skia2/include/core/SkPathMeasure.h

/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkPathMeasure_DEFINED
#define SkPathMeasure_DEFINED

#include "../private/SkTDArray.h"
#include "SkPath.h"

struct SkConic;

class SK_API SkPathMeasure : SkNoncopyable {
public:
    SkPathMeasure();
    /** Initialize the pathmeasure with the specified path. The path must remain valid
        for the lifetime of the measure object, or until setPath() is called with
        a different path (or null), since the measure object keeps a pointer to the
        path object (does not copy its data).

        resScale controls the precision of the measure. values > 1 increase the
        precision (and possible slow down the computation).
    */
    SkPathMeasure(const SkPath& path, bool forceClosed, SkScalar resScale = 1);
    ~SkPathMeasure();

    /** Reset the pathmeasure with the specified path. The path must remain valid
        for the lifetime of the measure object, or until setPath() is called with
        a different path (or null), since the measure object keeps a pointer to the
        path object (does not copy its data).
    */
    void setPath(const SkPath*, bool forceClosed);

    /** Return the total length of the current contour, or 0 if no path
        is associated (e.g. resetPath(null))
    */
    SkScalar getLength();

    /** Pins distance to 0 <= distance <= getLength(), and then computes
        the corresponding position and tangent.
        Returns false if there is no path, or a zero-length path was specified, in which case
        position and tangent are unchanged.
    */
    bool SK_WARN_UNUSED_RESULT getPosTan(SkScalar distance, SkPoint* position,
                                         SkVector* tangent);

    enum MatrixFlags {
        kGetPosition_MatrixFlag     = 0x01,
        kGetTangent_MatrixFlag      = 0x02,
        kGetPosAndTan_MatrixFlag    = kGetPosition_MatrixFlag | kGetTangent_MatrixFlag
    };

    /** Pins distance to 0 <= distance <= getLength(), and then computes
        the corresponding matrix (by calling getPosTan).
        Returns false if there is no path, or a zero-length path was specified, in which case
        matrix is unchanged.
    */
    bool SK_WARN_UNUSED_RESULT getMatrix(SkScalar distance, SkMatrix* matrix,
                                  MatrixFlags flags = kGetPosAndTan_MatrixFlag);

    /** Given a start and stop distance, return in dst the intervening segment(s).
        If the segment is zero-length, return false, else return true.
        startD and stopD are pinned to legal values (0..getLength()). If startD > stopD
        then return false (and leave dst untouched).
        Begin the segment with a moveTo if startWithMoveTo is true
    */
    bool getSegment(SkScalar startD, SkScalar stopD, SkPath* dst, bool startWithMoveTo);

    /** Return true if the current contour is closed()
    */
    bool isClosed();

    /** Move to the next contour in the path. Return true if one exists, or false if
        we're done with the path.
    */
    bool nextContour();

#ifdef SK_DEBUG
    void    dump();
#endif

private:
    SkPath::Iter    fIter;
    SkPath          fPath;
    SkScalar        fTolerance;
    SkScalar        fLength;            // relative to the current contour
    unsigned        fFirstPtIndex;      // relative to the current contour
    bool            fIsClosed;          // relative to the current contour
    bool            fForceClosed;

    struct Segment {
        SkScalar    fDistance;  // total distance up to this point
        unsigned    fPtIndex; // index into the fPts array
        unsigned    fTValue : 30;
        unsigned    fType : 2;  // actually the enum SkSegType
                                // See SkPathMeasurePriv.h

        SkScalar getScalarT() const;
    };
    SkTDArray<Segment>  fSegments;
    SkTDArray<SkPoint>  fPts; // Points used to define the segments

    static const Segment* NextSegment(const Segment*);

    void     buildSegments();
    SkScalar compute_quad_segs(const SkPoint pts[3], SkScalar distance,
                                int mint, int maxt, unsigned ptIndex);
    SkScalar compute_conic_segs(const SkConic&, SkScalar distance,
                                int mint, const SkPoint& minPt,
                                int maxt, const SkPoint& maxPt, unsigned ptIndex);
    SkScalar compute_cubic_segs(const SkPoint pts[3], SkScalar distance,
                                int mint, int maxt, unsigned ptIndex);
    const Segment* distanceToSegment(SkScalar distance, SkScalar* t);
    bool quad_too_curvy(const SkPoint pts[3]);
    bool conic_too_curvy(const SkPoint& firstPt, const SkPoint& midTPt,const SkPoint& lastPt);
    bool cheap_dist_exceeds_limit(const SkPoint& pt, SkScalar x, SkScalar y);
    bool cubic_too_curvy(const SkPoint pts[4]);
};

#endif