SkHalfPlane Struct Reference

Public Types
enum	Result {   kAllNegative , kAllPositive , kMixed , kAllNegative ,   kAllPositive , kMixed }
enum	Result {   kAllNegative , kAllPositive , kMixed , kAllNegative ,   kAllPositive , kMixed }

Public Member Functions
SkScalar	eval (SkScalar x, SkScalar y) const
SkScalar	operator() (SkScalar x, SkScalar y) const
bool	normalize ()
Result	test (const SkRect &bounds) const
SkScalar	eval (SkScalar x, SkScalar y) const
SkScalar	operator() (SkScalar x, SkScalar y) const
bool	twoPts (SkPoint pts[2]) const
Result	test (const SkRect &bounds) const

Public Attributes
SkScalar	fA
SkScalar	fB
SkScalar	fC

Detailed Description

Definition at line 3818 of file SkPath.cpp.

Member Enumeration Documentation

Result [1/2]

enum SkHalfPlane::Result

Enumerator
kAllNegative
kAllPositive
kMixed
kAllNegative
kAllPositive
kMixed

Definition at line 3854 of file SkPath.cpp.

                {
        kAllNegative,
        kAllPositive,
        kMixed
    };

Result [2/2]

enum SkHalfPlane::Result

Enumerator
kAllNegative
kAllPositive
kMixed
kAllNegative
kAllPositive
kMixed

Definition at line 179 of file ClipSlide.cpp.

                {
        kAllNegative,
        kAllPositive,
        kMixed
    };

Member Function Documentation

eval() [1/2]

SkScalar SkHalfPlane::eval ( SkScalar  x, SkScalar  y  ) const

inline

Definition at line 3821 of file SkPath.cpp.

                                                {
        return fA * x + fB * y + fC;
    }

eval() [2/2]

SkScalar SkHalfPlane::eval ( SkScalar  x, SkScalar  y  ) const

inline

Definition at line 146 of file ClipSlide.cpp.

                                                {
        return fA * x + fB * y + fC;
    }

normalize()

bool SkHalfPlane::normalize ( )

inline

Definition at line 3826 of file SkPath.cpp.

                     {
        double a = fA;
        double b = fB;
        double c = fC;
        double dmag = sqrt(a * a + b * b);
        // length of initial plane normal is zero
        if (dmag == 0) {
           fA = fB = 0;
           fC = SK_Scalar1;
           return true;
        }
        double dscale = sk_ieee_double_divide(1.0, dmag);
        a *= dscale;
        b *= dscale;
        c *= dscale;
        // check if we're not finite, or normal is zero-length
        if (!SkIsFinite(a, b, c) ||
            (a == 0 && b == 0)) {
            fA = fB = 0;
            fC = SK_Scalar1;
            return false;
        }
        fA = a;
        fB = b;
        fC = c;
        return true;
    }

operator()() [1/2]

SkScalar SkHalfPlane::operator() ( SkScalar  x, SkScalar  y  ) const

inline

Definition at line 3824 of file SkPath.cpp.

{ return this->eval(x, y); }

operator()() [2/2]

SkScalar SkHalfPlane::operator() ( SkScalar  x, SkScalar  y  ) const

inline

Definition at line 149 of file ClipSlide.cpp.

{ return this->eval(x, y); }

test() [1/2]

Result SkHalfPlane::test ( const SkRect &  bounds ) const

inline

Definition at line 3859 of file SkPath.cpp.

                                            {
        // check whether the diagonal aligned with the normal crosses the plane
        SkPoint diagMin, diagMax;
        if (fA >= 0) {
            diagMin.fX = bounds.fLeft;
            diagMax.fX = bounds.fRight;
        } else {
            diagMin.fX = bounds.fRight;
            diagMax.fX = bounds.fLeft;
        }
        if (fB >= 0) {
            diagMin.fY = bounds.fTop;
            diagMax.fY = bounds.fBottom;
        } else {
            diagMin.fY = bounds.fBottom;
            diagMax.fY = bounds.fTop;
        }
        SkScalar test = this->eval(diagMin.fX, diagMin.fY);
        SkScalar sign = test*this->eval(diagMax.fX, diagMax.fY);
        if (sign > 0) {
            // the path is either all on one side of the half-plane or the other
            if (test < 0) {
                return kAllNegative;
            } else {
                return kAllPositive;
            }
        }
        return kMixed;
    }

test() [2/2]

Result SkHalfPlane::test ( const SkRect &  bounds ) const

inline

Definition at line 184 of file ClipSlide.cpp.

                                            {
        SkPoint diagMin, diagMax;
        if (fA >= 0) {
            diagMin.fX = bounds.fLeft;
            diagMax.fX = bounds.fRight;
        } else {
            diagMin.fX = bounds.fRight;
            diagMax.fX = bounds.fLeft;
        }
        if (fB >= 0) {
            diagMin.fY = bounds.fTop;
            diagMax.fY = bounds.fBottom;
        } else {
            diagMin.fY = bounds.fBottom;
            diagMax.fY = bounds.fTop;
        }
        SkScalar test = this->eval(diagMin.fX, diagMin.fY);
        SkScalar sign = test*this->eval(diagMax.fX, diagMin.fY);
        if (sign > 0) {
            // the path is either all on one side of the half-plane or the other
            if (test < 0) {
                return kAllNegative;
            } else {
                return kAllPositive;
            }
        }
        return kMixed;
    }

twoPts()

bool SkHalfPlane::twoPts ( SkPoint  pts[2] ) const

inline

Definition at line 151 of file ClipSlide.cpp.

                                      {
        // normalize plane to help with the perpendicular step, below
        SkScalar len = SkScalarSqrt(fA*fA + fB*fB);
        if (!len) {
            return false;
        }
        SkScalar denom = SkScalarInvert(len);
        SkScalar a = fA * denom;
        SkScalar b = fB * denom;
        SkScalar c = fC * denom;
 
        // We compute p0 on the half-plane by setting one of the components to 0
        // We compute p1 by stepping from p0 along a perpendicular to the normal
        if (b) {
            pts[0] = { 0, -c / b };
            pts[1] = { b, pts[0].fY - a};
        } else if (a) {
            pts[0] = { -c / a,        0 };
            pts[1] = { pts[0].fX + b, -a };
        } else {
            return false;
        }
 
        SkASSERT(SkScalarNearlyZero(this->operator()(pts[0].fX, pts[0].fY)));
        SkASSERT(SkScalarNearlyZero(this->operator()(pts[1].fX, pts[1].fY)));
        return true;
    }

Member Data Documentation

fA

SkScalar SkHalfPlane::fA

Definition at line 3819 of file SkPath.cpp.

fB

SkScalar SkHalfPlane::fB

Definition at line 3819 of file SkPath.cpp.

fC

SkScalar SkHalfPlane::fC

Definition at line 3819 of file SkPath.cpp.

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

• third_party/skia/src/core/SkPath.cpp
• third_party/skia/tools/viewer/ClipSlide.cpp