From: Po Lu <luangruo@yahoo.com>
To: Eli Zaretskii <eliz@gnu.org>
Cc: rpluim@gmail.com, emacs-devel@gnu.org
Subject: Re: master e37eb7f: Add support for pixel wheel deltas on NS
Date: Fri, 26 Nov 2021 19:44:59 +0800 [thread overview]
Message-ID: <877dcvf8ec.fsf@yahoo.com> (raw)
In-Reply-To: <83r1b32lvr.fsf@gnu.org> (Eli Zaretskii's message of "Fri, 26 Nov 2021 13:32:08 +0200")
Eli Zaretskii <eliz@gnu.org> writes:
> Thanks. But if this conversion is arbitrary (see below), I think I
> know how to implement the MS-Windows version of "arbitrary".
Thanks! I really appreciate it.
>> On X, the states of the mouse wheels in each axis are stored as absolute
>> values inside "valuators" attached to each mouse device. To obtain the
>> delta of the scroll wheel from a motion event (which is used to report
>> that some valuator has changed), it is necessary to iterate over every
>> valuator that changed, and compare its previous value to the current
>> value of the valuator.
>>
>> Each individual valuator also has an "interval", which is the amount you
>> must divide that delta by in order to obtain a delta in the terms of
>> scroll units.
>>
>> This delta however is still intermediate, to make driver implementations
>> easier. The XInput developers recommend the following algorithm to
>> convert from scroll unit deltas to pixel deltas:
>>
>> pixels_scrolled = pow (window_height, 2.0 / 3.0) * delta;
>
> All of this should be in comments in xterm.c.
>
> Btw, the code calculates pixels_scrolled when it is not yet clear that
> the value will be used, which is a waste of cycles, AFAICT. How about
> moving this closer to where the value is actually used?
I'll do that, thanks.
> In any case, are you saying that the conversion to pixels is somewhat
> arbitrary? And that users of X based systems have no control on this
> conversion, i.e. users cannot determine the pixel equivalent of each
> "delta"?
Yes, I'm using the method recommended by the XInput 2 developers, and on
X-based systems there's no option to control that arbitrary behaviour
that I know of.
It seems to be that every X-Windows program I checked (which includes
non-GTK programs such as Mozilla Firefox and Qt) also computes the pixel
information the same way.
>> Yes. The PGTK port can do something similar if it gains support for
>> this, as GTK also reports it in pixels directly.
> Same question here: do users have any system-wide control on the
> conversion to pixels under these environments?
I don't know about NS, but there's no such option in GTK based systems.
next prev parent reply other threads:[~2021-11-26 11:44 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20211125030922.2353.1129@vcs0.savannah.gnu.org>
[not found] ` <20211125030924.7258E2094B@vcs0.savannah.gnu.org>
2021-11-25 10:26 ` master e37eb7f: Add support for pixel wheel deltas on NS Robert Pluim
2021-11-25 10:34 ` Po Lu
2021-11-25 10:47 ` Robert Pluim
2021-11-25 11:02 ` Eli Zaretskii
2021-11-26 0:39 ` Po Lu
2021-11-26 6:35 ` Eli Zaretskii
2021-11-26 7:00 ` Po Lu
2021-11-26 8:17 ` Eli Zaretskii
2021-11-26 9:37 ` Po Lu
2021-11-26 11:32 ` Eli Zaretskii
2021-11-26 11:44 ` Po Lu [this message]
2021-11-26 16:55 ` Eli Zaretskii
2021-11-27 0:02 ` Po Lu
2021-11-27 6:09 ` Eli Zaretskii
2021-11-27 6:41 ` Po Lu
2021-11-27 7:05 ` Eli Zaretskii
2021-11-27 7:14 ` Po Lu
2021-11-27 10:47 ` Eli Zaretskii
2021-11-27 10:54 ` Po Lu
2021-11-27 11:03 ` Eli Zaretskii
2021-11-27 11:05 ` Po Lu
2021-11-27 11:13 ` Po Lu
2021-11-27 11:32 ` Eli Zaretskii
2021-11-27 11:34 ` Po Lu
2021-11-27 11:40 ` Eli Zaretskii
2021-11-27 11:44 ` Po Lu
2021-11-27 12:02 ` Eli Zaretskii
2021-11-27 12:11 ` Po Lu
2021-11-27 12:36 ` Eli Zaretskii
2021-11-27 12:48 ` Po Lu
2021-11-26 11:48 ` Eli Zaretskii
2021-11-26 12:05 ` Po Lu
2021-11-26 12:23 ` Eli Zaretskii
2021-11-26 12:37 ` Po Lu
2021-11-26 19:39 ` Alan Third
2021-11-26 19:45 ` Eli Zaretskii
2021-11-26 19:54 ` Alan Third
2021-11-28 2:54 ` Po Lu
2021-11-28 7:53 ` Eli Zaretskii
2021-11-28 7:58 ` Po Lu
2021-11-28 8:28 ` Eli Zaretskii
2021-11-29 7:39 ` Po Lu
2021-11-29 12:50 ` Eli Zaretskii
2021-11-29 13:19 ` Po Lu
2021-11-25 11:00 ` Eli Zaretskii
2021-11-25 18:46 ` Stefan Monnier
2021-11-25 18:58 ` Eli Zaretskii
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