⚡ Optimize minmap performance

frontend/src/views/editor/extensions/minimap/lineGeometry.ts

@@ -0,0 +1,85 @@
+import { Lines } from "./linesState";
+
+const DEFAULT_LINE_NUMBER = 0;
+
+function lineBoundary(spans: Lines[number]) {
+  if (!spans || spans.length === 0) {
+    return { start: 0, end: 0 };
+  }
+  const start = spans[0].from;
+  const end = spans[spans.length - 1].to;
+  return { start, end };
+}
+
+export function lineNumberAt(lines: Lines, position: number): number {
+  if (!lines.length) {
+    return DEFAULT_LINE_NUMBER;
+  }
+
+  const first = lineBoundary(lines[0]);
+  const last = lineBoundary(lines[lines.length - 1]);
+
+  let target = position;
+  if (target < first.start) {
+    target = first.start;
+  } else if (target > last.end) {
+    target = last.end;
+  }
+
+  let low = 0;
+  let high = lines.length - 1;
+
+  while (low <= high) {
+    const mid = (low + high) >> 1;
+    const spans = lines[mid];
+    const { start, end } = lineBoundary(spans);
+
+    if (target < start) {
+      high = mid - 1;
+      continue;
+    }
+
+    if (target > end) {
+      low = mid + 1;
+      continue;
+    }
+
+    return mid + 1;
+  }
+
+  return Math.max(1, Math.min(lines.length, low + 1));
+}
+
+export function lineLength(spans: Lines[number]) {
+  if (!spans) {
+    return 1;
+  }
+
+  let length = 0;
+  for (const span of spans) {
+    length += span.folded ? 1 : Math.max(0, span.to - span.from);
+  }
+
+  return Math.max(1, length);
+}
+
+export function offsetWithinLine(pos: number, spans: Lines[number]) {
+  if (!spans) {
+    return 0;
+  }
+
+  let offset = 0;
+
+  for (const span of spans) {
+    const spanLength = span.folded ? 1 : Math.max(0, span.to - span.from);
+    if (!span.folded && pos < span.to) {
+      return offset + Math.max(0, pos - span.from);
+    }
+    if (span.folded && pos <= span.to) {
+      return offset;
+    }
+    offset += spanLength;
+  }
+
+  return offset;
+}