tdf#150557: svx: don't factor in transparence twice for cell shadows

multiplying child transparence with shadow alpha to get the
correct shadow alpha has been incorrect maybe since commits:
7eb4f92ed90e13ce5cbf7286fae623770e71324c,
e735ad1c57cddaf17d6ffc0cf15b5e14fa63c4ad

In ShadowPrimitive2D::create2DDecomposition the
shadow-casting primitive's alpha(mask) itself is already
being taken into account.

Therefore getting cell shadow alpha by multiplying child
transparence with shadow alpha, has the effect of child
transparence being applied twice for the table cell.

Change-Id: I78f9bbfcb0694a86eabc061330677784e887b5dc
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/156528
Tested-by: Jenkins
Reviewed-by: Sarper Akdemir <sarper.akdemir.extern@allotropia.de>

2 files changed, 8 insertions, 19 deletions

diff --git a/svx/qa/unit/table.cxx b/svx/qa/unit/table.cxx
index dc3ad1e2bf67..72359dbc7820 100644
--- a/svx/qa/unit/table.cxx
+++ b/svx/qa/unit/table.cxx
@@ -73,17 +73,15 @@ CPPUNIT_TEST_FIXTURE(Test, testTableShadowBlur)
     drawinglayer::primitive2d::Primitive2DContainer xPrimitiveSequence
         = renderPageToPrimitives(xDrawPage);
 
-    // Then make sure that the cell fill part of the shadow is excluded from blurring:
+    // Then make sure that the cell fill part of the shadow has the expected transparency:
     drawinglayer::Primitive2dXmlDump aDumper;
     xmlDocUniquePtr pDocument = aDumper.dumpAndParse(xPrimitiveSequence);
     // Without the accompanying fix in place, this test would have failed with:
-    // - number of nodes is incorrect
-    // - Expected: 1
-    // - Actual  : 0
-    // i.e. the shadow itself was not transparent and that resulted in a non-transparent rendering
-    // as well, while the rendering transparency should be based on the transparency of the shadow
-    // itself and the transparency of the cell fill.
-    assertXPath(pDocument, "//objectinfo/unifiedtransparence[1]", "transparence", "80");
+    //- Expected: 0
+    //- Actual  : 2
+    //- In <>, XPath contents of child does not match
+    // i.e. the shadow's transparency was miscalculated.
+    assertXPathContent(pDocument, "count(//objectinfo/unifiedtransparence)", "0");
 }
 
 CPPUNIT_TEST_FIXTURE(Test, testSvxTableControllerSetAttrToSelectedShape)
diff --git a/svx/source/sdr/primitive2d/sdrdecompositiontools.cxx b/svx/source/sdr/primitive2d/sdrdecompositiontools.cxx
index b5df830d73fe..33e42efc6d23 100644
--- a/svx/source/sdr/primitive2d/sdrdecompositiontools.cxx
+++ b/svx/source/sdr/primitive2d/sdrdecompositiontools.cxx
@@ -850,25 +850,16 @@ sal_uInt32 SlideBackgroundFillPrimitive2D::getPrimitive2DID() const
             Primitive2DContainer aRetval;
             for (const auto& xChild : rContentForShadow)
             {
-                double fChildTransparence = 0.0;
-                auto pChild = dynamic_cast<BufferedDecompositionPrimitive2D*>(xChild.get());
-                if (pChild)
-                {
-                        fChildTransparence = pChild->getTransparenceForShadow();
-                        fChildTransparence /= 100;
-                }
                 aRetval.push_back(Primitive2DReference(
                     new ShadowPrimitive2D(aShadowOffset, rShadow.getColor(), rShadow.getBlur(),
                                             Primitive2DContainer({ xChild }))));
-                if (rShadow.getTransparence() != 0.0 || fChildTransparence != 0.0)
+                if (rShadow.getTransparence() != 0.0)
                 {
                     Primitive2DContainer aTempContent{ aRetval.back() };
 
-                    double fChildAlpha = 1.0 - fChildTransparence;
                     double fShadowAlpha = 1.0 - rShadow.getTransparence();
-                    double fTransparence = 1.0 - fChildAlpha * fShadowAlpha;
                     aRetval.back() = Primitive2DReference(new UnifiedTransparencePrimitive2D(
-                            std::move(aTempContent), fTransparence));
+                            std::move(aTempContent), fShadowAlpha));
                 }
             }