * `useOmittable` - wrap types that have no value with "null" semantics (i.e. number types and custom-defined data structures) into a special `Omittable<>` template defined in `converters.h` - a substitute for `std::optional` from C++17 (we're still at C++14 yet). * `omittedValue` - an alternative for `useOmittable`, just provide a value used for an omitted parameter. This is used for bool parameters which normally are considered false if omitted (or they have an explicit default value, passed in the "official" GTAD's `defaultValue` variable). * `initializer` - this is a _partial_ (see GTAD and Mustache documentation for explanations but basically it's a variable that is a Mustache template itself) that specifies how exactly a default value should be passed to the parameter. E.g., the default value for a `QString` parameter is enclosed into `QStringLiteral`. Instead of relying on the event structure definition in the OpenAPI files, `gtad.yaml` uses pointers to libQuotient's event structures: `EventPtr`, `RoomEventPtr` and `StateEventPtr`. Respectively, arrays of events, when encountered in OpenAPI definitions, are converted to `Events`, `RoomEvents` and `StateEvents` containers. When there's no way to figure the type from the definition, an opaque `QJsonObject` is used, leaving the conversion to the library and/or client code. ## How to check proposed changes before submitting them Checking the code on at least one configuration is essential; if you only have a hasty fix that doesn't even compile, better make an issue and put a link to your commit into it (with an explanation what it is about and why). ### Standard checks The following warnings configuration is applied with GCC and Clang when using CMake: `-W -Wall -Wextra -pedantic -Werror=return-type -Wno-unused-parameter -Wno-gnu-zero-variadic-macro-arguments` (the last one is to mute a warning triggered by Qt code for debug logging). We don't turn most of the warnings to errors but please treat them as such. If you use Qt Creator, the following line can be used with the Clang code model: `-Weverything -Werror=return-type -Wno-c++98-compat -Wno-c++98-compat-pedantic -Wno-unused-macros -Wno-newline-eof -Wno-exit-time-destructors -Wno-global-constructors -Wno-gnu-zero-variadic-macro-arguments -Wno-documentation -Wno-missing-prototypes -Wno-shadow-field-in-constructor -Wno-padded -Wno-weak-vtables -Wno-unknown-attributes -Wno-comma -Wno-string-conversion -Wno-return-std-move-in-c++11`. ### Continuous Integration We use CI to check buildability and smoke-testing on Linux (GCC, Clang), MacOS (Clang), and Windows (MSVC). Every PR will go through these, and you'll see the traffic lights from them on the PR page. If your PR fails on any platform double-check that it's not your code causing it - and fix (or ask how to fix if you don't know) if it is. ### clang-format We strongly recommend using clang-format or, even better, use an IDE that supports it. This will lay over a tedious task of following the assumed code style from your shoulders (and fingers) to your computer. ### Other tools Recent versions of Qt Creator and CLion can automatically run your code through clang-tidy. The following list of clang-tidy checks gives a good insight without too many false positives: `-*,bugprone-argument-comment,bugprone-assert-side-effect,bugprone-bool-pointer-implicit-conversion,bugprone-copy-constructor-init,bugprone-dangling-handle,bugprone-fold-init-type,bugprone-forward-declaration-namespace,bugprone-forwarding-reference-overload,bugprone-inaccurate-erase,bugprone-integer-division,bugprone-lambda-function-name,bugprone-macro-*,bugprone-move-forwarding-reference,bugprone-multiple-statement-macro,bugprone-parent-virtual-call,bugprone-signed-char-misuse,bugprone-sizeof-*,bugprone-string-constructor,bugprone-string-integer-assignment,bugprone-suspicious-*,bugprone-terminating-continue,bugprone-undefined-memory-manipulation,bugprone-undelegated-constructor,bugprone-unused-*,bugprone-use-after-move,bugprone-virtual-near-miss,cert-dcl03-c,cert-dcl21-cpp,cert-dcl50-cpp,cert-dcl54-cpp,cert-dcl58-cpp,cert-env33-c,cert-err09-cpp,cert-err34-c,cert-err52-cpp,cert-err60-cpp,cert-err61-cpp,cert-fio38-c,cert-flp30-c,cert-msc30-c,cert-msc50-cpp,cert-oop11-cpp,clang-analyzer-apiModeling.StdCLibraryFunctions,clang-analyzer-core.CallAndMessage,clang-analyzer-core.NullDereference,clang-analyzer-cplusplus.*,clang-analyzer-optin.cplusplus.*,cppcoreguidelines-c-copy-assignment-signature,cppcoreguidelines-non-private-member-variables-in-classes,cppcoreguidelines-pro-type-cstyle-cast,cppcoreguidelines-slicing,hicpp-deprecated-headers,hicpp-invalid-access-moved,hicpp-member-init,hicpp-move-const-arg,hicpp-new-delete-operators,hicpp-static-assert,hicpp-undelegated-constructor,hicpp-use-*,misc-*,-misc-definitions-in-headers,-misc-no-recursion,-misc-non-private-member-variables-in-classes,modernize-loop-convert,modernize-pass-by-value,modernize-return-braced-init-list,modernize-shrink-to-fit,modernize-unary-static-assert,modernize-use-*,-modernize-use-trailing-return-type,performance-*,-performance-no-automatic-move,-performance-noexcept-move-constructor,-performance-unnecessary-*,readability-*,-readability-braces-around-statements,-readability-implicit-bool-conversion,-readability-isolate-declaration,-readability-magic-numbers,-readability-named-parameter,-readability-qualified-auto`. Qt Creator, in addition, knows about clazy, an even deeper Qt-aware static analysis tool that produces some notices about Qt-specific issues that are easy to overlook otherwise, such as possible unintended copying of a Qt container, or unguarded null pointers. You can use this time to time (see Analyze menu in Qt Creator) instead of hogging your machine with deep analysis as you type (or after each saving, depending on your version of Qt Creator). Most of clazy checks are relevant to our code, except: `fully-qualified-moc-types,overloaded-signal,qstring-comparison-to-implicit-char,foreach,non-pod-global-static,qstring-allocations,jni-signatures,qt4-qstring-from-array`. ### Submitting API changes If you changed the API definitions, the path to upstream becomes somewhat intricate, as you have to coordinate with two projects, making up to 4 PRs along the way. The recommended sequence depends on whether or not you have to [write an Matrix Spec Change aka MSC](https://matrix.org/docs/spec/proposals). Usually you have to, unless your API changes keep API semantics intact. In that case: 1. Submit an MSC before submitting changes to the API definition files and libQuotient. 2. The MSC gets reviewed by the Spec Core Team. This can be a lengthy process but it's necessary for the Matrix ecosystem integrity. 3. When your MSC has at least some approvals (not necessarily a complete acceptance but at least some approvals should be there) submit a PR to libQuotient, referring to your `matrix-doc` repo. Make sure that generated files are committed separately from non-generated ones (no need to make two PRs; just separate them in different commits). 4. If your libQuotient PR is approved and MSC is not there yet you'll be asked to submit a PR with API definition files at `https://github.com/quotient-im/matrix-doc`. Note that this is _not_ an official repo; but you can refer to your libQuotient PR as an _implementation_ of the MSC - a necessary step before making a so-called "spec PR". 5. Once MSC is accepted, submit your `matrix-doc` changes as a PR to `https://github.com/matrix-org/matrix-doc` (the "spec PR" mentioned above). This will require that your submission meets the standards set by this project (they are quite reasonable and not too hard to meet). If your changes don't need an MSC, it becomes a more straightforward combination of 2 PRs: one to `https://github.com/matrix-org/matrix-doc` ("spec PR") and one to libQuotient (with the same guidance about putting generated and non-generated files in different commits). ## Git commit messages When writing git commit messages, try to follow the guidelines in [How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/): 1. Separate subject from body with a blank line 2. Be reasonable on the subject line length, because this is what we see in commit logs. Try to fit in 50 characters whenever possible. 3. Capitalize the subject line 4. Do not end the subject line with a period 5. Use the imperative mood in the subject line (*command* form) (we don't always practice this ourselves but let's try). 6. Use the body to explain what and why vs. how (git tracks how it was changed in detail, don't repeat that). Sometimes a quick overview of "how" is acceptable if a commit is huge - but maybe split a commit into smaller ones, to begin with? ## Reuse (libraries, frameworks, etc.) C++ is unfortunately not very coherent about SDK/package management, and we try to keep building the library as easy as possible. Because of that we are very conservative about adding dependencies to libQuotient. That relates to additional Qt components and even more to other libraries. Fortunately, even the Qt components now in use (Qt Core and Network) are very feature-rich and provide plenty of ready-made stuff. Regardless of the above paragraph (and as mentioned earlier in the text), we're now looking at possible options for futures and automated testing, so PRs onboarding those will be considered with much gratitude. Some cases need additional explanation: * Before rolling out your own super-optimised container or algorithm written from scratch, take a good long look through documentation on Qt and C++ standard library. Please try to reuse the existing facilities as much as possible. * You should have a good reason (or better several ones) to add a component from KDE Frameworks. We don't rule this out and there's no prejudice against KDE; it just so happened that KDE Frameworks is one of most obvious reuse candidates but so far none of these components survived as libQuotient deps. So we are cautious. Extra notice to KDE folks: I'll be happy if an addon library on top of libQuotient is made using KDE facilities, and I'm willing to take part in its evolution; but please also respect LXDE people who normally don't have KDE frameworks installed. * Never forget that libQuotient is aimed to be a non-visual library; QtGui in dependencies is only driven by (entirely offscreen) dealing with QImages. While there's a bunch of visual code (in C++ and QML) shared between Quotient-enabled _applications_, this is likely to end up in a separate (Quotient-enabled) library, rather than libQuotient itself. ## Attribution This text is based on CONTRIBUTING.md from CII Best Practices Badge project, which is a collective work of its contributors (many thanks!). The text itself is licensed under CC-BY-4.0.