feat: add key filtering configuration and logging

README.md

@@ -43,7 +43,7 @@ By filtering such anomalies, we can hopefully remove chatter without impeding ac
 
 ## Installation
 
-Download the repository as a zip and extract the file. The dependencies are listed in the requirements.txt. And you can install it with the command below. 
+Download the repository as a zip and extract the file. The dependencies are listed in the requirements.txt. And you can install it with the command below.
 
 ```shell
 sudo pip3 install -r requirements.txt
@@ -57,6 +57,49 @@ sudo pip3 install -r requirements.txt
 sudo python3 -m src
 ```
 
+### Key Filtering Configuration
+
+The filter has two operating modes:
+
+#### Mode 1: Filter ALL keys (original default behavior)
+By default, the filter works as it always has - applying the anti-chattering filter to all keyboard keys. This is the behavior when `FILTERED_KEYS` is set to `None` or empty in `src/constants.py`.
+
+#### Mode 2: Filter only specific keys
+You can configure the filter to apply only to specific keys that exhibit chattering. To do this:
+
+1. Open `src/constants.py`
+2. Uncomment and modify the `FILTERED_KEYS` variable with the desired keys
+3. Use only the key name (e.g., `"KEY_A"`, `"KEY_SPACE"`) - no need for the `libevdev.EV_KEY.` prefix
+
+**Configuration examples:**
+
+```python
+# Filter only specific keys
+FILTERED_KEYS = {
+    "KEY_A",      # A key with chattering
+    "KEY_SPACE",  # Spacebar with chattering
+    "KEY_ENTER",  # Enter key with chattering
+}
+
+# Filter all letters and numbers
+FILTERED_KEYS = {
+    "KEY_A", "KEY_B", "KEY_C", "KEY_D", "KEY_E", "KEY_F", "KEY_G", "KEY_H",
+    "KEY_I", "KEY_J", "KEY_K", "KEY_L", "KEY_M", "KEY_N", "KEY_O", "KEY_P",
+    "KEY_Q", "KEY_R", "KEY_S", "KEY_T", "KEY_U", "KEY_V", "KEY_W", "KEY_X",
+    "KEY_Y", "KEY_Z", "KEY_0", "KEY_1", "KEY_2", "KEY_3", "KEY_4", "KEY_5",
+    "KEY_6", "KEY_7", "KEY_8", "KEY_9", "KEY_SPACE", "KEY_ENTER",
+}
+
+# Return to original behavior (filter all keys)
+FILTERED_KEYS = None
+```
+
+**Advantages of specific mode:**
+- ✅ Better performance (processes only problematic keys)
+- ✅ Preserves modifier keys (Ctrl, Alt, Shift)
+- ✅ Doesn't interfere with function or special keys
+- ✅ Flexible per-key configuration
+
 ### Customization Options
 
 - -k KEYBOARD, --keyboard KEYBOARD
@@ -90,12 +133,12 @@ Then, copy the `chattering_fix.service` to `/etc/systemd/system/` and enable it
 ```shell
 systemctl enable --now chattering_fix
 ```
-You can check if the systemd unit file is properly working using 
+You can check if the systemd unit file is properly working using
 ```shell
 systemctl status chattering_fix.service
 ```
-You can also use 
+You can also use
 ```shell
 journalctl -xeu chattering_fix.service
 ```
-just to make sure that there are no errors.
+just to make sure that there are no errors.

src/constants.py

@@ -0,0 +1,42 @@
+"""
+Constants for keyboard chattering filter configuration.
+
+DEFAULT BEHAVIOR:
+- If FILTERED_KEYS is empty (None or empty list), ALL keys will be filtered (original behavior)
+- If FILTERED_KEYS contains keys, only those specific keys will be filtered
+
+To customize which keys should be filtered, define the FILTERED_KEYS list with key names.
+Use only the key name (e.g., "KEY_A", "KEY_SPACE") instead of the full code.
+
+Examples of key names:
+- Letters: "KEY_A", "KEY_B", "KEY_C", etc.
+- Numbers: "KEY_0", "KEY_1", "KEY_2", etc.
+- Special: "KEY_SPACE", "KEY_ENTER", "KEY_BACKSPACE", "KEY_TAB"
+- Function: "KEY_F1", "KEY_F2", etc.
+- Modifiers: "KEY_LEFTSHIFT", "KEY_RIGHTSHIFT", "KEY_LEFTCTRL", etc.
+- Arrows: "KEY_UP", "KEY_DOWN", "KEY_LEFT", "KEY_RIGHT"
+"""
+
+from typing import Optional, Set
+
+# KEY FILTERING CONFIGURATION
+
+FILTERED_KEYS = {
+    # Example: filter only some letters that have chattering
+    "KEY_P",
+}
+
+# Option 1: Filter ALL keys (original default behavior)
+# Leave as None or empty list to maintain original behavior
+# FILTERED_KEYS: Optional[Set[str]] = None
+
+# Option 2: Filter only specific keys
+# Uncomment and modify the list below to filter only specific keys
+# FILTERED_KEYS = {
+#     # Example: filter only some letters that have chattering
+#     "KEY_A",
+#     "KEY_S",
+#     "KEY_D",
+#     "KEY_SPACE",
+#     "KEY_ENTER",
+# }

src/filtering.py

@@ -1,16 +1,51 @@
 import logging
 from collections import defaultdict
-from typing import DefaultDict, Dict, NoReturn
+from typing import DefaultDict, Dict, NoReturn, Set
 
 import libevdev
 
+from src.constants import FILTERED_KEYS
+
+
+def _get_filtered_keys_set() -> Set[libevdev.EventCode]:
+    """
+    Converts the list of key names to libevdev codes.
+    If FILTERED_KEYS is None or empty, returns None (filter all keys).
+    """
+    if not FILTERED_KEYS:
+        return None
+
+    filtered_codes = set()
+    for key_name in FILTERED_KEYS:
+        try:
+            # Converts "KEY_A" to libevdev.EV_KEY.KEY_A
+            key_code = getattr(libevdev.EV_KEY, key_name)
+            filtered_codes.add(key_code)
+        except AttributeError:
+            logging.warning(f"Key name '{key_name}' not found in libevdev.EV_KEY. Skipping...")
+
+    return filtered_codes
+
+
+# Converts the key list once at initialization
+_FILTERED_KEYS_CODES = _get_filtered_keys_set()
+
 
 def filter_chattering(evdev: libevdev.Device, threshold: int) -> NoReturn:
     # grab the device - now only we see the events it emits
     evdev.grab()
     # create a copy of the device that we can write to - this will emit the filtered events to anyone who listens
     ui_dev = evdev.create_uinput_device()
 
+    # Log filtering mode
+    if _FILTERED_KEYS_CODES is None:
+        logging.info("Filtering mode: ALL keys (original behavior)")
+    else:
+        logging.info(f"Filtering mode: SPECIFIC keys only ({len(_FILTERED_KEYS_CODES)} keys configured)")
+        if logging.getLogger().isEnabledFor(logging.DEBUG):
+            key_names = [name for name in FILTERED_KEYS]
+            logging.debug(f"Filtered keys: {', '.join(sorted(key_names))}")
+
     logging.info("Listening to input events...")
 
     while True:
@@ -30,6 +65,10 @@ def _from_keystroke(event: libevdev.InputEvent, threshold: int) -> bool:
         logging.debug(f'FORWARDING {event.code}')
         return True
 
+    if _FILTERED_KEYS_CODES is not None and event.code not in _FILTERED_KEYS_CODES:
+        logging.debug(f'FORWARDING {event.code} (not in filtered keys list)')
+        return True
+
     # the values are 0 for up, 1 for down and 2 for hold
     if event.value == 0:
         if _key_pressed[event.code]:
@@ -55,4 +94,4 @@ def _from_keystroke(event: libevdev.InputEvent, threshold: int) -> bool:
 
 
 _last_key_up: Dict[libevdev.EventCode, int] = {}
-_key_pressed: DefaultDict[libevdev.EventCode, bool] = defaultdict(bool)
+_key_pressed: DefaultDict[libevdev.EventCode, bool] = defaultdict(bool)