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make SalLayoutGlyphsImpl::cloneCharRange() work for RTL runs too

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Glyphs are in the reverse order in this case, so the character
positions for the wanted range must be treated that way. This improves
e.g. the second attachment from tdf#112989. Unfortunately it's
not that significant, as arabic glyphs are often unsafe to break at.

Change-Id: I836ebff6282c420462c5cd5906d30d2e9431f218
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/133494
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>
This commit is contained in:
Luboš Luňák
2022-04-27 09:36:45 +02:00
parent e3c0a4eb7d
commit 2b418c16cd
1 changed files with 32 additions and 10 deletions
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42
vcl/source/gdi/impglyphitem.cxx
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@@ -95,15 +95,33 @@ SalLayoutGlyphsImpl* SalLayoutGlyphsImpl::cloneCharRange(sal_Int32 index, sal_In
{
std::unique_ptr<SalLayoutGlyphsImpl> copy(new SalLayoutGlyphsImpl(*GetFont()));
copy->SetFlags(GetFlags());
if (empty())
return copy.release();
copy->reserve(std::min<size_t>(size(), length));
// Skip glyphs that are in the string before the given index (glyphs are sorted by charPos()).
const_iterator pos = std::partition_point(
begin(), end(), [index](const GlyphItem& it) { return it.charPos() < index; });
sal_Int32 beginPos = index;
sal_Int32 endPos = index + length;
const_iterator pos;
bool rtl = front().IsRTLGlyph();
if (rtl)
{
// Glyphs are in reverse order for RTL.
beginPos = index + length - 1;
endPos = index - 1;
// Skip glyphs that are in the string after the given index, i.e. are before the glyphs
// we want.
pos = std::partition_point(
begin(), end(), [beginPos](const GlyphItem& it) { return it.charPos() > beginPos; });
}
else
{
// Skip glyphs that are in the string before the given index (glyphs are sorted by charPos()).
pos = std::partition_point(
begin(), end(), [beginPos](const GlyphItem& it) { return it.charPos() < beginPos; });
}
if (pos == end())
return nullptr;
// Require a start at the exact position given, otherwise bail out.
// TODO: This bails out also for RTL text.
if (pos->charPos() != index)
if (pos->charPos() != beginPos)
return nullptr;
// Don't create a subset if it's not safe to break at the beginning or end of the sequence
// (https://harfbuzz.github.io/harfbuzz-hb-buffer.html#hb-glyph-flags-t).
@@ -113,15 +131,17 @@ SalLayoutGlyphsImpl* SalLayoutGlyphsImpl::cloneCharRange(sal_Int32 index, sal_In
// that's how it's computed in GenericSalLayout::LayoutText().
DevicePoint zeroPoint = pos->linearPos() - DevicePoint(pos->xOffset(), pos->yOffset());
// Add and adjust all glyphs until the given length.
// The check is written as 'charPos + charCount <= index + length' rather than
// 'charPos < index + length' to make sure we include complete glyphs. If a glyph is composed
// The check is written as 'charPos + charCount <= endPos' rather than 'charPos < endPos'
// (or similarly for RTL) to make sure we include complete glyphs. If a glyph is composed
// from several characters, we should not cut in the middle of those characters, so this
// checks the glyph is entirely in the given character range. If it is not, this will end
// the loop and the later 'pos->charPos() != endPos' check will fail and bail out.
// CppunitTest_sw_layoutwriter's testCombiningCharacterCursorPosition would fail without this.
while (pos != end() && pos->charPos() + pos->charCount() <= index + length)
while (pos != end()
&& (rtl ? pos->charPos() - pos->charCount() >= endPos
: pos->charPos() + pos->charCount() <= endPos))
{
if (pos->IsRTLGlyph())
if (pos->IsRTLGlyph() != rtl)
return nullptr; // Don't mix RTL and non-RTL runs.
copy->push_back(*pos);
copy->back().setLinearPos(copy->back().linearPos() - zeroPoint);
@@ -129,7 +149,9 @@ SalLayoutGlyphsImpl* SalLayoutGlyphsImpl::cloneCharRange(sal_Int32 index, sal_In
}
if (pos != end())
{
if (pos->charPos() != index + length)
// Fail if the next character is at the expected past-end position. For RTL check
// that we're not cutting in the middle of a multi-character glyph.
if (rtl ? pos->charPos() + pos->charCount() != endPos + 1 : pos->charPos() != endPos)
return nullptr;
if (pos->IsUnsafeToBreak() || (pos->IsInCluster() && !pos->IsClusterStart()))
return nullptr;