Note that you don't need to know all of the `CONTRIBUTING.md` – it is there to
help you with things as you go, and make things easier, not harder.

Skim through it, and when you will be doing something that relevant section
will apply to, just go back to it and read in more detail about what is the
best course of action. You don't even need to memorize the section – after all,
it still will be there next time you might need it. `:-)`


# Filing an issue

### Must read
* If you aren't sure, you can ask on the
  [**IRC channel**](https://webchat.freenode.net/?channels=qtox) or read our
  [**wiki**](https://github.com/qTox/qTox/wiki) first.
* Do a quick **search**. Others might have already reported the issue.
* Write in **English**!
* Provide **version** information (you can find version numbers in menu
  `Settings → About`):
```
OS: 
qTox version: 
Commit hash: 
toxcore: 
Qt: 
```
* Provide **steps** to reproduce the problem, it will be easier to pinpoint the
  fault.
* **Screenshots**! A screenshot is worth a thousand words. Just upload it.
  [(How?)](https://help.github.com/articles/file-attachments-on-issues-and-pull-requests)

### Good to know
* **Patience**. The dev team is small and resource limited. Devs have to find
  time, analyze the problem and fix the issue, it all takes time. :clock3:
* If you can code, why not become a **contributor** by fixing the issue and
  opening a pull request? :wink:
* Harsh words or threats won't help your situation. What's worse, your complaint
  will (very likely) be **ignored**. :fearful:


# How to start contributing
## Before you start…

Before you start contributing, first decide for a specific topic you want to
work on. Pull requests, which are spanning multiple topics (e.g. "general qTox
code cleanup") or introduce fundamental architectural changes are rare and
require additional attention and maintenance. Please also read the following
simple rules we need to keep qTox a "smooth experience" for everybody involved.

## Must read:
* Use [**commit message format**](#commit-message-format).
* Read our [**coding guidelines**](#coding-guidelines).
* Keep the title **short** and provide a **clear** description about what your
  pull request does.
* Provide **screenshots** for UI related changes.
* Keep your git commit history **clean** and **precise** by continuously
  rebasing/amending your PR. Commits like `xxx fixup` are not needed and
  rejected during review.
* Commit message should state not only what has been changed, but also why a
  change is needed.
* If your commit fixes a reported issue (for example #4134), add the following
  message to the commit `Fixes #4134.`.  [Here is an
  example](https://github.com/qTox/qTox/commit/87160526d5bafcee7869d6741a06045e13d731d5).


## Pull request

*PR = Pull request*

Ideally for simple PRs (most of them):

* One topic per PR
* One commit per PR
* If you have several commits on different topics, close the PR and create one
  PR per topic
* If you still have several commits, squash them into only one commit
* Amend commit after making changes (`git commit --amend path/to/file`)
* Rebase your PR branch on top of upstream `master` before submitting the PR

For complex PRs (big refactoring, etc):

* Squash only the commits with uninteresting changes like typos, docs
  improvements, etc… and keep the important and isolated steps in different
  commits.

It's important to keep amount of changes in the PR small, since smaller PRs are
easier to review and merging them is quicker. PR diff shouldn't exceed `300`
changed lines, unless it has to.

## How to open a pull request
1. Fork the qTox repository on Github to your existing account.
2. Open a Terminal and do the following steps:
```bash
# Go to a directory of your choice, where the qTox directory will be created:
cd /to/the/directory

# Clone the forked repo:
git clone git@github.com:<YOUR_USER>/qTox.git

# Add the "upstream" remote to be able to fetch from the qTox upstream repository:
git remote add upstream https://github.com/qTox/qTox.git

# Point the local "master" branch to the "upstream" repository
git branch master --set-upstream-to=upstream/master
```

You're now all set to create your first pull request! Hooray! :)

Still in Terminal, do the following steps to actually create the pull request:

```bash
# Fetch from the "upstream" repository:
git fetch upstream master:master

# Checkout a local branch on up-to-date "master" and give it a sane name, e.g.:
git checkout -b feat/brandnew-feature master
```

Now do your changes and commit them by your heart's desire. When you think
you're ready to push for the first time, do the following:

```bash
# Push to the new upstream branch and link it for synchronization
git push -u origin feat/brandnew-feature

# From now on, you can simply…
git push
# ...to your brand new pull request.
```

That's it! Happy contributing!

## How to deal with large amounts of merge conflicts

Usually you want to avoid conflicts and they should be rare. If conflicts
appear anyway, they are usually easy enough to solve quickly and safely.
However, if you find yourself in a situation with large amounts of merge
conflicts, this is an indication that you're doing something wrong and you
should change your strategy. Still… you probably don't want to throw away and
lose all your valuable work. So don't worry, there's a way to get out of that
mess. The basic idea is to divide the conflicts into smaller – easier to solve
– chunks and probably several (topic) branches. Here's a little "Rule of Thumb"
list to get out of it:

1. Split your commit history into topic related chunks (by
   rebasing/cherry-picking "good" commits).
2. Split "API" and "UI" (widget related) changes into separate commits.
3. Probably split PR into several smaller ones.

In addition it helps to regularly keep rebasing on the upstream repository's
recent master branch. If you don't have the upstream remote in your repo, add
it as described in [How to open a pull request](#how-to-open-a-pull-request).

~~~bash
# If not on PR branch, check it out:
git checkout my/pr-branch

# Now fetch master ALWAYS from upstream repo
git fetch upstream master:master

# Last, rebase PR branch onto master…
git rebase -i master

# …and, if everything's clear, force push to YOUR repo (your "origin" Git remote)
git push -f
~~~

## Good to know
* **Search** the pull request history! Others might have already implemented
  your idea and it could be waiting to be merged (or have been rejected
  already). Save your precious time by doing a search first.
* When resolving merge conflicts, do `git rebase <target_branch_name>`, don't
  do `git pull`. Then you can start fixing the conflicts.  [Here is a good
  explanation](https://www.atlassian.com/git/tutorials/merging-vs-rebasing).


## <a name="commit"></a> Git Commit Guidelines

We have very precise rules over how our git commit messages can be formatted.
This leads to **more readable messages** that are easy to follow when looking
through the **project history**.  But also, we use the git commit messages to
**generate the qTox change log** using
[clog-cli](https://github.com/clog-tool/clog-cli).


### Commit Message Format
Each commit message consists of a **header** and a **body**.  The header has a
special format that includes a **type**, a **scope** and a **subject**:

```
<type>(<scope>): <subject>
<BLANK LINE>
<body>
```

The **header** is mandatory and the **body** is optional. The **scope** of the
header is also optional.

### Header

The header must be a short (72 characters or less) summary of the changes made.

#### Type

Must be one of the following:

* **feat**: A new feature
* **fix**: A bug fix
* **docs**: Documentation only changes
* **style**: Changes that do not affect the meaning of the code (white-space,
  formatting, etc), but change the style to a more appropriate one
* **refactor**: A code change that only improves code readability and reduces
  complexity, without changing any functionality
* **perf**: A code change that improves performance
* **revert**: Reverts a previous commit
* **test**: Adding missing tests
* **chore**: Changes to the build process or auxiliary tools and libraries such
  as documentation generation

##### Revert

If the commit reverts a previous commit, it should begin with `revert: `,
followed by the header of the reverted commit. In the body it should say:
`Revert commit <hash>.`, where the hash is the SHA of the commit being
reverted.

#### Scope

The scope could be anything specifying place of the commit change. Note that
"place" doesn't necessarily mean location in source code.

For example:

* `audio` – change affects audio
* `video` – change affects video
* `settings` – change affects qTox settings
* `chatform`
* `tray` – change affects tray icon
* `l10n` – translation update
* `i18n` – something has been made translatable
* `build` – change affects build system / scripts, e.g. `qtox.pro`,
  `simple_make.sh`, etc.
* `travis` – change affects Travis CI
* `CONTRIBUTING` – change to the contributing guidelines

Since people were abusing length of the scope, it's limited to 12 characters.
If you're running into the limit, you're doing it wrong.

#### Subject

The subject contains succinct description of the change:

* use the imperative, present tense: "change" not "changed" nor "changes"
* don't capitalize first letter
* no dot (.) at the end

A properly formed git commit subject line should always be able to complete the
following sentence:

> If applied, this commit will ___your subject line here___

### Body

Wrap the body at 72 characters whenever possible (for example, don't modify
long links to follow this rule). Just as in the **subject**, use the
imperative, present tense: "change" not "changed" nor "changes". The body
should include the motivation for the change and contrast this with previous
behavior.

The body contains (in order of appearance):

* A detailed **description** of the committed changes.
* References to GitHub issues that the commit **closes** (e.g., `Closes #000`
  or `Fixes #000`).
* Any **breaking changes**.

Include every section of the body that is relevant for your commit.

**Breaking changes** should start with the phrase `BREAKING CHANGE:` with a
space or two newlines. The rest of the commit message is then used for this.


## Reviews

Currently `reviewable.io` is being used to review changes that land in qTox.

How to review:

1. Click on the `Reviewable` button in [pull request].
2. Once Reviewable opens, comment on the lines that need changes.
3. Mark as reviewed only those files that don't require any changes – this
   makes it easier to see which files need to be changed & reviewed again once
   change is made.
4. If pull request is good to be merged, press `LGTM` button in Reviewable.
5. Once you're done with evaluating PR, press `Publish` to make comments
   visible on GitHub.

When responding to review:

1. Click on the `Reviewable` button in [pull request].
2. Once you push changes to the pull request, make drafts of responses to the
   change requests.
   - if you're just informing that you've made a requested change, use
     `Reviewable`'s provided `Done` button.
   - if you want discuss the change, write a response draft.
3. When discussion points are addressed, press `Publish` button to make
   response visible on GitHub.

Note:

* when no one is assigned to the PR, *anyone* can review it
* when there are assigned people, only they can mark review as passed

### Testing PRs

The easiest way is to use [`test-pr.sh`] script to get PR merged on top of
current `master`.  E.g. to get pull request `#1234`:

```bash
./test-pr.sh 1234
```

That should create branches named `1234` and `test1234`. `test1234` is what you
would want to test.  If script fails to merge branch because of conflicts, fret
not, it doesn't need testing until PR author fixes merge conflicts.  You might
want to leave a comment on the PR saying that it needs a rebase :smile:

As for testing itself, there's a nice entry on the wiki:
https://github.com/qTox/qTox/wiki/Testing


## Git config

*Not a requirement, just a friendly tip. :wink:*

It's nice when commits are being GPG-signed.  Github has a few articles about
configuring & signing.

https://help.github.com/articles/signing-commits-using-gpg/

And *tl;dr* version:

```
gpg --gen-key
gpg --send-keys <your generated key ID>
git config --global commit.gpgsign true
```


# Coding Guidelines

Use `C++11`.

## Includes

On the project level, include files starting with the module name, e.g. 
`core/core.h` from `widget/widget.cpp`:

```C++
#include "core/core.h"
```

Do **not** use `<>` tags to include files on the project level, e.g.
`core/core.h` from `widget/widget.cpp`:

```C++
#include <core.h>    // WRONG
```

If including files from the operating system, external libraries, frameworks
or Qt classes use `<>` tags, e.g. `cstdio` and `QString` from `src/main.cpp`:

```C++
#include <cstdio>
#include <QString>
```

## Coding style

```C++
function()
{
    1st_line;
    2nd_line;
}

// if / while / for / switch
// always use curly brackets
if () // ← note the space between `if` and parenthesis
{
    1_line_curly;
}
else if ()
{
    just_one_line;
}
else
{
    each_condition_in_curly;
}

QObject* asterisksGoWithTheType;
uint8_t* array = new uint8_t[count];

// camelCase for variables, CamelCase for classes
QObject notToMentionThatWeUseCamelCase;
```


## Dynamic casts / RTTI

qTox is compiled without support for RTTI, as such PRs making use of
`dynamic_cast()` will fail to compile and may be rejected on this basis. For
manipulating Qt-based objects, use `qobject_cast()` instead.

Compiling qTox without RTTI support gives up to 5-6% size reductions on
compiled binary files. The usage of `dynamic_cast()` can also be completely
mitigated when dealing with Qt objects through use of `qobject_cast()` which
behaves very much like C++'s `dynamic_cast()` but without the RTTI overhead.

Enforced with `-fno-rtti`.

## Documentation

If you added a new function, also add a doxygen comment before the
implementation. If you changed an old function, make sure the doxygen comment
is still correct. If it doesn't exist add it.

Don't put docs in .h files, if there is a corresponding .cpp file.

### Documentation style

```C++
/*...license info...*/
#include "blabla.h"

/**
 * @brief I can be briefly described as well!
 *
 * And here goes my longer descrption!
 *
 * @param x Description for the first parameter
 * @param y Description for the second paramater
 * @return An amazing result
 */
static int example(int x, int y)
{
    // Function implementation...
}

/**
 * @class OurClass
 * @brief Exists for some reason...!?
 * 
 * Longer description
 */

/**
 * @enum OurClass::OurEnum
 * @brief The brief description line.
 * 
 * @var EnumValue1
 * means something
 * 
 * @var EnumValue2
 * means something else
 * 
 * Optional long description
 */

/**
 * @fn OurClass::somethingHappened(const QString &happened)
 * @param[in] happened    tells what has happened...
 * @brief This signal is emitted when something has happened in the class.
 * 
 * Here's an optional longer description of what the signal additionally does.
 */
```

## No translatable HTML tags

Do not put HTML in UI files, or inside `tr()`. Instead, you can put put it in
C++ code in the following way, to make only user-facing text translatable:
```C++
someWidget->setTooltip(
    QStringLiteral("<html><!-- some HTML text -->") + tr("Translatable text…") +
    QStringLiteral("</html>");
```

## Limitations

### Filesystem

Windows' unbeaten beauty and clarity:

https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx

Symbols that should be forbidden for filenames under Windows:

`<` `>` `:` `"` `/` `\` `|` `?` `*`


[pull request]: https://github.com/qTox/qTox/pulls
[`test-pr.sh`]: /test-pr.sh