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Change: make for smooth-scrolling based on actual time

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This means if rendering takes a bit longer, scrolling goes a bit
quicker, making travel time always about the same time for the
same distance.
This commit is contained in:
Patric Stout
2024-01-22 16:45:00 +01:00
committed by Patric Stout
parent cbb24b5d71
commit ea8c1d8597
5 changed files with 61 additions and 29 deletions
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65
src/viewport.cpp
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@@ -1868,11 +1868,65 @@ static inline void ClampViewportToMap(const Viewport *vp, int *scroll_x, int *sc
}
}
/**
* Clamp the smooth scroll to a maxmimum speed and distance based on time elapsed.
*
* Every 30ms, we move 1/4th of the distance, to give a smooth movement experience.
* But we never go over the max_scroll speed.
*
* @param delta_ms Time elapsed since last update.
* @param delta_hi The distance to move in highest dimension (can't be zero).
* @param delta_lo The distance to move in lowest dimension.
* @param[out] delta_hi_clamped The clamped distance to move in highest dimension.
* @param[out] delta_lo_clamped The clamped distance to move in lowest dimension.
*/
static void ClampSmoothScroll(uint32_t delta_ms, int64_t delta_hi, int64_t delta_lo, int &delta_hi_clamped, int &delta_lo_clamped)
{
/** A tile is 64 pixels in width at 1x zoom; viewport coordinates are in 4x zoom. */
constexpr int PIXELS_PER_TILE = TILE_PIXELS * 2 * ZOOM_LVL_BASE;
constexpr int MS_PER_STEP = 30; ///< Time between each step in the smooth scroll.
static uint32_t remainder_time = 0;
assert(delta_hi != 0);
int64_t delta_left = delta_hi;
int max_scroll = 0;
for (uint count = 0; count < (delta_ms + remainder_time) / MS_PER_STEP; count++) {
/* We move 1/4th of the distance per 30ms, to give a smooth movement experience. */
delta_left = delta_left * 3 / 4;
/* But we don't allow more than 16 tiles movement per 30ms; longer distances take longer.
* This means that the full width of a map would take ~1 second, ignoring the slowdown:
* 256 / 16 * 30ms = 480ms. */
max_scroll += Map::ScaleBySize1D(16 * PIXELS_PER_TILE);
}
remainder_time = (delta_ms + remainder_time) % MS_PER_STEP;
/* We never go over the max_scroll speed. */
delta_hi_clamped = Clamp(delta_hi - delta_left, -max_scroll, max_scroll);
/* The lower delta is in ratio of the higher delta, so we keep going straight at the destination. */
delta_lo_clamped = delta_lo * delta_hi_clamped / delta_hi;
/* Ensure we always move (delta_hi can't be zero). */
if (delta_hi_clamped == 0) {
delta_hi_clamped = delta_hi > 0 ? 1 : -1;
}
/* Also ensure we always move on the lower delta. This is mostly to avoid a
* situation at borders, where you can't move from (x, y) to (x + 1, y),
* but you can move to (x + 1, y + 1). This due to how viewport clamping
* works and rounding issue. */
if (delta_lo_clamped == 0 && delta_lo != 0) {
delta_lo_clamped = delta_lo > 0 ? 1 : -1;
}
}
/**
* Update the viewport position being displayed.
* @param w %Window owning the viewport.
*/
void UpdateViewportPosition(Window *w)
void UpdateViewportPosition(Window *w, uint32_t delta_ms)
{
const Viewport *vp = w->viewport;
@@ -1893,19 +1947,14 @@ void UpdateViewportPosition(Window *w)
bool update_overlay = false;
if (delta_x != 0 || delta_y != 0) {
if (_settings_client.gui.smooth_scroll) {
int max_scroll = Map::ScaleBySize1D(512 * ZOOM_LVL_BASE);
int delta_x_clamped;
int delta_y_clamped;
if (abs(delta_x) > abs(delta_y)) {
delta_x_clamped = Clamp(DivAwayFromZero(delta_x, 4), -max_scroll, max_scroll);
delta_y_clamped = delta_y * delta_x_clamped / delta_x;
ClampSmoothScroll(delta_ms, delta_x, delta_y, delta_x_clamped, delta_y_clamped);
} else {
delta_y_clamped = Clamp(DivAwayFromZero(delta_y, 4), -max_scroll, max_scroll);
delta_x_clamped = delta_x * delta_y_clamped / delta_y;
ClampSmoothScroll(delta_ms, delta_y, delta_x, delta_y_clamped, delta_x_clamped);
}
w->viewport->scrollpos_x += delta_x_clamped;
w->viewport->scrollpos_y += delta_y_clamped;
} else {