commit 0f67027dbf3774687a558127427ff26796f00328
author Khaled Hosny <khaled@libreoffice.org> Sun Jul 30 07:12:53 2023 +0300
committer Caolán McNamara <caolan.mcnamara@collabora.com> Mon Jul 31 22:15:10 2023 +0200
tree 3166cb2a95063ed0ef42d6855afde4f6b213f837
parent 8d2c3ba78550631ae991bdd517b3acc9749e41b7

tdf#107612: Include NNBSP and Mongolian characters in the same fallback run

When a Mongolian character is preceded by a Narrow No Break Space
(NNBSP), it is used to trigger special letter forms, but when we do font
fallback NNBSP is always taken from the main font (HarfBuzz synthesises
it when missing from the font, so we almost never use font fallback for
it).

We now check if the start of the fallback run is a Mongolian character
and the previous is NNBSP and extend the fallback run to include it.

Change-Id: I7607dba37ee51ff62bc9e86c3dbc555cd77e8d5d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155060
Tested-by: Jenkins
Reviewed-by: خالد حسني <khaled@libreoffice.org>
(cherry picked from commit 3aac74005230500e2d0cb72b3a1198d07e985e84)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155037
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>

vcl/inc/sallayout.hxx

diff --git a/vcl/inc/sallayout.hxx b/vcl/inc/sallayout.hxx
index d48edaa..e54a73b 100644
--- a/vcl/inc/sallayout.hxx
+++ b/vcl/inc/sallayout.hxx
@@ -57,7 +57,7 @@ namespace vcl::text {
    class TextLayoutCache;
}

class MultiSalLayout final : public SalLayout
class VCL_DLLPUBLIC MultiSalLayout final : public SalLayout
{
public:
    void            DrawText(SalGraphics&) const override;
@@ -86,6 +86,8 @@ public:
                                          vcl::text::ImplLayoutArgs& rMultiArgs,
                                          const double* pMultiDXArray);

    SAL_DLLPRIVATE ImplLayoutRuns* GetFallbackRuns() { return maFallbackRuns; }

    virtual         ~MultiSalLayout() override;

private:

vcl/qa/cppunit/complextext.cxx

diff --git a/vcl/qa/cppunit/complextext.cxx b/vcl/qa/cppunit/complextext.cxx
index bcf96cb..5c6297e 100644
--- a/vcl/qa/cppunit/complextext.cxx
+++ b/vcl/qa/cppunit/complextext.cxx
@@ -531,4 +531,37 @@ CPPUNIT_TEST_FIXTURE(VclComplexTextTest, testTdf107718)
#endif
}

CPPUNIT_TEST_FIXTURE(VclComplexTextTest, testTdf107612)
{
#if HAVE_MORE_FONTS
    vcl::Font aFont(u"DejaVu Sans", u"Book", Size(0, 72));

    ScopedVclPtrInstance<VirtualDevice> pOutDev;
    pOutDev->SetFont(aFont);

    auto pLayout = pOutDev->ImplLayout(u"a\u202F\u1823", 0, -1, Point(0, 0), 0, {}, {});

    // If font fallback happened, then the returned layout must be a
    // MultiSalLayout instance.
    auto pMultiLayout = dynamic_cast<MultiSalLayout*>(pLayout.get());
    CPPUNIT_ASSERT(pMultiLayout);

    auto pFallbackRuns = pMultiLayout->GetFallbackRuns();
    CPPUNIT_ASSERT(!pFallbackRuns->IsEmpty());

    bool bRTL;
    int nCharPos = -1;
    std::vector<sal_Int32> aFallbacks;
    while (pFallbackRuns->GetNextPos(&nCharPos, &bRTL))
        aFallbacks.push_back(nCharPos);

    // Assert that U+202F is included in the fallback run.
    // Without the fix this fails with:
    // - Expected: { 2 }
    // - Actual  : { 1, 2 }
    std::vector<sal_Int32> aExpctedFallbacks = { 1, 2 };
    CPPUNIT_ASSERT_EQUAL(aFallbacks, aExpctedFallbacks);
#endif
}

/* vim:set shiftwidth=4 softtabstop=4 expandtab: */

vcl/source/gdi/CommonSalLayout.cxx

diff --git a/vcl/source/gdi/CommonSalLayout.cxx b/vcl/source/gdi/CommonSalLayout.cxx
index 7ea3ba6..944587f 100644
--- a/vcl/source/gdi/CommonSalLayout.cxx
+++ b/vcl/source/gdi/CommonSalLayout.cxx
@@ -170,6 +170,21 @@ void GenericSalLayout::SetNeedFallback(vcl::text::ImplLayoutArgs& rArgs, sal_Int
        mxBreak->previousCharacters(rArgs.mrStr, nCharPos, aLocale,
            i18n::CharacterIteratorMode::SKIPCELL, 1, nDone);

    // tdf#107612
    // If the start of the fallback run is Mongolian character and the previous
    // character is NNBSP, we want to include the NNBSP in the fallback since
    // it has special uses in Mongolian and have to be in the same text run to
    // work.
    sal_Int32 nTempPos = nGraphemeStartPos;
    if (nGraphemeStartPos > 0)
    {
        auto nCurrChar = rArgs.mrStr.iterateCodePoints(&nTempPos, 0);
        auto nPrevChar = rArgs.mrStr.iterateCodePoints(&nTempPos, -1);
        if (nPrevChar == 0x202F
            && u_getIntPropertyValue(nCurrChar, UCHAR_SCRIPT) == USCRIPT_MONGOLIAN)
            nGraphemeStartPos = nTempPos;
    }

    //stay inside the Layout range (e.g. with tdf124116-1.odt)
    nGraphemeStartPos = std::max(rArgs.mnMinCharPos, nGraphemeStartPos);
    nGraphemeEndPos = std::min(rArgs.mnEndCharPos, nGraphemeEndPos);