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normalize decay speed before applying

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Rick Choi
2024-10-24 07:01:58 +09:00
parent 5e7e512d8a
commit bbc5003014
1 changed files with 32 additions and 14 deletions
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46
kitty/cursor_trail.c
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@@ -70,30 +70,48 @@ update_cursor_trail_corners(CursorTrail *ct, Window *w, monotonic_t now, OSWindo
float cursor_diag_2 = norm(EDGE(x, 1) - EDGE(x, 0), EDGE(y, 1) - EDGE(y, 0)) * 0.5f;
float dt = (float)monotonic_t_to_s_double(now - ct->updated_at);
float dx[4], dy[4];
float dot[4]; // dot product of "direction vector" and "cursor center to corner vector"
// dot product here is used to dynamically adjust the decay speed of
// each corner. The closer the corner is to the cursor, the faster it
// moves.
for (int i = 0; i < 4; ++i) {
float dx = EDGE(x, ci[i][0]) - ct->corner_x[i];
float dy = EDGE(y, ci[i][1]) - ct->corner_y[i];
if (fabsf(dx) < dx_threshold && fabsf(dy) < dy_threshold) {
dx[i] = EDGE(x, ci[i][0]) - ct->corner_x[i];
dy[i] = EDGE(y, ci[i][1]) - ct->corner_y[i];
if (fabsf(dx[i]) < dx_threshold && fabsf(dy[i]) < dy_threshold) {
dx[i] = dy[i] = 0.0f;
dot[i] = 1.0f;
continue;
}
dot[i] = (dx[i] * (EDGE(x, ci[i][0]) - cursor_center_x) +
dy[i] * (EDGE(y, ci[i][1]) - cursor_center_y)) /
cursor_diag_2 / norm(dx[i], dy[i]);
}
float min_dot = FLT_MAX, max_dot = -FLT_MAX;
for (int i = 0; i < 4; ++i) {
min_dot = fminf(min_dot, dot[i]);
max_dot = fmaxf(max_dot, dot[i]);
}
for (int i = 0; i < 4; ++i) {
if ((dx[i] == 0 && dy[i] == 0) || min_dot == FLT_MAX) {
ct->corner_x[i] = EDGE(x, ci[i][0]);
ct->corner_y[i] = EDGE(y, ci[i][1]);
continue;
}
// Corner that is closer to the cursor moves faster.
// It creates dynamic effect that looks like the trail is being pulled towards the cursor.
float dot = (dx * (EDGE(x, ci[i][0]) - cursor_center_x) +
dy * (EDGE(y, ci[i][1]) - cursor_center_y)) /
cursor_diag_2 / norm(dx, dy);
float decay_seconds = decay_slow + (decay_fast - decay_slow) * (1.0f + dot) * 0.5f;
float step = 1.0f - 1.0f / exp2f(10.0f * dt / decay_seconds);
ct->corner_x[i] += dx * step;
ct->corner_y[i] += dy * step;
float decay = (min_dot == max_dot)
? decay_slow
: decay_slow + (decay_fast - decay_slow) * (dot[i] - min_dot) / (max_dot - min_dot);
float step = 1.0f - exp2f(-10.0f * dt / decay);
ct->corner_x[i] += dx[i] * step;
ct->corner_y[i] += dy[i] * step;
}
}
ct->updated_at = now;
// check if any corner is still far from the cursor corner, so it should be rendered
for (int i = 0; i < 4; ++i) {
float dx = fabsf(EDGE(x, ci[i][0]) - ct->corner_x[i]);
float dy = fabsf(EDGE(y, ci[i][1]) - ct->corner_y[i]);