<br><br>

<div style="width: 100%;">
<img src="./logo/raster.png" width="128px" style="display: block; margin-left: auto; margin-right: auto;"/>
<h1 style="text-align: center; top:-1em;">fennec</h1>
<div style="text-align: center; top:-4em;">a free and open source game engine</div>
</div>

<br><br>

<a id="table-of-contents"></a>
<h2>Table of Contents</h2>

  * [Table of Contents](#table-of-contents)
  * [Introduction](#introduction)
    * [Coding Standards](#coding-standards)
  * [Building from Source](#building-from-source)
    * [Building from Terminal](#building-from-terminal)
      * [Git](#git) &rarr; `git`
      * [Debian](#debian) &rarr; `apt`
      * [Arch](#arch) &rarr; `pacman`
      * [Fedora](#fedora) &rarr; `dnf`
    * [Building on Windows](#building-on-windows)
  * [Running the Test Suite](#running-the-test-suite)
  * [Usage](#usage)
    * [Licensing](#licensing)
  * [Contribution](#contribution)


<br>
<br>


<a id="introduction"></a>
## Introduction

&ensp; fennec is designed to be a general purpose, educational game engine. fennec
may be used through the provided editor application, or as a standalone library to 
link against your application.



<br>

<a id="coding-standards"></a>
### Coding Standards

Interfacing with the API in C++ follows the [GNU Coding Standards](https://www.gnu.org/prep/standards/html_node/index.html).
Some main areas where the engine strays from the GNU standard includes the following:

* [Section 4.7, Standards for Graphical Interfaces](https://www.gnu.org/prep/standards/html_node/Graphical-Interfaces.html).
  fennec provides an implementation for X11, however it does not use the GTK toolkit.
- [Section 5.1, Formatting Your Source Code](https://www.gnu.org/prep/standards/html_node/index.html).
  fennec uses Allman (BSD) for namespaces, otherwise K&R.
* [Section 6.1, GNU Manuals](https://www.gnu.org/prep/standards/html_node/GNU-Manuals.html)
  fennec does not use Texinfo and instead uses Doxygen. Otherwise, it follows the other standards of this section.
- [Section 7, The Release Process](https://www.gnu.org/prep/standards/html_node/Managing-Releases.html)
  fennec follows most of the conventions in this section, however the build system used is CMake and not
  Makefile. CMake, although overwhelming at first, is much more friendly to those who are learning build systems for the first time.

<br>

fennec Standards:

 * As per the GNU standard, macros should be `SCREAMING_SNAKE_CASE`. Additionally, Macros should be preceded by
   `<APP_NAME>_`. Macros that wrap C-Style functions may use normal `snake_case`.

 - Header Guards should be implemented using `#ifndef`, `#define`, and `#endif` for portability.
   The naming convention for Header Guards is as follows: `<APP_NAME>_<DIRECTORY_PATH>_<FILE_NAME>_H`,
   e.g. the engine file `fennec/lang/utility.h` has the Header Guard `FENNEC_LANG_UTILITY_H`.

 * Helper Functions, in the case of classes, should be private.
   In the case of global functions, helpers should be placed in a similarly named file in a subdirectory and namespace
   called `detail`. Helper functions should be documented with C-Style comments, however it is not necessary to provide
   Doxygen documentation.

 - **DO NOT USE C++ EXCEPTIONS** they will not be supported because they are shit.<sup>[[1]](#f1)</sup>

 * Most behaviours should be type independent. Specifically interactions with the core systems of the engine.

 - Classes should have banners between each distinct group of definitions, with the access specifier on the following 
   line. E.G.
   ```c++
   class foo {
   // Definitions ============================
   public:
       using bar = int;
       
   // Constructors & Destructor ==============
   public:
       foo();
       ~foo();
   };
   ```
   This helps significantly with readability, and it also serves to reduce bugs related to mistakes involving access
   specifiers. E.G. in the example above, bar is changed to private, the constructors are still labeled public in the
   case the person forgets to update the succeeding access specifiers.

<br><br>

<a id="f1"></a>
<sup>[[1]](#f1)</sup> If we were to use the exception paradigm for all erroneous behaviour, we couldn't guarantee
               that the state will not be corrupted when an exception is thrown. The behaviour afterward is undefined
               because of this, and we also don't really know when, how, or where that exception will be handled.
               The assertion paradigm is better at handling this because you are defining erroneous behaviour in the
               code and how it is handled. In a debug build we can immediately halt the program, we don't care about
               the state afterward, only beforehand. Now for a release build, this is first and foremost a game engine,
               so we want to crash as gracefully as possible, prevent data loss, and get some debug information for it.
               fennec defines its own `assert` macro to be used, defining a hook in the private version of the
               function. This hook is used to clean up any state information within the engine and may be used to send
               immediate events to listeners so that outside functionality may decide how to handle the impending crash.
               In Debug Mode there is nothing that can be done to stop the crash, as soon as the branch finishes,
               `abort()` will be called.


<br>

The C++ stdlib is reimplemented in the fennec engine. 
There are a few reasons for this:

 1. Standardize implementations across compilers
 2. Set proper naming conventions, i.e. `std::vector` &rarr; `fennec::dynarray`
 3. Optimize compilation times, binary size, and performance.
 4. Inject debugging information when necessary.
 5. Expose functionality in a readable manner for those interested in learning the
    intricacies of the implementation.

<br>


<a id="building-from-source"></a>
## Building from Source

&ensp; fennec uses the CMake build manager. The CMake build script provides several
targets for building parts of the engine.

&ensp; Using an IDE will streamline the build process for you and add additional configuration
options. Eclipse, Visual Studio, and CLion provide built-in support for CMake. VSCode
is also a viable IDE but involves some extra setup.

| Target                 | Description                                                                            |
|------------------------|----------------------------------------------------------------------------------------|
| fennec                 | The main engine target.                                                                |
| fennec-metaprogramming | Generate metaprogramming info for the fennec library. A dependency of the main engine. |
| fennecdocs             | Generate html documentation for the engine. Requires Doxygen.                          |
| fennecdocs-clean       | Cleans the generated html documentation files.                                         |
| fennec-test            | Test suite for verifying engine functionality.                                         |

<br>

<a id="dependencies"></a>
### Dependencies

| Dependency                   | Notes                                                                                                    |
|------------------------------|----------------------------------------------------------------------------------------------------------|
| C/C++ Compiler               | GCC/G++ is the compiler that fennec is designed around, however, Clang, MSVC, and MinGW may also be used |
| CMake                        | The build manager used by the engine                                                                     |
| A build system               | Any build system will work, however, `build.sh` uses Ninja by default.                                   |
| A memory debugger            | Any memory debugger will work, however, `test.sh` uses Valgrind by default.                              |
| Doxygen<sup>[*](#opt)</sup>  | Doxygen is required for building the documentation for fennec.                                           |
| Graphviz<sup>[*](#opt)</sup> | Graphviz is a required dependency for Doxygen                                                            |


<a id="opt"></a>
<sup>[*](#opt)</sup> Optional Dependency

<br>

<a id="building-from-terminal"></a>
### Building from Terminal

`build.sh` provides profiles for building the main engine. Run `./build.sh --help`
for more info.

&ensp; By default, the CMake generator used is Ninja, which requires Ninja to be installed. You can modify the
build scripts to use another build manager, see the [CMake documentation for available generators](https://cmake.org/cmake/help/latest/manual/cmake-generators.7.html).

&ensp; I will at no point provide official cross-compilation toolchains for fennec. However, I will provide tools for
using specific toolchains for specific platforms that necessitate this. The primary examples would be Android and iOS.
If you wish to build for Windows *and* Linux, your options are WSL or Dual Boot. I recommend Dual Boot over WSL.

<a id="git"></a>
#### Git

Install git dependencies with the following command:
```shell
git submodule update --force --init --recursive --remote
```

<a id="debian"></a>
#### Debian

On Debian-based distributions, you can install dependencies using the following command:
```shell
sudo apt install build-essential cmake ninja-build valgrind libvulkan-volk-dev vulkan-validationlayers
```

for Doxygen run:
```shell
sudo apt install doxygen graphviz
```

<a id="arch"></a>
#### Arch

On Arch-based distributions, you can install dependencies using the following command:
```shell
sudo pacman -S base-devel cmake ninja valgrind vulkan-devel
```

for Doxygen run:
```shell
sudo pacman -S doxygen graphviz
```

<a id="fedora"></a>
#### Fedora

On Fedora-based distributions, you can install dependencies using the following command:
```shell
sudo dnf install build-essential g++ cmake ninja-build valgrind vulkan-volk-devel vulkan-validation-layers
```

for Doxygen run:
```shell
sudo dnf install doxygen graphviz
```

<br>

<a id="building-on-windows"></a>
### Building on Windows

&ensp; The bash script can be run natively on Windows when WSL is enabled. You do not need to run the
script in WSL, simply use the "bash" command in Command Prompt or PowerShell.  The script will require
the build [dependencies](#dependencies) installed and configured to be available on the `PATH` environment variable.

For more details, [see this blog post](https://blogs.windows.com/windows-insider/2016/04/06/announcing-windows-10-insider-preview-build-14316/) for Windows Build 14316.

Otherwise, follow the sequence of commands provided in the bash script.

```console
mkdir -p build/<profile>
cd ./build/<profile>
cmake -G Ninja -DCMAKE_BUILD_TYPE=<profile> -S ../.. -B .
cmake --build . --target fennec
```

The value of `<profile>` may be one of the following:

| Profile        | Description                                                                      |
|----------------|----------------------------------------------------------------------------------|
| Debug          | Build in debug mode, provides full debugging information to use with a debugger. |
| Release        | Build in release mode, provides full optimizations, eliminating debug info.      |
| RelWithDebInfo | Build in release mode with extra debug info, provides partial optimizations.     |
| MinSizeRel     | Build in release mode but optimizing for minimum binary size.                    |


<br>

&ensp; If you would like to use Visual Studio without CMake, you can use the build script to generate
a Visual Studio project for the source. For a list of available Visual Studio generators, [see this section](https://cmake.org/cmake/help/latest/manual/cmake-generators.7.html)
of the CMake docs. Running the following command will generate the Visual Studio project.

```commandline
cmake -G "Visual Studio 17 2022" -A x64
```

<br>
<br>

<a id="running-the-test-suite"></a>
## Running the Test Suite

`test.sh` provides profiles for building the test suite and executes them.

&ensp; By default, the program runs in debug mode and the first failed test will throw an assertion.
Any tests that involve running as an application will spawn a subprocess with a window, and give
a short description of the behaviour in the terminal. It will then have you confirm whether the
information displayed is correct.

<br>
<br>

<a id="usage"></a>
## Usage


<a id="licensing"></a>
### Licensing

The following content of this section is not legal advice, nor is it legally binding, and nor does it change the terms
of the license. Please seek legal council if you have any concerns.

TLDR; You may license your game under whichever license you please. Any C++ code that is by definition a derivative work
must be licensed under GPLv3 and freely available, everything else; assets, scripts, design documents, etc. may be under
the license of your choosing and remain proprietary.

&ensp; fennec is licensed under GPLv3. The primary reason for the choice of license is to dissuade corporations from 
modifying fennec and using it in a commercial manner. This of course does not bar them from using fennec commercially, 
however it will prevent them from being able to make the derivative work proprietary. You are free to use and redistribute
fennec however you wish according to the terms of the license, which does not bar you from commercializing software based 
on fennec. 

&ensp; If you wish to protect your game files, assets and generated content do not constitute a covered work and may be
copyrighted under a non-compliant license. Think of it in terms of using Blender to create a mesh for a game, then
licensing that mesh under another license.

&ensp; Later down the line, I plan on implementing scripts in a manner that allows the script itself to remain proprietary.
The scripts will likely be trans-compiled to another language before being compiled to binary, but this is only an 
intermediate step and will be erased when no longer needed.

&ensp; As long as you use the official editor, it will properly include licenses in project content when provided a license
and the name of the license holder. Archive packs will include the license holders non-GPLv3 license in them and any
linked code will be covered by GPLv3 under the name of the license holder. Be aware that the parts of your project
licensed under GPLv3 must be available upon request.

&ensp; A release project will consist of an executable, a shared library for your code, an archive pak, and streamable assets.
The executable and shared library are under the GPLv3 license, while the archive pak and streamable assets are under your license.

It is to my discretion whether I enforce the terms of the license on a party.

The following practices are more likely to get my attention and enforcement:
 - Redistributing a modified version of fennec that is not licensed under GPLv3
 - Distributing an engine that is, by definition, a derivative work of fennec that is not licensed under GPLv3
 - Distributing an editor that runs on fennec or its derivatives that is not licensed under GPLv3
 - Using fennec to train a Machine Learning or Artificial Intelligence algorithm that is not licensed under GPLv3
 - Non-compliance of GPLv3 in games with the following mechanics:
   - Gacha Mechanics
   - Gambling with real currency
   - Subscription-Based Sales Model
   - NFTs or Nonfungible Tokens

I encourage those who wish to commercialize derivative works crowdfund rather than use a sales model. I also ask
that you kindly support me as a developer, I will set up a Buy Me a Coffee link at some point.

GPLv3 is bound by fair use; here is the clause, 17 U.S. Code § 107:

```
107. Limitations on exclusive rights: Fair use

Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by 
reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, 
comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an 
infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the 
factors to be considered shall include—

 (1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit 
     educational purposes;
 (2) the nature of the copyrighted work;
 (3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
 (4) the effect of the use upon the potential market for or value of the copyrighted work.

The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon 
consideration of all the above factors.
```

If you have any questions or concerns, please seek legal council. If you believe someone else has violated the terms
of this license, please contact me at [mslockbo@gmail.com](mailto:mslockbo@gmail.com).

I am aware of Universities with Game Development programs such as DigiPen Institute of Technology and Full-Sail
University which license student work to protect them and the faculty.

Champlain College does not license student projects and constitutes fair use.

I have not worked with Full-Sail University before, so I am not familiar with any of their staff members, and I will
require legal council to consult with them which may dissuade permission to use my engine. 

I hold a Bachelor's Degree in Computer Science and Real-Time Interactive Simulation from DigiPen Institute of Technology,
so I am familiar with their copyright policy. Ask your professor about usage of my engine, and they or someone with
appropriate standing will reach out to me. Eventually, with interest, I may reach out on my own terms to negotiate usage 
of fennec for educative purposes at DigiPen while retaining their license on student work.

If your University is not listed here, reach out to your professor for permission. Ask them to reach out to me, I am
willing to work with educational institutes to protect both fennec and student work in accordance to university policy.

<br>
<br>

<a id="contribution"></a>
## Contribution

There are some principles to keep in mind when contributing to fennec. 

 1. You must follow the [standards provided above](#coding-standards).
 2. Any changes must allow all projects to be forward compatible with newer engine versions.
