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; Another improvement for documentation of pixelwise scrolling

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* doc/lispref/commands.texi (Misc Events): More details about
pixelwise mouse-wheel scrolling events.  (Bug#65070)
This commit is contained in:
Eli Zaretskii 2023-08-20 11:09:40 +03:00
parent baeb2d71ae
commit 3296031ad7
1 changed files with 22 additions and 10 deletions
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32
doc/lispref/commands.texi
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@ -2242,11 +2242,12 @@ mouse cursor when the finger moved off the mouse wheel.
@cindex @code{wheel-down} event @cindex @code{wheel-down} event
@item (wheel-up @var{position} @var{clicks} @var{lines} @var{pixel-delta}) @item (wheel-up @var{position} @var{clicks} @var{lines} @var{pixel-delta})
@itemx (wheel-down @var{position} @var{clicks} @var{lines} @var{pixel-delta}) @itemx (wheel-down @var{position} @var{clicks} @var{lines} @var{pixel-delta})
These kinds of event are generated by moving a mouse wheel. The These events are generated by moving a mouse wheel. The
@var{position} element is a mouse position list (@pxref{Click @var{position} element is a mouse position list (@pxref{Click
Events}), specifying the position of the mouse cursor when the event Events}), specifying the position of the mouse cursor when the event
occurred. occurred.
@vindex mwheel-coalesce-scroll-events
@var{clicks}, if present, is the number of times that the wheel was @var{clicks}, if present, is the number of times that the wheel was
moved in quick succession. @xref{Repeat Events}. @var{lines}, if moved in quick succession. @xref{Repeat Events}. @var{lines}, if
present and not @code{nil}, is the positive number of screen lines present and not @code{nil}, is the positive number of screen lines
@ -2254,24 +2255,35 @@ that should be scrolled (either up, when the event is @code{wheel-up},
or down when the event is @code{wheel-down}). @var{pixel-delta}, if or down when the event is @code{wheel-down}). @var{pixel-delta}, if
present, is a cons cell of the form @w{@code{(@var{x} . @var{y})}}, present, is a cons cell of the form @w{@code{(@var{x} . @var{y})}},
where @var{x} and @var{y} are the numbers of pixels by which to scroll where @var{x} and @var{y} are the numbers of pixels by which to scroll
in each axis, a.k.a.@: @dfn{pixelwise deltas}. in each axis, a.k.a.@: @dfn{pixelwise deltas}. Usually, only one of
the two will be non-zero, the other will be either zero or very close
to zero; the larger number indicates the axis to scroll the window.
When the variable @code{mwheel-coalesce-scroll-events} is @code{nil},
the scroll commands ignore the @var{lines} element, even if it's
non-@code{nil}, and use the @var{pixel-delta} data instead; in that
case, the direction of scrolling is determined by the sign of the
pixelwise deltas, and the direction (up or down) implied by the event
kind is ignored.
@cindex pixel-resolution wheel events @cindex pixel-resolution wheel events
You can use these @var{x} and @var{y} pixelwise deltas to determine You can use these @var{x} and @var{y} pixelwise deltas to determine
how much the mouse wheel has actually moved at pixel resolution. For how much the mouse wheel has actually moved at pixel resolution. For
example, the pixelwise deltas could be used to scroll the display at example, the pixelwise deltas could be used to scroll the display at
pixel resolution, exactly according to the user's turning the mouse pixel resolution, exactly according to the user's turning the mouse
wheel. wheel. This pixelwise scrolling is possible only when
@code{mwheel-coalesce-scroll-events} is @code{nil}, and in general the
@var{pixel-delta} data is not generated when that variable is
non-@code{nil}.
@vindex mouse-wheel-up-event @vindex mouse-wheel-up-event
@vindex mouse-wheel-down-event @vindex mouse-wheel-down-event
This kind of event is generated only on some kinds of systems. On The @code{wheel-up} and @code{wheel-down} events are generated only on
some systems, @code{mouse-4} and @code{mouse-5} are used instead. For some kinds of systems. On other systems, @code{mouse-4} and
portable code, use the variables @code{mouse-wheel-up-event}, @code{mouse-5} are used instead. For portable code, use the variables
@code{mouse-wheel-up-alternate-event}, @code{mouse-wheel-down-event} @code{mouse-wheel-up-event}, @code{mouse-wheel-up-alternate-event},
and @code{mouse-wheel-down-alternate-event} defined in @code{mouse-wheel-down-event} and
@file{mwheel.el} to determine what event types to expect for the mouse @code{mouse-wheel-down-alternate-event} defined in @file{mwheel.el} to
wheel. determine what event types to expect from the mouse wheel.
@vindex mouse-wheel-left-event @vindex mouse-wheel-left-event
@vindex mouse-wheel-right-event @vindex mouse-wheel-right-event