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#include <mbgl/renderer/frame_history.hpp>
using namespace mbgl;
// Record frame history that will be used to calculate fading params
void FrameHistory::record(timestamp now, float zoom) {
// first frame ever
if (!history.size()) {
history.emplace_back(FrameSnapshot{0, zoom});
history.emplace_back(FrameSnapshot{0, zoom});
}
if (history.size() > 0 || history.back().z != zoom) {
history.emplace_back(FrameSnapshot{now, zoom});
}
}
bool FrameHistory::needsAnimation(const timestamp duration) const {
if (!history.size()) {
return false;
}
// If we have a value that is older than duration and whose z value is the
// same as the most current z value, and if all values inbetween have the
// same z value, we don't need animation, otherwise we probably do.
const FrameSnapshot &pivot = history.back();
int i = -1;
while ((int)history.size() > i + 1 && history[i + 1].t + duration < pivot.t) {
i++;
}
if (i < 0) {
// There is no frame that is older than the duration time, so we need to
// check all frames.
i = 0;
}
// Make sure that all subsequent snapshots have the same zoom as the last
// pivot element.
for (; (int)history.size() > i; i++) {
if (history[i].z != pivot.z) {
return true;
}
}
return false;
}
FadeProperties FrameHistory::getFadeProperties(timestamp duration)
{
const timestamp currentTime = util::now();
// Remove frames until only one is outside the duration, or until there are only three
while (history.size() > 3 && history[1].t + duration < currentTime) {
history.pop_front();
}
if (history[1].t + duration < currentTime) {
history[0].z = history[1].z;
}
// Find the range of zoom levels we want to fade between
float startingZ = history.front().z;
const FrameSnapshot lastFrame = history.back();
float endingZ = lastFrame.z;
float lowZ = std::fmin(startingZ, endingZ);
float highZ = std::fmax(startingZ, endingZ);
// Calculate the speed of zooming, and how far it would zoom in terms of zoom levels in one
// duration
float zoomDiff = endingZ - history[1].z, timeDiff = lastFrame.t - history[1].t;
float fadedist = zoomDiff / (timeDiff / duration);
// At end of a zoom when the zoom stops changing continue pretending to zoom at that speed
// bump is how much farther it would have been if it had continued zooming at the same rate
float bump = (currentTime - lastFrame.t) / duration * fadedist;
return FadeProperties {
fadedist,
lowZ,
highZ,
bump
};
}
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