The Tor Browser: gfx/skia/trunk/src/core/SkEdge.cpp@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkEdge.cpp@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkEdge.cpp

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /*
  * 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 "SkEdge.h"
 #include "SkFDot6.h"
 #include "SkMath.h"
 /*
     In setLine, setQuadratic, setCubic, the first thing we do is to convert
     the points into FDot6. This is modulated by the shift parameter, which
     will either be 0, or something like 2 for antialiasing.
     In the float case, we want to turn the float into .6 by saying pt * 64,
     or pt * 256 for antialiasing. This is implemented as 1 << (shift + 6).
     In the fixed case, we want to turn the fixed into .6 by saying pt >> 10,
     or pt >> 8 for antialiasing. This is implemented as pt >> (10 - shift).
 */
 static inline SkFixed SkFDot6ToFixedDiv2(SkFDot6 value) {
     // we want to return SkFDot6ToFixed(value >> 1), but we don't want to throw
     // away data in value, so just perform a modify up-shift
     return value << (16 - 6 - 1);
 }
 /////////////////////////////////////////////////////////////////////////
 int SkEdge::setLine(const SkPoint& p0, const SkPoint& p1, const SkIRect* clip,
                     int shift) {
     SkFDot6 x0, y0, x1, y1;
     {
         float scale = float(1 << (shift + 6));
         x0 = int(p0.fX * scale);
         y0 = int(p0.fY * scale);
         x1 = int(p1.fX * scale);
         y1 = int(p1.fY * scale);
     }
     int winding = 1;
     if (y0 > y1) {
         SkTSwap(x0, x1);
         SkTSwap(y0, y1);
         winding = -1;
     }
     int top = SkFDot6Round(y0);
     int bot = SkFDot6Round(y1);
     // are we a zero-height line?
     if (top == bot) {
         return 0;
     }
     // are we completely above or below the clip?
     if (NULL != clip && (top >= clip->fBottom || bot <= clip->fTop)) {
         return 0;
     }
     SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0);
     const int dy  = SkEdge_Compute_DY(top, y0);
     fX          = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy));   // + SK_Fixed1/2
     fDX         = slope;
     fFirstY     = top;
     fLastY      = bot - 1;
     fCurveCount = 0;
     fWinding    = SkToS8(winding);
     fCurveShift = 0;
     if (clip) {
         this->chopLineWithClip(*clip);
     }
     return 1;
 }
 // called from a curve subclass
 int SkEdge::updateLine(SkFixed x0, SkFixed y0, SkFixed x1, SkFixed y1)
 {
     SkASSERT(fWinding == 1 || fWinding == -1);
     SkASSERT(fCurveCount != 0);
 //    SkASSERT(fCurveShift != 0);
     y0 >>= 10;
     y1 >>= 10;
     SkASSERT(y0 <= y1);
     int top = SkFDot6Round(y0);
     int bot = SkFDot6Round(y1);
 //  SkASSERT(top >= fFirstY);
     // are we a zero-height line?
     if (top == bot)
         return 0;
     x0 >>= 10;
     x1 >>= 10;
     SkFixed slope = SkFDot6Div(x1 - x0, y1 - y0);
     const int dy  = SkEdge_Compute_DY(top, y0);
     fX          = SkFDot6ToFixed(x0 + SkFixedMul(slope, dy));   // + SK_Fixed1/2
     fDX         = slope;
     fFirstY     = top;
     fLastY      = bot - 1;
     return 1;
 }
 void SkEdge::chopLineWithClip(const SkIRect& clip)
 {
     int top = fFirstY;
     SkASSERT(top < clip.fBottom);
     // clip the line to the top
     if (top < clip.fTop)
     {
         SkASSERT(fLastY >= clip.fTop);
         fX += fDX * (clip.fTop - top);
         fFirstY = clip.fTop;
     }
 }
 ///////////////////////////////////////////////////////////////////////////////
 /*  We store 1<<shift in a (signed) byte, so its maximum value is 1<<6 == 64.
     Note that this limits the number of lines we use to approximate a curve.
     If we need to increase this, we need to store fCurveCount in something
     larger than int8_t.
 */
 #define MAX_COEFF_SHIFT     6
 static inline SkFDot6 cheap_distance(SkFDot6 dx, SkFDot6 dy)
 {
     dx = SkAbs32(dx);
     dy = SkAbs32(dy);
     // return max + min/2
     if (dx > dy)
         dx += dy >> 1;
     else
         dx = dy + (dx >> 1);
     return dx;
 }
 static inline int diff_to_shift(SkFDot6 dx, SkFDot6 dy)
 {
     // cheap calc of distance from center of p0-p2 to the center of the curve
     SkFDot6 dist = cheap_distance(dx, dy);
     // shift down dist (it is currently in dot6)
     // down by 5 should give us 1/2 pixel accuracy (assuming our dist is accurate...)
     // this is chosen by heuristic: make it as big as possible (to minimize segments)
     // ... but small enough so that our curves still look smooth
     dist = (dist + (1 << 4)) >> 5;
     // each subdivision (shift value) cuts this dist (error) by 1/4
     return (32 - SkCLZ(dist)) >> 1;
 }
 int SkQuadraticEdge::setQuadratic(const SkPoint pts[3], int shift)
 {
     SkFDot6 x0, y0, x1, y1, x2, y2;
     {
         float scale = float(1 << (shift + 6));
         x0 = int(pts[0].fX * scale);
         y0 = int(pts[0].fY * scale);
         x1 = int(pts[1].fX * scale);
         y1 = int(pts[1].fY * scale);
         x2 = int(pts[2].fX * scale);
         y2 = int(pts[2].fY * scale);
     }
     int winding = 1;
     if (y0 > y2)
     {
         SkTSwap(x0, x2);
         SkTSwap(y0, y2);
         winding = -1;
     }
     SkASSERT(y0 <= y1 && y1 <= y2);
     int top = SkFDot6Round(y0);
     int bot = SkFDot6Round(y2);
     // are we a zero-height quad (line)?
     if (top == bot)
         return 0;
     // compute number of steps needed (1 << shift)
     {
         SkFDot6 dx = ((x1 << 1) - x0 - x2) >> 2;
         SkFDot6 dy = ((y1 << 1) - y0 - y2) >> 2;
         shift = diff_to_shift(dx, dy);
         SkASSERT(shift >= 0);
     }
     // need at least 1 subdivision for our bias trick
     if (shift == 0) {
         shift = 1;
     } else if (shift > MAX_COEFF_SHIFT) {
         shift = MAX_COEFF_SHIFT;
     }
     fWinding    = SkToS8(winding);
     //fCubicDShift only set for cubics
     fCurveCount = SkToS8(1 << shift);
     /*
      *  We want to reformulate into polynomial form, to make it clear how we
      *  should forward-difference.
      *
      *  p0 (1 - t)^2 + p1 t(1 - t) + p2 t^2 ==> At^2 + Bt + C
      *
      *  A = p0 - 2p1 + p2
      *  B = 2(p1 - p0)
      *  C = p0
      *
      *  Our caller must have constrained our inputs (p0..p2) to all fit into
      *  16.16. However, as seen above, we sometimes compute values that can be
      *  larger (e.g. B = 2*(p1 - p0)). To guard against overflow, we will store
      *  A and B at 1/2 of their actual value, and just apply a 2x scale during
      *  application in updateQuadratic(). Hence we store (shift - 1) in
      *  fCurveShift.
      */
     fCurveShift = SkToU8(shift - 1);
     SkFixed A = SkFDot6ToFixedDiv2(x0 - x1 - x1 + x2);  // 1/2 the real value
     SkFixed B = SkFDot6ToFixed(x1 - x0);                // 1/2 the real value
     fQx     = SkFDot6ToFixed(x0);
     fQDx    = B + (A >> shift);     // biased by shift
     fQDDx   = A >> (shift - 1);     // biased by shift
     A = SkFDot6ToFixedDiv2(y0 - y1 - y1 + y2);  // 1/2 the real value
     B = SkFDot6ToFixed(y1 - y0);                // 1/2 the real value
     fQy     = SkFDot6ToFixed(y0);
     fQDy    = B + (A >> shift);     // biased by shift
     fQDDy   = A >> (shift - 1);     // biased by shift
     fQLastX = SkFDot6ToFixed(x2);
     fQLastY = SkFDot6ToFixed(y2);
     return this->updateQuadratic();
 }
 int SkQuadraticEdge::updateQuadratic()
 {
     int     success;
     int     count = fCurveCount;
     SkFixed oldx = fQx;
     SkFixed oldy = fQy;
     SkFixed dx = fQDx;
     SkFixed dy = fQDy;
     SkFixed newx, newy;
     int     shift = fCurveShift;
     SkASSERT(count > 0);
     do {
         if (--count > 0)
         {
             newx    = oldx + (dx >> shift);
             dx    += fQDDx;
             newy    = oldy + (dy >> shift);
             dy    += fQDDy;
         }
         else    // last segment
         {
             newx    = fQLastX;
             newy    = fQLastY;
         }
         success = this->updateLine(oldx, oldy, newx, newy);
         oldx = newx;
         oldy = newy;
     } while (count > 0 && !success);
     fQx         = newx;
     fQy         = newy;
     fQDx        = dx;
     fQDy        = dy;
     fCurveCount = SkToS8(count);
     return success;
 }
 /////////////////////////////////////////////////////////////////////////
 static inline int SkFDot6UpShift(SkFDot6 x, int upShift) {
     SkASSERT((x << upShift >> upShift) == x);
     return x << upShift;
 }
 /*  f(1/3) = (8a + 12b + 6c + d) / 27
     f(2/3) = (a + 6b + 12c + 8d) / 27
     f(1/3)-b = (8a - 15b + 6c + d) / 27
     f(2/3)-c = (a + 6b - 15c + 8d) / 27
     use 16/512 to approximate 1/27
 */
 static SkFDot6 cubic_delta_from_line(SkFDot6 a, SkFDot6 b, SkFDot6 c, SkFDot6 d)
 {
     SkFDot6 oneThird = ((a << 3) - ((b << 4) - b) + 6*c + d) * 19 >> 9;
     SkFDot6 twoThird = (a + 6*b - ((c << 4) - c) + (d << 3)) * 19 >> 9;
     return SkMax32(SkAbs32(oneThird), SkAbs32(twoThird));
 }
 int SkCubicEdge::setCubic(const SkPoint pts[4], const SkIRect* clip, int shift)
 {
     SkFDot6 x0, y0, x1, y1, x2, y2, x3, y3;
     {
         float scale = float(1 << (shift + 6));
         x0 = int(pts[0].fX * scale);
         y0 = int(pts[0].fY * scale);
         x1 = int(pts[1].fX * scale);
         y1 = int(pts[1].fY * scale);
         x2 = int(pts[2].fX * scale);
         y2 = int(pts[2].fY * scale);
         x3 = int(pts[3].fX * scale);
         y3 = int(pts[3].fY * scale);
     }
     int winding = 1;
     if (y0 > y3)
     {
         SkTSwap(x0, x3);
         SkTSwap(x1, x2);
         SkTSwap(y0, y3);
         SkTSwap(y1, y2);
         winding = -1;
     }
     int top = SkFDot6Round(y0);
     int bot = SkFDot6Round(y3);
     // are we a zero-height cubic (line)?
     if (top == bot)
         return 0;
     // are we completely above or below the clip?
     if (clip && (top >= clip->fBottom || bot <= clip->fTop))
         return 0;
     // compute number of steps needed (1 << shift)
     {
         // Can't use (center of curve - center of baseline), since center-of-curve
         // need not be the max delta from the baseline (it could even be coincident)
         // so we try just looking at the two off-curve points
         SkFDot6 dx = cubic_delta_from_line(x0, x1, x2, x3);
         SkFDot6 dy = cubic_delta_from_line(y0, y1, y2, y3);
         // add 1 (by observation)
         shift = diff_to_shift(dx, dy) + 1;
     }
     // need at least 1 subdivision for our bias trick
     SkASSERT(shift > 0);
     if (shift > MAX_COEFF_SHIFT) {
         shift = MAX_COEFF_SHIFT;
     }
     /*  Since our in coming data is initially shifted down by 10 (or 8 in
         antialias). That means the most we can shift up is 8. However, we
         compute coefficients with a 3*, so the safest upshift is really 6
     */
     int upShift = 6;    // largest safe value
     int downShift = shift + upShift - 10;
     if (downShift < 0) {
         downShift = 0;
         upShift = 10 - shift;
     }
     fWinding    = SkToS8(winding);
     fCurveCount = SkToS8(-1 << shift);
     fCurveShift = SkToU8(shift);
     fCubicDShift = SkToU8(downShift);
     SkFixed B = SkFDot6UpShift(3 * (x1 - x0), upShift);
     SkFixed C = SkFDot6UpShift(3 * (x0 - x1 - x1 + x2), upShift);
     SkFixed D = SkFDot6UpShift(x3 + 3 * (x1 - x2) - x0, upShift);
     fCx     = SkFDot6ToFixed(x0);
     fCDx    = B + (C >> shift) + (D >> 2*shift);    // biased by shift
     fCDDx   = 2*C + (3*D >> (shift - 1));           // biased by 2*shift
     fCDDDx  = 3*D >> (shift - 1);                   // biased by 2*shift
     B = SkFDot6UpShift(3 * (y1 - y0), upShift);
     C = SkFDot6UpShift(3 * (y0 - y1 - y1 + y2), upShift);
     D = SkFDot6UpShift(y3 + 3 * (y1 - y2) - y0, upShift);
     fCy     = SkFDot6ToFixed(y0);
     fCDy    = B + (C >> shift) + (D >> 2*shift);    // biased by shift
     fCDDy   = 2*C + (3*D >> (shift - 1));           // biased by 2*shift
     fCDDDy  = 3*D >> (shift - 1);                   // biased by 2*shift
     fCLastX = SkFDot6ToFixed(x3);
     fCLastY = SkFDot6ToFixed(y3);
     if (clip)
     {
         do {
             if (!this->updateCubic()) {
                 return 0;
             }
         } while (!this->intersectsClip(*clip));
         this->chopLineWithClip(*clip);
         return 1;
     }
     return this->updateCubic();
 }
 int SkCubicEdge::updateCubic()
 {
     int     success;
     int     count = fCurveCount;
     SkFixed oldx = fCx;
     SkFixed oldy = fCy;
     SkFixed newx, newy;
     const int ddshift = fCurveShift;
     const int dshift = fCubicDShift;
     SkASSERT(count < 0);
     do {
         if (++count < 0)
         {
             newx    = oldx + (fCDx >> dshift);
             fCDx    += fCDDx >> ddshift;
             fCDDx   += fCDDDx;
             newy    = oldy + (fCDy >> dshift);
             fCDy    += fCDDy >> ddshift;
             fCDDy   += fCDDDy;
         }
         else    // last segment
         {
         //  SkDebugf("LastX err=%d, LastY err=%d\n", (oldx + (fCDx >> shift) - fLastX), (oldy + (fCDy >> shift) - fLastY));
             newx    = fCLastX;
             newy    = fCLastY;
         }
         // we want to say SkASSERT(oldy <= newy), but our finite fixedpoint
         // doesn't always achieve that, so we have to explicitly pin it here.
         if (newy < oldy) {
             newy = oldy;
         }
         success = this->updateLine(oldx, oldy, newx, newy);
         oldx = newx;
         oldy = newy;
     } while (count < 0 && !success);
     fCx         = newx;
     fCy         = newy;
     fCurveCount = SkToS8(count);
     return success;
 }

The Tor Browser / annotate

gfx/skia/trunk/src/core/SkEdge.cpp@129ffea94266 (annotated)

gfx/skia/trunk/src/core/SkEdge.cpp