Add README section about configuration

README.md

@@ -3,7 +3,7 @@
 Linux utility to create custom key bindings for the Huion Kamvas Pro (2019),
 Inspiroy Q620M, and potentially other tablets.
 
-![Image of Huion Kamvas Pro 22 (2019)](https://prd-huion.oss-accelerate.aliyuncs.com/5/739/kamvas-pro-22-pen-display-01.jpg)
+![Image of Huion Kamvas Pro 22 (2019) and Inspiroy Q620M](https://i.imgur.com/zdBHGvX.png)
 
 ## Requirements
 
@@ -19,14 +19,55 @@ Inspiroy Q620M, and potentially other tablets.
 2. Clone this repository.
 3. Install the Python cffi module (either using Pipenv and the included Pipfile, through your system's package manager, or however you prefer to install Python packages).
 4. Run the `xdo_build.py` script. It should create a file named `_xdo_cffi.cpython-...-linux-gnu.so`.
-5. Run `huion_keys.py`. It will create an example config file at `~/.config/huion_keys`.
+5. Run `huion_keys.py`. It will create an example config file at `~/.config/huion_keys.conf`.
-6. Edit the config file to set up your key bindings. The key sequences are sent to xdotool, so look at xdotool's documentation for more details. There's also this [handy list of key codes](
+6. Edit the config file to set up your key bindings. See the below section for more instructions. 
-    https://gitlab.com/cunidev/gestures/-/wikis/xdotool-list-of-key-codes
-) that may be helpful.
 7. Run `huion_keys.py` as root or give yourself read permission for your tablet's hidraw file. For example:
     `chmod o+r /dev/hidraw3`
 8. When you push your tablet's buttons or swipe the scroll strips, this program should display information about what's going on.
 
+## Configuration
+
+The first time you start this program, it will create an example config file at `~/.config/huion_keys.conf`. The configuration file is in INI format that has, at minimum, a `[Bindings]` section.
+
+Each button is numbered, so assigning button 3 to be "ctrl+z" looks like this:
+
+```
+[Bindings]
+3=ctrl+z
+```
+
+The keys need to be in a format understood by xdotool, so look at xdotool's
+documentation for more details. There's also this [handy list of key codes](
+    https://gitlab.com/cunidev/gestures/-/wikis/xdotool-list-of-key-codes
+) that may be helpful.
+
+Normal key bindings are pressed and released immediately once you push down the button. If you need the keys to be held down for as long as you hold the button down, put its binding in the `[Hold]` section instead. This is useful for modifier keys such as the Control key.
+
+```
+[Hold]
+4=ctrl
+```
+
+The scroll strip and rotating dial can be configured with the following button names:
+
+* `scroll_up` and `scroll_down`
+* `dial_cw` and `dial_ccw`
+
+You can configure alternative bindings as separate "modes". For example, you can configure the dial knob to adjust brush size in one mode and zoom in a different mode. A separate button needs to be configured to switch to the next mode. Here's an example that uses button 9 to switch modes:
+
+```
+[Mode 1]
+dial_cw=bracketright
+dial_ccw=bracketleft
+
+[Mode 2]
+dial_cw=ctrl+shift+equal
+dial_ccw=ctrl+minus
+
+[Dial]
+cycle=9
+```
+
 ## How does it work?
 
 It works by listening on the tablet's hidraw interface for button presses and sending key events to X using xdotool.