Summary

Hold down a hotkey to turn your trackball into a scroll wheel! You can either set it to snap to the X-Y axes, or have it scroll along both axes at once to emulate 2D panning!

You don't have to install AutoHotKey to use this - check the releases for a .exe download.

Other people have written several great alternatives to this script, such as TrackballScroll. However, this script seeks to differentiate itself by implementing continuous scrolling motion, as opposed to stepped.

Settings

Setting Your Hotkeys:

• Hotkey 1: What key to use as the hotkey.
  • See the AHK docs for more information on how to format this.
  • Only single keys (keyboard or mouse) can be used - no combinations or modifiers.
  • If you end up accidently locking yourself out of your system, first use CTRL+SHIFT+ESCAPE to launch task manager and kill smooth_trackball_scrolling.exe. Then, run smooth_trackball_scrolling_reset.exe. This will reset all your settings back to default.
• Hotkey 2: A second hotkey, if you're using a 2 key mode. See below for more details.
  • Formatted the same way as Hotkey 1.

Setting Hotkey Mode:

• Mode: Provides various options depending on how you want things to work.
  • MO (1 key): Smooth scrolling is active when Hotkey 1 is held, and inactive when Hotkey 1 isn't held. Hotkey 2 doesn't do anything.
  • TG (1 key): Smooth scrolling is toggled when Hotkey 1 is pressed down. Hotkey 2 doesn't do anything.
  • MO (2 key sym.): Smooth scrolling is active when Hotkey 1 and Hotkey 2 are both held.
    • You can start holding the two hotkeys in either order.
    • The original functionality of both hotkeys can still be used by tapping/holding the key individually.
      • If you tap a hotkey individually, the tap action will be sent upon key release.
      • If you hold a hotkey individually, the hold will start after a hold delay (configurable via Hold Duration).
  • MO (2 key asym.): Smooth scrolling is active when Hotkey 1 and Hotkey 2 are both held.
    • This mode is primarily intended for use with the two mouse buttons (LButton and RButton), though of course you can use other hotkeys as well.
    • You must start holding Hotkey 2 before Hotkey 1.
    • The original functionality of both hotkeys can still be used by tapping/holding the key individually.
      • If you tap Hotkey 1 individually, the tap action will be sent immediately.
      • If you hold Hotkey 1 individually, the hold action will start immediately.
      • If you tap Hotkey 2 individually, the tap action will be sent upon key release.
      • If you hold Hotkey 2 individually, the hold action will start after a hold delay (configurable via Hold Duration).
    • This mode is identical to MO (2 key sym.), but with the following tradeoff:
      • PRO: Hotkey 1 is much more responsive, since tap and hold actions start immediately when you first press the key/button. If you're using the mouse buttons, this means that left-clicks are much more responsive.
      • CON: Instead of being able to press them in either order, you now must activate Hotkey 2 before Hotkey 1. If you're using the mouse buttons, this means you'll have to "roll" from right-click to left-click, instead of just pressing them both at the same time.
  • TG (2 key asym.): Hotkey1 turns smooth scrolling on, while Hotkey2 turns smooth scrolling off.
    • This mode is intended to make it easier to integrate this script with QMK keyboard firmware and stuff.
• Hold Duration: Only applicable when using 2 key MO modes. The duration of the delay before a hold action starts.

Responsiveness, Smoothing, and Sensitivity:

• Refresh Interval: How often the script sends mouse wheel updates. The minimum and default value is 10 (ms). I recommend trying to use this value, but if you experience some apps behaving weirdly or inconsistently in response to scrolling, try bumping it up to something like 16 or 20. Basically set this to as low as it can go without causing problems.
• Smoothing Window Size: How much smoothing to apply. Higher values correspond to more smoothing and "momentum". Lower settings are snappier and more responsive. I recommend a value around 3 to 10, depending on your personal preference. If you increase your Refresh Interval, you might want to decrease your Smoothing Window Size, as the total amount of smoothing actually scales with the product of these two parameters.
• Sensitivity: Movement sensitivity.
• Invert Direction: Inverts scrolling direction.

Angle Snapping

• Angle Snapping Threshold: Controls how hard it is to break away from being snapped to an axis. This parameter sets how much you have to move perpendiular to the axis to become un-snapped. A higher value will make it harder to un-snap from an axis. I recommend a value around 10, but this depends on how you want your snapping to work.
• Angle Snapping Ratio: Controls how hard it is to break away from being snapped to an axis. This parameter sets how much your movement direction can deviate angularly from the axis before you become un-snapped. A higher value will make it harder to un-snap from an axis. I recommend a value around 1.5, but this depends on how you want your snapping to work.
• Angle Snapping On: Whether or not you want angle snapping at all.
• Always Angle Snap: If this is on, when you become un-snapped from one axis, you snap to the other axis. If this is off, when you un-snap from one axis, you stay un-snapped.

Modifier Emulation

• Emulate Ctrl, Emulate Shift, and Emulate Alt: If you check one or more of these boxes, the hotkey will add the respective key or key combination when you scroll with your real physical scroll wheel (not your trackball). This is to allow you to use your mouse wheel to zoom while holding down the hotkey (check the box or boxes corresponding to your software's zoom modifier key), thus allowing you to control pan and zoom using a single hotkey.

Known Issues

• Unfortunately, I've found that some programs will not respond to the scroll inputs from my script, most notably Windows Explorer. I think a re-write of this script in a low-level language that can interface properly with the Windows input API will solve this, but I won't have time for this in the forseeable future.
• Some software, most notably Chromium-based browsers, do not respond well to simultaneous scrolling inputs along both the X and Y axes. Using angle snap will fix this.