float getAdvance(const float* advances, const char* src) {
const size_t BUF_SIZE = 256;
uint16_t buf[BUF_SIZE];
size_t offset;
size_t size;
ParseUnicode(buf, BUF_SIZE, src, &size, &offset);
return getRunAdvance(advances, buf, 0, size, offset);
}
/**
* Essentially the inverse of getRunAdvance. Compute the value of offset for which the
* measured caret comes closest to the provided advance param, and which is on a grapheme
* cluster boundary.
*
* The actual implementation fast-forwards through clusters to get "close", then does a finer-grain
* search within the cluster and grapheme breaks.
*/
size_t getOffsetForAdvance(const float* advances, const uint16_t* buf, size_t start, size_t count,
float advance) {
float x = 0.0f, xLastClusterStart = 0.0f, xSearchStart = 0.0f;
size_t lastClusterStart = start, searchStart = start;
for (size_t i = start; i < start + count; i++) {
if (GraphemeBreak::isGraphemeBreak(advances, buf, start, count, i)) {
searchStart = lastClusterStart;
xSearchStart = xLastClusterStart;
}
float width = advances[i - start];
if (width != 0.0f) {
lastClusterStart = i;
xLastClusterStart = x;
x += width;
if (x > advance) {
break;
}
}
}
size_t best = searchStart;
float bestDist = FLT_MAX;
for (size_t i = searchStart; i <= start + count; i++) {
if (GraphemeBreak::isGraphemeBreak(advances, buf, start, count, i)) {
// "getRunAdvance(layout, buf, start, count, i) - advance" but more efficient
float delta = getRunAdvance(advances, buf, start, searchStart, count - searchStart, i)
+ xSearchStart - advance;
if (std::abs(delta) < bestDist) {
bestDist = std::abs(delta);
best = i;
}
if (delta >= 0.0f) {
break;
}
}
}
return best;
}
float getRunAdvance(const float* advances, const uint16_t* buf, size_t start, size_t count,
size_t offset) {
return getRunAdvance(advances, buf, start, start, count, offset);
}
