05-10-26

Precision Mouse Movement Lua Script

This Lua script for hardware input slows down mouse movement when a key is held, perfect for precise pixel selection. It uses the Rebind SDK to modify mouse behavior.

rebindlua scriptmouseprecisionslow downhardware inputscript

Question

I need a script to slow down mouse movement when I hold a modifier key for precise pixel selection.

Rebind AI

I'll create a script that slows down mouse movement when you hold a modifier key. This is perfect for precise pixel-level selection in image editors, design tools, or any application requiring fine cursor control.

lua

-- rebind: min_sdk=0.1.0 mouse_block=true
-- rebind: name=Precision Mouse
-- rebind: description=Hold a key to slow down mouse movement for precise selection

local cfg = UI.Schema({
    hold_key = UI.Keybind("Mouse3", { label = "Precision Key", tooltip = "Hold this to activate slow mode" }),
    slowdown = UI.Slider(25, { 
        min = 5, 
        max = 75, 
        suffix = "%", 
        label = "Movement Speed",
        tooltip = "Lower % = slower movement"
    }),
    acceleration = UI.Toggle(false, {
        label = "Enable Acceleration",
        tooltip = "Gradually speed up longer movements"
    }),
})

function OnMove(dx, dy)
    if not Input.IsDown(cfg.hold_key) then
        return true -- pass through normally
    end

    local factor = cfg.slowdown / 100
    
    if cfg.acceleration then
        -- longer movements get slightly more acceleration
        local magnitude = math.sqrt(dx * dx + dy * dy)
        if magnitude > 5 then
            factor = factor * (1 + (magnitude - 5) * 0.02)
        end
    end

    HID.Move(dx * factor, dy * factor)
    return false -- swallow the original movement
end

How it works:

Hold to activate — When you hold the configured key (default: Mouse3/middle-click), the script intercepts all mouse movements
Precision scaling — Each movement is multiplied by your speed percentage (e.g., 25% means 1/4 normal speed)
Optional acceleration — If enabled, longer swipes gradually speed up, making both small adjustments and larger sweeps feel natural
Block original input — The original fast movement is swallowed; only the scaled version reaches your PC

Usage tips:

Use Mouse3 (middle-click) as the precision key to keep it separate from selection buttons
Set speed to 15–30% for fine pixel work, 50–75% for general precision
Toggle acceleration on if you want to make both tiny tweaks and larger movements without lifting the key
In Photoshop or similar tools, hold the precision key while selecting or painting

Why mouse_block=true? This modeline directive forces the engine to validate every mouse movement, which enables the return value to block input. Without it, OnMove would fire asynchronously and blocking wouldn't work.

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