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#include <mbgl/text/collision_feature.hpp>
#include <mbgl/util/math.hpp>
namespace mbgl {
CollisionFeature::CollisionFeature(const std::vector<Coordinate> &line, const Anchor &anchor,
const float top, const float bottom, const float left, const float right,
const float boxScale, const float padding, const bool alongLine) {
if (top == 0 && bottom == 0 && left == 0 && right == 0) return;
const float y1 = top * boxScale - padding;
const float y2 = bottom * boxScale + padding;
const float x1 = left * boxScale - padding;
const float x2 = right * boxScale + padding;
if (alongLine) {
float height = y2 - y1;
const float length = x2 - x1;
if (height <= 0.0f) return;
height = std::max(10.0f * boxScale, height);
bboxifyLabel(line, anchor, length, height);
} else {
boxes.emplace_back(anchor, x1, y1, x2, y2, std::numeric_limits<float>::infinity());
}
}
void CollisionFeature::bboxifyLabel(const std::vector<Coordinate> &line,
const Anchor &anchor, const float labelLength, const float boxSize) {
const float step = boxSize / 2;
const unsigned int nBoxes = std::floor(labelLength / step);
// offset the center of the first box by half a box so that the edge of the
// box is at the edge of the label.
const float firstBoxOffset = -boxSize / 2;
Coordinate anchorPoint = Coordinate{ (int16_t)anchor.x, (int16_t)anchor.y };
Coordinate &p = anchorPoint;
int index = anchor.segment + 1;
float anchorDistance = firstBoxOffset;
// move backwards along the line to the first segment the label appears on
do {
index--;
// there isn't enough room for the label after the beginning of the line
// checkMaxAngle should have already caught this
if (index < 0) return;
anchorDistance -= util::dist<float>(line[index], p);
p = line[index];
} while (anchorDistance > -labelLength / 2);
float segmentLength = util::dist<float>(line[index], line[index + 1]);
for (unsigned int i = 0; i < nBoxes; i++) {
// the distance the box will be from the anchor
const float boxDistanceToAnchor = -labelLength / 2 + i * step;
// the box is not on the current segment. Move to the next segment.
while (anchorDistance + segmentLength < boxDistanceToAnchor) {
anchorDistance += segmentLength;
index++;
// There isn't enough room before the end of the line.
if (index + 1 >= (int)line.size()) return;
segmentLength = util::dist<float>(line[index], line[index + 1]);
}
// the distance the box will be from the beginning of the segment
const float segmentBoxDistance = boxDistanceToAnchor - anchorDistance;
const auto& p0 = line[index];
const auto& p1 = line[index + 1];
vec2<float> boxAnchor = {
p0.x + segmentBoxDistance / segmentLength * (p1.x - p0.x),
p0.y + segmentBoxDistance / segmentLength * (p1.y - p0.y)
};
const float distanceToInnerEdge = std::max(std::fabs(boxDistanceToAnchor - firstBoxOffset) - step / 2, 0.0f);
const float maxScale = labelLength / 2 / distanceToInnerEdge;
boxes.emplace_back(boxAnchor, -boxSize / 2, -boxSize / 2, boxSize / 2, boxSize / 2, maxScale);
}
}
}
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