tdf#149800 SVG export: remove extra white line of semi-transparent shape

A shape is exported using two svg:paths, first one is for the
fill, and the second one is for the line. Semi-transparency of
shapes enabled the disabled stroke of the first path, resulting
an ~1 pt width extra white line behind the normal line of the
shape. It was visible only, if the normal shape line was thinner
than 1 pt, or if the normal line was semi-transparent or disabled.
The extra line got the same transparency value, as the fill,
so its visibility depended on that, too.

Change-Id: Idc40971cc73ec9e4f241974ae29c876d06cc0658
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/143003
Tested-by: Jenkins
Reviewed-by: László Németh <nemeth@numbertext.org>

3 files changed, 37 insertions, 1 deletions

diff --git a/filter/qa/unit/data/semi-transparent-fill.odg b/filter/qa/unit/data/semi-transparent-fill.odg
new file mode 100644
index 000000000000..713f48991bcb
--- /dev/null
+++ b/filter/qa/unit/data/semi-transparent-fill.odg
diff --git a/filter/qa/unit/svg.cxx b/filter/qa/unit/svg.cxx
index a650deb1fc72..824b73383af4 100644
--- a/filter/qa/unit/svg.cxx
+++ b/filter/qa/unit/svg.cxx
@@ -105,6 +105,38 @@ CPPUNIT_TEST_FIXTURE(SvgFilterTest, testSemiTransparentLine)
     CPPUNIT_ASSERT_EQUAL(30, nPercent);
 }
 
+CPPUNIT_TEST_FIXTURE(SvgFilterTest, testSemiTransparentFillWithTransparentLine)
+{
+    // Load a document with a shape with semi-transparent fill and line
+    loadFromURL(u"semi-transparent-fill.odg");
+
+    // Export it to SVG.
+    uno::Reference<frame::XStorable> xStorable(mxComponent, uno::UNO_QUERY_THROW);
+    SvMemoryStream aStream;
+    uno::Reference<io::XOutputStream> xOut = new utl::OOutputStreamWrapper(aStream);
+    utl::MediaDescriptor aMediaDescriptor;
+    aMediaDescriptor["FilterName"] <<= OUString("draw_svg_Export");
+    aMediaDescriptor["OutputStream"] <<= xOut;
+    xStorable->storeToURL("private:stream", aMediaDescriptor.getAsConstPropertyValueList());
+    aStream.Seek(STREAM_SEEK_TO_BEGIN);
+
+    // Get the style of the group around the actual <path> element.
+    xmlDocUniquePtr pXmlDoc = parseXmlStream(&aStream);
+    OUString aStyle = getXPath(
+        pXmlDoc, "//svg:g[@class='com.sun.star.drawing.EllipseShape']/svg:g/svg:g", "style");
+    CPPUNIT_ASSERT(aStyle.startsWith("opacity: ", &aStyle));
+    int nPercent = std::round(aStyle.toDouble() * 100);
+    // Make sure that the line is still 50% opaque
+    CPPUNIT_ASSERT_EQUAL(50, nPercent);
+
+    // Get the stroke of the fill of the EllipseShape (it must be "none")
+    OUString aStroke = getXPath(
+        pXmlDoc, "//svg:g[@class='com.sun.star.drawing.EllipseShape']/svg:g/svg:path", "stroke");
+    // Without the accompanying fix in place, this test would have failed, as the stroke was
+    // "rgb(255,255,255)", not "none".
+    CPPUNIT_ASSERT_EQUAL(OUString("none"), aStroke);
+}
+
 CPPUNIT_TEST_FIXTURE(SvgFilterTest, testSemiTransparentText)
 {
     // Two shapes, one with transparent text and the other one with
diff --git a/filter/source/svg/svgwriter.cxx b/filter/source/svg/svgwriter.cxx
index ec976ccb6f12..65ccab68bbb0 100644
--- a/filter/source/svg/svgwriter.cxx
+++ b/filter/source/svg/svgwriter.cxx
@@ -3329,7 +3329,11 @@ void SVGActionWriter::ImplWriteActions( const GDIMetaFile& rMtf,
                     {
                         Color aNewLineColor( mpVDev->GetLineColor() ), aNewFillColor( mpVDev->GetFillColor() );
 
-                        aNewLineColor.SetAlpha( 255 - sal::static_int_cast<sal_uInt8>( FRound( pA->GetTransparence() * 2.55 ) ) );
+                        // tdf#149800 do not change transparency of fully transparent
+                        // i.e. invisible line, because it makes it visible,
+                        // resulting an extra line behind the normal shape line
+                        if ( aNewLineColor.GetAlpha() > 0 )
+                            aNewLineColor.SetAlpha( 255 - sal::static_int_cast<sal_uInt8>( FRound( pA->GetTransparence() * 2.55 ) ) );
                         aNewFillColor.SetAlpha( 255 - sal::static_int_cast<sal_uInt8>( FRound( pA->GetTransparence() * 2.55 ) ) );
 
                         maAttributeWriter.AddPaintAttr( aNewLineColor, aNewFillColor );