update docs

Author: candytaco

docs/assets/general settings.png

@@ -16,6 +16,12 @@ A standalone executable is available. Linux may require additional system librar
 
 There are no prebuilt executable for macOS. To run on macOS, [build the project from source](./building.md).
 
+## Eyelink files
+
+<img src="assets/general%20settings.png" width="600" />
+
+SharpEyes can parse Eyelink files. The text files that you get out of the Eyelink coverter are out-of-the-box parsable. To be able to parse the EDF files directly, you need to provide your own copy of SR Research's edfapi library. It has to be either in the system library path, or you can set a path in the settings for SharpEyes to look for it.
+
 ## Python interop setup
 
 SharpEyes handles all eyetracking processing internally, but computing motion-energy features requires [PyMoten](https://github.com/gallantlab/pymoten) to be installed in a Python environment. SharpEyes will manage this for you. You can use either system python at a location you specify, a conda environment if you have conda installed, or have SharpEyes manage its own standalone python environment.

docs/assets/motion-energy.png

@@ -8,6 +8,8 @@ The Motion-Energy tab computes motion-energy features from a video using [PyMote
 
 These control how the input video frames are prepared before being passed to PyMoten.
 
+By default the video is shown as a preview by sliding the original video around on the drawing canvas. Toggle the "preview" button on to preview the actual pixel values that the motion-energy code will see.
+
 | Control | Description |
 |---|---|
 | Pad percent | Amount of padding added around each frame as a percentage of the frame size. Must be at least 100 (i.e. the padded frame is at least the original size). Recentered/retinotopic videos must be padded, but a raw video can do without padding. |