Top-level symbols

Before we start the loop that iterates all characters visible on screen, we define some constants and variables.

The most important one is prev_sep: it controls when we can start to parse something new. If this variable isn't set correctly where it needs to be, highlighting of will be likely broken.

in_string, which tells us if we're in a string or not, is checked early since inside strings we should ignore everything else, except escaped characters (for which we have an escaped variable).

Similarly for in_mlcomment: also in this case we don't parse anything until we find the sequence that closes the comment.

    //////////////////////////////////////////
    //          Top-level symbols
    //////////////////////////////////////////

    // length of the rendered row
    const rowlen = row.render.len;

    // syntax definition
    const s = e.buffer.syndef.?;

    // line comment leader
    const lc = s.lcmt;

    // multiline comment leaders
    const mlc = s.mlcmt;

    // syntax flags
    const flags = s.flags;

    // character is preceded by a separator
    var prev_sep = true;

    // character is preceded by a backslash
    var escaped = false;

    // character is inside a string or char literal
    var in_string = false;
    var in_char = false;
    var delimiter: u8 = 0;

    // line is in a multiline comment
    var in_mlcomment = ix > 0 and e.buffer.rows.items[ix - 1].ml_comment;

    // all keywords in the syntax definition, subdivided by kinds
    // each kind has its own specific highlight
    const all_syn_keywords = [_]struct {
        kind: []const []const u8, // array with keywords of some kind
        hl: t.Highlight,
    }{
        .{ .kind = s.keywords, .hl = t.Highlight.keyword },
        .{ .kind = s.types,    .hl = t.Highlight.types },
        .{ .kind = s.builtin,  .hl = t.Highlight.builtin },
        .{ .kind = s.constant, .hl = t.Highlight.constant },
        .{ .kind = s.preproc,  .hl = t.Highlight.preproc },
    };

The top-level loop

We'll have multiple nested loops, so we will use labels to break to an outer loop. The top-level loop has the toplevel label.

We'll use labels for all loops, and all break and continue statements. This way it should be clearer from which loop we're breaking.

At the bottom of the top-level loop we'll increase the row index and set the critical prev_sep variable.

First thing we do is to skip whitespaces, which are also a valid separator.

    var i: usize = 0;
    toplevel: while (i < rowlen) {
        if (asc.isWhitespace(row.render[i])) { // skip whitespaces
            prev_sep = true;
            i += 1;
            continue :toplevel;
        }

        // rest of parsing goes here...

        prev_sep = str.isSeparator(row.render[i]);
        i += 1;
    }