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- /*
- * 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 SkAnalyticEdge_DEFINED
- #define SkAnalyticEdge_DEFINED
- #include "include/private/SkTo.h"
- #include "src/core/SkEdge.h"
- #include <utility>
- struct SkAnalyticEdge {
- // Similar to SkEdge, the conic edges will be converted to quadratic edges
- enum Type {
- kLine_Type,
- kQuad_Type,
- kCubic_Type
- };
- SkAnalyticEdge* fNext;
- SkAnalyticEdge* fPrev;
- // During aaa_walk_edges, if this edge is a left edge,
- // then fRiteE is its corresponding right edge. Otherwise it's nullptr.
- SkAnalyticEdge* fRiteE;
- SkFixed fX;
- SkFixed fDX;
- SkFixed fUpperX; // The x value when y = fUpperY
- SkFixed fY; // The current y
- SkFixed fUpperY; // The upper bound of y (our edge is from y = fUpperY to y = fLowerY)
- SkFixed fLowerY; // The lower bound of y (our edge is from y = fUpperY to y = fLowerY)
- SkFixed fDY; // abs(1/fDX); may be SK_MaxS32 when fDX is close to 0.
- // fDY is only used for blitting trapezoids.
- SkFixed fSavedX; // For deferred blitting
- SkFixed fSavedY; // For deferred blitting
- SkFixed fSavedDY; // For deferred blitting
- int8_t fCurveCount; // only used by kQuad(+) and kCubic(-)
- uint8_t fCurveShift; // appled to all Dx/DDx/DDDx except for fCubicDShift exception
- uint8_t fCubicDShift; // applied to fCDx and fCDy only in cubic
- int8_t fWinding; // 1 or -1
- static const int kDefaultAccuracy = 2; // default accuracy for snapping
- static inline SkFixed SnapY(SkFixed y) {
- const int accuracy = kDefaultAccuracy;
- // This approach is safer than left shift, round, then right shift
- return ((unsigned)y + (SK_Fixed1 >> (accuracy + 1))) >> (16 - accuracy) << (16 - accuracy);
- }
- // Update fX, fY of this edge so fY = y
- inline void goY(SkFixed y) {
- if (y == fY + SK_Fixed1) {
- fX = fX + fDX;
- fY = y;
- } else if (y != fY) {
- // Drop lower digits as our alpha only has 8 bits
- // (fDX and y - fUpperY may be greater than SK_Fixed1)
- fX = fUpperX + SkFixedMul(fDX, y - fUpperY);
- fY = y;
- }
- }
- inline void goY(SkFixed y, int yShift) {
- SkASSERT(yShift >= 0 && yShift <= kDefaultAccuracy);
- SkASSERT(fDX == 0 || y - fY == SK_Fixed1 >> yShift);
- fY = y;
- fX += fDX >> yShift;
- }
- inline void saveXY(SkFixed x, SkFixed y, SkFixed dY) {
- fSavedX = x;
- fSavedY = y;
- fSavedDY = dY;
- }
- bool setLine(const SkPoint& p0, const SkPoint& p1);
- bool updateLine(SkFixed ax, SkFixed ay, SkFixed bx, SkFixed by, SkFixed slope);
- // return true if we're NOT done with this edge
- bool update(SkFixed last_y, bool sortY = true);
- #ifdef SK_DEBUG
- void dump() const {
- SkDebugf("edge: upperY:%d lowerY:%d y:%g x:%g dx:%g w:%d\n",
- fUpperY, fLowerY, SkFixedToFloat(fY), SkFixedToFloat(fX),
- SkFixedToFloat(fDX), fWinding);
- }
- void validate() const {
- SkASSERT(fPrev && fNext);
- SkASSERT(fPrev->fNext == this);
- SkASSERT(fNext->fPrev == this);
- SkASSERT(fUpperY < fLowerY);
- SkASSERT(SkAbs32(fWinding) == 1);
- }
- #endif
- };
- struct SkAnalyticQuadraticEdge : public SkAnalyticEdge {
- SkQuadraticEdge fQEdge;
- // snap y to integer points in the middle of the curve to accelerate AAA path filling
- SkFixed fSnappedX, fSnappedY;
- bool setQuadratic(const SkPoint pts[3]);
- bool updateQuadratic();
- inline void keepContinuous() {
- // We use fX as the starting x to ensure the continuouty.
- // Without it, we may break the sorted edge list.
- SkASSERT(SkAbs32(fX - SkFixedMul(fY - fSnappedY, fDX) - fSnappedX) < SK_Fixed1);
- SkASSERT(SkAbs32(fY - fSnappedY) < SK_Fixed1); // This may differ due to smooth jump
- fSnappedX = fX;
- fSnappedY = fY;
- }
- };
- struct SkAnalyticCubicEdge : public SkAnalyticEdge {
- SkCubicEdge fCEdge;
- SkFixed fSnappedY; // to make sure that y is increasing with smooth jump and snapping
- bool setCubic(const SkPoint pts[4], bool sortY = true);
- bool updateCubic(bool sortY = true);
- inline void keepContinuous() {
- SkASSERT(SkAbs32(fX - SkFixedMul(fDX, fY - SnapY(fCEdge.fCy)) - fCEdge.fCx) < SK_Fixed1);
- fCEdge.fCx = fX;
- fSnappedY = fY;
- }
- };
- struct SkBezier {
- int fCount; // 2 line, 3 quad, 4 cubic
- SkPoint fP0;
- SkPoint fP1;
- // See if left shift, covert to SkFDot6, and round has the same top and bottom y.
- // If so, the edge will be empty.
- static inline bool IsEmpty(SkScalar y0, SkScalar y1, int shift = 2) {
- #ifdef SK_RASTERIZE_EVEN_ROUNDING
- return SkScalarRoundToFDot6(y0, shift) == SkScalarRoundToFDot6(y1, shift);
- #else
- SkScalar scale = (1 << (shift + 6));
- return SkFDot6Round(int(y0 * scale)) == SkFDot6Round(int(y1 * scale));
- #endif
- }
- };
- struct SkLine : public SkBezier {
- bool set(const SkPoint pts[2]){
- if (IsEmpty(pts[0].fY, pts[1].fY)) {
- return false;
- }
- fCount = 2;
- fP0 = pts[0];
- fP1 = pts[1];
- return true;
- }
- };
- struct SkQuad : public SkBezier {
- SkPoint fP2;
- bool set(const SkPoint pts[3]){
- if (IsEmpty(pts[0].fY, pts[2].fY)) {
- return false;
- }
- fCount = 3;
- fP0 = pts[0];
- fP1 = pts[1];
- fP2 = pts[2];
- return true;
- }
- };
- struct SkCubic : public SkBezier {
- SkPoint fP2;
- SkPoint fP3;
- bool set(const SkPoint pts[4]){
- // We do not chop at y extrema for cubics so pts[0], pts[1], pts[2], pts[3] may not be
- // monotonic. Therefore, we have to check the emptiness for all three pairs, instead of just
- // checking IsEmpty(pts[0].fY, pts[3].fY).
- if (IsEmpty(pts[0].fY, pts[1].fY) && IsEmpty(pts[1].fY, pts[2].fY) &&
- IsEmpty(pts[2].fY, pts[3].fY)) {
- return false;
- }
- fCount = 4;
- fP0 = pts[0];
- fP1 = pts[1];
- fP2 = pts[2];
- fP3 = pts[3];
- return true;
- }
- };
- #endif
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