Overstrike convention for bold/underline?

[trantor]

Hi @tstack .

I was browsing through the release notes and stumbled upon this

The "overstrike" convention for doing bold and underline is now
supported. (Overstrike is a character followed by a backspace
and then the same character for bold or an underscore for
underline.)

I don't quite get the context for this or find the related commits to get an idea about it.
Do you have some pointer? (Last time I saw an overstrike was when I was using a typewriter XD )

[trantor]

Btw, nice to see the project chugging along nicely :)

[tstack]

(Last time I saw an overstrike was when I was using a typewriter XD)

That's pretty much what it's about. You can use lnav to view man pages with export "MANPAGER=lnav -q" and the way roff does bold/underline is to write out the character, then a backspace, and then either the character again for bold or an underscore for underline.

The relevant code is in the following block:

lnav/src/base/ansi_scrubber.cc

Lines 146 to 238 in 016bca0

	ssize_t fill_index = sf.sf_begin;
	line_range bold_range;
	line_range ul_range;
	auto sub_sf = sf;
	while (!sub_sf.empty()) {
	auto lhs_opt = sub_sf.consume_codepoint();
	if (!lhs_opt) {
	return;
	}
	auto lhs_pair = lhs_opt.value();
	auto mid_opt = lhs_pair.second.consume_codepoint();
	if (!mid_opt) {
	return;
	}
	auto mid_pair = mid_opt.value();
	auto rhs_opt = mid_pair.second.consume_codepoint();
	if (!rhs_opt) {
	return;
	}
	auto rhs_pair = rhs_opt.value();
	sub_sf = rhs_pair.second;
	if (lhs_pair.first == '_' || rhs_pair.first == '_') {
	if (sa != nullptr && bold_range.is_valid()) {
	sa->emplace_back(bold_range,
	VC_STYLE.value(text_attrs{A_BOLD}));
	bold_range.clear();
	}
	if (ul_range.is_valid()) {
	ul_range.lr_end += 1;
	} else {
	ul_range.lr_start = fill_index;
	ul_range.lr_end = fill_index + 1;
	}
	auto cp = lhs_pair.first == '_' ? rhs_pair.first
	: lhs_pair.first;
	ww898::utf::utf8::write(cp, [&str, &fill_index](auto ch) {
	str[fill_index++] = ch;
	});
	} else {
	if (sa != nullptr && ul_range.is_valid()) {
	sa->emplace_back(
	ul_range, VC_STYLE.value(text_attrs{A_UNDERLINE}));
	ul_range.clear();
	}
	if (bold_range.is_valid()) {
	bold_range.lr_end += 1;
	} else {
	bold_range.lr_start = fill_index;
	bold_range.lr_end = fill_index + 1;
	}
	try {
	ww898::utf::utf8::write(lhs_pair.first,
	[&str, &fill_index](auto ch) {
	str[fill_index++] = ch;
	});
	} catch (const std::runtime_error& e) {
	log_error("invalid UTF-8 at %d", sf.sf_begin);
	return;
	}
	}
	}
	auto output_size = fill_index - sf.sf_begin;
	auto erased_size = sf.length() - output_size;
	if (sa != nullptr) {
	#if 0
	shift_string_attrs(
	*sa, caps->c_begin + sf.length() / 3, -erased_size);
	#endif
	sa->emplace_back(line_range{last_origin_offset_end,
	sf.sf_begin + (int) output_size},
	SA_ORIGIN_OFFSET.value(origin_offset));
	}
	if (sa != nullptr && ul_range.is_valid()) {
	sa->emplace_back(ul_range,
	VC_STYLE.value(text_attrs{A_UNDERLINE}));
	ul_range.clear();
	}
	if (sa != nullptr && bold_range.is_valid()) {
	sa->emplace_back(bold_range,
	VC_STYLE.value(text_attrs{A_BOLD}));
	bold_range.clear();
	}
	str.erase(str.begin() + fill_index, str.begin() + sf.sf_end);
	last_origin_offset_end = sf.sf_begin + output_size;
	origin_offset += erased_size;
	matcher.reload_input(str, last_origin_offset_end);
	continue;