feat: movement-based M3/drg button (hold = scroll, tap = m3)

[dann-huang]

Hello. Big fan, used your firmware for around half a year.

This PR introduces 2 keycodes.

• One is a combined m3/drag scroll keycode that acts as m3 when tapped and better_dragscroll_momentary when held.
• Another changes the behaviour of the first to just m3.

motivation

I use the ploopy adept and found 6 face btns surprisingly not abundant. I also really like drag scroll, but dedicating an entire button feels slightly wasteful since "click" on scroll isn't meaningful. On the flip side, I rarely use drag with m3. Hence this addition.

how it works

• key down: starts recording drag distance
• movement (exceeding deadzone): scroll
• key up (movement under deadzone): send m3

re: drag scroll with layer

I did notice that drag scroll with (another) layer was added in the interim. That seems like it would solve the same problem via a LT(_, KC_MS_BTN_3) perhaps. However in practice that does not feel great due to the latency between key press and registering the layer change to allow scroll. The deadzone approach feels much more responsive.

testing

I'm the only person who has tested/used this specific impl. But it's very simple and I've been dailying on my adept for around half a year. I find it very comfortable to use and it generally succeeds in saving me a button.

Unsure if this is useful to anybody not using the adept, but hopefully there's value in this.

[plodah]

Several build failures.
It's probably my environment, as I'm seeing the same/similar on main
I've recently switched distro and likely have an old/er compiler.

Will revisit this later

[plodah]$ qmk userspace-compile
...
Build ploopyco/madromys/rev1_001:viam                                  [OK]
Build ploopyco/madromys/rev1_001_8button:viam                          [OK]
Build ploopyco/mouse/rev1_002:viam                                     [ERRORS]
Build ploopyco/mouse/rev1_003:viam                                     [OK]
Build ploopyco/nano_2/rev2_003:viam                                    [OK]
Build ploopyco/trackball/rev1_005:viam                                 [ERRORS]
Build ploopyco/trackball/rev1_004:viam                                 [ERRORS]
Build ploopyco/trackball/rev1_007:viam                                 [OK]
Build ploopyco/trackball_mini/rev1_001:viam                            [WARNINGS]
Build ploopyco/trackball_mini/rev1_002:viam                            [WARNINGS]
Build ploopyco/trackball_nano/rev1_001:viam                            [OK]
Build ploopyco/trackball_thumb/rev1_001:viam                           [ERRORS]
Build ploopyco/trackball_thumb/rev1_002:viam                           [OK]

[plodah]$ qmk compile -kb ploopyco/trackball/rev1_004 -km viam
...
Checking file size of ploopyco_trackball_rev1_004_viam.hex                                         
 * The firmware is too large! 29894/28672 (1222 bytes over)
 [ERRORS]
 
[plodah]$  qmk compile -kb ploopyco/trackball_thumb/rev1_001 -km viam
 ...
 Checking file size of ploopyco_trackball_thumb_rev1_001_viam.hex                                   
 * The firmware is too large! 28702/28672 (30 bytes over)
 [ERRORS]
...

[dann-huang]

Just as a point of reference I made temp changes to run gh action workflows on this branch. Both seem to finish successfully.
https://github.com/dann-huang/ploopy_viamenus/actions/runs/26387084402
https://github.com/dann-huang/ploopy_viamenus/actions/runs/26387091450

There are some warnings, but seemingly no errors nor size issues. I didn't actually test the build artifacts since I only have an adept on hand, but gh runners seem somewhat happy with the changes.
No rush on revisiting, just want to leave these here in case it's useful info.