Hi Matt,
This works because when amt is smaller than WHEEL_DELTA, the amt value is
used directly, see first branch of the cond :
(cond
* [((abs amt) . < . WHEEL_DELTA_S)*
(case wheel-steps-mode
[(one integer) amt]
[(fraction)
(unless (zero? amt)
(do-key w msg down lParam #f #f void (/ amt
(exact->inexact WHEEL_DELTA_S))))
0.0])]
I logged the values with and without the fix. In both cases, I scrolled
slowly down :
WHEEL_DELTA_S:120
wheel-scale:4
amt:-8
WHEEL_DELTA_S:120
wheel-scale:4
amt:-40
WHEEL_DELTA_S:120
wheel-scale:4
amt:-168
WHEEL_DELTA_S:120
wheel-scale:4
amt:-48
WHEEL_DELTA_S:120
wheel-scale:4
amt:-200
WHEEL_DELTA_S:120
wheel-scale:4
amt:-80
WHEEL_DELTA_S:120
wheel-scale:4
amt:-332
WHEEL_DELTA_S:120
wheel-scale:4
amt:-92
WHEEL_DELTA_S:120
wheel-scale:4
amt:-376
Amt is often larger than WHEEL_DELTA. After applying the changes
(dividing WHEEL-DELTA and removing the wheel-scale mul) :
WHEEL_DELTA_S:30
wheel-scale:4
amt:-2
WHEEL_DELTA_S:30
wheel-scale:4
amt:-4
WHEEL_DELTA_S:30
wheel-scale:4
amt:-6
WHEEL_DELTA_S:30
wheel-scale:4
amt:-8
WHEEL_DELTA_S:30
wheel-scale:4
amt:-11
WHEEL_DELTA_S:30
wheel-scale:4
amt:-13
WHEEL_DELTA_S:30
wheel-scale:4
amt:-15
WHEEL_DELTA_S:30
wheel-scale:4
amt:-17
WHEEL_DELTA_S:30
wheel-scale:4
amt:-19
WHEEL_DELTA_S:30
wheel-scale:4
amt:-22
Amt is never above WHEEL_DELTA, which triggers only the first branch of the
cond. The amt value is used with no adjustment, hense the precise behaviour.
Dex
On Thursday, April 15, 2021 at 1:49:53 PM UTC+2 Matthew Flatt wrote:
> Thanks for this summary! But I remain puzzled...
>
> As I understand it, `wheel-scale` ends up being 4 on your machine. So
> removing the multiplication by `wheel-scale` means that `amt` is 1/4 of
> what it used to be. But `amt` is effectively always divided by
> `WHEEL_DELTA`, which you've also divided by 4 in switching to
> `WHEEL_DELTA_S`.
>
> It seems like those factors of 1/4 would cancel out. Do the numbers
> passed to `do-key` end up being different in some way that I'm missing?
>
> Matthew
>
> At Mon, 12 Apr 2021 04:13:16 -0700 (PDT), Dexter Lagan wrote:
> > I started a new thread as the original topic no longer matched.
> > I installed 8.1.0.2 x64 CS and enabled logging in gen-wheels. Matt was
> > right: wheel-steps-mode is indeed set to 'integer while gen-wheels runs
> in
> > DrRacket's editor. The only two changes required to get smooth/accurate
> > scrolling on touchpad gestures and trackpoint are therefore:
> >
> > In share\pkgs\gui-lib\mred\private\wx\win32\window.rkt's gen-wheels
> private
> > method:
> >
> > (let loop ([amt (* wheel-scale amt)])
> > to
> > (let loop ([amt amt])
> >
> > and reduce WHEEL_DELTA by a factor of 4, such as gen-wheels looks like:
> >
> > (define/private (gen-wheels w msg lParam amt down up)
> > (define WHEEL_DELTA_S (/ WHEEL_DELTA 4))
> > (let loop ([amt amt])
> > (cond
> > [((abs amt) . < . WHEEL_DELTA_S)
> > (case wheel-steps-mode
> > [(one integer) amt]
> > [(fraction)
> > (unless (zero? amt)
> > (do-key w msg down lParam #f #f void (/ amt (exact->inexact
> > WHEEL_DELTA_S))))
> > 0.0])]
> > [(negative? amt)
> > (case wheel-steps-mode
> > [(one)
> > (do-key w msg down lParam #f #f void 1.0)
> > (loop (+ amt WHEEL_DELTA_S))]
> > [(integer)
> > (define steps (quotient (- amt) WHEEL_DELTA_S))
> > (do-key w msg down lParam #f #f void (exact->inexact steps))
> > (loop (+ amt (* steps WHEEL_DELTA_S)))]
> > [else
> > (do-key w msg down lParam #f #f void (/ (- amt) (exact->inexact
> > WHEEL_DELTA_S)))
> > 0.0])]
> > [else
> > (case wheel-steps-mode
> > [(one)
> > (do-key w msg up lParam #f #f void 1.0)
> > (loop (- amt WHEEL_DELTA_S))]
> > [(integer)
> > (define steps (quotient amt WHEEL_DELTA_S))
> > (do-key w msg up lParam #f #f void (exact->inexact steps))
> > (loop (- amt (* steps WHEEL_DELTA_S)))]
> > [else
> > (do-key w msg up lParam #f #f void (/ amt (exact->inexact
> > WHEEL_DELTA_S)))
> > 0.0])])))
> >
> > Happy Monday,
> >
> > Dex
> >
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