| |
| /* |
| * 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. |
| */ |
| |
| |
| #include "SkStrokerPriv.h" |
| #include "SkGeometry.h" |
| #include "SkPath.h" |
| |
| static void ButtCapper(SkPath* path, const SkPoint& pivot, |
| const SkVector& normal, const SkPoint& stop, |
| SkPath*) |
| { |
| path->lineTo(stop.fX, stop.fY); |
| } |
| |
| static void RoundCapper(SkPath* path, const SkPoint& pivot, |
| const SkVector& normal, const SkPoint& stop, |
| SkPath*) |
| { |
| SkScalar px = pivot.fX; |
| SkScalar py = pivot.fY; |
| SkScalar nx = normal.fX; |
| SkScalar ny = normal.fY; |
| SkScalar sx = SkScalarMul(nx, CUBIC_ARC_FACTOR); |
| SkScalar sy = SkScalarMul(ny, CUBIC_ARC_FACTOR); |
| |
| path->cubicTo(px + nx + CWX(sx, sy), py + ny + CWY(sx, sy), |
| px + CWX(nx, ny) + sx, py + CWY(nx, ny) + sy, |
| px + CWX(nx, ny), py + CWY(nx, ny)); |
| path->cubicTo(px + CWX(nx, ny) - sx, py + CWY(nx, ny) - sy, |
| px - nx + CWX(sx, sy), py - ny + CWY(sx, sy), |
| stop.fX, stop.fY); |
| } |
| |
| static void SquareCapper(SkPath* path, const SkPoint& pivot, |
| const SkVector& normal, const SkPoint& stop, |
| SkPath* otherPath) |
| { |
| SkVector parallel; |
| normal.rotateCW(¶llel); |
| |
| if (otherPath) |
| { |
| path->setLastPt(pivot.fX + normal.fX + parallel.fX, pivot.fY + normal.fY + parallel.fY); |
| path->lineTo(pivot.fX - normal.fX + parallel.fX, pivot.fY - normal.fY + parallel.fY); |
| } |
| else |
| { |
| path->lineTo(pivot.fX + normal.fX + parallel.fX, pivot.fY + normal.fY + parallel.fY); |
| path->lineTo(pivot.fX - normal.fX + parallel.fX, pivot.fY - normal.fY + parallel.fY); |
| path->lineTo(stop.fX, stop.fY); |
| } |
| } |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| static bool is_clockwise(const SkVector& before, const SkVector& after) |
| { |
| return SkScalarMul(before.fX, after.fY) - SkScalarMul(before.fY, after.fX) > 0; |
| } |
| |
| enum AngleType { |
| kNearly180_AngleType, |
| kSharp_AngleType, |
| kShallow_AngleType, |
| kNearlyLine_AngleType |
| }; |
| |
| static AngleType Dot2AngleType(SkScalar dot) |
| { |
| // need more precise fixed normalization |
| // SkASSERT(SkScalarAbs(dot) <= SK_Scalar1 + SK_ScalarNearlyZero); |
| |
| if (dot >= 0) // shallow or line |
| return SkScalarNearlyZero(SK_Scalar1 - dot) ? kNearlyLine_AngleType : kShallow_AngleType; |
| else // sharp or 180 |
| return SkScalarNearlyZero(SK_Scalar1 + dot) ? kNearly180_AngleType : kSharp_AngleType; |
| } |
| |
| static void HandleInnerJoin(SkPath* inner, const SkPoint& pivot, const SkVector& after) |
| { |
| #if 1 |
| /* In the degenerate case that the stroke radius is larger than our segments |
| just connecting the two inner segments may "show through" as a funny |
| diagonal. To pseudo-fix this, we go through the pivot point. This adds |
| an extra point/edge, but I can't see a cheap way to know when this is |
| not needed :( |
| */ |
| inner->lineTo(pivot.fX, pivot.fY); |
| #endif |
| |
| inner->lineTo(pivot.fX - after.fX, pivot.fY - after.fY); |
| } |
| |
| static void BluntJoiner(SkPath* outer, SkPath* inner, const SkVector& beforeUnitNormal, |
| const SkPoint& pivot, const SkVector& afterUnitNormal, |
| SkScalar radius, SkScalar invMiterLimit, bool, bool) |
| { |
| SkVector after; |
| afterUnitNormal.scale(radius, &after); |
| |
| if (!is_clockwise(beforeUnitNormal, afterUnitNormal)) |
| { |
| SkTSwap<SkPath*>(outer, inner); |
| after.negate(); |
| } |
| |
| outer->lineTo(pivot.fX + after.fX, pivot.fY + after.fY); |
| HandleInnerJoin(inner, pivot, after); |
| } |
| |
| static void RoundJoiner(SkPath* outer, SkPath* inner, const SkVector& beforeUnitNormal, |
| const SkPoint& pivot, const SkVector& afterUnitNormal, |
| SkScalar radius, SkScalar invMiterLimit, bool, bool) |
| { |
| SkScalar dotProd = SkPoint::DotProduct(beforeUnitNormal, afterUnitNormal); |
| AngleType angleType = Dot2AngleType(dotProd); |
| |
| if (angleType == kNearlyLine_AngleType) |
| return; |
| |
| SkVector before = beforeUnitNormal; |
| SkVector after = afterUnitNormal; |
| SkRotationDirection dir = kCW_SkRotationDirection; |
| |
| if (!is_clockwise(before, after)) |
| { |
| SkTSwap<SkPath*>(outer, inner); |
| before.negate(); |
| after.negate(); |
| dir = kCCW_SkRotationDirection; |
| } |
| |
| SkPoint pts[kSkBuildQuadArcStorage]; |
| SkMatrix matrix; |
| matrix.setScale(radius, radius); |
| matrix.postTranslate(pivot.fX, pivot.fY); |
| int count = SkBuildQuadArc(before, after, dir, &matrix, pts); |
| SkASSERT((count & 1) == 1); |
| |
| if (count > 1) |
| { |
| for (int i = 1; i < count; i += 2) |
| outer->quadTo(pts[i].fX, pts[i].fY, pts[i+1].fX, pts[i+1].fY); |
| |
| after.scale(radius); |
| HandleInnerJoin(inner, pivot, after); |
| } |
| } |
| |
| #ifdef SK_SCALAR_IS_FLOAT |
| #define kOneOverSqrt2 (0.707106781f) |
| #else |
| #define kOneOverSqrt2 (46341) |
| #endif |
| |
| static void MiterJoiner(SkPath* outer, SkPath* inner, const SkVector& beforeUnitNormal, |
| const SkPoint& pivot, const SkVector& afterUnitNormal, |
| SkScalar radius, SkScalar invMiterLimit, |
| bool prevIsLine, bool currIsLine) |
| { |
| // negate the dot since we're using normals instead of tangents |
| SkScalar dotProd = SkPoint::DotProduct(beforeUnitNormal, afterUnitNormal); |
| AngleType angleType = Dot2AngleType(dotProd); |
| SkVector before = beforeUnitNormal; |
| SkVector after = afterUnitNormal; |
| SkVector mid; |
| SkScalar sinHalfAngle; |
| bool ccw; |
| |
| if (angleType == kNearlyLine_AngleType) |
| return; |
| if (angleType == kNearly180_AngleType) |
| { |
| currIsLine = false; |
| goto DO_BLUNT; |
| } |
| |
| ccw = !is_clockwise(before, after); |
| if (ccw) |
| { |
| SkTSwap<SkPath*>(outer, inner); |
| before.negate(); |
| after.negate(); |
| } |
| |
| /* Before we enter the world of square-roots and divides, |
| check if we're trying to join an upright right angle |
| (common case for stroking rectangles). If so, special case |
| that (for speed an accuracy). |
| Note: we only need to check one normal if dot==0 |
| */ |
| if (0 == dotProd && invMiterLimit <= kOneOverSqrt2) |
| { |
| mid.set(SkScalarMul(before.fX + after.fX, radius), |
| SkScalarMul(before.fY + after.fY, radius)); |
| goto DO_MITER; |
| } |
| |
| /* midLength = radius / sinHalfAngle |
| if (midLength > miterLimit * radius) abort |
| if (radius / sinHalf > miterLimit * radius) abort |
| if (1 / sinHalf > miterLimit) abort |
| if (1 / miterLimit > sinHalf) abort |
| My dotProd is opposite sign, since it is built from normals and not tangents |
| hence 1 + dot instead of 1 - dot in the formula |
| */ |
| sinHalfAngle = SkScalarSqrt(SkScalarHalf(SK_Scalar1 + dotProd)); |
| if (sinHalfAngle < invMiterLimit) |
| { |
| currIsLine = false; |
| goto DO_BLUNT; |
| } |
| |
| // choose the most accurate way to form the initial mid-vector |
| if (angleType == kSharp_AngleType) |
| { |
| mid.set(after.fY - before.fY, before.fX - after.fX); |
| if (ccw) |
| mid.negate(); |
| } |
| else |
| mid.set(before.fX + after.fX, before.fY + after.fY); |
| |
| mid.setLength(SkScalarDiv(radius, sinHalfAngle)); |
| DO_MITER: |
| if (prevIsLine) |
| outer->setLastPt(pivot.fX + mid.fX, pivot.fY + mid.fY); |
| else |
| outer->lineTo(pivot.fX + mid.fX, pivot.fY + mid.fY); |
| |
| DO_BLUNT: |
| after.scale(radius); |
| if (!currIsLine) |
| outer->lineTo(pivot.fX + after.fX, pivot.fY + after.fY); |
| HandleInnerJoin(inner, pivot, after); |
| } |
| |
| ///////////////////////////////////////////////////////////////////////////// |
| |
| SkStrokerPriv::CapProc SkStrokerPriv::CapFactory(SkPaint::Cap cap) |
| { |
| static const SkStrokerPriv::CapProc gCappers[] = { |
| ButtCapper, RoundCapper, SquareCapper |
| }; |
| |
| SkASSERT((unsigned)cap < SkPaint::kCapCount); |
| return gCappers[cap]; |
| } |
| |
| SkStrokerPriv::JoinProc SkStrokerPriv::JoinFactory(SkPaint::Join join) |
| { |
| static const SkStrokerPriv::JoinProc gJoiners[] = { |
| MiterJoiner, RoundJoiner, BluntJoiner |
| }; |
| |
| SkASSERT((unsigned)join < SkPaint::kJoinCount); |
| return gJoiners[join]; |
| } |
