Highlight contiguous phrase matches as one block

src/lib/pageHighlight.ts

@@ -4,35 +4,63 @@ function supported(): boolean {
   return typeof CSS !== "undefined" && "highlights" in CSS;
 }
 
-// Highlight every occurrence of the terms inside the given roots using the
+function escapeRe(s: string): string {
-// CSS Custom Highlight API, which paints ranges without touching the DOM, so
+  return s.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
-// it never conflicts with Svelte re-renders. Returns the first match in
+}
-// document order (for scrolling), or null. No-op on unsupported browsers.
+
+// Highlight the query inside the given roots using the CSS Custom Highlight
+// API, which paints ranges without touching the DOM, so it never conflicts
+// with Svelte re-renders. Where the terms appear contiguously as the whole
+// query, one range covers the phrase; individual terms are only marked
+// outside those. Returns the first match in document order (for scrolling),
+// or null. No-op on unsupported browsers.
 export function applyHighlights(
   roots: Iterable<Element>,
-  terms: string[],
+  query: string,
 ): Range | null {
   if (!supported()) return null;
   CSS.highlights.delete(HIGHLIGHT_NAME);
-  const lowers = [...new Set(terms.map((t) => t.toLowerCase()))].filter(
+  const terms = [
-    (t) => t.length >= 2,
+    ...new Set(query.toLowerCase().split(/\s+/).filter((t) => t.length >= 2)),
-  );
+  ];
-  if (lowers.length === 0) return null;
+  if (terms.length === 0) return null;
+  const phraseRe =
+    terms.length > 1
+      ? new RegExp(terms.map(escapeRe).join("\\s+"), "gi")
+      : null;
 
   const ranges: Range[] = [];
   for (const root of roots) {
     const walker = document.createTreeWalker(root, NodeFilter.SHOW_TEXT);
     let node: Node | null;
     while ((node = walker.nextNode())) {
-      const lower = (node.textContent ?? "").toLowerCase();
+      const text = node.textContent ?? "";
-      for (const term of lowers) {
+      const taken: [number, number][] = [];
+
+      if (phraseRe) {
+        phraseRe.lastIndex = 0;
+        let m: RegExpExecArray | null;
+        while ((m = phraseRe.exec(text))) {
+          taken.push([m.index, m.index + m[0].length]);
+          const range = new Range();
+          range.setStart(node, m.index);
+          range.setEnd(node, m.index + m[0].length);
+          ranges.push(range);
+        }
+      }
+
+      const lower = text.toLowerCase();
+      for (const term of terms) {
         let i = 0;
         while ((i = lower.indexOf(term, i)) !== -1) {
+          const end = i + term.length;
+          if (!taken.some(([s, e]) => i < e && end > s)) {
             const range = new Range();
             range.setStart(node, i);
-          range.setEnd(node, i + term.length);
+            range.setEnd(node, end);
             ranges.push(range);
-          i += term.length;
+          }
+          i = end;
         }
       }
     }

src/lib/searchState.svelte.ts

@@ -45,10 +45,16 @@ export function createSearchState() {
     return s.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
   }
 
-  // Split into alternating plain/matched segments for <mark> rendering
+  // Split into alternating plain/matched segments for <mark> rendering. The
+  // whole query goes first in the alternation, so a contiguous phrase match
+  // becomes a single mark instead of one per word.
   function highlight(text: string): { text: string; hit: boolean }[] {
     if (!text || terms.length === 0) return [{ text, hit: false }];
-    const alts = terms.map(escapeRe).join("|");
+    const phrase =
+      terms.length > 1
+        ? [escapeRe(resultsQuery.trim()).replace(/\s+/g, "\\s+")]
+        : [];
+    const alts = [...phrase, ...terms.map(escapeRe)].join("|");
     const exact = new RegExp(`^(${alts})$`, "i");
     return text
       .split(new RegExp(`(${alts})`, "gi"))

src/routes/thread/[id]/+page.svelte

@@ -224,7 +224,7 @@
       return;
     }
     const roots = threadEl.querySelectorAll("h1, [data-quote-post-index]");
-    const first = applyHighlights(roots, q.split(/\s+/));
+    const first = applyHighlights(roots, q);
     const key = `${page.params.id}|${q}`;
     if (first && scrolledFor !== key) {
       scrolledFor = key;