Macos – Mac OSX: Scroll half a page

hotkeyskeyboardkeyboard shortcutsmacosscrolling

I am no longer using the trackpad on my macbook and using a separate wired apple keyboard instead. I miss the scrolling functionality on my trackpad, I'm having to make do with the keyboard (the mouse is too far away for efficient scrolling).

Is there a way to map a key combination (such as cmd+pagedown) such that I scroll up/down half a page instead of a full page?

Even better, is there a way to map key combinations to arbitrary scrolling distances?

Thanks for your time

Best Answer

I have no idea why it hasn't been answered for so long, but there is a way - you can do it using ControllerMate. It's an overkill, that's for sure (and it costs $25), but it does do the job.

In a nutshell: Open ControllerMate, create a new page in "Programming items" section. In Palette, open "Controllers" (⌥⌘1), choose your keyboard and press the key you want to bind the action to (for example, Cmd key). It will highlight there.
If you want to group several keys (such as Cmd+Pagedown), drag the second (third... nth...) key there too and connect them using "AND" operator in "Logic" (⌥⌘4) palette. Then use the "Scroll Wheel Building Block" in an "Output" (⌥⌘2) palette. You can customize the scrolling step in the "Inspector" window.

You will end with something like that:
enter image description here

Do the same for the Cmd+PageUp hotkey (don't forget to change the direction of scrolling).