servo/README.md

# The Servo Parallel Browser Engine Project

[![Linux Build Status](https://img.shields.io/travis/servo/servo/master.svg?label=Linux%20build)](https://travis-ci.com/servo/servo)  [![Windows Build Status](https://img.shields.io/appveyor/ci/servo/servo/master.svg?label=Windows%20build)](https://ci.appveyor.com/project/servo/servo/branch/master)  [![Changelog #228](https://img.shields.io/badge/changelog-%23228-9E978E.svg)](https://changelog.com/podcast/228)

Servo is a prototype web browser engine written in the
[Rust](https://github.com/rust-lang/rust) language. It is currently developed on
64-bit macOS, 64-bit Linux, 64-bit Windows, and Android.

Servo welcomes contribution from everyone.  See
[`CONTRIBUTING.md`](CONTRIBUTING.md) and [`HACKING_QUICKSTART.md`](docs/HACKING_QUICKSTART.md)
for help getting started.

Visit the [Servo Project page](https://servo.org/) for news and guides.

## Setting up your environment

### Rustup.rs

Building servo requires [rustup](https://rustup.rs/), version 1.8.0 or more recent.
If you have an older version, run `rustup self update`.

To install on Windows, download and run [`rustup-init.exe`](https://win.rustup.rs/)
then follow the onscreen instructions.

To install on other systems, run:

```sh
curl https://sh.rustup.rs -sSf | sh
```

This will also download the current stable version of Rust, which Servo won’t use.
To skip that step, run instead:

```
curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain none
```

See also [Other installation methods](
https://github.com/rust-lang-nursery/rustup.rs/#other-installation-methods)

### Other dependencies

Please select your operating system:
* [macOS](#macos)
* [Debian-based Linuxes](#on-debian-based-linuxes)
* [Fedora](#on-fedora)
* [Arch Linux](#on-arch-linux)
* [openSUSE](#on-opensuse-linux)
* [Gentoo Linux](#on-gentoo-linux)
* [Microsoft Windows](#on-windows-msvc)
* [Android](#cross-compilation-for-android)

#### macOS

Xcode version 10.2 or above is recommended.

##### On macOS (Homebrew)

``` sh
brew bundle install --file=etc/taskcluster/macos/Brewfile
brew bundle install --file=etc/taskcluster/macos/Brewfile-gstreamer
pip install virtualenv
```

#### On Debian-based Linuxes

Please run `./mach bootstrap`.

If this doesn't work, file a bug, and, run the commands below:

``` sh
sudo apt install git curl autoconf libx11-dev \
    libfreetype6-dev libgl1-mesa-dri libglib2.0-dev xorg-dev \
    gperf g++ build-essential cmake virtualenv python-pip \
    libssl-dev libbz2-dev liblzma-dev libosmesa6-dev libxmu6 libxmu-dev \
    libglu1-mesa-dev libgles2-mesa-dev libegl1-mesa-dev libdbus-1-dev \
    libharfbuzz-dev ccache clang libunwind-dev \
    libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev libgstreamer-plugins-bad1.0-dev autoconf2.13
```

Additionally, you'll need a local copy of GStreamer with a version later than 12.0. You can place it in `support/linux/gstreamer/gst`, or run `./mach bootstrap-gstreamer` to set it up.

If you are using **Ubuntu 16.04** or **Linux Mint 18.*** run `export HARFBUZZ_SYS_NO_PKG_CONFIG=1` before building to avoid an error with harfbuzz.

If you get an undefined symbol error on `gst_player_get_config` try removing `gir1.2-gst-plugins-bad-1.0` and all old versions of clang, see [#22016](https://github.com/servo/servo/issues/22016)

If you are on **Ubuntu 14.04** and encountered errors on installing these dependencies involving `libcheese`, see [#6158](https://github.com/servo/servo/issues/6158) for a workaround. You may also need to install gcc 4.9, clang 4.0, and cmake 3.2:

<details>
gcc 4.9:

```sh
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt-get update
sudo apt-get install gcc-4.9 g++-4.9
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.9
```

clang 4.0:

```sh
wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
sudo apt-add-repository "deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-4.0 main"
sudo apt-get update
sudo apt-get install -y clang-4.0
```

cmake 3.2:

```sh
sudo apt-get install software-properties-common
sudo add-apt-repository ppa:george-edison55/cmake-3.x
sudo apt-get update
sudo apt-get install cmake
```

</details>

If `virtualenv` does not exist, try `python-virtualenv`.

#### On Fedora

Please run `./mach bootstrap`.

If this doesn't work, file a bug, and, run the commands below:

``` sh
sudo dnf install curl libtool gcc-c++ libXi-devel libunwind-devel \
    freetype-devel mesa-libGL-devel mesa-libEGL-devel glib2-devel libX11-devel libXrandr-devel gperf \
    fontconfig-devel cabextract ttmkfdir python2 python2-virtualenv python2-pip expat-devel \
    rpm-build openssl-devel cmake bzip2-devel libX11-devel libXcursor-devel libXmu-devel mesa-libOSMesa-devel \
    dbus-devel ncurses-devel harfbuzz-devel ccache mesa-libGLU-devel clang clang-libs gstreamer1-devel \
    gstreamer1-plugins-base-devel gstreamer1-plugins-bad-free-devel autoconf213
```
#### On CentOS


Please run `./mach bootstrap`.

If this doesn't work, file a bug, and, run the commands below:

``` sh
sudo yum install curl libtool gcc-c++ libXi-devel \
    freetype-devel mesa-libGL-devel mesa-libEGL-devel glib2-devel libX11-devel libXrandr-devel gperf \
    fontconfig-devel cabextract ttmkfdir python python-virtualenv python-pip expat-devel \
    rpm-build openssl-devel cmake3 bzip2-devel libXcursor-devel libXmu-devel mesa-libOSMesa-devel \
    dbus-devel ncurses-devel python34 harfbuzz-devel ccache clang clang-libs llvm-toolset-7
```

Build inside `llvm-toolset` and `devtoolset`:

```sh
scl enable devtoolset-7 llvm-toolset-7 bash
```

with the following environmental variables set:

```sh
export CMAKE=cmake3
export LIBCLANG_PATH=/opt/rh/llvm-toolset-7/root/usr/lib64
```
#### On openSUSE Linux
``` sh
sudo zypper install libX11-devel libexpat-devel libbz2-devel Mesa-libEGL-devel Mesa-libGL-devel cabextract cmake \
    dbus-1-devel fontconfig-devel freetype-devel gcc-c++ git glib2-devel gperf \
    harfbuzz-devel libOSMesa-devel libXcursor-devel libXi-devel libXmu-devel libXrandr-devel libopenssl-devel \
    python-pip python-virtualenv rpm-build glu-devel ccache llvm-clang libclang autoconf213 gstreamer-devel \
    gstreamer-plugins-base-devel gstreamer-plugins-bad-devel
```
#### On Arch Linux

``` sh
sudo pacman -S --needed base-devel git python2 python2-virtualenv python2-pip mesa cmake bzip2 libxmu glu \
    pkg-config ttf-fira-sans harfbuzz ccache llvm clang autoconf2.13 gstreamer gstreamer-vaapi
```
#### On Gentoo Linux

```sh
sudo emerge net-misc/curl \
    media-libs/freetype media-libs/mesa dev-util/gperf \
    dev-python/virtualenv dev-python/pip dev-libs/openssl \
    media-libs/harfbuzz dev-util/ccache sys-libs/libunwind \
    x11-libs/libXmu media-libs/glu x11-base/xorg-server sys-devel/clang \
    media-libs/gstreamer media-libs/gst-plugins-bad media-libs/gst-plugins-base
```

With the following environment variable set:
```sh
export LIBCLANG_PATH=$(llvm-config --prefix)/lib64
```
#### On Windows (MSVC)

1. Install Python 2.7 for Windows (https://www.python.org/downloads/release/python-2716/). The Windows x86-64 MSI installer is fine. This is required for the build system execution and many dependencies.

You should change the installation to install the "Add python.exe to Path" feature.

2. Install Python 3.7 for Windows (https://www.python.org/downloads/release/python-374/). The Windows x86-64 MSI installer is fine. This is required in order to build the JavaScript engine, SpiderMonkey.

You will also need to set the `PYTHON3` environment variable, e.g., to 'C:\Python37\python.exe' by doing:
```
setx PYTHON3 "C:\Python37\python.exe" /m
```
The `/m` will set it system-wide for all future command windows.

3. Install virtualenv.

 In a normal Windows Shell (cmd.exe or "Command Prompt" from the start menu), do:
 ```
pip install virtualenv
```
 If this does not work, you may need to reboot for the changed PATH settings (by the python installer) to take effect.

4. Install `pkg-config` either via [Chocolatey](https://chocolatey.org/install#installing-chocolatey)(`choco install pkgconfiglite`) or from [here](https://sourceforge.net/projects/pkgconfiglite/).

5. Install the most recent [GStreamer](https://gstreamer.freedesktop.org/data/pkg/windows/) MSVC packages. You need to download the two `.msi` files for your platform from the [GStreamer](https://gstreamer.freedesktop.org/data/pkg/windows/) website and install them. The currently recommended version is 1.16.0. i.e.:

- [gstreamer-1.0-msvc-x86_64-1.16.0.msi](https://gstreamer.freedesktop.org/data/pkg/windows/1.16.0/gstreamer-1.0-msvc-x86_64-1.16.0.msi)
- [gstreamer-1.0-devel-msvc-x86_64-1.16.0.msi](https://gstreamer.freedesktop.org/data/pkg/windows/1.16.0/gstreamer-1.0-devel-msvc-x86_64-1.16.0.msi)

Note that the MinGW binaries will not work, so make sure that you install the MSVC the ones.

Note that you should ensure that _all_ components are installed from gstreamer, as we require many of the optional libraries that are not installed by default.

6. Install Git for Windows (https://git-scm.com/download/win). DO allow it to add git.exe to the PATH (default
settings for the installer are fine).

7. Install Visual Studio Community 2017 (https://www.visualstudio.com/vs/community/). You MUST add "Visual C++" to the
list of installed components as well as the "Windows Universal C runtime." They are not on by default. Visual Studio 2017 MUST installed to the default location or mach.bat will not find it.

##### [Optional] Install LLVM for faster link times

You may experience much faster builds on Windows by following these steps. (Related Rust issue: https://github.com/rust-lang/rust/issues/37543)

1. Download the latest version of LLVM (https://releases.llvm.org/).
2. Run the installer and choose to add LLVM to the system PATH.
3. Add the following to your Cargo config (Found at `%USERPROFILE%\.cargo\config`). You may need to change the triple to match your environment.

```
[target.x86_64-pc-windows-msvc]
linker = "lld-link.exe"
```

##### Troubleshooting a Windows environment

> If you encountered errors with the environment above, do the following for a workaround:
> 1.  Download and install [Build Tools for Visual Studio 2017](https://www.visualstudio.com/thank-you-downloading-visual-studio/?sku=BuildTools&rel=15)
> 2.  Install `python2.7 x86-x64` and `virtualenv`
> 3.  Run `mach.bat build -d`.

>If you have troubles with `x64 type` prompt as `mach.bat` set by default:
> 1. You may need to choose and launch the type manually, such as `x86_x64 Cross Tools Command Prompt for VS 2017` in the Windows menu.)
> 2. `cd to/the/path/servo`
> 3. `python mach build -d`

> If you got the error `Cannot run mach in a path on a case-sensitive file system on Windows`:
> 1. Open Command Prompt or PowerShell as administrator.
> 2. Disable case-sensitive for servo path, `fsutil.exe file SetCaseSensitiveInfo X:\path\to\servo disable`

#### Cross-compilation for Android

Run `./mach bootstrap-android --build` to get Android-specific tools. See wiki for
[details](https://github.com/servo/servo/wiki/Building-for-Android).

## The Rust compiler

Servo's build system uses rustup.rs to automatically download a Rust compiler.
This is a specific version of Rust Nightly determined by the
[`rust-toolchain`](https://github.com/servo/servo/blob/master/rust-toolchain) file.

## Building

Servo is built with [Cargo](https://crates.io/), the Rust package manager. We also use Mozilla's
Mach tools to orchestrate the build and other tasks.

### Normal build

To build Servo in development mode.  This is useful for development, but
the resulting binary is very slow.

``` sh
git clone https://github.com/servo/servo
cd servo
./mach build --dev
./mach run tests/html/about-mozilla.html
```

Or on Windows MSVC, in a normal Command Prompt (cmd.exe):
``` cmd
git clone https://github.com/servo/servo
cd servo
mach.bat build --dev
```

For benchmarking, performance testing, or
real-world use, add the `--release` flag to create an optimized build:

``` sh
./mach build --release
./mach run --release tests/html/about-mozilla.html
```

**Note:** `mach build ` will build both `servo` and `libsimpleservo`. To make compilation a bit faster, it's possible to only compile the servo binary: `./mach build --dev -p servo`.

### Checking for build errors, without building

If you’re making changes to one crate that cause build errors in another crate,
consider this instead of a full build:

```sh
./mach check
```

It will run `cargo check`, which runs the analysis phase of the compiler
(and so shows build errors if any) but skips the code generation phase.
This can be a lot faster than a full build,
though of course it doesn’t produce a binary you can run.

### Building for Android target

For ARM (`armv7-linux-androideabi`, most phones):

``` sh
./mach build --release --android
./mach package --release --android
```

For x86 (typically for the emulator):

```sh
./mach build --release --target i686-linux-android
./mach package --release --target i686-linux-android
```

## Running

Run Servo with the command:

```sh
./servo [url] [arguments] # if you run with nightly build
./mach run [url] [arguments] # if you run with mach

# For example
./mach run https://www.google.com
```

### Commandline Arguments

- `-p INTERVAL` turns on the profiler and dumps info to the console every
  `INTERVAL` seconds
- `-s SIZE` sets the tile size for painting; defaults to 512
- `-z` disables all graphical output; useful for running JS / layout tests
- `-Z help` displays useful output to debug servo

### Keyboard Shortcuts

- `Ctrl`+`L` opens URL prompt (`Cmd`+`L` on Mac)
- `Ctrl`+`R` reloads current page (`Cmd`+`R` on Mac)
- `Ctrl`+`-` zooms out (`Cmd`+`-` on Mac)
- `Ctrl`+`=` zooms in (`Cmd`+`=` on Mac)
- `Alt`+`left arrow` goes backwards in the history (`Cmd`+`left arrow` on Mac)
- `Alt`+`right arrow` goes forwards in the history (`Cmd`+`right arrow` on Mac)
- `Esc` or `Ctrl`+`Q` exits Servo (`Cmd`+`Q` on Mac)

## Developing

There are lots of mach commands you can use. You can list them with `./mach
--help`.


The generated documentation can be found on https://doc.servo.org/servo/index.html