MCGR: Model data changes for ColorSteps (II)

The biggest change here is to allow multiple ColorStops
with the same Offset. That allows to define gradients
with 'hard' color changes at any place using two
ColorStops with the same Offset and different Colors.
This required quite some adaptions, but works well.

Also removed in this context checking for all Colors
being the same to not mix up things. Also works well.

Also changed the need for having Start/EndColors AKA
ColorStops for 0.0 and 1.0 in place, instead 'imply'
the 1st ColorStop to also define the StartColor and
the last one the EndColor. This allows e.g. Gradient
definitions with two GradientStops at the same
Offset e.g. 0.5 with different colors to already
define a full Gradient.

Also added a tooling method to reverse ColorSteps,
which changes the order and mirrors the Offsets
(what even keeps an existing sort valid).
This is useful e.g. for GradientAxial which is the
only one where for decomposition the Gradient had
to be interpreted 'reverse' since it's defined
from center to edge, but for creating correct filled
polygons to represent this the inverse order had to
be used, creating polygons from edge to center.
This led to 'wild' code for this one of six cases
and prevented unifications with the other cases
(also made your brain flip).
Thus I adapted this now to use the reversed
ColorSteps consequently, and the same principle
loops than the other implementations to make things
easier for the future and to use common tooling.

Change-Id: If2943348d17d5b9cd165f4d78f22638a1dff5237
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/149208
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>

3 files changed, 159 insertions, 31 deletions

diff --git a/drawinglayer/inc/texture/texture.hxx b/drawinglayer/inc/texture/texture.hxx
index 8eff5bee261a..8a5c411d320f 100644
--- a/drawinglayer/inc/texture/texture.hxx
+++ b/drawinglayer/inc/texture/texture.hxx
@@ -60,6 +60,9 @@ namespace drawinglayer::texture
             basegfx::ColorStops                 mnColorStops;
             double                              mfBorder;
 
+            // check if we need last-ColorStop-correction
+            bool checkPenultimate();
+
         public:
             GeoTexSvxGradient(
                 const basegfx::B2DRange& rDefinitionRange,
diff --git a/drawinglayer/source/processor2d/vclpixelprocessor2d.cxx b/drawinglayer/source/processor2d/vclpixelprocessor2d.cxx
index 1b85cf9d519f..c49deaf3f369 100644
--- a/drawinglayer/source/processor2d/vclpixelprocessor2d.cxx
+++ b/drawinglayer/source/processor2d/vclpixelprocessor2d.cxx
@@ -940,12 +940,24 @@ void VclPixelProcessor2D::processFillGradientPrimitive2D(
 
     // MCGR: If GradientStops are used, use decomposition since vcl is not able
     // to render multi-color gradients
-    if (rFillGradient.getColorStops().size() > 2)
+    if (rFillGradient.getColorStops().size() != 2)
     {
         process(rPrimitive);
         return;
     }
 
+    // MCGR: If GradientStops do not start and stop at traditional Start/EndColor,
+    // use decomposition since vcl is not able to render this
+    if (!rFillGradient.getColorStops().empty())
+    {
+        if (!basegfx::fTools::equalZero(rFillGradient.getColorStops().front().getStopOffset())
+            || !basegfx::fTools::equal(rFillGradient.getColorStops().back().getStopOffset(), 1.0))
+        {
+            process(rPrimitive);
+            return;
+        }
+    }
+
     // VCL should be able to handle all styles, but for tdf#133477 the VCL result
     // is different from processing the gradient manually by drawinglayer
     // (and the Writer unittest for it fails). Keep using the drawinglayer code
diff --git a/drawinglayer/source/texture/texture.cxx b/drawinglayer/source/texture/texture.cxx
index 5cd708243143..136284635e1b 100644
--- a/drawinglayer/source/texture/texture.cxx
+++ b/drawinglayer/source/texture/texture.cxx
@@ -97,6 +97,42 @@ namespace drawinglayer::texture
                 && mfBorder == pCompare->mfBorder);
         }
 
+        bool GeoTexSvxGradient::checkPenultimate()
+        {
+            // not needed when no ColorStops
+            if (mnColorStops.empty())
+                return false;
+
+            // not needed when last ColorStop at the end or outside
+            if (basegfx::fTools::moreOrEqual(mnColorStops.back().getStopOffset(), 1.0))
+                return false;
+
+            // get penultimate entry
+            const auto penultimate(mnColorStops.rbegin() + 1);
+
+            // if there is none, we need no correction and are done
+            if (penultimate == mnColorStops.rend())
+                return false;
+
+            // not needed when the last two ColorStops have different offset, then
+            // a visible range will be pocessed already
+            if (!basegfx::fTools::equal(mnColorStops.back().getStopOffset(), penultimate->getStopOffset()))
+                return false;
+
+            // not needed when the last two ColorStops have the same Color, then the
+            // range before solves the problem
+            if (mnColorStops.back().getStopColor() == penultimate->getStopColor())
+                return false;
+
+            // Here we need to temporarily add a ColorStop entry with the
+            // same color as the last entry to correctly 'close' the
+            // created gradient geometry.
+            // The simplest way is to temporarily add an entry to the local
+            // ColorStops for this at 1.0 (using same color)
+            mnColorStops.emplace_back(1.0, mnColorStops.back().getStopColor());
+            return true;
+        }
+
         GeoTexSvxGradientLinear::GeoTexSvxGradientLinear(
             const basegfx::B2DRange& rDefinitionRange,
             const basegfx::B2DRange& rOutputRange,
@@ -145,6 +181,9 @@ namespace drawinglayer::texture
             if (mnColorStops.size() < 2)
                 return;
 
+            // check if we need last-ColorStop-correction
+            const bool bPenultimateUsed(checkPenultimate());
+
             // prepare unit range transform
             basegfx::B2DHomMatrix aPattern;
 
@@ -159,16 +198,22 @@ namespace drawinglayer::texture
             // outer loop over ColorStops, each is from cs_l to cs_r
             for (auto cs_l(mnColorStops.begin()), cs_r(cs_l + 1); cs_r != mnColorStops.end(); cs_l++, cs_r++)
             {
+                // get offsets
+                const double fOffsetStart(cs_l->getStopOffset());
+                const double fOffsetEnd(cs_r->getStopOffset());
+
+                // same offset, empty ColorStopRange, continue with next step
+                if (basegfx::fTools::equal(fOffsetStart, fOffsetEnd))
+                    continue;
+
                 // get colors & calculate steps
                 const basegfx::BColor aCStart(cs_l->getStopColor());
                 const basegfx::BColor aCEnd(cs_r->getStopColor());
                 const sal_uInt32 nSteps(basegfx::utils::calculateNumberOfSteps(
                     maGradientInfo.getRequestedSteps(), aCStart, aCEnd));
 
-                // get offsets & calculate StripeWidth
+                // calculate StripeWidth
                 // nSteps is >= 1, see getRequestedSteps, so no check needed here
-                const double fOffsetStart(cs_l->getStopOffset());
-                const double fOffsetEnd(cs_r->getStopOffset());
                 const double fStripeWidth((fOffsetEnd - fOffsetStart) / nSteps);
 
                 // for the 1st color range we do not need to create the 1st step
@@ -206,6 +251,9 @@ namespace drawinglayer::texture
                     rEntries.push_back(aB2DHomMatrixAndBColor);
                 }
             }
+
+            if (bPenultimateUsed)
+                mnColorStops.pop_back();
         }
 
         void GeoTexSvxGradientLinear::modifyBColor(const basegfx::B2DPoint& rUV, basegfx::BColor& rBColor, double& /*rfOpacity*/) const
@@ -237,6 +285,12 @@ namespace drawinglayer::texture
         , mfUnitMinX(0.0)
         , mfUnitWidth(1.0)
         {
+            // ARGH! GradientAxial uses the ColorStops in reverse order compared
+            // with the other gradients. Either stay 'thinking reverse' for the
+            // rest of time or adapt it here and go in same order as the other five,
+            // so unifications/tooling will be possible
+            basegfx::utils::reverseColorStops(mnColorStops);
+
             maGradientInfo = basegfx::utils::createAxialODFGradientInfo(
                 rDefinitionRange,
                 nRequestedSteps,
@@ -266,13 +320,15 @@ namespace drawinglayer::texture
                 return;
 
             // fill in return parameter rOuterColor before returning
-            // CAUTION: for GradientAxial the color range is inverted (!)
-            rOuterColor = mnColorStops.back().getStopColor();
+            rOuterColor = mnColorStops.front().getStopColor();
 
             // only one color, done
             if (mnColorStops.size() < 2)
                 return;
 
+            // check if we need last-ColorStop-correction
+            const bool bPenultimateUsed(checkPenultimate());
+
             // prepare unit range transform
             basegfx::B2DHomMatrix aPattern;
 
@@ -285,42 +341,49 @@ namespace drawinglayer::texture
             aPattern.translate(mfUnitMinX, 0.0);
 
             // outer loop over ColorStops, each is from cs_l to cs_r
-            // CAUTION: for GradientAxial the color range is used inverted (!)
-            //          thus, to loop backward, use rbegin/rend
-            for (auto cs_r(mnColorStops.rbegin()), cs_l(cs_r + 1); cs_l != mnColorStops.rend(); cs_l++, cs_r++)
+            for (auto cs_l(mnColorStops.begin()), cs_r(cs_l + 1); cs_r != mnColorStops.end(); cs_l++, cs_r++)
             {
+                // get offsets
+                const double fOffsetStart(cs_l->getStopOffset());
+                const double fOffsetEnd(cs_r->getStopOffset());
+
+                // same offset, empty ColorStopRange, continue with next step
+                if (basegfx::fTools::equal(fOffsetStart, fOffsetEnd))
+                    continue;
+
                 // get colors & calculate steps
                 const basegfx::BColor aCStart(cs_l->getStopColor());
                 const basegfx::BColor aCEnd(cs_r->getStopColor());
                 const sal_uInt32 nSteps(basegfx::utils::calculateNumberOfSteps(
                     maGradientInfo.getRequestedSteps(), aCStart, aCEnd));
 
-                // get offsets & calculate StripeWidth
+                // calculate StripeWidth
                 // nSteps is >= 1, see getRequestedSteps, so no check needed here
-                const double fOffsetStart(cs_l->getStopOffset());
-                const double fOffsetEnd(cs_r->getStopOffset());
                 const double fStripeWidth((fOffsetEnd - fOffsetStart) / nSteps);
 
                 // for the 1st color range we do not need to create the 1st step, see above
-                const sal_uInt32 nStartInnerLoop(cs_r == mnColorStops.rbegin() ? 1 : 0);
+                const sal_uInt32 nStartInnerLoop(cs_l == mnColorStops.begin() ? 1 : 0);
 
                 for (sal_uInt32 innerLoop(nStartInnerLoop); innerLoop < nSteps; innerLoop++)
                 {
                     // calculate pos in Y
-                    const double fPos(fOffsetEnd - (fStripeWidth * innerLoop));
+                    const double fPos(fOffsetStart + (fStripeWidth * innerLoop));
 
                     // already centered in Y on X-Axis, just scale in Y
                     basegfx::B2DHomMatrix aNew(aPattern);
-                    aNew.scale(1.0, fPos);
+                    aNew.scale(1.0, 1.0 - fPos);
 
                     // set and add at target
                     B2DHomMatrixAndBColor aB2DHomMatrixAndBColor;
 
                     aB2DHomMatrixAndBColor.maB2DHomMatrix = maGradientInfo.getTextureTransform() * aNew;
-                    aB2DHomMatrixAndBColor.maBColor = interpolate(aCEnd, aCStart, double(innerLoop) / double(nSteps - 1));
+                    aB2DHomMatrixAndBColor.maBColor = interpolate(aCStart, aCEnd, double(innerLoop) / double(nSteps - 1));
                     rEntries.push_back(aB2DHomMatrixAndBColor);
                 }
             }
+
+            if (bPenultimateUsed)
+                mnColorStops.pop_back();
         }
 
         void GeoTexSvxGradientAxial::modifyBColor(const basegfx::B2DPoint& rUV, basegfx::BColor& rBColor, double& /*rfOpacity*/) const
@@ -332,14 +395,16 @@ namespace drawinglayer::texture
             // just single color, done
             if (mnColorStops.size() < 2)
             {
-                // CAUTION: for GradientAxial the color range is used inverted (!)
-                rBColor = mnColorStops.back().getStopColor();
+                // we use the reverse ColorSteps here, so use front value
+                rBColor = mnColorStops.front().getStopColor();
                 return;
             }
 
             // texture-back-transform X/Y -> t [0.0..1.0] and determine color
             const double fScaler(basegfx::utils::getAxialGradientAlpha(rUV, maGradientInfo));
-            rBColor = basegfx::utils::modifyBColor(mnColorStops, fScaler, mnRequestedSteps);
+
+                // we use the reverse ColorSteps here, so mirror scaler value
+            rBColor = basegfx::utils::modifyBColor(mnColorStops, 1.0 - fScaler, mnRequestedSteps);
         }
 
 
@@ -378,18 +443,27 @@ namespace drawinglayer::texture
             if (mnColorStops.size() < 2)
                 return;
 
+            // check if we need last-ColorStop-correction
+            const bool bPenultimateUsed(checkPenultimate());
+
             // outer loop over ColorStops, each is from cs_l to cs_r
             for (auto cs_l(mnColorStops.begin()), cs_r(cs_l + 1); cs_r != mnColorStops.end(); cs_l++, cs_r++)
             {
+                // get offsets
+                const double fOffsetStart(cs_l->getStopOffset());
+                const double fOffsetEnd(cs_r->getStopOffset());
+
+                // same offset, empty ColorStopRange, continue with next step
+                if (basegfx::fTools::equal(fOffsetStart, fOffsetEnd))
+                    continue;
+
                 // get colors & calculate steps
                 const basegfx::BColor aCStart(cs_l->getStopColor());
                 const basegfx::BColor aCEnd(cs_r->getStopColor());
                 const sal_uInt32 nSteps(basegfx::utils::calculateNumberOfSteps(
                     maGradientInfo.getRequestedSteps(), aCStart, aCEnd));
 
-                // get offsets & calculate StripeWidth
-                const double fOffsetStart(cs_l->getStopOffset());
-                const double fOffsetEnd(cs_r->getStopOffset());
+                // calculate StripeWidth
                 const double fStripeWidth((fOffsetEnd - fOffsetStart) / nSteps);
 
                 // get correct start for inner loop (see above)
@@ -408,6 +482,9 @@ namespace drawinglayer::texture
                     rEntries.push_back(aB2DHomMatrixAndBColor);
                 }
             }
+
+            if (bPenultimateUsed)
+                mnColorStops.pop_back();
         }
 
         void GeoTexSvxGradientRadial::modifyBColor(const basegfx::B2DPoint& rUV, basegfx::BColor& rBColor, double& /*rfOpacity*/) const
@@ -466,6 +543,9 @@ namespace drawinglayer::texture
             if (mnColorStops.size() < 2)
                 return;
 
+            // check if we need last-ColorStop-correction
+            const bool bPenultimateUsed(checkPenultimate());
+
             // prepare vars dependent on aspect ratio
             const double fAR(maGradientInfo.getAspectRatio());
             const bool bMTO(fAR > 1.0);
@@ -473,15 +553,21 @@ namespace drawinglayer::texture
             // outer loop over ColorStops, each is from cs_l to cs_r
             for (auto cs_l(mnColorStops.begin()), cs_r(cs_l + 1); cs_r != mnColorStops.end(); cs_l++, cs_r++)
             {
+                // get offsets
+                const double fOffsetStart(cs_l->getStopOffset());
+                const double fOffsetEnd(cs_r->getStopOffset());
+
+                // same offset, empty ColorStopRange, continue with next step
+                if (basegfx::fTools::equal(fOffsetStart, fOffsetEnd))
+                    continue;
+
                 // get colors & calculate steps
                 const basegfx::BColor aCStart(cs_l->getStopColor());
                 const basegfx::BColor aCEnd(cs_r->getStopColor());
                 const sal_uInt32 nSteps(basegfx::utils::calculateNumberOfSteps(
                     maGradientInfo.getRequestedSteps(), aCStart, aCEnd));
 
-                // get offsets & calculate StripeWidth
-                const double fOffsetStart(cs_l->getStopOffset());
-                const double fOffsetEnd(cs_r->getStopOffset());
+                // calculate StripeWidth
                 const double fStripeWidth((fOffsetEnd - fOffsetStart) / nSteps);
 
                 // get correct start for inner loop (see above)
@@ -503,6 +589,9 @@ namespace drawinglayer::texture
                     rEntries.push_back(aB2DHomMatrixAndBColor);
                 }
             }
+
+            if (bPenultimateUsed)
+                mnColorStops.pop_back();
         }
 
         void GeoTexSvxGradientElliptical::modifyBColor(const basegfx::B2DPoint& rUV, basegfx::BColor& rBColor, double& /*rfOpacity*/) const
@@ -561,18 +650,27 @@ namespace drawinglayer::texture
             if (mnColorStops.size() < 2)
                 return;
 
+            // check if we need last-ColorStop-correction
+            const bool bPenultimateUsed(checkPenultimate());
+
             // outer loop over ColorStops, each is from cs_l to cs_r
             for (auto cs_l(mnColorStops.begin()), cs_r(cs_l + 1); cs_r != mnColorStops.end(); cs_l++, cs_r++)
             {
+                // get offsets
+                const double fOffsetStart(cs_l->getStopOffset());
+                const double fOffsetEnd(cs_r->getStopOffset());
+
+                // same offset, empty ColorStopRange, continue with next step
+                if (basegfx::fTools::equal(fOffsetStart, fOffsetEnd))
+                    continue;
+
                 // get colors & calculate steps
                 const basegfx::BColor aCStart(cs_l->getStopColor());
                 const basegfx::BColor aCEnd(cs_r->getStopColor());
                 const sal_uInt32 nSteps(basegfx::utils::calculateNumberOfSteps(
                     maGradientInfo.getRequestedSteps(), aCStart, aCEnd));
 
-                // get offsets & calculate StripeWidth
-                const double fOffsetStart(cs_l->getStopOffset());
-                const double fOffsetEnd(cs_r->getStopOffset());
+                // calculate StripeWidth
                 const double fStripeWidth((fOffsetEnd - fOffsetStart) / nSteps);
 
                 // get correct start for inner loop (see above)
@@ -591,6 +689,9 @@ namespace drawinglayer::texture
                     rEntries.push_back(aB2DHomMatrixAndBColor);
                 }
             }
+
+            if (bPenultimateUsed)
+                mnColorStops.pop_back();
         }
 
         void GeoTexSvxGradientSquare::modifyBColor(const basegfx::B2DPoint& rUV, basegfx::BColor& rBColor, double& /*rfOpacity*/) const
@@ -649,6 +750,9 @@ namespace drawinglayer::texture
             if (mnColorStops.size() < 2)
                 return;
 
+            // check if we need last-ColorStop-correction
+            const bool bPenultimateUsed(checkPenultimate());
+
             // prepare vars dependent on aspect ratio
             const double fAR(maGradientInfo.getAspectRatio());
             const bool bMTO(fAR > 1.0);
@@ -656,15 +760,21 @@ namespace drawinglayer::texture
             // outer loop over ColorStops, each is from cs_l to cs_r
             for (auto cs_l(mnColorStops.begin()), cs_r(cs_l + 1); cs_r != mnColorStops.end(); cs_l++, cs_r++)
             {
+                // get offsets
+                const double fOffsetStart(cs_l->getStopOffset());
+                const double fOffsetEnd(cs_r->getStopOffset());
+
+                // same offset, empty ColorStopRange, continue with next step
+                if (basegfx::fTools::equal(fOffsetStart, fOffsetEnd))
+                    continue;
+
                 // get colors & calculate steps
                 const basegfx::BColor aCStart(cs_l->getStopColor());
                 const basegfx::BColor aCEnd(cs_r->getStopColor());
                 const sal_uInt32 nSteps(basegfx::utils::calculateNumberOfSteps(
                     maGradientInfo.getRequestedSteps(), aCStart, aCEnd));
 
-                // get offsets & calculate StripeWidth
-                const double fOffsetStart(cs_l->getStopOffset());
-                const double fOffsetEnd(cs_r->getStopOffset());
+                // calculate StripeWidth
                 const double fStripeWidth((fOffsetEnd - fOffsetStart) / nSteps);
 
                 // get correct start for inner loop (see above)
@@ -686,6 +796,9 @@ namespace drawinglayer::texture
                     rEntries.push_back(aB2DHomMatrixAndBColor);
                 }
             }
+
+            if (bPenultimateUsed)
+                mnColorStops.pop_back();
         }
 
         void GeoTexSvxGradientRect::modifyBColor(const basegfx::B2DPoint& rUV, basegfx::BColor& rBColor, double& /*rfOpacity*/) const