MCGR: tdf#155479 repair gradient SVG export for MCGR

Unfortunately SVG export is based on metafiles and thus there
is (in principle) no way to get the BGradient/ColorStop/MCGR
data transfered as needed. For that, using UNO API to read the
model or using B2DPrimitives would help - as is better for the
export respectively.

Since there is not the time to re-design SVG export I added
this 'compromize' as a fix. It gets the needed data transported
over the metafile (that part is the compromize). It then
exports the MCGR data to SVG (at least - as was already there -
if it's a linear/axial gradient). This happens now with all
Gradient Stops when there is a MCGR gradient. That part is/will
hopefully be re-usable if SVG export  gets redesigned.

I also added a handling for StepCount feature, so when used (in
LO, others do not have that) 'hard' color stops get generated
to make the gradient look identical for SVG export.

Had to make adding of that extra-information in metafiles
dependent on exporting really to SVG. There are 51 cases which
use 'MetaActionType::COMMENT' which would potentially have
to be adapted.

Also added code to solve the problem for TransparencePrimitive2D
at VclMetafileProcessor2D::processTransparencePrimitive2D. This
will now - also only for SVG export - directly create the needed
MetaFloatTransparentAction and add additional MCGR information.
This will be used on SVG export to write a 'Mask' as was done
before. This is now capable of creating fill MCGR-Masks in
the sense that any number of TransparencyStops will be supported.

Change-Id: Ic6d022714eae96b8fbc09e60652851ac5799b757
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/152623
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>

1 files changed, 14 insertions, 42 deletions

diff --git a/oox/source/export/drawingml.cxx b/oox/source/export/drawingml.cxx
index bd58cbf21249..5b0772550471 100644
--- a/oox/source/export/drawingml.cxx
+++ b/oox/source/export/drawingml.cxx
@@ -761,6 +761,15 @@ void DrawingML::WriteGradientFill(
         basegfx::utils::prepareColorStops(*pTransparenceGradient, aAlphaStops, aSingleAlpha);
     }
 
+    // apply steps if used. Need to do that before synchronizeColorStops
+    // since that may add e.g. for AlphaStops all-the-same no-data entries,
+    // so the number of entries might change
+    if (pGradient->GetSteps())
+    {
+        aColorStops.doApplySteps(pGradient->GetSteps());
+        aAlphaStops.doApplySteps(pGradient->GetSteps());
+    }
+
     // synchronize ColorStops and AlphaStops as preparation to export
     // so also gradients 'coupled' indirectly using the 'FillTransparenceGradient'
     // method (at import time) will be exported again
@@ -790,48 +799,11 @@ void DrawingML::WriteGradientFill(
         }
         case awt::GradientStyle_AXIAL:
         {
-            // we need to 'double' the gradient to make it appear as what we call
-            // 'axial', but also scale and mirror in doing so
-            basegfx::BColorStops aNewColorStops;
-            basegfx::BColorStops aNewAlphaStops;
-
-            // add mirrored gradients, scaled to [0.0 .. 0.5]
-            basegfx::BColorStops::const_reverse_iterator aRevCurrColor(aColorStops.rbegin());
-            basegfx::BColorStops::const_reverse_iterator aRevCurrAlpha(aAlphaStops.rbegin());
-
-            while (aRevCurrColor != aColorStops.rend() && aRevCurrAlpha != aAlphaStops.rend())
-            {
-                aNewColorStops.emplace_back((1.0 - aRevCurrColor->getStopOffset()) * 0.5, aRevCurrColor->getStopColor());
-                aNewAlphaStops.emplace_back((1.0 - aRevCurrAlpha->getStopOffset()) * 0.5, aRevCurrAlpha->getStopColor());
-                aRevCurrColor++;
-                aRevCurrAlpha++;
-            }
-
-            basegfx::BColorStops::const_iterator aCurrColor(aColorStops.begin());
-            basegfx::BColorStops::const_iterator aCurrAlpha(aAlphaStops.begin());
-
-            if (basegfx::fTools::equalZero(aCurrColor->getStopOffset()))
-            {
-                // Caution: do not add 1st entry again, that would be double since it was
-                // already added as last element of the inverse run above. But only if
-                // the gradient has a start entry for 0.0 aka StartColor, else it is correct.
-                // Since aColorStops and aAlphaStops are already synched (see
-                // synchronizeColorStops above), testing one of them is sufficient here.
-                aCurrColor++;
-                aCurrAlpha++;
-            }
-
-            // add non-mirrored gradients, translated and scaled to [0.5 .. 1.0]
-            while (aCurrColor != aColorStops.end() && aCurrAlpha != aAlphaStops.end())
-            {
-                aNewColorStops.emplace_back((aCurrColor->getStopOffset() * 0.5) + 0.5, aCurrColor->getStopColor());
-                aNewAlphaStops.emplace_back((aCurrAlpha->getStopOffset() * 0.5) + 0.5, aCurrAlpha->getStopColor());
-                aCurrColor++;
-                aCurrAlpha++;
-            }
-
-            aColorStops = aNewColorStops;
-            aAlphaStops = aNewAlphaStops;
+            // use tooling to convert from GradientStyle_AXIAL to GradientStyle_LINEAR
+            // NOTE: Since aColorStops and aAlphaStops are already synched (see
+            // synchronizeColorStops above) this can be done directly here
+            aColorStops.doApplyAxial();
+            aAlphaStops.doApplyAxial();
 
             // remember being axial
             bAxial = true;