feat: add RTL support in epub and txt readers (#1700)
Co-authored-by: Zach Nelson <zach@zdnelson.com>
This commit is contained in:
Uri Tauber
co-authored by
Zach Nelson
Zach Nelson
parent
cc2079a578
commit
f5bc554ae7
@@ -0,0 +1,234 @@
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#include "BidiUtils.h"
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extern "C" {
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#include "minibidi.h"
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}
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#undef when
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#undef otherwise
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#include <Logging.h>
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#include <Utf8.h>
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#include <cstring>
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namespace {
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bool isNaturalDirectionClass(const uchar cls) {
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switch (cls) {
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case L:
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case R:
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case AL:
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case EN:
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case AN:
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return true;
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default:
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return false;
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}
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}
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} // namespace
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namespace BidiUtils {
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bool startsWithRtl(const char* utf8, int maxStrongChars) {
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if (!utf8 || maxStrongChars <= 0) return false;
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auto* p = reinterpret_cast<const unsigned char*>(utf8);
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int checked = 0;
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while (*p) {
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const uint32_t cp = utf8NextCodepoint(&p);
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if (!cp || cp == REPLACEMENT_GLYPH) break;
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const uchar cls = bidi_class(cp);
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if (cls == R || cls == AL) return true;
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if (cls == L) return false;
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checked++;
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if (checked >= maxStrongChars) break;
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}
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return false;
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}
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int detectParagraphLevel(const char* utf8, const int fallbackLevel, const int maxStrongChars) {
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if (!utf8 || maxStrongChars <= 0) return fallbackLevel & 1;
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auto* p = reinterpret_cast<const unsigned char*>(utf8);
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int checked = 0;
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while (*p) {
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const uint32_t cp = utf8NextCodepoint(&p);
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if (!cp || cp == REPLACEMENT_GLYPH) break;
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const uchar cls = bidi_class(cp);
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if (cls == R || cls == AL) return 1;
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if (cls == L) return 0;
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checked++;
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if (checked >= maxStrongChars) break;
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}
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return fallbackLevel & 1;
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}
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bool applyBidiVisual(const char* utf8, std::string& out, int paragraphLevel) {
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if (!utf8 || !*utf8) return false;
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static bidi_char line[BIDI_MAX_LINE];
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int count = 0;
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auto* p = reinterpret_cast<const unsigned char*>(utf8);
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while (*p) {
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if (count >= BIDI_MAX_LINE) {
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LOG_DBG("BIDI", "applyBidiVisual: input exceeds BIDI_MAX_LINE (%d chars), returning unprocessed", BIDI_MAX_LINE);
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return false;
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}
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const uint32_t cp = utf8NextCodepoint(&p);
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if (!cp || cp == REPLACEMENT_GLYPH) break;
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line[count].origwc = line[count].wc = cp;
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line[count].index = static_cast<uint16_t>(count);
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count++;
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}
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if (!count) return false;
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const bool autodir = (paragraphLevel < 0);
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const int level = autodir ? 0 : (paragraphLevel & 1);
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do_bidi(autodir, level, line, count);
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out.clear();
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out.reserve(std::strlen(utf8));
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for (int i = 0; i < count; i++) {
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utf8AppendCodepoint(line[i].wc, out);
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}
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return true;
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}
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bool computeVisualWordOrder(const std::vector<std::string>& words, bool paragraphIsRtl,
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std::vector<uint16_t>& visualOrder) {
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visualOrder.clear();
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const size_t nWords = words.size();
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if (nWords <= 1 || nWords > BIDI_MAX_LINE) return false;
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static bidi_char line[BIDI_MAX_LINE];
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int count = 0;
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bool truncated = false;
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for (size_t w = 0; w < nWords && !truncated; w++) {
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auto* p = reinterpret_cast<const unsigned char*>(words[w].c_str());
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while (*p) {
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if (count >= BIDI_MAX_LINE) {
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truncated = true;
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break;
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}
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const uint32_t cp = utf8NextCodepoint(&p);
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if (!cp || cp == REPLACEMENT_GLYPH) break;
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line[count].origwc = line[count].wc = cp;
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line[count].index = static_cast<uint16_t>(w);
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count++;
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}
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if (!truncated && w + 1 < nWords) {
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if (count >= BIDI_MAX_LINE) {
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truncated = true;
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break;
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}
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line[count].origwc = line[count].wc = ' ';
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line[count].index = static_cast<uint16_t>(nWords);
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count++;
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}
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}
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if (truncated || count == 0) return false;
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// Fast-path for homogeneous lines: skip UAX#9 if there's no mixing.
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bool hasL = false, hasR = false;
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for (int i = 0; i < count; i++) {
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uchar bc = bidi_class(line[i].wc);
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if (bc == L || bc == EN || bc == AN)
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hasL = true;
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else if (bc == R || bc == AL)
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hasR = true;
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}
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// Purely LTR line in RTL paragraph: identity order, but we might still need to reorder
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// if some characters are mirrored or neutral resolution differs.
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// Actually, UAX#9 rule L1/L2 says purely LTR in RTL para stays as is (identity).
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// Purely RTL line: just reverse the words.
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if (!hasL && hasR && paragraphIsRtl) {
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visualOrder.reserve(nWords);
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for (int i = static_cast<int>(nWords) - 1; i >= 0; i--) {
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visualOrder.push_back(static_cast<uint16_t>(i));
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}
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return true;
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}
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if (!hasR) {
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if (!paragraphIsRtl) {
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// Pure LTR in LTR paragraph: nothing to do.
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return false;
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}
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// Pure LTR in RTL paragraph: no word reordering, but must use the
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// willReorder (left-to-right) positioning path, not the RTL right-to-left path.
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visualOrder.reserve(nWords);
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for (size_t i = 0; i < nWords; i++) {
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visualOrder.push_back(static_cast<uint16_t>(i));
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}
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return true;
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}
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do_bidi(/*autodir=*/false, paragraphIsRtl ? 1 : 0, line, count);
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uint16_t firstAny[BIDI_MAX_LINE];
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uint16_t firstNatural[BIDI_MAX_LINE];
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for (size_t w = 0; w < nWords; w++) {
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firstAny[w] = UINT16_MAX;
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firstNatural[w] = UINT16_MAX;
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}
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for (int i = 0; i < count; i++) {
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const uint16_t w = line[i].index;
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if (w >= nWords) continue;
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if (firstAny[w] == UINT16_MAX) {
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firstAny[w] = static_cast<uint16_t>(i);
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}
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if (firstNatural[w] == UINT16_MAX && isNaturalDirectionClass(bidi_class(line[i].wc))) {
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firstNatural[w] = static_cast<uint16_t>(i);
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}
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}
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visualOrder.reserve(nWords);
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for (int i = 0; i < count; i++) {
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const uint16_t w = line[i].index;
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if (w >= nWords) continue;
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const uint16_t anchor = firstNatural[w] != UINT16_MAX ? firstNatural[w] : firstAny[w];
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if (anchor == UINT16_MAX) {
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visualOrder.clear();
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return false;
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}
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if (anchor == static_cast<uint16_t>(i)) {
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visualOrder.push_back(w);
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}
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}
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if (visualOrder.size() != nWords) {
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visualOrder.clear();
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return false;
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}
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// Check if the order is exactly the same as the original input
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bool needsReorder = false;
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for (size_t i = 0; i < nWords; i++) {
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if (visualOrder[i] != i) {
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needsReorder = true;
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break;
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}
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}
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if (!needsReorder) {
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visualOrder.clear();
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return false;
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}
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return true;
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}
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} // namespace BidiUtils
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