QTriangulatingStroker Class Reference

#include <qtriangulatingstroker_p.h>

Public Functions
void	process (const QVectorPath &path, const QPen &pen, const QRectF &clip)
	QTriangulatingStroker ()
void	setInvScale (qreal invScale)
int	vertexCount () const
const float *	vertices () const

Private Functions
void	arcPoints (float cx, float cy, float fromX, float fromY, float toX, float toY, QVarLengthArray< float > &points)
void	cubicTo (const qreal *pts)
void	emitLineSegment (float x, float y, float nx, float ny)
void	endCap (const qreal *pts)
void	endCapOrJoinClosed (const qreal *start, const qreal *cur, bool implicitClose, bool endsAtStart)
void	join (const qreal *pts)
void	lineTo (const qreal *pts)
void	moveTo (const qreal *pts)
void	normalVector (float x1, float y1, float x2, float y2, float *nx, float *ny)

Properties
Qt::PenCapStyle	m_cap_style
qreal	m_cos_theta
float	m_curvyness_add
float	m_curvyness_mul
float	m_cx
float	m_cy
qreal	m_inv_scale
Qt::PenJoinStyle	m_join_style
qreal	m_miter_limit
float	m_nvx
float	m_nvy
int	m_roundness
qreal	m_sin_theta
QDataBuffer< float >	m_vertices
float	m_width

Detailed Description

Definition at line 54 of file qtriangulatingstroker_p.h.

Constructors and Destructors

QTriangulatingStroker()

QTriangulatingStroker::QTriangulatingStroker ( )

inline

Definition at line 57 of file qtriangulatingstroker_p.h.

: m_vertices(0) {}

Functions

arcPoints()

void QTriangulatingStroker::arcPoints ( float  cx, float  cy, float  fromX, float  fromY, float  toX, float  toY, QVarLengthArray< float > &  points  )

private

Definition at line 426 of file qtriangulatingstroker.cpp.

Referenced by endCap(), join(), moveTo(), and setInvScale().

{
    float dx1 = fromX - cx;
    float dy1 = fromY - cy;
    float dx2 = toX - cx;
    float dy2 = toY - cy;

    // while more than 180 degrees left:
    while (dx1 * dy2 - dx2 * dy1 < 0) {
        float tmpx = dx1 * m_cos_theta - dy1 * m_sin_theta;
        float tmpy = dx1 * m_sin_theta + dy1 * m_cos_theta;
        dx1 = tmpx;
        dy1 = tmpy;
        points.append(cx + dx1);
        points.append(cy + dy1);
    }

    // while more than 90 degrees left:
    while (dx1 * dx2 + dy1 * dy2 < 0) {
        float tmpx = dx1 * m_cos_theta - dy1 * m_sin_theta;
        float tmpy = dx1 * m_sin_theta + dy1 * m_cos_theta;
        dx1 = tmpx;
        dy1 = tmpy;
        points.append(cx + dx1);
        points.append(cy + dy1);
    }

    // while more than 0 degrees left:
    while (dx1 * dy2 - dx2 * dy1 > 0) {
        float tmpx = dx1 * m_cos_theta - dy1 * m_sin_theta;
        float tmpy = dx1 * m_sin_theta + dy1 * m_cos_theta;
        dx1 = tmpx;
        dy1 = tmpy;
        points.append(cx + dx1);
        points.append(cy + dy1);
    }

    // remove last point which was rotated beyond [toX, toY].
    if (!points.isEmpty())
        points.resize(points.size() - 2);
}

cubicTo()

void QTriangulatingStroker::cubicTo ( const qreal *  pts )

private

Definition at line 285 of file qtriangulatingstroker.cpp.

Referenced by process(), and setInvScale().

{
    const QPointF *p = (const QPointF *) pts;
    QBezier bezier = QBezier::fromPoints(*(p - 1), p[0], p[1], p[2]);

    QRectF bounds = bezier.bounds();
    float rad = qMax(bounds.width(), bounds.height());
    int threshold = qMin<float>(64, (rad + m_curvyness_add) * m_curvyness_mul);
    if (threshold < 4)
        threshold = 4;
    qreal threshold_minus_1 = threshold - 1;
    float vx, vy;

    float cx = m_cx, cy = m_cy;
    float x, y;

    for (int i=1; i<threshold; ++i) {
        qreal t = qreal(i) / threshold_minus_1;
        QPointF p = bezier.pointAt(t);
        x = p.x();
        y = p.y();

        normalVector(cx, cy, x, y, &vx, &vy);

        emitLineSegment(x, y, vx, vy);

        cx = x;
        cy = y;
    }

    m_cx = cx;
    m_cy = cy;

    m_nvx = vx;
    m_nvy = vy;
}

emitLineSegment()

void QTriangulatingStroker::emitLineSegment ( float  x, float  y, float  nx, float  ny  )

inlineprivate

Definition at line 140 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), endCap(), join(), lineTo(), moveTo(), and setInvScale().

{
    m_vertices.add(x + vx);
    m_vertices.add(y + vy);
    m_vertices.add(x - vx);
    m_vertices.add(y - vy);
}

endCap()

void QTriangulatingStroker::endCap ( const qreal *  pts )

private

Definition at line 397 of file qtriangulatingstroker.cpp.

Referenced by endCapOrJoinClosed(), and setInvScale().

{
    switch (m_cap_style) {
    case Qt::FlatCap:
        break;
    case Qt::SquareCap:
        emitLineSegment(m_cx + m_nvy, m_cy - m_nvx, m_nvx, m_nvy);
        break;
    case Qt::RoundCap: {
        QVarLengthArray<float> points;
        int count = m_vertices.size();
        arcPoints(m_cx, m_cy, m_vertices.at(count - 2), m_vertices.at(count - 1), m_vertices.at(count - 4), m_vertices.at(count - 3), points);
        int front = 0;
        int end = points.size() / 2;
        while (front != end) {
            m_vertices.add(points[2 * end - 2]);
            m_vertices.add(points[2 * end - 1]);
            --end;
            if (front == end)
                break;
            m_vertices.add(points[2 * front + 0]);
            m_vertices.add(points[2 * front + 1]);
            ++front;
        }
        break; }
    default: break; // to shut gcc up...
    }
}

endCapOrJoinClosed()

void QTriangulatingStroker::endCapOrJoinClosed ( const qreal *  start, const qreal *  cur, bool  implicitClose, bool  endsAtStart  )

private

Definition at line 52 of file qtriangulatingstroker.cpp.

Referenced by process(), and setInvScale().

{
    if (endsAtStart) {
        join(start + 2);
    } else if (implicitClose) {
        join(start);
        lineTo(start);
        join(start+2);
    } else {
        endCap(cur);
    }
    int count = m_vertices.size();

    // Copy the (x, y) values because QDataBuffer::add(const float& t)
    // may resize the buffer, which will leave t pointing at the
    // previous buffer's memory region if we don't copy first.
    float x = m_vertices.at(count-2);
    float y = m_vertices.at(count-1);
    m_vertices.add(x);
    m_vertices.add(y);
}

join()

void QTriangulatingStroker::join ( const qreal *  pts )

private

Definition at line 322 of file qtriangulatingstroker.cpp.

Referenced by endCapOrJoinClosed(), process(), and setInvScale().

{
    // Creates a join to the next segment (m_cx, m_cy) -> (pts[0], pts[1])
    normalVector(m_cx, m_cy, pts[0], pts[1], &m_nvx, &m_nvy);

    switch (m_join_style) {
    case Qt::BevelJoin:
        break;
    case Qt::SvgMiterJoin:
    case Qt::MiterJoin: {
        // Find out on which side the join should be.
        int count = m_vertices.size();
        float prevNvx = m_vertices.at(count - 2) - m_cx;
        float prevNvy = m_vertices.at(count - 1) - m_cy;
        float xprod = prevNvx * m_nvy - prevNvy * m_nvx;
        float px, py, qx, qy;

        // If the segments are parallel, use bevel join.
        if (qFuzzyIsNull(xprod))
            break;

        // Find the corners of the previous and next segment to join.
        if (xprod < 0) {
            px = m_vertices.at(count - 2);
            py = m_vertices.at(count - 1);
            qx = m_cx - m_nvx;
            qy = m_cy - m_nvy;
        } else {
            px = m_vertices.at(count - 4);
            py = m_vertices.at(count - 3);
            qx = m_cx + m_nvx;
            qy = m_cy + m_nvy;
        }

        // Find intersection point.
        float pu = px * prevNvx + py * prevNvy;
        float qv = qx * m_nvx + qy * m_nvy;
        float ix = (m_nvy * pu - prevNvy * qv) / xprod;
        float iy = (prevNvx * qv - m_nvx * pu) / xprod;

        // Check that the distance to the intersection point is less than the miter limit.
        if ((ix - px) * (ix - px) + (iy - py) * (iy - py) <= m_miter_limit * m_miter_limit) {
            m_vertices.add(ix);
            m_vertices.add(iy);
            m_vertices.add(ix);
            m_vertices.add(iy);
        }
        // else
        // Do a plain bevel join if the miter limit is exceeded or if
        // the lines are parallel. This is not what the raster
        // engine's stroker does, but it is both faster and similar to
        // what some other graphics API's do.

        break; }
    case Qt::RoundJoin: {
        QVarLengthArray<float> points;
        int count = m_vertices.size();
        float prevNvx = m_vertices.at(count - 2) - m_cx;
        float prevNvy = m_vertices.at(count - 1) - m_cy;
        if (m_nvx * prevNvy - m_nvy * prevNvx < 0) {
            arcPoints(0, 0, m_nvx, m_nvy, -prevNvx, -prevNvy, points);
            for (int i = points.size() / 2; i > 0; --i)
                emitLineSegment(m_cx, m_cy, points[2 * i - 2], points[2 * i - 1]);
        } else {
            arcPoints(0, 0, -prevNvx, -prevNvy, m_nvx, m_nvy, points);
            for (int i = 0; i < points.size() / 2; ++i)
                emitLineSegment(m_cx, m_cy, points[2 * i + 0], points[2 * i + 1]);
        }
        break; }
    default: break; // gcc warn--
    }

    emitLineSegment(m_cx, m_cy, m_nvx, m_nvy);
}

lineTo()

void QTriangulatingStroker::lineTo ( const qreal *  pts )

inlineprivate

Definition at line 148 of file qtriangulatingstroker_p.h.

Referenced by endCapOrJoinClosed(), process(), and setInvScale().

{
    emitLineSegment(pts[0], pts[1], m_nvx, m_nvy);
    m_cx = pts[0];
    m_cy = pts[1];
}

moveTo()

void QTriangulatingStroker::moveTo ( const qreal *  pts )

private

Definition at line 226 of file qtriangulatingstroker.cpp.

Referenced by process(), and setInvScale().

{
    m_cx = pts[0];
    m_cy = pts[1];

    float x2 = pts[2];
    float y2 = pts[3];
    normalVector(m_cx, m_cy, x2, y2, &m_nvx, &m_nvy);


    // To acheive jumps we insert zero-area tringles. This is done by
    // adding two identical points in both the end of previous strip
    // and beginning of next strip
    bool invisibleJump = m_vertices.size();

    switch (m_cap_style) {
    case Qt::FlatCap:
        if (invisibleJump) {
            m_vertices.add(m_cx + m_nvx);
            m_vertices.add(m_cy + m_nvy);
        }
        break;
    case Qt::SquareCap: {
        float sx = m_cx - m_nvy;
        float sy = m_cy + m_nvx;
        if (invisibleJump) {
            m_vertices.add(sx + m_nvx);
            m_vertices.add(sy + m_nvy);
        }
        emitLineSegment(sx, sy, m_nvx, m_nvy);
        break; }
    case Qt::RoundCap: {
        QVarLengthArray<float> points;
        arcPoints(m_cx, m_cy, m_cx + m_nvx, m_cy + m_nvy, m_cx - m_nvx, m_cy - m_nvy, points);
        m_vertices.resize(m_vertices.size() + points.size() + 2 * int(invisibleJump));
        int count = m_vertices.size();
        int front = 0;
        int end = points.size() / 2;
        while (front != end) {
            m_vertices.at(--count) = points[2 * end - 1];
            m_vertices.at(--count) = points[2 * end - 2];
            --end;
            if (front == end)
                break;
            m_vertices.at(--count) = points[2 * front + 1];
            m_vertices.at(--count) = points[2 * front + 0];
            ++front;
        }

        if (invisibleJump) {
            m_vertices.at(count - 1) = m_vertices.at(count + 1);
            m_vertices.at(count - 2) = m_vertices.at(count + 0);
        }
        break; }
    default: break; // ssssh gcc...
    }
    emitLineSegment(m_cx, m_cy, m_nvx, m_nvy);
}

normalVector()

void QTriangulatingStroker::normalVector ( float  x1, float  y1, float  x2, float  y2, float *  nx, float *  ny  )

inlineprivate

Definition at line 121 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), join(), moveTo(), and setInvScale().

{
    float dx = x2 - x1;
    float dy = y2 - y1;

    float pw;

    if (dx == 0)
        pw = m_width / qAbs(dy);
    else if (dy == 0)
        pw = m_width / qAbs(dx);
    else
        pw = m_width / sqrt(dx*dx + dy*dy);

    *nx = -dy * pw;
    *ny = dx * pw;
}

process()

void QTriangulatingStroker::process	(	const QVectorPath &	path,
		const QPen &	pen,
		const QRectF &	clip
	)

Definition at line 76 of file qtriangulatingstroker.cpp.

Referenced by QTriangulatingStroker().

{
    const qreal *pts = path.points();
    const QPainterPath::ElementType *types = path.elements();
    int count = path.elementCount();
    if (count < 2)
        return;

    float realWidth = qpen_widthf(pen);
    if (realWidth == 0)
        realWidth = 1;

    m_width = realWidth / 2;

    bool cosmetic = pen.isCosmetic();
    if (cosmetic) {
        m_width = m_width * m_inv_scale;
    }

    m_join_style = qpen_joinStyle(pen);
    m_cap_style = qpen_capStyle(pen);
    m_vertices.reset();
    m_miter_limit = pen.miterLimit() * qpen_widthf(pen);

    // The curvyness is based on the notion that I originally wanted
    // roughly one line segment pr 4 pixels. This may seem little, but
    // because we sample at constantly incrementing B(t) E [0<t<1], we
    // will get longer segments where the curvature is small and smaller
    // segments when the curvature is high.
    //
    // To get a rough idea of the length of each curve, I pretend that
    // the curve is a 90 degree arc, whose radius is
    // qMax(curveBounds.width, curveBounds.height). Based on this
    // logic we can estimate the length of the outline edges based on
    // the radius + a pen width and adjusting for scale factors
    // depending on if the pen is cosmetic or not.
    //
    // The curvyness value of PI/14 was based on,
    // arcLength = 2*PI*r/4 = PI*r/2 and splitting length into somewhere
    // between 3 and 8 where 5 seemed to be give pretty good results
    // hence: Q_PI/14. Lower divisors will give more detail at the
    // direct cost of performance.

    // simplfy pens that are thin in device size (2px wide or less)
    if (realWidth < 2.5 && (cosmetic || m_inv_scale == 1)) {
        if (m_cap_style == Qt::RoundCap)
            m_cap_style = Qt::SquareCap;
        if (m_join_style == Qt::RoundJoin)
            m_join_style = Qt::MiterJoin;
        m_curvyness_add = 0.5;
        m_curvyness_mul = CURVE_FLATNESS / m_inv_scale;
        m_roundness = 1;
    } else if (cosmetic) {
        m_curvyness_add = realWidth / 2;
        m_curvyness_mul = CURVE_FLATNESS;
        m_roundness = qMax<int>(4, realWidth * CURVE_FLATNESS);
    } else {
        m_curvyness_add = m_width;
        m_curvyness_mul = CURVE_FLATNESS / m_inv_scale;
        m_roundness = qMax<int>(4, realWidth * m_curvyness_mul);
    }

    // Over this level of segmentation, there doesn't seem to be any
    // benefit, even for huge penWidth
    if (m_roundness > 24)
        m_roundness = 24;

    m_sin_theta = qFastSin(Q_PI / m_roundness);
    m_cos_theta = qFastCos(Q_PI / m_roundness);

    const qreal *endPts = pts + (count<<1);
    const qreal *startPts = 0;

    Qt::PenCapStyle cap = m_cap_style;

    if (!types) {
        // skip duplicate points
        while((pts + 2) < endPts && pts[0] == pts[2] && pts[1] == pts[3])
            pts += 2;
        if ((pts + 2) == endPts)
            return;

        startPts = pts;

        bool endsAtStart = startPts[0] == *(endPts-2) && startPts[1] == *(endPts-1);

        if (endsAtStart || path.hasImplicitClose())
            m_cap_style = Qt::FlatCap;
        moveTo(pts);
        m_cap_style = cap;
        pts += 2;
        lineTo(pts);
        pts += 2;
        while (pts < endPts) {
            if (m_cx != pts[0] || m_cy != pts[1]) {
                join(pts);
                lineTo(pts);
            }
            pts += 2;
        }

        endCapOrJoinClosed(startPts, pts-2, path.hasImplicitClose(), endsAtStart);

    } else {
        bool endsAtStart = false;
        while (pts < endPts) {
            switch (*types) {
            case QPainterPath::MoveToElement: {
                if (pts != path.points())
                    endCapOrJoinClosed(startPts, pts-2, path.hasImplicitClose(), endsAtStart);

                startPts = pts;
                int end = (endPts - pts) / 2;
                int i = 2; // Start looking to ahead since we never have two moveto's in a row
                while (i<end && types[i] != QPainterPath::MoveToElement) {
                    ++i;
                }
                endsAtStart = startPts[0] == pts[i*2 - 2] && startPts[1] == pts[i*2 - 1];
                if (endsAtStart || path.hasImplicitClose())
                    m_cap_style = Qt::FlatCap;

                moveTo(pts);
                m_cap_style = cap;
                pts+=2;
                ++types;
                break; }
            case QPainterPath::LineToElement:
                if (*(types - 1) != QPainterPath::MoveToElement)
                    join(pts);
                lineTo(pts);
                pts+=2;
                ++types;
                break;
            case QPainterPath::CurveToElement:
                if (*(types - 1) != QPainterPath::MoveToElement)
                    join(pts);
                cubicTo(pts);
                pts+=6;
                types+=3;
                break;
            default:
                Q_ASSERT(false);
                break;
            }
        }

        endCapOrJoinClosed(startPts, pts-2, path.hasImplicitClose(), endsAtStart);
    }
}

setInvScale()

void QTriangulatingStroker::setInvScale ( qreal  invScale )

inline

Definition at line 63 of file qtriangulatingstroker_p.h.

Referenced by QGL2PaintEngineExPrivate::updateMatrix().

{ m_inv_scale = invScale; }

vertexCount()

int QTriangulatingStroker::vertexCount ( ) const

inline

Definition at line 60 of file qtriangulatingstroker_p.h.

{ return m_vertices.size(); }

vertices()

const float* QTriangulatingStroker::vertices ( ) const

inline

Definition at line 61 of file qtriangulatingstroker_p.h.

{ return m_vertices.data(); }

Properties

m_cap_style

Qt::PenCapStyle QTriangulatingStroker::m_cap_style

private

Definition at line 92 of file qtriangulatingstroker_p.h.

Referenced by endCap(), moveTo(), and process().

m_cos_theta

qreal QTriangulatingStroker::m_cos_theta

private

Definition at line 86 of file qtriangulatingstroker_p.h.

Referenced by arcPoints(), and process().

m_curvyness_add

float QTriangulatingStroker::m_curvyness_add

private

Definition at line 89 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), and process().

m_curvyness_mul

float QTriangulatingStroker::m_curvyness_mul

private

Definition at line 88 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), and process().

m_cx

float QTriangulatingStroker::m_cx

private

Definition at line 79 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), endCap(), join(), lineTo(), moveTo(), and process().

m_cy

float QTriangulatingStroker::m_cy

private

Definition at line 79 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), endCap(), join(), lineTo(), moveTo(), and process().

m_inv_scale

qreal QTriangulatingStroker::m_inv_scale

private

Definition at line 87 of file qtriangulatingstroker_p.h.

Referenced by process(), setInvScale(), and QDashedStrokeProcessor::setInvScale().

m_join_style

Qt::PenJoinStyle QTriangulatingStroker::m_join_style

private

Definition at line 91 of file qtriangulatingstroker_p.h.

Referenced by join(), and process().

m_miter_limit

qreal QTriangulatingStroker::m_miter_limit

private

Definition at line 82 of file qtriangulatingstroker_p.h.

Referenced by join(), and process().

m_nvx

float QTriangulatingStroker::m_nvx

private

Definition at line 80 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), endCap(), join(), lineTo(), and moveTo().

m_nvy

float QTriangulatingStroker::m_nvy

private

Definition at line 80 of file qtriangulatingstroker_p.h.

Referenced by cubicTo(), endCap(), join(), lineTo(), and moveTo().

m_roundness

int QTriangulatingStroker::m_roundness

private

Definition at line 84 of file qtriangulatingstroker_p.h.

Referenced by process().

m_sin_theta

qreal QTriangulatingStroker::m_sin_theta

private

Definition at line 85 of file qtriangulatingstroker_p.h.

Referenced by arcPoints(), and process().

m_vertices

QDataBuffer<float> QTriangulatingStroker::m_vertices

private

Definition at line 77 of file qtriangulatingstroker_p.h.

Referenced by emitLineSegment(), endCap(), endCapOrJoinClosed(), join(), moveTo(), process(), vertexCount(), and vertices().

m_width

float QTriangulatingStroker::m_width

private

Definition at line 81 of file qtriangulatingstroker_p.h.

Referenced by normalVector(), and process().

---

The documentation for this class was generated from the following files:

• /src/opengl/gl2paintengineex/qtriangulatingstroker_p.h
• /src/opengl/gl2paintengineex/qtriangulatingstroker.cpp