81 lines
2.7 KiB
C++
81 lines
2.7 KiB
C++
#include <mbgl/text/check_max_angle.hpp>
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#include <mbgl/geometry/anchor.hpp>
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#include <mbgl/util/math.hpp>
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#include <queue>
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namespace mbgl {
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struct Corner {
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Corner(float _distance, float _angleDelta)
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: distance(_distance),
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angleDelta(_angleDelta) {}
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float distance;
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float angleDelta;
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};
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bool checkMaxAngle(const GeometryCoordinates& line,
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const Anchor& anchor,
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const float labelLength,
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const float windowSize,
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const float maxAngle) {
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// horizontal labels always pass
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if (!anchor.segment) return true;
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GeometryCoordinate anchorPoint = convertPoint<int16_t>(anchor.point);
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GeometryCoordinate& p = anchorPoint;
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std::size_t index = *anchor.segment + 1;
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float anchorDistance = 0;
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// move backwards along the line to the first segment the label appears on
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while (anchorDistance > -labelLength / 2) {
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// there isn't enough room for the label after the beginning of the line
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if (index == 0u) return false;
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index--;
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anchorDistance -= util::dist<float>(line[index], p);
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p = line[index];
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}
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anchorDistance += util::dist<float>(line[index], line[index + 1]);
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index++;
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// store recent corners and their total angle difference
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std::queue<Corner> recentCorners;
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float recentAngleDelta = 0;
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// move forwards by the length of the label and check angles along the way
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while (anchorDistance < labelLength / 2) {
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// there isn't enough room for the label before the end of the line
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if (index + 1 >= line.size()) return false;
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auto& prev = line[index - 1];
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auto& current = line[index];
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auto& next = line[index + 1];
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double angleDelta = util::angle_to(prev, current) - util::angle_to(current, next);
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// restrict angle to -pi..pi range
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angleDelta = std::fabs(std::fmod(angleDelta + 3 * M_PI, M_PI * 2) - M_PI);
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recentCorners.emplace(anchorDistance, static_cast<float>(angleDelta));
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recentAngleDelta += static_cast<float>(angleDelta);
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// remove corners that are far enough away from the list of recent anchors
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while (anchorDistance - recentCorners.front().distance > windowSize) {
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recentAngleDelta -= recentCorners.front().angleDelta;
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recentCorners.pop();
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}
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// the sum of angles within the window area exceeds the maximum allowed value. check fails.
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if (recentAngleDelta > maxAngle) return false;
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index++;
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anchorDistance += util::dist<float>(current, next);
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}
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// no part of the line had an angle greater than the maximum allowed. check passes.
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return true;
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}
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} // namespace mbgl
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