update readme regarding custom tables feature

README.md

@@ -4,8 +4,6 @@
 A keyboard layout switcher. Just highlight the text and press a preconfigured
 hotkey to switch the layout.
 
-<img src="assets/happensdemo.gif" alt="workflow demonstration"/>
-
 ### Installation
 
 1. Install `xdotool`:
@@ -17,8 +15,122 @@ sudo apt install xdotool
 2. Grab the binary from releases and put it in any folder that is visible in
 `$PATH`.
 
-3. [Bind the binary to a hotkey](https://help.ubuntu.com/stable/ubuntu-help/keyboard-shortcuts-set.html.en) in your desktop environment. Note the `--table`
-argument. Currently, the only supported tables are `eng-to-ru` and `ru-to-eng`
-but new ones are coming.
+> **Note:**
+>
+> If there is no  pre-built binary for your platform, you may build it
+> yourself from source like this (Rust tooling is required):
+
+```
+git clone https://github.com/v-spassky/happens.git
+```
+
+```
+cd happens
+```
+
+```
+cargo build --release
+```
+
+```
+cp target/release/happens ~/.local/bin/
+```
+
+```
+chmod u+x ~/.local/bin/happens
+```
+
+3. [Bind the binary to a hotkey](https://help.ubuntu.com/stable/ubuntu-help/keyboard-shortcuts-set.html.en)
+in your desktop environment.
+
+<img src="assets/hotkey-binding-example.png" alt="ubuntu hotkey binding example"/>
+
+You may set up the binding in two distinct modes:
+
+##### Using one of the precompiled tables:
+
+```
+happens --table [ru-to-eng | eng-to-ru]
+```
+
+Example:
+
+```
+happens --table ru-to-eng
+```
+
+With such configuration, the program will work like this:
+
+<img src="assets/happensdemo.gif" width="500" alt="workflow demonstration"/>
+
+##### Using your own custom table:
+
+```
+happens --from-file /<...>/table.txt
+```
+
+In this case, the `table.txt` file should be formatted as follows:
 
-<img src="assets/hotkey-binding-example.png" alt="workflow demonstration"/>
+```
+<key1_before>: <key1_after>
+<key2_before>: <key2_after>
+...
+<keyN_before>: <keyN_after>
+```
+
+Example:
+
+```
+a: R
+s: R
+d: R
+f: R
+g: R
+```
+
+With the configuration above using the custom table shown above, the program
+will work like this:
+
+<img src="assets/happensdemo2.gif" width="500" alt="workflow demonstration 2"/>
+
+### Development notes
+
+To set up the program up and running, first set up a hotkey binding to call
+such command:
+
+```
+happens --from-file /<...>/happens/samples/custom_table.txt --logfile-name /<...>/happens/logs.txt
+```
+
+Alternatively, if you want to use the a precompiled table:
+
+```
+happens --table [ru-to-eng | eng-to-ru] --logfile-name /<...>/happens/logs.txt
+```
+
+Then, copy the binary from project folder to a folder, visible in `$PATH`
+and make it executable:
+
+```
+cargo build
+```
+
+```
+cp target/debug/happens ~/.local/bin/
+```
+
+```
+chmod u+x ~/.local/bin/happens
+```
+
+Or, as a shortcut:
+
+```
+cargo build && cp target/debug/happens ~/.local/bin/ && chmod u+x ~/.local/bin/happens
+```
+
+It is also possible to run the program via a terminal like this:
+
+```
+cargo run -- --from-file /<...>/happens/samples/custom_table.txt
+```