Integrated new triangulating stroker into Qt

1 files changed, 299 insertions, 0 deletions

diff --git a/src/opengl/gl2paintengineex/qtriangulatingstroker.cpp b/src/opengl/gl2paintengineex/qtriangulatingstroker.cpp
new file mode 100644
index 0000000..250dab6
--- /dev/null
+++ b/src/opengl/gl2paintengineex/qtriangulatingstroker.cpp
@@ -0,0 +1,299 @@
+#include "qtriangulatingstroker_p.h"
+#include <qmath.h>
+
+
+#define CURVE_FLATNESS Q_PI / 8
+
+
+
+
+void QTriangulatingStroker::endCapOrJoinClosed(const qreal *start, const qreal *cur,
+                                               bool implicitClose, bool endsAtStart)
+{
+    if (endsAtStart) {
+        join(start + 2);
+    } else if (implicitClose) {
+        join(start);
+        lineTo(start);
+        join(start+2);
+    } else {
+        endCap(cur);
+    }
+}
+
+
+void QTriangulatingStroker::process(const QVectorPath &path, const QPen &pen)
+{
+    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/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_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 = qSin(Q_PI / m_roundness); // ### Use qFastSin
+    m_cos_theta = qCos(Q_PI / m_roundness);
+
+    const qreal *endPts = pts + (count<<1);
+    const qreal *startPts;
+
+    Qt::PenCapStyle cap = m_cap_style;
+
+    if (!types) {
+        startPts = pts;
+
+        bool endsAtStart = startPts[0] == *(endPts-2) && startPts[1] == *(endPts-1);
+
+        Qt::PenCapStyle cap = m_cap_style;
+        if (endsAtStart || path.hasImplicitClose())
+            m_cap_style = Qt::FlatCap;
+        moveTo(pts);
+        m_cap_style = cap;
+        pts += 2;
+        lineTo(pts);
+        pts += 2;
+        while (pts < endPts) {
+            join(pts);
+            lineTo(pts);
+            pts += 2;
+        }
+
+        endCapOrJoinClosed(startPts, pts-2, path.hasImplicitClose(), endsAtStart);
+
+    } else {
+        bool endsAtStart;
+        while (pts < endPts) {
+            switch (*types) {
+            case QPainterPath::MoveToElement: {
+                if (pts != path.points())
+                    endCapOrJoinClosed(startPts, pts, 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);
+    }
+}
+
+void QTriangulatingStroker::cubicTo(const qreal *pts)
+{
+    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;
+}
+
+
+
+static void qdashprocessor_moveTo(qreal x, qreal y, void *data)
+{
+    ((QDashedStrokeProcessor *) data)->addElement(QPainterPath::MoveToElement, x, y);
+}
+
+static void qdashprocessor_lineTo(qreal x, qreal y, void *data)
+{
+    ((QDashedStrokeProcessor *) data)->addElement(QPainterPath::LineToElement, x, y);
+}
+
+static void qdashprocessor_cubicTo(qreal, qreal, qreal, qreal, qreal, qreal, void *)
+{
+    Q_ASSERT(0); // The dasher should not produce curves...
+}
+
+QDashedStrokeProcessor::QDashedStrokeProcessor()
+    : m_dash_stroker(0), m_inv_scale(1)
+{
+    m_dash_stroker.setMoveToHook(qdashprocessor_moveTo);
+    m_dash_stroker.setLineToHook(qdashprocessor_lineTo);
+    m_dash_stroker.setCubicToHook(qdashprocessor_cubicTo);
+}
+
+void QDashedStrokeProcessor::process(const QVectorPath &path, const QPen &pen)
+{
+
+    const qreal *pts = path.points();
+    const QPainterPath::ElementType *types = path.elements();
+    int count = path.elementCount();
+
+    m_points.reset();
+    m_types.reset();
+
+    qreal width = pen.width();
+    if (width == 0)
+        width = 1;
+
+    m_dash_stroker.setDashPattern(pen.dashPattern());
+    m_dash_stroker.setStrokeWidth(width);
+    m_dash_stroker.setMiterLimit(pen.miterLimit());
+    qreal curvyness = sqrt(width) * m_inv_scale / 8;
+
+    if (count < 2)
+        return;
+
+    const qreal *endPts = pts + (count<<1);
+
+    m_dash_stroker.begin(this);
+
+    if (!types) {
+        m_dash_stroker.moveTo(pts[0], pts[1]);
+        pts += 2;
+        while (pts < endPts) {
+            m_dash_stroker.lineTo(pts[0], pts[1]);
+            pts += 2;
+        }
+    } else {
+        while (pts < endPts) {
+            switch (*types) {
+            case QPainterPath::MoveToElement:
+                m_dash_stroker.moveTo(pts[0], pts[1]);
+                pts += 2;
+                ++types;
+                break;
+            case QPainterPath::LineToElement:
+                m_dash_stroker.lineTo(pts[0], pts[1]);
+                pts += 2;
+                ++types;
+                break;
+            case QPainterPath::CurveToElement: {
+                QBezier b = QBezier::fromPoints(*(((const QPointF *) pts) - 1),
+                                                *(((const QPointF *) pts)),
+                                                *(((const QPointF *) pts) + 1),
+                                                *(((const QPointF *) pts) + 2));
+                QRectF bounds = b.bounds();
+                int threshold = qMin<float>(64, qMax(bounds.width(), bounds.height()) * curvyness);
+                if (threshold < 4)
+                    threshold = 4;
+                qreal threshold_minus_1 = threshold - 1;
+                for (int i=0; i<threshold; ++i) {
+                    QPointF pt = b.pointAt(i / threshold_minus_1);
+                    m_dash_stroker.lineTo(pt.x(), pt.y());
+                }
+                pts += 6;
+                types += 3;
+                break; }
+            default: break;
+            }
+        }
+    }
+
+    m_dash_stroker.end();
+}