Applying the highlight

We have now all we need to apply the highlight. This should be done where rows are drawn, in drawRows(). There, until now, we were simply drawing the rendered row as-is. This must change into:

We get the portion of the line that starts at coloff, and we iterate it for len characters, so that we only iterate the part of the line that can fit the screen:

            if (len > 0) {
                try e.toSurface(rows[ix].render[V.coloff .. V.coloff + len]);
            }

            // part of the line after coloff, and its highlight
            const rline = if (len > 0) rows[ix].render[V.coloff..] else &.{};
            const hl = if (len > 0) rows[ix].hl[V.coloff..] else &.{};

Inside the inner loop we check the character highlight, if it's different, we apply the highlight attribute, which will remain enabled until a different highlight is found in the row.hl array:

            var current_color = t.Highlight.normal;

            // loop characters of the rendered row
            for (rline[0..len], 0..) |c, i| {
                if (hl[i] != current_color) {
                    const color = hl[i];
                    current_color = color;
                    try e.toSurface(t.HlGroup.attr(color));
                }

We draw the character. At the end of the line we restore default highlight, otherwise the last highlight would carry over beyond the end of the line, and onto the next line:

                try e.toSurface(c);
            }
            // end of the line, reset highlight
            try e.toSurface(ansi.ResetColors);

    const line: []const u8 = &.{};
    for (line) |c| {
        std.debug.print("{}\n", .{c});
        break;
    } else {
        std.debug.print("nothing\n", .{});
    }