Allow starting line numbering at an offset

Also remove the offset when looking for a line within a section for consistency
Also allow the regex to be empty to get the first line within a section
to determine which line number to start with more consistently

Author: ISSOtm

js/linenos.js

@@ -1,5 +1,7 @@
 // This is done as JS so as to occur *after* `highlight.js` inserts its `<span>`s
 
+let linenoRegex = /^start=([0-9]+)$/;
+
 for (let element of document.querySelectorAll('pre > code.linenos')) {
 	let text = element.innerHTML;
 	element.textContent = ''; // Remove all the code
@@ -18,4 +20,12 @@ for (let element of document.querySelectorAll('pre > code.linenos')) {
 		node.innerHTML = line + '\n';
 		element.appendChild(node);
 	});
+
+
+	for (let className of element.classList) {
+		let match = linenoRegex.exec(className);
+		if (match) {
+			element.style.setProperty('counter-reset', 'lineno ' + (parseInt(match[1]) - 1));
+		}
+	}
 }

preproc/src/links.rs

@@ -135,7 +135,6 @@ impl<'a> Link<'a> {
                             // Section start
                             sect_regex.1 = &ANCHOR_END;
                             try_matching = true;
-                            line_no = 0;
                         } else {
                             // Section end
                             break;
@@ -211,14 +210,14 @@ impl<'a> Iterator for LinkIter<'a> {
 
 fn find_links(contents: &str) -> LinkIter<'_> {
     // lazily compute the following regex:
-    // r#"\{\{#line_no_of\s*"([^"]+)"\s+([^}]+)\}\}"#)?;
+    // r#"\{\{#line_no_of\s*"([^"]*)"\s+([^}]+)\}\}"#)?;
     lazy_static! {
         static ref RE: Regex = Regex::new(
             r#"(?x)         # insignificant whitespace mode
             \{\{\s*         # link opening parens and whitespace
             \#line_no_of    # link type
             \s+             # separating whitespace
-            "([^"]+)"       # regex being searched for
+            "([^"]*)"       # regex being searched for
             \s+             # separating whitespace
             ([^}]+)         # path to search
             \}\}            # link closing parens"#

src/part1/jumps.md

@@ -43,7 +43,7 @@ Don't worry, we will see later why it's required.
 Now to the *really* interesting part.
 Let's examine the loop responsible for copying tiles:
 
-```rgbasm,linenos
+```rgbasm,linenos,start={{#line_no_of "" ../assets/hello-world.asm:memcpy}}
 {{#include ../assets/hello-world.asm:memcpy}}
 ```
 

src/part1/memory.md

@@ -119,9 +119,9 @@ It functions as `[hl]`, but `hl` is *incremented* just after memory is accessed.
 
 ## An example
 
-So, if we look at the first two instructions of `.copyTiles`:
+So, if we look at the first two instructions of `CopyTiles`:
 
-```rgbasm
+```rgbasm,linenos,start={{#line_no_of "" ../assets/hello-world.asm:memcpy_first_two}}
 {{#include ../assets/hello-world.asm:memcpy_first_two}}
 ```