Method NextLine

src/gfx_layout_fallback.cpp:212–307

* Construct a new line with a maximum width. * @param max_width The maximum width of the string. * @return A Line, or nullptr when at the end of the paragraph. */

 * @return A Line, or nullptr when at the end of the paragraph.
 */
std::unique_ptr<const ParagraphLayouter::Line> FallbackParagraphLayout::NextLine(int max_width)
{
	/* Simple idea:
	 *  - split a line at a newline character, or at a space where we can break a line.
	 *  - split for a visual run whenever a new line happens, or the font changes.
	 */
	if (this->buffer == nullptr) return nullptr;

	std::unique_ptr<FallbackLine> l = std::make_unique<FallbackLine>();

	if (*this->buffer == '\0') {
		/* Only a newline. */
		this->buffer = nullptr;
		l->emplace_back(this->runs.begin()->second, this->buffer, 0, 0, 0);
		return l;
	}

	int offset = this->buffer - this->buffer_begin;
	FontMap::iterator iter = this->runs.begin();
	while (iter->first <= offset) {
		++iter;
		assert(iter != this->runs.end());
	}

	const FontCache *fc = iter->second->fc;
	const char32_t *next_run = this->buffer_begin + iter->first;

	const char32_t *begin = this->buffer;
	const char32_t *last_space = nullptr;
	const char32_t *last_char;
	int width = 0;
	for (;;) {
		char32_t c = *this->buffer;
		last_char = this->buffer;

		if (c == '\0') {
			this->buffer = nullptr;
			break;
		}

		if (this->buffer == next_run) {
			int w = l->GetWidth();
			l->emplace_back(iter->second, begin, this->buffer - begin, begin - this->buffer_begin, w);
			++iter;
			assert(iter != this->runs.end());

			next_run = this->buffer_begin + iter->first;
			begin = this->buffer;
			/* Since a next run is started, there is already some text that
			 * will be shown for this line. However, we do not want to break
			 * this line at the previous space, so pretend we passed a space
			 * just before this next run. */
			last_space = begin - 1;
		}

		if (IsWhitespace(c)) last_space = this->buffer;

		if (IsPrintable(c) && !IsTextDirectionChar(c)) {