selection update

lib/mouse.js

@@ -0,0 +1,65 @@
+import { escapeChar } from "./html.js";
+
+function bufferColToDomOffset(lineText, col) {
+  let offset = 0;
+  for (let i = 0; i < col && i < lineText.length; i++)
+    offset += escapeChar(lineText[i]).length;
+  return offset;
+}
+
+function findTextNode(parent, targetOffset) {
+  let remaining = targetOffset;
+  const walker = document.createTreeWalker(parent, NodeFilter.SHOW_TEXT);
+  let node;
+  while ((node = walker.nextNode())) {
+    if (remaining <= node.textContent.length)
+      return { node, offset: remaining };
+    remaining -= node.textContent.length;
+  }
+  return { node: parent, offset: parent.childNodes.length };
+}
+
+function posToElement(line, col, buffer) {
+  const spans = document.querySelectorAll("#text > span");
+  if (line >= spans.length) return null;
+  const span = spans[line];
+  const range = document.createRange();
+  const lineText = buffer[line] || "";
+  const offset = bufferColToDomOffset(lineText, col);
+  const tn = findTextNode(span, offset);
+  range.setStart(tn.node, tn.offset);
+  range.collapse(true);
+  const rect = range.getBoundingClientRect();
+  return { x: rect.left, y: rect.top, height: rect.height };
+}
+
+export function elementToPos(x, y, buffer) {
+  const spans = document.querySelectorAll("#text > span");
+  let bestLine = 0;
+  let bestDistY = Infinity;
+
+  for (let i = 0; i < spans.length; i++) {
+    const rect = spans[i].getBoundingClientRect();
+    const midY = rect.top + rect.height / 2;
+    const distY = Math.abs(y - midY);
+    if (distY < bestDistY) {
+      bestDistY = distY;
+      bestLine = i;
+    }
+  }
+
+  let bestCol = 0;
+  let bestDistX = Infinity;
+  const lineText = buffer[bestLine] || "";
+  for (let c = 0; c <= lineText.length; c++) {
+    const pos = posToElement(bestLine, c, buffer);
+    if (!pos) continue;
+    const dist = Math.abs(x - pos.x);
+    if (dist < bestDistX) {
+      bestDistX = dist;
+      bestCol = c;
+    }
+  }
+
+  return { line: bestLine, col: bestCol };
+}