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