use linear time calculation when applicable in timingdata for etaner

src/TimingData.cpp

@@ -1415,8 +1415,38 @@ float TimingData::WhereUAtBroNoOffset(float beat) const {
 
 const vector<float>& TimingData::BuildAndGetEtaner(const vector<int>& nerv) {
 	ElapsedTimesAtNonEmptyRows.clear();
-	for (size_t i = 0; i < nerv.size(); i++)
-		ElapsedTimesAtNonEmptyRows.emplace_back(GetElapsedTimeFromBeatNoOffset(NoteRowToBeat(nerv[i])));
+	const vector<TimingSegment*>* segs = m_avpTimingSegments;
+	const vector<TimingSegment*>& bpms = segs[SEGMENT_BPM];
+	const vector<TimingSegment*>& warps = segs[SEGMENT_WARP];
+	const vector<TimingSegment*>& stops = segs[SEGMENT_STOP];
+	const vector<TimingSegment*>& delays = segs[SEGMENT_DELAY];
+
+	// use linear calculations if linear time is determined -mina
+	if (warps.size() + stops.size() + delays.size() == 0 && nerv.size() > 0) {
+		float last_time = 0.f;
+		float bps = GetBPMAtRow(0) / 60.0f;
+		int lastbpmrow = 0;
+		size_t idx = 0;
+
+		for (auto& b : bpms) {
+			int event_row = b->GetRow();
+			float time_to_next_event = NoteRowToBeat(event_row - lastbpmrow) / bps;
+			float next_event_time = last_time + time_to_next_event;
+			while (nerv[idx] <= event_row && idx < nerv.size()) {
+				float perc = (nerv[idx] - lastbpmrow) / static_cast<float>(event_row - lastbpmrow);
+				float minatime = last_time + time_to_next_event * perc - m_fBeat0OffsetInSeconds;
+				ElapsedTimesAtNonEmptyRows.emplace_back(minatime);
+				++idx;
+			}
+			last_time = next_event_time;
+			bps = GetBPMAtRow(event_row) / 60.0f;
+			lastbpmrow = event_row;
+		}
+		return ElapsedTimesAtNonEmptyRows;
+	}
+
+	for(auto& n : nerv)
+		ElapsedTimesAtNonEmptyRows.emplace_back(GetElapsedTimeFromBeatNoOffset(NoteRowToBeat(n)));
 	return ElapsedTimesAtNonEmptyRows;
 }