Change mouse buttons to x11 map and libevdev names

This modifies the way mouse bindings are parsed. Instead of adding to
BTN_LEFT, which results in button numbers that may not be expected,
buttons will be parsed in one of the following ways:

1. `button[1-9]` will now map to their x11 equivalents. This is already
the case for bar bindings. This adds support for binding to axis events,
which was not possible in the previous approach.

2. Anything that starts with `BTN_` will be parsed as an event code name
using `libevdev_event_code_from_name`. This allows for any button to be
mapped to instead of limiting usage to the ones near BTN_LEFT. This also
adds a dependency on libevdev, but since libevdev is already a dependency
of libinput, this should be fine. If needed, this option can have dependency
guards added.

Binding changes:
- button1: BTN_LEFT -> BTN_LEFT
- button2: BTN_RIGHT -> BTN_MIDDLE
- button3: BTN_MIDDLE -> BTN_RIGHT
- button4: BTN_SIDE -> SWAY_SCROLL_UP
- button5: BTN_EXTRA -> SWAY_SCROLL_DOWN
- button6: BTN_FORWARD -> SWAY_SCROLL_LEFT
- button7: BTN_BACK -> SWAY_SCROLL_RIGHT
- button8: BTN_TASK -> BTN_SIDE
- button9: BTN_JOYSTICK -> BTN_EXTRA

Since the axis events need to be mapped to an event code, this uses the
following mappings to avoid any conflicts:
- SWAY_SCROLL_UP: KEY_MAX + 1
- SWAY_SCROLL_DOWN: KEY_MAX + 2
- SWAY_SCROLL_LEFT: KEY_MAX + 3
- SWAY_SCROLL_RIGHT: KEY_MAX + 4

1 files changed, 7 insertions, 0 deletions

diff --git a/sway/sway.5.scd b/sway/sway.5.scd
index 2fe4e372..e6abef56 100644
--- a/sway/sway.5.scd
+++ b/sway/sway.5.scd
@@ -288,6 +288,13 @@ runtime.
         overwrite a binding, swaynag will give you a warning. To silence this, use
         the _--no-warn_ flag.
 
+        Mouse buttons can either be specified in the form _button[1-9]_ or by using
+        the name of the event code (ex _BTN\_LEFT_ or _BTN\_RIGHT_). For the former
+        option, the buttons will be mapped to their values in X11 (1=left, 2=middle,
+        3=right, 4=scroll up, 5=scroll down, 6=scroll left, 7=scroll right, 8=back,
+        9=forward). For the latter option, you can find the event names using
+        _libinput debug-events_.
+
         Example:
 ```
                 # Execute firefox when alt, shift, and f are pressed together