Update development.md

readme/development.md

@@ -1,7 +1,8 @@
 # Development
 
 Contributions are very welcome, I will gladly review and discuss any merge
-requests.
+requests. This file should give an overview about some notable internals of
+key-mapper.
 
 ## Roadmap
 
@@ -148,6 +149,18 @@ readme/capabilities.md
 
 Modify `should_map_as_btn`
 
+## How it works
+
+It uses evdev
+
+1. It grabs a device (e.g. /dev/input/event3), so that the key events won't reach X11/Wayland anymore [source](https://github.com/sezanzeb/key-mapper/blob/0.7.0/keymapper/injection/injector.py#L182)
+2. Reads the events from it (`evtest` can do it, you can also do `cat /dev/input/event3` which yields binary stuff) [source](https://github.com/sezanzeb/key-mapper/blob/0.7.0/keymapper/injection/injector.py#L413)
+3. Looks up the mapping if that event maps to anything [source](https://github.com/sezanzeb/key-mapper/blob/0.7.0/keymapper/injection/keycode_mapper.py#L421)
+4. Injects the output event in a new device that key-mapper created (another new path in /dev/input, device name is suffixed by "mapped") [source](https://github.com/sezanzeb/key-mapper/blob/0.7.0/keymapper/injection/keycode_mapper.py#L227), [new device](https://github.com/sezanzeb/key-mapper/blob/0.7.0/keymapper/injection/injector.py#L324)
+5. Forwards any events that should not be mapped to anything in another new device (device name is suffixed by "forwarded") [source](https://github.com/sezanzeb/key-mapper/blob/0.7.0/keymapper/injection/keycode_mapper.py#L232), [new device](https://github.com/sezanzeb/key-mapper/blob/0.7.0/keymapper/injection/injector.py#L342)
+
+This stuff is going on as a daemon in the background
+
 ## Resources
 
 - [Guidelines for device capabilities](https://www.kernel.org/doc/Documentation/input/event-codes.txt)