# Installation

The library installation involves three easy (famous last words) steps.

### Install SR Research EyeLink Developers Kit

This package relies on edfapi library that is as part of the EyeLink Developers Kit. Therefore, `read_edf()` function will not work without it but you will still be able to use utility functions. The EyeLink Developers Kit can be downloaded from www.sr-research.com/support website. Note that you need to register and wait for your account to be activated. Next, follow instructions to install EyeLink Developers Kit for your platform. The forum thread should be under SR Support Forum › Downloads › EyeLink Developers Kit / API › Download: EyeLink Developers Kit / API Downloads (Windows, macOS, Linux).

### Configure R environment variables

The package needs to configure compiler flags for its dependency on EDF API library. Specifically, it needs to specify paths to include header files ( edf.h, edf_data.h, and edftypes.h) and to the library itself. The package will try to compile using sensible defaults for each platform, i.e., default installation paths for EyeLink Developers Kit v2.1.1. However, these defaults may change in the future or you may wish to install the library to a non-standard location (relevant primarily for Windows).

If compilation with default paths fails, you need to define R environment variables as described below. These variables must be defined either in user or project .Renviron file. The simplest way to edit it is via usethis library and edit_r_environ() function. Type `usethis::edit_r_environ()` for user and `usethis::edit_r_environ('project')` for projects environments (note that the latter shadows the former, read documentation for details). In the case of Windows, note that you do not need to worry about forward vs. backward slashes as R will normalize strings for you. Once you define the variables, restart session and check them by typing `Sys.getenv()` (to see all variables) or `Sys.getenv("EDFAPI_INC")` to check a specific one.

#### Windows

Default values assume that the EyeLink Developers Kit is installed in `c:/Program Files (x86)/SR Research/EyeLink` (default installation path).

- `EDFAPI_LIB` : path to `edfapi.dll` for 32-bit systems. Defaults to `c:/Program Files (x86)/SR Research/EyeLink/libs`.
- `EDFAPI_LIB64` (optional): path to `edfapi64.dll` for 64-bit systems. By default, the 64-bit library is in x64 subfolder, i.e., `c:/Program Files (x86)/SR Research/EyeLink/libs/x64`. This variable is optional, as the package will try to guess this by itself by appending `/x64` to `EDFAPI_LIB` path. However, you should specify this variable explicitly if 64-libraries are in a non-standard folder (or SR Research changed it, or you just want to be sure).
- `EDFAPI_INC` : path to C header files necessary for compilation. Specifically, the package requires edf.h, edf_data.h, and edftypes.h. Defaults to `c:/Program Files (x86)/SR Research/EyeLink/Includes/eyelink`.

Your `.Renviron` file include lines similar to the ones below

    EDFAPI_LIB="c:/Program Files (x86)/SR Research/EyeLink/libs"
    EDFAPI_LIB64="c:/Program Files (x86)/SR Research/EyeLink/libs/x64"
    EDFAPI_INC="c:/Program Files (x86)/SR Research/EyeLink/Includes/eyelink"

#### Linux

- `EDFAPI_INC` : path to C header files necessary for compilation. Specifically, the package requires edf.h, edf_data.h, and edftypes.h. Defaults to `/usr/include/EyeLink`.

Your `.Renviron` file should include a line like this

    EDFAPI_INC="/usr/include/EyeLink"

#### Mac OS

- `EDFAPI_LIB`: path to EDF API framework. Defaults to `/Library/Frameworks`
- `EDFAPI_INC` : path to C header files necessary for compilation. Specifically, the package requires edf.h, edf_data.h, and edftypes.h. Defaults to `/Library/Frameworks/edfapi.framework/Headers`

Your `.Renviron` file include lines similar to the ones below

    EDFAPI_LIB="/Library/Frameworks"
    EDFAPI_INC="/Library/Frameworks/edfapi.framework/Headers"

### Install the library

To install from github

    library("devtools")
    install_github("alexander-pastukhov/eyelinkReader", dependencies=TRUE,  build_vignettes = TRUE)