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#include <memory>
#include <mbgl/text/bidi.hpp>
#include <unicode/ubidi.h>
#include <unicode/ushape.h>
namespace mbgl {
class BiDiImpl {
public:
BiDiImpl() : bidiText(ubidi_open()), bidiLine(ubidi_open()) {}
~BiDiImpl() { ubidi_close(bidiText); ubidi_close(bidiLine); }
UBiDi* bidiText = nullptr;
UBiDi* bidiLine = nullptr;
};
// Takes UTF16 input in logical order and applies Arabic shaping to the input while maintaining
// logical order
// Output won't be intelligible until the bidirectional algorithm is applied
std::u16string applyArabicShaping(const std::u16string& input) {
UErrorCode errorCode = U_ZERO_ERROR;
int32_t outputLength =
u_shapeArabic(input.c_str(), static_cast<int32_t>(input.size()), NULL, 0,
(U_SHAPE_LETTERS_SHAPE & U_SHAPE_LETTERS_MASK) |
(U_SHAPE_TEXT_DIRECTION_LOGICAL & U_SHAPE_TEXT_DIRECTION_MASK),
&errorCode);
// Pre-flighting will always set U_BUFFER_OVERFLOW_ERROR
errorCode = U_ZERO_ERROR;
std::unique_ptr<UChar[]> outputText = std::make_unique<UChar[]>(outputLength);
u_shapeArabic(input.c_str(), static_cast<int32_t>(input.size()), outputText.get(), outputLength,
(U_SHAPE_LETTERS_SHAPE & U_SHAPE_LETTERS_MASK) |
(U_SHAPE_TEXT_DIRECTION_LOGICAL & U_SHAPE_TEXT_DIRECTION_MASK),
&errorCode);
// If the algorithm fails for any reason, fall back to non-transformed text
if (U_FAILURE(errorCode))
return input;
return std::u16string(outputText.get(), outputLength);
}
ProcessedBiDiText::ProcessedBiDiText(BiDi& p_bidi) : bidi(p_bidi) {
}
void ProcessedBiDiText::mergeParagraphLineBreaks(std::set<int32_t>& lineBreakPoints) {
int32_t paragraphCount = ubidi_countParagraphs(bidi.impl->bidiText);
for (int32_t i = 0; i < paragraphCount; i++) {
UErrorCode errorCode = U_ZERO_ERROR;
int32_t paragraphEndIndex;
ubidi_getParagraphByIndex(bidi.impl->bidiText, i, NULL, ¶graphEndIndex, NULL, &errorCode);
if (U_FAILURE(errorCode))
throw std::runtime_error(std::string("ProcessedBiDiText::mergeParagraphLineBreaks: ") +
u_errorName(errorCode));
lineBreakPoints.insert(paragraphEndIndex);
}
}
std::vector<std::u16string>
ProcessedBiDiText::applyLineBreaking(std::set<int32_t> lineBreakPoints) {
// BiDi::getLine will error if called across a paragraph boundary, so we need to ensure that all
// paragraph
// boundaries are included in the set of line break points. The calling code might not include
// the line break because it
// didn't need to wrap at that point, or because the text was separated with a more exotic code
// point such as (U+001C)
mergeParagraphLineBreaks(lineBreakPoints);
std::vector<std::u16string> transformedLines;
int32_t start = 0;
for (int32_t lineBreakPoint : lineBreakPoints) {
transformedLines.push_back(bidi.getLine(start, lineBreakPoint));
start = lineBreakPoint;
}
return transformedLines;
}
BiDi::BiDi() : impl(std::make_unique<BiDiImpl>())
{
}
BiDi::~BiDi() {
}
ProcessedBiDiText BiDi::processText(const std::u16string& input) {
UErrorCode errorCode = U_ZERO_ERROR;
ubidi_setPara(impl->bidiText, input.c_str(), static_cast<int32_t>(input.size()), UBIDI_DEFAULT_LTR,
NULL, &errorCode);
if (U_FAILURE(errorCode))
throw std::runtime_error(std::string("BiDi::processText: ") + u_errorName(errorCode));
return ProcessedBiDiText(*this);
}
std::u16string BiDi::getLine(int32_t start, int32_t end) {
UErrorCode errorCode = U_ZERO_ERROR;
ubidi_setLine(impl->bidiText, start, end, impl->bidiLine, &errorCode);
if (U_FAILURE(errorCode))
throw std::runtime_error(std::string("BiDi::getLine (setLine): ") + u_errorName(errorCode));
// Because we set UBIDI_REMOVE_BIDI_CONTROLS, the output may be smaller than what we reserve
// Setting UBIDI_INSERT_LRM_FOR_NUMERIC would require
// ubidi_getLength(pBiDi)+2*ubidi_countRuns(pBiDi)
int32_t outputLength = ubidi_getProcessedLength(impl->bidiLine);
std::unique_ptr<UChar[]> outputText = std::make_unique<UChar[]>(outputLength);
// UBIDI_DO_MIRRORING: Apply unicode mirroring of characters like parentheses
// UBIDI_REMOVE_BIDI_CONTROLS: Now that all the lines are set, remove control characters so that
// they don't show up on screen (some fonts have glyphs representing them)
ubidi_writeReordered(impl->bidiLine, outputText.get(), outputLength,
UBIDI_DO_MIRRORING | UBIDI_REMOVE_BIDI_CONTROLS, &errorCode);
if (U_FAILURE(errorCode))
throw std::runtime_error(std::string("BiDi::getLine (writeReordered): ") + u_errorName(errorCode));
return std::u16string(outputText.get(), outputLength);
}
} // end namespace mbgl
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