From 57f32dc1d36650a5f282f1ba3906e9772b89709d Mon Sep 17 00:00:00 2001
From: Brian Cully <bjc@spork.org>
Date: Sun, 24 Aug 2025 12:19:45 -0400
Subject: use css custom highlights for in-text blinken

---
 index.html |  5 ++---
 main.css   |  3 ++-
 main.mjs   | 26 +++++++++-----------------
 3 files changed, 13 insertions(+), 21 deletions(-)

diff --git a/index.html b/index.html
index 0882b65..77c2bdc 100644
--- a/index.html
+++ b/index.html
@@ -12,15 +12,14 @@
       <div id='code'>
         <button id='compile'>compile</button>
         <br>
-        <pre id='src' contenteditable='plaintext-only'>
-: fac
+        <div id='src' contenteditable='plaintext-only'>: fac
     dup
     1 > if
         dup 1 - fac *
     then
     ;
 5 fac
-drop</pre>
+drop</div>
       </div>
 
       <div id='state-container'>
diff --git a/main.css b/main.css
index a1ea31a..9f7381d 100644
--- a/main.css
+++ b/main.css
@@ -22,9 +22,10 @@ html {
     margin-top: 1ex;
     padding: 1em;
     border: 2px inset lightgray;
+    white-space: pre-wrap;
 }
 
-#src .exec {
+::highlight(exec) {
     background-color: yellowgreen;
 }
 
diff --git a/main.mjs b/main.mjs
index 801736e..701659f 100644
--- a/main.mjs
+++ b/main.mjs
@@ -55,26 +55,18 @@ function renderCallStack(interp) {
     });
 }
 
+const highRange = new Range();
+const highlight = new Highlight(highRange);
+CSS.highlights.set('exec', highlight);
+
 function renderTextHighlight(interp) {
     const ip = interp.ip();
     const anno = interp.annotation_at(ip)
-    const src = document.querySelector('#src')
-    const text = src.textContent;
-
-    // split textcontent into 3 spans: pre-highlight, highlight,
-    // post-highlight
-    const pre = document.createElement('span');
-    pre.textContent = text.substring(0, anno.start);
-    const high = document.createElement('span');
-    high.classList.add('exec');
-    high.textContent = text.substring(anno.start, anno.end);
-    const post = document.createElement('span');
-    post.textContent = text.substring(anno.end);
-
-    while (src.lastChild) { src.removeChild(src.lastChild) }
-    src.appendChild(pre);
-    src.appendChild(high);
-    src.appendChild(post);
+    const src = document.querySelector('#src');
+
+    // this assumes the text node is the first child, maybe it isn't?
+    highRange.setStart(src.childNodes[0], anno.start);
+    highRange.setEnd(src.childNodes[0], anno.end);
 }
 
 function tick(interp) {
-- 
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