Method getTextBounds

lib/EpdFont/EpdFont.cpp:7–72

#include <algorithm>

void EpdFont::getTextBounds(const char* string, const int startX, const int startY, int* minX, int* minY, int* maxX,
                            int* maxY) const {
  *minX = startX;
  *minY = startY;
  *maxX = startX;
  *maxY = startY;

  if (*string == '\0') {
    return;
  }

  int lastBaseX = startX;
  int lastBaseLeft = 0;
  int lastBaseWidth = 0;
  int lastBaseTop = 0;
  int32_t prevAdvanceFP = 0;  // 12.4 fixed-point: prev glyph's advance + next kern for snap
  uint32_t cp;
  uint32_t prevCp = 0;
  while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&string)))) {
    const bool isCombining = utf8IsCombiningMark(cp);

    if (!isCombining) {
      cp = applyLigatures(cp, string);
    }

    const EpdGlyph* glyph = getGlyph(cp);
    if (!glyph) {
      // Keep cursor movement stable when a base glyph is missing, but don't attach subsequent
      // combining marks to stale base metrics.
      if (!isCombining) {
        lastBaseX += fp4::toPixel(prevAdvanceFP);  // flush pending advance before resetting
        prevCp = 0;
        prevAdvanceFP = 0;
        lastBaseLeft = 0;
        lastBaseWidth = 0;
        lastBaseTop = 0;
      }
      continue;
    }

    const int raiseBy = isCombining ? combiningMark::raiseAboveBase(glyph->top, glyph->height, lastBaseTop) : 0;

    if (!isCombining && prevCp != 0) {
      const auto kernFP = getKerning(prevCp, cp);  // 4.4 fixed-point kern
      lastBaseX += fp4::toPixel(prevAdvanceFP + kernFP);
    }

    const int glyphBaseX =
        isCombining ? combiningMark::centerOver(lastBaseX, lastBaseLeft, lastBaseWidth, glyph->left, glyph->width)
                    : lastBaseX;
    const int glyphBaseY = startY - raiseBy;

    *minX = std::min(*minX, glyphBaseX + glyph->left);
    *maxX = std::max(*maxX, glyphBaseX + glyph->left + glyph->width);
    *minY = std::min(*minY, glyphBaseY + glyph->top - glyph->height);
    *maxY = std::max(*maxY, glyphBaseY + glyph->top);

    if (!isCombining) {