sw: add rendering for semi-transparent text

I considered passing the text color's alpha value down to the various
vcl backends, but this would need changes everywhere (cairo, opengl, pdf
export, etc). It's much easier to go via DrawTransparent(), that's how
semi-transparent text in Draw/Impress already works.

(cherry picked from commit bf540873f5e258452fed5006f65a403c95e7872a)

Conflicts:
sw/CppunitTest_sw_core_text.mk
sw/qa/core/text/text.cxx
sw/source/core/text/inftxt.cxx

Change-Id: I96f15e6764c3c88ba67dd72dc8708414d7c6050c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/89219
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>

4 files changed, 211 insertions, 0 deletions

diff --git a/sw/CppunitTest_sw_core_text.mk b/sw/CppunitTest_sw_core_text.mk
new file mode 100644
index 000000000000..c9537c9d1a98
--- /dev/null
+++ b/sw/CppunitTest_sw_core_text.mk
@@ -0,0 +1,69 @@
+# -*- Mode: makefile-gmake; tab-width: 4; indent-tabs-mode: t -*-
+#*************************************************************************
+#
+# This file is part of the LibreOffice project.
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+#
+#*************************************************************************
+
+$(eval $(call gb_CppunitTest_CppunitTest,sw_core_text))
+
+$(eval $(call gb_CppunitTest_use_common_precompiled_header,sw_core_text))
+
+$(eval $(call gb_CppunitTest_add_exception_objects,sw_core_text, \
+    sw/qa/core/text/text \
+))
+
+$(eval $(call gb_CppunitTest_use_libraries,sw_core_text, \
+    comphelper \
+    cppu \
+    cppuhelper \
+    sal \
+    sfx \
+    sw \
+    test \
+    unotest \
+    utl \
+    vcl \
+))
+
+$(eval $(call gb_CppunitTest_use_externals,sw_core_text,\
+    boost_headers \
+    libxml2 \
+))
+
+$(eval $(call gb_CppunitTest_set_include,sw_core_text,\
+    -I$(SRCDIR)/sw/inc \
+    -I$(SRCDIR)/sw/source/core/inc \
+    -I$(SRCDIR)/sw/source/uibase/inc \
+    -I$(SRCDIR)/sw/qa/extras/inc \
+    $$(INCLUDE) \
+))
+
+$(eval $(call gb_CppunitTest_use_api,sw_core_text,\
+	udkapi \
+	offapi \
+	oovbaapi \
+))
+
+$(eval $(call gb_CppunitTest_use_ure,sw_core_text))
+$(eval $(call gb_CppunitTest_use_vcl,sw_core_text))
+
+$(eval $(call gb_CppunitTest_use_rdb,sw_core_text,services))
+
+$(eval $(call gb_CppunitTest_use_custom_headers,sw_core_text,\
+    officecfg/registry \
+))
+
+$(eval $(call gb_CppunitTest_use_configuration,sw_core_text))
+
+$(eval $(call gb_CppunitTest_use_uiconfigs,sw_core_text, \
+    modules/swriter \
+))
+
+$(eval $(call gb_CppunitTest_use_more_fonts,sw_core_text))
+
+# vim: set noet sw=4 ts=4:
diff --git a/sw/Module_sw.mk b/sw/Module_sw.mk
index 1e4c723043c5..e2b4344af06c 100644
--- a/sw/Module_sw.mk
+++ b/sw/Module_sw.mk
@@ -101,6 +101,7 @@ $(eval $(call gb_Module_add_slowcheck_targets,sw,\
     CppunitTest_sw_core_doc \
     CppunitTest_sw_uibase_shells \
     CppunitTest_sw_core_layout \
+    CppunitTest_sw_core_text \
 ))
 
 ifneq ($(DISABLE_GUI),TRUE)
diff --git a/sw/qa/core/text/text.cxx b/sw/qa/core/text/text.cxx
new file mode 100644
index 000000000000..687c4c2b792c
--- /dev/null
+++ b/sw/qa/core/text/text.cxx
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <swmodeltestbase.hxx>
+
+#include <vcl/gdimtf.hxx>
+#include <test/mtfxmldump.hxx>
+
+#include <wrtsh.hxx>
+
+static char const DATA_DIRECTORY[] = "/sw/qa/core/text/data/";
+
+/// Covers sw/source/core/text/ fixes.
+class SwCoreTextTest : public SwModelTestBase
+{
+public:
+    SwDoc* createDoc(const char* pName = nullptr);
+};
+
+SwDoc* SwCoreTextTest::createDoc(const char* pName)
+{
+    load(DATA_DIRECTORY, pName);
+
+    SwXTextDocument* pTextDoc = dynamic_cast<SwXTextDocument*>(mxComponent.get());
+    CPPUNIT_ASSERT(pTextDoc);
+    return pTextDoc->GetDocShell()->GetDoc();
+}
+
+CPPUNIT_TEST_FIXTURE(SwCoreTextTest, testSemiTransparentText)
+{
+    // Create an in-memory empty document.
+    loadURL("private:factory/swriter", nullptr);
+
+    // Set text to half-transparent and type a character.
+    uno::Reference<beans::XPropertySet> xParagraph(getParagraph(1), uno::UNO_QUERY);
+    CPPUNIT_ASSERT(xParagraph.is());
+    sal_Int16 nTransparence = 50;
+    xParagraph->setPropertyValue("CharTransparence", uno::makeAny(nTransparence));
+    uno::Reference<text::XTextRange> xTextRange(xParagraph, uno::UNO_QUERY);
+    CPPUNIT_ASSERT(xTextRange.is());
+    xTextRange->setString("x");
+
+    // Render the document to a metafile.
+    SwXTextDocument* pTextDoc = dynamic_cast<SwXTextDocument*>(mxComponent.get());
+    CPPUNIT_ASSERT(pTextDoc);
+    SwDocShell* pDocShell = pTextDoc->GetDocShell();
+    CPPUNIT_ASSERT(pDocShell);
+    std::shared_ptr<GDIMetaFile> xMetaFile = pDocShell->GetPreviewMetaFile();
+    CPPUNIT_ASSERT(xMetaFile);
+
+    // Make sure that DrawTransparent() was used during rendering.
+    MetafileXmlDump dumper;
+    xmlDocPtr pXmlDoc = dumper.dumpAndParse(*xMetaFile);
+    CPPUNIT_ASSERT(pXmlDoc);
+    assertXPath(pXmlDoc, "//floattransparent");
+}
+
+CPPUNIT_PLUGIN_IMPLEMENT();
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/sw/source/core/text/inftxt.cxx b/sw/source/core/text/inftxt.cxx
index f2c4a3f2bcf4..ee04fe11a8b2 100644
--- a/sw/source/core/text/inftxt.cxx
+++ b/sw/source/core/text/inftxt.cxx
@@ -69,6 +69,9 @@
 #include <docufld.hxx>
 #include <frmfmt.hxx>
 #include <unomid.h>
+#include <vcl/gdimtf.hxx>
+#include <vcl/virdev.hxx>
+#include <vcl/gradient.hxx>
 
 using namespace ::com::sun::star;
 using namespace ::com::sun::star::linguistic2;
@@ -557,6 +560,71 @@ static bool lcl_IsDarkBackground( const SwTextPaintInfo& rInf )
     return pCol->IsDark();
 }
 
+namespace
+{
+/**
+ * Context class that captures the draw operations on rDrawInf's output device for transparency
+ * purposes.
+ */
+class SwTransparentTextGuard
+{
+    ScopedVclPtrInstance<VirtualDevice> m_aContentVDev;
+    GDIMetaFile m_aContentMetafile;
+    MapMode m_aNewMapMode;
+    SwRect m_aPorRect;
+    SwTextPaintInfo& m_rPaintInf;
+    SwDrawTextInfo& m_rDrawInf;
+
+public:
+    SwTransparentTextGuard(const SwLinePortion& rPor, SwTextPaintInfo& rPaintInf,
+                           SwDrawTextInfo& rDrawInf);
+    ~SwTransparentTextGuard();
+};
+
+SwTransparentTextGuard::SwTransparentTextGuard(const SwLinePortion& rPor,
+                                               SwTextPaintInfo& rPaintInf, SwDrawTextInfo& rDrawInf)
+    : m_aNewMapMode(rPaintInf.GetOut()->GetMapMode())
+    , m_rPaintInf(rPaintInf)
+    , m_rDrawInf(rDrawInf)
+{
+    rPaintInf.CalcRect(rPor, &m_aPorRect);
+    rDrawInf.SetOut(*m_aContentVDev);
+    m_aContentVDev->SetMapMode(rPaintInf.GetOut()->GetMapMode());
+    m_aContentMetafile.Record(m_aContentVDev.get());
+    m_aContentVDev->SetLineColor(rPaintInf.GetOut()->GetLineColor());
+    m_aContentVDev->SetFillColor(rPaintInf.GetOut()->GetFillColor());
+    m_aContentVDev->SetFont(rPaintInf.GetOut()->GetFont());
+    m_aContentVDev->SetDrawMode(rPaintInf.GetOut()->GetDrawMode());
+    m_aContentVDev->SetSettings(rPaintInf.GetOut()->GetSettings());
+    m_aContentVDev->SetRefPoint(rPaintInf.GetOut()->GetRefPoint());
+}
+
+SwTransparentTextGuard::~SwTransparentTextGuard()
+{
+    m_aContentMetafile.Stop();
+    m_aContentMetafile.WindStart();
+    m_aNewMapMode.SetOrigin(m_aPorRect.TopLeft());
+    m_aContentMetafile.SetPrefMapMode(m_aNewMapMode);
+    m_aContentMetafile.SetPrefSize(m_aPorRect.SSize());
+    m_rDrawInf.SetOut(*m_rPaintInf.GetOut());
+    Gradient aVCLGradient;
+    sal_uInt8 nTransPercentVcl = m_rPaintInf.GetFont()->GetColor().GetTransparency();
+    const Color aTransColor(nTransPercentVcl, nTransPercentVcl, nTransPercentVcl);
+    aVCLGradient.SetStyle(GradientStyle::Linear);
+    aVCLGradient.SetStartColor(aTransColor);
+    aVCLGradient.SetEndColor(aTransColor);
+    aVCLGradient.SetAngle(0);
+    aVCLGradient.SetBorder(0);
+    aVCLGradient.SetOfsX(0);
+    aVCLGradient.SetOfsY(0);
+    aVCLGradient.SetStartIntensity(100);
+    aVCLGradient.SetEndIntensity(100);
+    aVCLGradient.SetSteps(2);
+    m_rPaintInf.GetOut()->DrawTransparent(m_aContentMetafile, m_aPorRect.TopLeft(),
+                                          m_aPorRect.SSize(), aVCLGradient);
+}
+}
+
 void SwTextPaintInfo::DrawText_( const OUString &rText, const SwLinePortion &rPor,
                                 TextFrameIndex const nStart, TextFrameIndex const nLength,
                                 const bool bKern, const bool bWrong,
@@ -683,6 +751,13 @@ void SwTextPaintInfo::DrawText_( const OUString &rText, const SwLinePortion &rPo
             aFontPos.setY( 0 );
     }
 
+    // Handle semi-transparent text if necessary.
+    std::unique_ptr<SwTransparentTextGuard> pTransparentText;
+    if (m_pFnt->GetColor() != COL_AUTO && m_pFnt->GetColor().GetTransparency() != 0)
+    {
+        pTransparentText.reset(new SwTransparentTextGuard(rPor, *this, aDrawInf));
+    }
+
     if( GetTextFly().IsOn() )
     {
         // aPos needs to be the TopLeft, because we cannot calculate the