Move SVG path blend state to its own object

Source/core/svg/SVGPathBlender.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010, 2011. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 #include "core/svg/SVGPathBlender.h"
 
 #include "core/svg/SVGPathConsumer.h"
 #include "core/svg/SVGPathSeg.h"
 #include "core/svg/SVGPathSource.h"
 #include "platform/animation/AnimationUtilities.h"
-#include "wtf/TemporaryChange.h"
 
 namespace blink {
 
-SVGPathBlender::SVGPathBlender(SVGPathSource* fromSource, SVGPathSource* toSource, SVGPathConsumer* consumer)
-    : m_fromSource(fromSource)
-    , m_toSource(toSource)
-    , m_consumer(consumer)
-    , m_progress(0)
-    , m_addTypesCount(0)
-    , m_isInFirstHalfOfAnimation(false)
-    , m_typesAreEqual(false)
-    , m_fromIsAbsolute(false)
-    , m_toIsAbsolute(false)
-{
-    ASSERT(m_fromSource);
-    ASSERT(m_toSource);
-    ASSERT(m_consumer);
-}
+enum FloatBlendMode {
+    BlendHorizontal,
+    BlendVertical
+};
 
-DEFINE_TRACE(SVGPathBlender)
-{
-    visitor->trace(m_fromSource);
-    visitor->trace(m_toSource);
-    visitor->trace(m_consumer);
-}
+class SVGPathBlender::BlendState {
+public:
+    BlendState(float progress, unsigned addTypesCount = 0)
+        : m_progress(progress)
+        , m_addTypesCount(addTypesCount)
+        , m_isInFirstHalfOfAnimation(progress < 0.5f)
+        , m_typesAreEqual(false)
+        , m_fromIsAbsolute(false)
+    {
+    }
+
+    bool blendSegments(const PathSegmentData& fromSeg, const PathSegmentData& toSeg, PathSegmentData&);
+
+private:
+    bool canBlend(const PathSegmentData& fromSeg, const PathSegmentData& toSeg);
+    float blendAnimatedDimensonalFloat(float, float, FloatBlendMode);
+    FloatPoint blendAnimatedFloatPoint(const FloatPoint& from, const FloatPoint& to);
+    FloatPoint blendAnimatedFloatPointSameCoordinates(const FloatPoint& from, const FloatPoint& to);
+
+    FloatPoint m_fromCurrentPoint;
+    FloatPoint m_toCurrentPoint;
+
+    float m_progress;
+    unsigned m_addTypesCount;
+    bool m_isInFirstHalfOfAnimation;
+    // This is per-segment blend state corresponding to the 'from' and 'to'
+    // segments currently being blended, and only used within blendSegments().
+    bool m_typesAreEqual;
+    bool m_fromIsAbsolute;
+};
 
 // Helper functions
 static inline FloatPoint blendFloatPoint(const FloatPoint& a, const FloatPoint& b, float progress)
 {
     return FloatPoint(blend(a.x(), b.x(), progress), blend(a.y(), b.y(), progress));
 }
 
-float SVGPathBlender::blendAnimatedDimensonalFloat(float from, float to, FloatBlendMode blendMode)
+float SVGPathBlender::BlendState::blendAnimatedDimensonalFloat(float from, float to, FloatBlendMode blendMode)
 {
     if (m_addTypesCount) {
         ASSERT(m_typesAreEqual);
         return from + to * m_addTypesCount;
     }
 
     if (m_typesAreEqual)
         return blend(from, to, m_progress);
 
     float fromValue = blendMode == BlendHorizontal ? m_fromCurrentPoint.x() : m_fromCurrentPoint.y();
     float toValue = blendMode == BlendHorizontal ? m_toCurrentPoint.x() : m_toCurrentPoint.y();
 
     // Transform toY to the coordinate mode of fromY
     float animValue = blend(from, m_fromIsAbsolute ? to + toValue : to - toValue, m_progress);
 
     // If we're in the first half of the animation, we should use the type of the from segment.
     if (m_isInFirstHalfOfAnimation)
         return animValue;
 
     // Transform the animated point to the coordinate mode, needed for the current progress.
     float currentValue = blend(fromValue, toValue, m_progress);
     return !m_fromIsAbsolute ? animValue + currentValue : animValue - currentValue;
 }
 
-FloatPoint SVGPathBlender::blendAnimatedFloatPointSameCoordinates(const FloatPoint& fromPoint, const FloatPoint& toPoint)
+FloatPoint SVGPathBlender::BlendState::blendAnimatedFloatPointSameCoordinates(const FloatPoint& fromPoint, const FloatPoint& toPoint)

[Stephen Chennney, 2015/04/02 15:00:30]

Minor nit: Could you swap the order of this and the next to match the header
declaration order. And put canBlend before both.

[fs, 2015/04/07 08:27:28]

Assuming you wanted the order of declarations and definitions to match, I did it
the other way around instead (i.e. reordered the declarations.) This yields a
smaller (more obvious) diff. If you wanted the definitions to actually move
around for another reason let me know and I'll fix that up.

 {
     if (m_addTypesCount) {
         FloatPoint repeatedToPoint = toPoint;
         repeatedToPoint.scale(m_addTypesCount, m_addTypesCount);
         return fromPoint + repeatedToPoint;
     }
     return blendFloatPoint(fromPoint, toPoint, m_progress);
 }
 
-FloatPoint SVGPathBlender::blendAnimatedFloatPoint(const FloatPoint& fromPoint, const FloatPoint& toPoint)
+FloatPoint SVGPathBlender::BlendState::blendAnimatedFloatPoint(const FloatPoint& fromPoint, const FloatPoint& toPoint)
 {
     if (m_typesAreEqual)
         return blendAnimatedFloatPointSameCoordinates(fromPoint, toPoint);
 
     // Transform toPoint to the coordinate mode of fromPoint
     FloatPoint animatedPoint = toPoint;
     if (m_fromIsAbsolute)
         animatedPoint += m_toCurrentPoint;
     else
         animatedPoint.move(-m_toCurrentPoint.x(), -m_toCurrentPoint.y());
 
     animatedPoint = blendFloatPoint(fromPoint, animatedPoint, m_progress);
 
     // If we're in the first half of the animation, we should use the type of the from segment.
     if (m_isInFirstHalfOfAnimation)
         return animatedPoint;
 
     // Transform the animated point to the coordinate mode, needed for the current progress.
     FloatPoint currentPoint = blendFloatPoint(m_fromCurrentPoint, m_toCurrentPoint, m_progress);
     if (!m_fromIsAbsolute)
         return animatedPoint + currentPoint;
 
     animatedPoint.move(-currentPoint.x(), -currentPoint.y());
     return animatedPoint;
 }
 
-PathSegmentData SVGPathBlender::blendMoveToSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
+bool SVGPathBlender::BlendState::canBlend(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
 {
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
+    // Update state first because we'll need it if we return true below.
+    m_typesAreEqual = fromSeg.command == toSeg.command;
+    m_fromIsAbsolute = isAbsolutePathSegType(fromSeg.command);
 
-    m_fromCurrentPoint = m_fromIsAbsolute ? fromSeg.targetPoint : m_fromCurrentPoint + fromSeg.targetPoint;
-    m_toCurrentPoint = m_toIsAbsolute ? toSeg.targetPoint : m_toCurrentPoint + toSeg.targetPoint;
-    return blendedSegment;
+    // If the types are equal, they'll blend regardless of parameters.
+    if (m_typesAreEqual)
+        return true;
+
+    // Addition require segments with the same type.
+    if (m_addTypesCount)
+        return false;
+
+    // Allow the segments to differ in "relativeness".
+    return toAbsolutePathSegType(fromSeg.command) == toAbsolutePathSegType(toSeg.command);
 }
 
-PathSegmentData SVGPathBlender::blendLineToSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
+static void updateCurrentPoint(FloatPoint& currentPoint, const PathSegmentData& segment)
 {
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
-
-    m_fromCurrentPoint = m_fromIsAbsolute ? fromSeg.targetPoint : m_fromCurrentPoint + fromSeg.targetPoint;
-    m_toCurrentPoint = m_toIsAbsolute ? toSeg.targetPoint : m_toCurrentPoint + toSeg.targetPoint;
-    return blendedSegment;
+    switch (segment.command) {
+    case PathSegMoveToRel:
+    case PathSegLineToRel:
+    case PathSegCurveToCubicRel:
+    case PathSegCurveToQuadraticRel:
+    case PathSegArcRel:
+    case PathSegLineToHorizontalRel:
+    case PathSegLineToVerticalRel:

[Stephen Chennney, 2015/04/02 15:00:30]

I think I get it. segment.targetPoint is already limited to just x or y, so you
can just add it here, while below you don't want to 0-out the existing y or x
position.

[fs, 2015/04/02 15:08:30]

Right, Horizontal/VerticalRel is essentially the same as LineRel but with an
implicit 0 as the other part. Horizontal/Vertical_Abs_ on the other hand is
(weird) so need to explicitly just set one of them.

+    case PathSegCurveToCubicSmoothRel:
+    case PathSegCurveToQuadraticSmoothRel:
+        currentPoint += segment.targetPoint;
+        break;
+    case PathSegMoveToAbs:
+    case PathSegLineToAbs:
+    case PathSegCurveToCubicAbs:
+    case PathSegCurveToQuadraticAbs:
+    case PathSegArcAbs:
+    case PathSegCurveToCubicSmoothAbs:
+    case PathSegCurveToQuadraticSmoothAbs:
+        currentPoint = segment.targetPoint;
+        break;
+    case PathSegLineToHorizontalAbs:
+        currentPoint.setX(segment.targetPoint.x());
+        break;
+    case PathSegLineToVerticalAbs:
+        currentPoint.setY(segment.targetPoint.y());
+        break;
+    case PathSegClosePath:
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+    }
 }
 
-PathSegmentData SVGPathBlender::blendLineToHorizontalSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
+bool SVGPathBlender::BlendState::blendSegments(const PathSegmentData& fromSeg, const PathSegmentData& toSeg, PathSegmentData& blendedSegment)
 {
-    PathSegmentData blendedSegment;
+    if (!canBlend(fromSeg, toSeg))
+        return false;
+
     blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint.setX(blendAnimatedDimensonalFloat(fromSeg.targetPoint.x(), toSeg.targetPoint.x(), BlendHorizontal));
 
-    m_fromCurrentPoint.setX(m_fromIsAbsolute ? fromSeg.targetPoint.x() : m_fromCurrentPoint.x() + fromSeg.targetPoint.x());
-    m_toCurrentPoint.setX(m_toIsAbsolute ? toSeg.targetPoint.x() : m_toCurrentPoint.x() + toSeg.targetPoint.x());
-    return blendedSegment;
-}
-
-PathSegmentData SVGPathBlender::blendLineToVerticalSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
-{
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint.setY(blendAnimatedDimensonalFloat(fromSeg.targetPoint.y(), toSeg.targetPoint.y(), BlendVertical));
-
-    m_fromCurrentPoint.setY(m_fromIsAbsolute ? fromSeg.targetPoint.y() : m_fromCurrentPoint.y() + fromSeg.targetPoint.y());
-    m_toCurrentPoint.setY(m_toIsAbsolute ? toSeg.targetPoint.y() : m_toCurrentPoint.y() + toSeg.targetPoint.y());
-    return blendedSegment;
-}
-
-PathSegmentData SVGPathBlender::blendCurveToCubicSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
-{
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
-    blendedSegment.point1 = blendAnimatedFloatPoint(fromSeg.point1, toSeg.point1);
-    blendedSegment.point2 = blendAnimatedFloatPoint(fromSeg.point2, toSeg.point2);
-
-    m_fromCurrentPoint = m_fromIsAbsolute ? fromSeg.targetPoint : m_fromCurrentPoint + fromSeg.targetPoint;
-    m_toCurrentPoint = m_toIsAbsolute ? toSeg.targetPoint : m_toCurrentPoint + toSeg.targetPoint;
-    return blendedSegment;
-}
-
-PathSegmentData SVGPathBlender::blendCurveToCubicSmoothSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
-{
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
-    blendedSegment.point2 = blendAnimatedFloatPoint(fromSeg.point2, toSeg.point2);
-
-    m_fromCurrentPoint = m_fromIsAbsolute ? fromSeg.targetPoint : m_fromCurrentPoint + fromSeg.targetPoint;
-    m_toCurrentPoint = m_toIsAbsolute ? toSeg.targetPoint : m_toCurrentPoint + toSeg.targetPoint;
-    return blendedSegment;
-}
-
-PathSegmentData SVGPathBlender::blendCurveToQuadraticSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
-{
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
-    blendedSegment.point1 = blendAnimatedFloatPoint(fromSeg.point1, toSeg.point1);
-
-    m_fromCurrentPoint = m_fromIsAbsolute ? fromSeg.targetPoint : m_fromCurrentPoint + fromSeg.targetPoint;
-    m_toCurrentPoint = m_toIsAbsolute ? toSeg.targetPoint : m_toCurrentPoint + toSeg.targetPoint;
-    return blendedSegment;
-}
-
-PathSegmentData SVGPathBlender::blendCurveToQuadraticSmoothSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
-{
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
-
-    m_fromCurrentPoint = m_fromIsAbsolute ? fromSeg.targetPoint : m_fromCurrentPoint + fromSeg.targetPoint;
-    m_toCurrentPoint = m_toIsAbsolute ? toSeg.targetPoint : m_toCurrentPoint + toSeg.targetPoint;
-    return blendedSegment;
-}
-
-PathSegmentData SVGPathBlender::blendArcToSegment(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
-{
-    ASSERT(!m_addTypesCount || fromSeg.command == toSeg.command);
-
-    PathSegmentData blendedSegment;
-    blendedSegment.command = m_isInFirstHalfOfAnimation ? fromSeg.command : toSeg.command;
-    blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
-    blendedSegment.point1 = blendAnimatedFloatPointSameCoordinates(fromSeg.arcRadii(), toSeg.arcRadii());
-    blendedSegment.point2 = blendAnimatedFloatPointSameCoordinates(fromSeg.point2, toSeg.point2);
-    if (m_addTypesCount) {
-        blendedSegment.arcLarge = fromSeg.arcLarge || toSeg.arcLarge;
-        blendedSegment.arcSweep = fromSeg.arcSweep || toSeg.arcSweep;
-    } else {
-        blendedSegment.arcLarge = m_isInFirstHalfOfAnimation ? fromSeg.arcLarge : toSeg.arcLarge;
-        blendedSegment.arcSweep = m_isInFirstHalfOfAnimation ? fromSeg.arcSweep : toSeg.arcSweep;
-    }
-
-    m_fromCurrentPoint = m_fromIsAbsolute ? fromSeg.targetPoint : m_fromCurrentPoint + fromSeg.targetPoint;
-    m_toCurrentPoint = m_toIsAbsolute ? toSeg.targetPoint : m_toCurrentPoint + toSeg.targetPoint;
-    return blendedSegment;
-}
-
-void SVGPathBlender::blendSegments(const PathSegmentData& fromSeg, const PathSegmentData& toSeg)
-{
-    PathSegmentData blendedSegment;
     switch (toSeg.command) {
+    case PathSegCurveToCubicRel:
+    case PathSegCurveToCubicAbs:
+        blendedSegment.point1 = blendAnimatedFloatPoint(fromSeg.point1, toSeg.point1);
+        /* fall through */
+    case PathSegCurveToCubicSmoothRel:
+    case PathSegCurveToCubicSmoothAbs:
+        blendedSegment.point2 = blendAnimatedFloatPoint(fromSeg.point2, toSeg.point2);
+        /* fall through */
     case PathSegMoveToRel:
     case PathSegMoveToAbs:
-        blendedSegment = blendMoveToSegment(fromSeg, toSeg);
-        break;
     case PathSegLineToRel:
     case PathSegLineToAbs:
-        blendedSegment = blendLineToSegment(fromSeg, toSeg);
+    case PathSegCurveToQuadraticSmoothRel:
+    case PathSegCurveToQuadraticSmoothAbs:
+        blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
         break;
     case PathSegLineToHorizontalRel:
     case PathSegLineToHorizontalAbs:
-        blendedSegment = blendLineToHorizontalSegment(fromSeg, toSeg);
+        blendedSegment.targetPoint.setX(blendAnimatedDimensonalFloat(fromSeg.targetPoint.x(), toSeg.targetPoint.x(), BlendHorizontal));
         break;
     case PathSegLineToVerticalRel:
     case PathSegLineToVerticalAbs:
-        blendedSegment = blendLineToVerticalSegment(fromSeg, toSeg);
+        blendedSegment.targetPoint.setY(blendAnimatedDimensonalFloat(fromSeg.targetPoint.y(), toSeg.targetPoint.y(), BlendVertical));
         break;
     case PathSegClosePath:
-        blendedSegment = toSeg;
-        break;
-    case PathSegCurveToCubicRel:
-    case PathSegCurveToCubicAbs:
-        blendedSegment = blendCurveToCubicSegment(fromSeg, toSeg);
-        break;
-    case PathSegCurveToCubicSmoothRel:
-    case PathSegCurveToCubicSmoothAbs:
-        blendedSegment = blendCurveToCubicSmoothSegment(fromSeg, toSeg);
         break;
     case PathSegCurveToQuadraticRel:
     case PathSegCurveToQuadraticAbs:
-        blendedSegment = blendCurveToQuadraticSegment(fromSeg, toSeg);
-        break;
-    case PathSegCurveToQuadraticSmoothRel:
-    case PathSegCurveToQuadraticSmoothAbs:
-        blendedSegment = blendCurveToQuadraticSmoothSegment(fromSeg, toSeg);
+        blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
+        blendedSegment.point1 = blendAnimatedFloatPoint(fromSeg.point1, toSeg.point1);
         break;
     case PathSegArcRel:
     case PathSegArcAbs:
-        blendedSegment = blendArcToSegment(fromSeg, toSeg);
+        blendedSegment.targetPoint = blendAnimatedFloatPoint(fromSeg.targetPoint, toSeg.targetPoint);
+        blendedSegment.point1 = blendAnimatedFloatPointSameCoordinates(fromSeg.arcRadii(), toSeg.arcRadii());
+        blendedSegment.point2 = blendAnimatedFloatPointSameCoordinates(fromSeg.point2, toSeg.point2);
+        if (m_addTypesCount) {
+            blendedSegment.arcLarge = fromSeg.arcLarge || toSeg.arcLarge;
+            blendedSegment.arcSweep = fromSeg.arcSweep || toSeg.arcSweep;
+        } else {
+            blendedSegment.arcLarge = m_isInFirstHalfOfAnimation ? fromSeg.arcLarge : toSeg.arcLarge;
+            blendedSegment.arcSweep = m_isInFirstHalfOfAnimation ? fromSeg.arcSweep : toSeg.arcSweep;
+        }
         break;
     default:
         ASSERT_NOT_REACHED();
     }
 
-    m_consumer->emitSegment(blendedSegment);
+    updateCurrentPoint(m_fromCurrentPoint, fromSeg);
+    updateCurrentPoint(m_toCurrentPoint, toSeg);
+
+    return true;
+}
+
+SVGPathBlender::SVGPathBlender(SVGPathSource* fromSource, SVGPathSource* toSource, SVGPathConsumer* consumer)
+    : m_fromSource(fromSource)
+    , m_toSource(toSource)
+    , m_consumer(consumer)
+{
+    ASSERT(m_fromSource);
+    ASSERT(m_toSource);
+    ASSERT(m_consumer);
+}
+
+DEFINE_TRACE(SVGPathBlender)
+{
+    visitor->trace(m_fromSource);
+    visitor->trace(m_toSource);
+    visitor->trace(m_consumer);
 }
 
 bool SVGPathBlender::addAnimatedPath(unsigned repeatCount)
 {
-    TemporaryChange<unsigned> change(m_addTypesCount, repeatCount);
-    return blendAnimatedPath(0);
+    BlendState blendState(0, repeatCount);
+    return blendAnimatedPath(blendState);
 }
 
 bool SVGPathBlender::blendAnimatedPath(float progress)
 {
-    m_isInFirstHalfOfAnimation = progress < 0.5f;
-    m_progress = progress;
+    BlendState blendState(progress);
+    return blendAnimatedPath(blendState);
+}
 
-    bool fromSourceHadData = m_fromSource->hasMoreData();
+bool SVGPathBlender::blendAnimatedPath(BlendState& blendState)
+{
+    bool fromSourceIsEmpty = !m_fromSource->hasMoreData();
     while (m_toSource->hasMoreData()) {
         PathSegmentData toSeg = m_toSource->parseSegment();
         if (toSeg.command == PathSegUnknown)
             return false;
 
         PathSegmentData fromSeg;
         fromSeg.command = toSeg.command;
 
         if (m_fromSource->hasMoreData()) {
             fromSeg = m_fromSource->parseSegment();
             if (fromSeg.command == PathSegUnknown)
                 return false;
         }

[Stephen Chennney, 2015/04/02 15:00:30]

The code implies that you can have an empty "from" sequence and everything will
work using the command from the "to" sequence. And in this case the "from"
sequence has the default point1, point2, targetPoint etc. Is that how it is
supposed to work?

[fs, 2015/04/02 15:08:30]

I don't know where this behavior actually stems from (the additive behavior I
suppose), but my interpretation matches yours. And all the "default" values are
0 (or false).

 
-        m_typesAreEqual = fromSeg.command == toSeg.command;
+        PathSegmentData blendedSeg;
+        if (!blendState.blendSegments(fromSeg, toSeg, blendedSeg))
+            return false;
 
-        // If the types are equal, they'll blend regardless of parameters.
-        if (!m_typesAreEqual) {
-            // Addition require segments with the same type.
-            if (m_addTypesCount)
-                return false;
-            // Allow the segments to differ in "relativeness".
-            if (toAbsolutePathSegType(fromSeg.command) != toAbsolutePathSegType(toSeg.command))
-                return false;
-        }
+        m_consumer->emitSegment(blendedSeg);
 
-        m_fromIsAbsolute = isAbsolutePathSegType(fromSeg.command);
-        m_toIsAbsolute = isAbsolutePathSegType(toSeg.command);
-
-        blendSegments(fromSeg, toSeg);
-
-        if (!fromSourceHadData)
+        if (fromSourceIsEmpty)
             continue;
         if (m_fromSource->hasMoreData() != m_toSource->hasMoreData())
             return false;
     }
     return true;
 }
 
 }