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Momentum scroller: discard unsuitable physical events

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This commit is contained in:
Kovid Goyal
2026-01-09 12:56:05 +05:30
parent 3c250a741d
commit 858240e324
1 changed files with 48 additions and 19 deletions
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67
glfw/momentum-scroll.c vendored
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@@ -31,10 +31,14 @@ typedef struct MomentumScroller {
struct { double x, y; } velocity;
int keyboard_modifiers;
monotonic_t timer_interval;
struct {
monotonic_t start, duration;
struct { double x, y; } displacement;
} physical_event;
} MomentumScroller;
static const MomentumScroller defaults = {
.friction = 0.035,
.friction = 0.04,
.min_velocity = 0.5,
.max_velocity = 100,
.velocity_scale = 0.9,
@@ -49,7 +53,7 @@ glfwConfigureMomentumScroller(double friction, double min_velocity, double max_v
}
static void
cancel_existing_scroll(void) {
cancel_existing_scroll(bool reset_velocity) {
if (s.timer_id) {
glfwRemoveTimer(s.timer_id);
s.timer_id = 0;
@@ -63,11 +67,12 @@ cancel_existing_scroll(void) {
s.keyboard_modifiers = 0;
deque_clear(&s.samples);
s.state = NONE;
if (reset_velocity) { s.velocity.x = 0; s.velocity.y = 0; }
}
static void
add_sample(double dx, double dy) {
deque_push_back(&s.samples, (ScrollSample){dx, dy, monotonic()}, NULL);
add_sample(double dx, double dy, monotonic_t now) {
deque_push_back(&s.samples, (ScrollSample){dx, dy, now}, NULL);
}
static void
@@ -95,9 +100,9 @@ add_velocity(double x, double y) {
}
static void
set_velocity_from_samples(void) {
set_velocity_from_samples(monotonic_t now) {
s.timer_interval = ms_to_monotonic_t(8);
trim_old_samples(monotonic());
trim_old_samples(now);
ScrollSample ss;
switch (deque_size(&s.samples)) {
case 0:
@@ -146,7 +151,7 @@ send_momentum_event(bool is_start) {
if (fabs(s.velocity.y) < s.min_velocity) s.velocity.y = 0;
_GLFWwindow *w = _glfwWindowForId(s.window_id);
if (!w || w != _glfwFocusedWindow()) {
cancel_existing_scroll();
cancel_existing_scroll(true);
return;
}
GLFWMomentumType m = is_start ? GLFW_MOMENTUM_PHASE_BEGAN : GLFW_MOMENTUM_PHASE_ACTIVE;
@@ -168,32 +173,56 @@ momentum_timer_fired(unsigned long long timer_id UNUSED, void *data UNUSED) {
}
static void
start_momentum_scroll(void) {
set_velocity_from_samples();
start_momentum_scroll(monotonic_t now) {
set_velocity_from_samples(now);
send_momentum_event(true);
s.timer_id = glfwAddTimer(s.timer_interval, true, momentum_timer_fired, NULL, NULL);
}
static bool
is_suitable_for_momentum(void) {
return (
MAX(fabs(s.physical_event.displacement.x), fabs(s.physical_event.displacement.y)) > 10 &&
s.physical_event.duration > ms_to_monotonic_t(2)
);
}
void
glfw_handle_scroll_event_for_momentum(
_GLFWwindow *w, const GLFWScrollEvent *ev, bool stopped, bool is_finger_based
) {
if (!w || (w->id != s.window_id && s.window_id) || s.state != PHYSICAL_EVENT_IN_PROGRESS) cancel_existing_scroll();
if (!w) return;
if (!w) { cancel_existing_scroll(true); return; }
if (!is_finger_based || ev->offset_type != GLFW_SCROLL_OFFEST_HIGHRES || s.friction <= 0) {
_glfwInputScroll(w, ev);
return;
}
monotonic_t now = monotonic();
if (s.state == PHYSICAL_EVENT_IN_PROGRESS) {
s.physical_event.displacement.x += ev->unscaled.x;
s.physical_event.displacement.y += ev->unscaled.y;
if (stopped) {
s.physical_event.duration = now - s.physical_event.start;
s.physical_event.start = 0;
}
} else {
s.physical_event.start = now;
s.physical_event.displacement.x = 0;
s.physical_event.displacement.y = 0;
}
if (s.window_id && s.window_id != w->id) cancel_existing_scroll(true);
if (s.state != PHYSICAL_EVENT_IN_PROGRESS) cancel_existing_scroll(false);
// Check for change in direction
double ldx, ldy; last_sample_delta(&ldx, &ldy);
if (ldx * ev->x_offset < 0 || ldy * ev->y_offset < 0) {
s.velocity.x = 0; s.velocity.y = 0;
cancel_existing_scroll();
}
if (ldx * ev->x_offset < 0 || ldy * ev->y_offset < 0) cancel_existing_scroll(true);
s.window_id = w->id;
s.keyboard_modifiers = ev->keyboard_modifiers;
if (is_finger_based && s.friction > 0) {
add_sample(ev->x_offset, ev->y_offset);
s.state = stopped ? MOMENTUM_IN_PROGRESS : PHYSICAL_EVENT_IN_PROGRESS;
if (ev->offset_type == GLFW_SCROLL_OFFEST_HIGHRES && s.friction > 0) {
add_sample(ev->x_offset, ev->y_offset, now);
if (stopped) s.state = is_suitable_for_momentum() ? MOMENTUM_IN_PROGRESS : NONE;
else s.state = PHYSICAL_EVENT_IN_PROGRESS;
} else {
s.state = stopped ? NONE : PHYSICAL_EVENT_IN_PROGRESS;
}
if (s.state == MOMENTUM_IN_PROGRESS) start_momentum_scroll();
if (s.state == MOMENTUM_IN_PROGRESS) start_momentum_scroll(now);
else _glfwInputScroll(w, ev);
}