libinput/plugins/10-pointer-go-slower.lua
Peter Hutterer 9e37bc0cfa plugins: add support for lua plugins to change evdev event streams
This patch adds support for Lua scripts to modify evdev devices and
event frames before libinput sees those events.

Plugins in Lua are sandboxed and restricted in what they can do: no IO,
no network, not much of anything else.

A plugin is notified about a new device before libinput handles it and
it can thus modify that device (changes are passed through to our libevdev
context). A plugin can then also connect an evdev frame handler which
gives it access to the evdev frames before libinput processes them. The
example plugin included shows how to swap left/right mouse buttons:

    libinput:register({1})

    function frame(device, frame)
        for _, v in ipairs(frame.events) do
            if v.usage == evdev.BTN_RIGHT then
                v.usage = evdev.BTN_LEFT
            elseif v.usage == evdev.BTN_LEFT then
                v.usage = evdev.BTN_RIGHT
            end
        end
        return frame
    end

    function device_new(plugin, device)
        local usages = device:usages()
        if usages[evdev.BTN_LEFT] and usages[evdev.BTN_RIGHT] then
            device:connect("evdev-frame", frame)
        end
    end

    libinput:connect("new-evdev-device", device_new)

A few other example plugins are included in this patch

Part-of: <https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/1192>
2025-08-01 16:04:09 +10:00

53 lines
1.4 KiB
Lua

-- SPDX-License-Identifier: MIT
--
-- An example plugin to make the pointer go three times as slow
--
-- Install this file in /etc/libinput/plugins and
--
-- UNCOMMENT THIS LINE TO ACTIVATE THE PLUGIN
-- libinput:register({1})
remainders = {}
function split(v)
if math.abs(v) >= 1.0 then
local i = math.floor(math.abs(v))
local r = math.abs(v) % 1.0
if v < 0.0 then
i = -i
r = -r
end
return i, r
else
return 0, v
end
end
function decelerate(device, x, y)
local remainder = remainders[device]
local rx, ry = 0, 0
if x ~= 0.0 then
rx, remainder.x = split(remainder.x + x/3.0)
end
if y ~= 0.0 then
ry, remainder.y = split(remainder.y + y/3.0)
end
return rx, ry
end
libinput:connect("new-evdev-device", function(device)
local usages = device:usages()
if usages[evdev.REL_X] then
remainders[device] = { x = 0.0, y = 0.0 }
device:connect("evdev-frame", function(_, frame, timestamp)
for _, v in ipairs(frame) do
if v.usage == evdev.REL_X then
v.value, _ = decelerate(device, v.value, 0.0)
elseif v.usage == evdev.REL_Y then
_, v.value = decelerate(device, 0.0, v.value)
end
end
return frame
end)
end
end)