fix: improve speculative updates

Append text to the previous node instead of to the start of the next one, when possible
BearToCode · Nov 7, 2024 · ddab992 · ddab992
1 parent 0a39360
commit ddab992
Showing 1 changed file with 11 additions and 4 deletions.
diff --git a/packages/carta-md/src/lib/internal/speculative.ts b/packages/carta-md/src/lib/internal/speculative.ts
@@ -44,14 +44,21 @@ export function speculativeHighlightUpdate(container: HTMLDivElement, from: stri
 		advance(change.value.length);
 	};
 	const addedCallback = (change: Change) => {
-		const node = textNodes.at(currentNodeIdx) ?? createTemporaryNode(container);
+		const node =
+			currentNodeCharIdx == 0
+				? textNodes.at(currentNodeIdx - 1)
+				: textNodes.at(currentNodeIdx) ?? createTemporaryNode(container);
 		if (!node) return; // Could not create a temporary node
 
 		const text = node.textContent ?? '';
-		const pre = text.slice(0, currentNodeCharIdx);
-		const post = text.slice(currentNodeCharIdx);
+		if (currentNodeCharIdx == 0) {
+			node.textContent = text + change.value;
+		} else {
+			const pre = text.slice(0, currentNodeCharIdx);
+			const post = text.slice(currentNodeCharIdx);
+			node.textContent = pre + change.value + post;
+		}
 
-		node.textContent = pre + change.value + post;
 		advance(change.value.length);
 	};
 	const removedCallback = (change: Change) => {