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cursor: prevent hi-res mice triggering scroll actions too often

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Hi-res mice produces mulitple scroll events with `delta_discrete` != 0
during a single "click". This patch makes them trigger `Scroll` actions
only when the accumulated `delta_discrete` exceeds 120 (= 1 click).

See https://lists.freedesktop.org/archives/wayland-devel/2019-April/040377.html
for how hi-res scroll events are reported.
This commit is contained in:
tokyo4j 2025-07-22 00:19:22 +09:00 • committed by Hiroaki Yamamoto
parent 1747d9e961
commit cb79eccea1
2 changed files with 42 additions and 40 deletions
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7
include/labwc.h
View file

@ -111,9 +111,10 @@ struct seat {
bool cursor_visible;
struct wlr_cursor *cursor;
struct wlr_xcursor_manager *xcursor_manager;
struct {
double x, y;
} smooth_scroll_offset;
struct accumulated_scroll {
double delta;
double delta_discrete;
} accumulated_scrolls[2]; /* indexed by wl_pointer_axis */
bool cursor_scroll_wheel_emulation;
/*

75
src/input/cursor.c
View file

@ -1245,38 +1245,44 @@ struct scroll_info {
};
static struct scroll_info
compare_delta(double delta, double delta_discrete, double *accum)
compare_delta(double delta, double delta_discrete, struct accumulated_scroll *accum)
{
/*
* Smooth scroll deltas are in surface space, so treating each unit as a
* scroll event would result in too-fast scrolling.
*
* This fudge factor (inherited from various historic projects, incl. Weston)
* produces events at a more reasonable rate.
*
* For historic context, see:
* https://lists.freedesktop.org/archives/wayland-devel/2019-April/040377.html
*/
const double SCROLL_THRESHOLD = 10.0;
struct scroll_info info = {0};
if (delta_discrete < 0 || delta < 0) {
info.direction = -1;
} else if (delta_discrete > 0 || delta > 0) {
info.direction = 1;
}
if (delta == 0.0) {
/* Delta 0 marks the end of a scroll */
*accum = 0.0;
if (delta_discrete) {
/* mice */
info.direction = delta_discrete > 0 ? 1 : -1;
accum->delta_discrete += delta_discrete;
/*
* Non-hi-res mice produce delta_discrete of ±120 for every
* "click", so it always triggers actions. But for hi-res mice
* that produce smaller delta_discrete, we accumulate it and
* run actions after it exceeds 120(= 1 click).
*/
if (fabs(accum->delta_discrete) >= 120.0) {
accum->delta_discrete = fmod(accum->delta_discrete, 120.0);
info.run_action = true;
}
} else {
/* Accumulate smooth scrolling until we hit threshold */
*accum += delta;
}
if (delta_discrete != 0 || fabs(*accum) > SCROLL_THRESHOLD) {
*accum = fmod(*accum, SCROLL_THRESHOLD);
info.run_action = true;
/* 2-finger scrolling on touchpads */
if (delta == 0) {
/* delta=0 marks the end of a scroll */
accum->delta = 0;
return info;
}
info.direction = delta > 0 ? 1 : -1;
accum->delta += delta;
/*
* The threshold of 10 is inherited from various historic
* projects including weston.
*
* For historic context, see:
* https://lists.freedesktop.org/archives/wayland-devel/2019-April/040377.html
*/
if (fabs(accum->delta) >= 10.0) {
accum->delta = fmod(accum->delta, 10.0);
info.run_action = true;
}
}
return info;
@ -1290,21 +1296,16 @@ process_cursor_axis(struct server *server, enum wl_pointer_axis orientation,
uint32_t modifiers = keyboard_get_all_modifiers(&server->seat);
enum direction direction = LAB_DIRECTION_INVALID;
struct scroll_info info = {0};
struct scroll_info info = compare_delta(delta, delta_discrete,
&server->seat.accumulated_scrolls[orientation]);
if (orientation == WL_POINTER_AXIS_HORIZONTAL_SCROLL) {
info = compare_delta(delta, delta_discrete,
&server->seat.smooth_scroll_offset.x);
if (info.direction < 0) {
direction = LAB_DIRECTION_LEFT;
} else if (info.direction > 0) {
direction = LAB_DIRECTION_RIGHT;
}
} else if (orientation == WL_POINTER_AXIS_VERTICAL_SCROLL) {
info = compare_delta(delta, delta_discrete,
&server->seat.smooth_scroll_offset.y);
if (info.direction < 0) {
direction = LAB_DIRECTION_UP;
} else if (info.direction > 0) {
@ -1324,8 +1325,8 @@ process_cursor_axis(struct server *server, enum wl_pointer_axis orientation,
&& mousebind->mouse_event == MOUSE_ACTION_SCROLL) {
handled = true;
/*
* Action may not be executed if the accumulated scroll
* delta on touchpads doesn't exceed the threshold
* Action may not be executed if the accumulated scroll delta
* on touchpads or hi-res mice doesn't exceed the threshold
*/
if (info.run_action) {
actions_run(ctx.view, server, &mousebind->actions, &ctx);