michael@0: 
michael@0: /*
michael@0:  * Copyright 2006 The Android Open Source Project
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: 
michael@0: #ifndef SkEdge_DEFINED
michael@0: #define SkEdge_DEFINED
michael@0: 
michael@0: #include "SkRect.h"
michael@0: #include "SkFDot6.h"
michael@0: #include "SkMath.h"
michael@0: 
michael@0: // This correctly favors the lower-pixel when y0 is on a 1/2 pixel boundary
michael@0: #define SkEdge_Compute_DY(top, y0)  ((top << 6) + 32 - (y0))
michael@0: 
michael@0: struct SkEdge {
michael@0:     enum Type {
michael@0:         kLine_Type,
michael@0:         kQuad_Type,
michael@0:         kCubic_Type
michael@0:     };
michael@0: 
michael@0:     SkEdge* fNext;
michael@0:     SkEdge* fPrev;
michael@0: 
michael@0:     SkFixed fX;
michael@0:     SkFixed fDX;
michael@0:     int32_t fFirstY;
michael@0:     int32_t fLastY;
michael@0:     int8_t fCurveCount;    // only used by kQuad(+) and kCubic(-)
michael@0:     uint8_t fCurveShift;    // appled to all Dx/DDx/DDDx except for fCubicDShift exception
michael@0:     uint8_t fCubicDShift;   // applied to fCDx and fCDy only in cubic
michael@0:     int8_t  fWinding;       // 1 or -1
michael@0: 
michael@0:     int setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip,
michael@0:                 int shiftUp);
michael@0:     // call this version if you know you don't have a clip
michael@0:     inline int setLine(const SkPoint& p0, const SkPoint& p1, int shiftUp);
michael@0:     inline int updateLine(SkFixed ax, SkFixed ay, SkFixed bx, SkFixed by);
michael@0:     void chopLineWithClip(const SkIRect& clip);
michael@0: 
michael@0:     inline bool intersectsClip(const SkIRect& clip) const {
michael@0:         SkASSERT(fFirstY < clip.fBottom);
michael@0:         return fLastY >= clip.fTop;
michael@0:     }
michael@0: 
michael@0: #ifdef SK_DEBUG
michael@0:     void dump() const {
michael@0:         SkDebugf("edge: firstY:%d lastY:%d x:%g dx:%g w:%d\n", fFirstY, fLastY, SkFixedToFloat(fX), SkFixedToFloat(fDX), fWinding);
michael@0:     }
michael@0: 
michael@0:     void validate() const {
michael@0:         SkASSERT(fPrev && fNext);
michael@0:         SkASSERT(fPrev->fNext == this);
michael@0:         SkASSERT(fNext->fPrev == this);
michael@0: 
michael@0:         SkASSERT(fFirstY <= fLastY);
michael@0:         SkASSERT(SkAbs32(fWinding) == 1);
michael@0:     }
michael@0: #endif
michael@0: };
michael@0: 
michael@0: struct SkQuadraticEdge : public SkEdge {
michael@0:     SkFixed fQx, fQy;
michael@0:     SkFixed fQDx, fQDy;
michael@0:     SkFixed fQDDx, fQDDy;
michael@0:     SkFixed fQLastX, fQLastY;
michael@0: 
michael@0:     int setQuadratic(const SkPoint pts[3], int shiftUp);
michael@0:     int updateQuadratic();
michael@0: };
michael@0: 
michael@0: struct SkCubicEdge : public SkEdge {
michael@0:     SkFixed fCx, fCy;
michael@0:     SkFixed fCDx, fCDy;
michael@0:     SkFixed fCDDx, fCDDy;
michael@0:     SkFixed fCDDDx, fCDDDy;
michael@0:     SkFixed fCLastX, fCLastY;
michael@0: 
michael@0:     int setCubic(const SkPoint pts[4], const SkIRect* clip, int shiftUp);
michael@0:     int updateCubic();
michael@0: };
michael@0: 
michael@0: int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, int shift) {
michael@0:     SkFDot6 x0, y0, x1, y1;
michael@0: 
michael@0:     {
michael@0:         float scale = float(1 << (shift + 6));
michael@0:         x0 = int(p0.fX * scale);
michael@0:         y0 = int(p0.fY * scale);
michael@0:         x1 = int(p1.fX * scale);
michael@0:         y1 = int(p1.fY * scale);
michael@0:     }
michael@0: 
michael@0:     int winding = 1;
michael@0: 
michael@0:     if (y0 > y1) {
michael@0:         SkTSwap(x0, x1);
michael@0:         SkTSwap(y0, y1);
michael@0:         winding = -1;
michael@0:     }
michael@0: 
michael@0:     int top = SkFDot6Round(y0);
michael@0:     int bot = SkFDot6Round(y1);
michael@0: 
michael@0:     // are we a zero-height line?
michael@0:     if (top == bot) {
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0);
michael@0:     const int dy  = SkEdge_Compute_DY(top, y0);
michael@0: 
michael@0:     fX          = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy));   // + SK_Fixed1/2
michael@0:     fDX         = slope;
michael@0:     fFirstY     = top;
michael@0:     fLastY      = bot - 1;
michael@0:     fCurveCount = 0;
michael@0:     fWinding    = SkToS8(winding);
michael@0:     fCurveShift = 0;
michael@0:     return 1;
michael@0: }
michael@0: 
michael@0: 
michael@0: #endif