65 lines
2.1 KiB
C++
65 lines
2.1 KiB
C++
#pragma once
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#include <qpoint.h>
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#include <qvector.h>
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#include <cmath>
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#include <cstdint>
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namespace ZShell::internal {
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// Shared curve construction for SparklineContent (QPainter) and LineGraphItem
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// (QCanvasPainter). Input and output coordinates are logical (item-local);
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// device-pixel quantization happens inside so a stroke lands on whole pixel
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// columns and its edges are not interpolated across several columns. Keeping the
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// math in one place means both graphs align and smooth their lines identically,
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// whatever backend they paint through.
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inline qint64 toDev(qreal logical, qreal dpr) {
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return std::llround(logical * dpr);
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}
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inline qreal fromDev(qint64 device, qreal dpr) {
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return qreal(device) / dpr;
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}
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// Snap a line center so a whole-pixel-wide stroke sits on pixel boundaries when
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// the device width is even and on pixel centers when it is odd.
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qreal snapLine(qreal logical, qint64 widthDev, qreal dpr);
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// Catmull-Rom control points for the segment points[i] -> points[i + 1], with the
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// control y clamped to the segment's own y span so a curve never overshoots past
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// its endpoints. When curveSmoothing is off (or there are too few points) the
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// tangents are flat.
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void segmentControls(
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const QVector<QPointF>& points,
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int i,
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bool curveSmoothing,
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QPointF& c1,
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QPointF& c2);
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// y of the cubic bezier p1-c1-c2-p2 at targetX, found by bisection on t.
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qreal cubicY(
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const QPointF& p1,
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const QPointF& c1,
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const QPointF& c2,
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const QPointF& p2,
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qreal targetX);
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// The curve point at targetX on the polyline, interpolating across the segment
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// that contains it. Assumes points ascend in x.
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QPointF pointAtX(
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const QVector<QPointF>& points,
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qreal targetX,
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bool curveSmoothing);
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// A dense polyline through points, adding one vertex per device-pixel column
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// inside each segment so an edge never interpolates across several columns. The
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// result starts at points.first() and ends at points.last(). points must ascend in
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// x and hold at least two entries. Backends consume it as a moveTo/lineTo chain.
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QVector<QPointF> curveVertices(
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const QVector<QPointF>& points,
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qreal dpr,
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bool curveSmoothing);
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} // namespace ZShell::internal
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