qTox/windows/cross-compile/README.md

# Cross-compile from Linux to Windows

## Intro

Following these instructions will show you how to cross-compile qTox for Windows.

This script can be used by qTox users and devs to compile qTox for windows themselves.

Please note that the compilation script doesn't build the updater.

## Usage


#### 1. [Install Docker](https://docs.docker.com/install).
***


#### 2. Create 3 directories for storing the files needed for cross-compiling.
***

  * `workspace` -- a directory that will contain a cache of qTox dependencies
  and the final qTox cross-compilation build. You should create this directory.

  * `script` -- a directory that contains the `build.sh` script. 
  Copy the `build.sh` script to this folder.

  * `qtox` -- the root directory of a qTox repository. This directory must contain
  the qTox source code that will be cross-compiled. You can use an existing qTox
  directory you've been using for development or check one out using 
  `git clone https://github.com/qTox/qTox.git folder-name`

These directories will be mounted inside a Docker container at`/workspace`,
`/script`and`/qtox`.

The contents of `qtox` and `script` directories are not modified during compilation. The
`build.sh` script makes a temporary copy of the `qtox` directory for compilation.


#### 3. Create the docker container and run the build script.
***
> Note that the`build.sh`script takes 2 arguments: architecture and build type.
> Valid values for the architecture are `i686` for 32-bit and `x86_64` for
> 64-bit. Valid values for the build type are `release` and `debug`. All case
> sensitive. You can modify the scripts below to fit your use case.
> To create the docker container and start cross-compiling run



```sh
sudo docker run --rm \
-v /absolute/path/to/your/workspace:/workspace \
-v /absolute/path/to/your/script:/script \
-v /absolute/path/to/your/qtox:/qtox \
debian:stretch-slim \
/bin/bash /script/build.sh i686 release
```


If you are a qTox developer, you might want to enable tty and leave stdin open by running the following script instead.

```sh
sudo docker run -it \
--rm \
-v /absolute/path/to/your/workspace:/workspace \
-v /absolute/path/to/your/script:/script \
-v /absolute/path/to/your/qtox:/qtox \
debian:stretch-slim \
/bin/bash /script/build.sh i686 release
```
These will cross-compile all of the qTox dependencies and qTox itself, storing
them in the `workspace` directory. The first time you run it for each
architecture, it will take a long time for the cross-compilation to finish, as
qTox has a lot of dependencies that need to be cross-compiled.


> Note that it takes my Intel Core i7 processor about 125 minutes on average for the cross-compilation
> to finish on a single core, and about 30 minutes using all 8 hyperthreads. Once you've compiled
> it, the dependencies will be cached inside the `workspace` directory. The next time
> you build qTox, the `build.sh` script will skip recompiling them
> which is a lot faster -- about 8 minutes on a single core and 2 minutes using 8 hyperthreads.


#### 4. After cross-compiling has finished
***
The `workspace\i686\qtox` and `workspace\x86_64\qtox\`directories will contain the compiled binaries in their respective debug or release folder depending on the compilation settings you chose in Step 3.

The `dep-cache` directory is where all the cross-compiled qTox dependencies will be
cached for the future builds. You can remove any directory inside the `deps` folder, which
will result in the `build.sh` re-compiling the removed dependency.


_The `workspace` direcory structure for reference_

```
workspace
├── i686
│   ├── dep-cache
│   │   ├── libffmpeg
│   │   ├── libfilteraudio
│   │   ├── libopenal
│   │   ├── libopenssl
│   │   ├── libopus
│   │   ├── libqrencode
│   │   ├── libqt5
│   │   ├── libsodium
│   │   ├── libsqlcipher
│   │   ├── libtoxcore
│   │   └── libvpx
│   └── qtox
│       ├── debug
│       └── release
└── x86_64
    ├── dep-cache
    │   ├── libffmpeg
    │   ├── libfilteraudio
    │   ├── libopenal
    │   ├── libopenssl
    │   ├── libopus
    │   ├── libqrencode
    │   ├── libqt5
    │   ├── libsodium
    │   ├── libsqlcipher
    │   ├── libtoxcore
    │   └── libvpx
    └── qtox
        ├── debug
        └── release
```