mirror of
https://github.com/firestar5683/StarPilot.git
synced 2026-11-08 05:23:41 +08:00
Trey Moen
65c411433b
* cabana: reduce downloader startup and dense chart rendering overhead * cabana: remove downloader spawn tests
40 lines
1.4 KiB
C++
40 lines
1.4 KiB
C++
#pragma once
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#include <algorithm>
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#include <array>
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#include <cstddef>
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#include <iterator>
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#include <vector>
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namespace chart {
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// Keep endpoints and both extrema in time order in each pixel column. Only rendering
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// uses this envelope; calculations, cursor values and exports retain every sample.
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template <class Iterator>
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auto pixelEnvelope(Iterator begin, Iterator end, double min, double max, int pixels) {
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using Point = typename std::iterator_traits<Iterator>::value_type;
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std::vector<Point> result;
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if (begin == end || pixels <= 0 || max <= min) return result;
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result.reserve(std::min<size_t>(end - begin, (size_t)pixels * 4));
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auto column = [&](const auto &p) {
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return (int)std::clamp((p.x - min) / (max - min) * pixels, 0.0, double(pixels - 1));
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};
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while (begin != end) {
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auto last = begin, low = begin, high = begin, next = begin + 1;
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const int bucket = column(*begin);
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while (next != end && column(*next) == bucket) {
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if (next->y < low->y) low = next;
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if (next->y > high->y) high = next;
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last = next++;
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}
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std::array<Iterator, 4> selected{begin, low, high, last};
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std::sort(selected.begin(), selected.end());
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auto unique_end = std::unique(selected.begin(), selected.end());
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for (auto it = selected.begin(); it != unique_end; ++it) result.push_back(**it);
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begin = next;
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}
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return result;
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}
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} // namespace chart
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