[Init] Initial commit - NetMesh terminal manager

components/terminal/autocomplete/xtermUtils.ts

@@ -0,0 +1,89 @@
+/**
+ * Utility functions for xterm.js cell dimension access.
+ * Centralizes access to xterm's internal renderer API to reduce upgrade risk.
+ * Falls back to DOM measurement if the internal API is unavailable.
+ */
+
+import type { Terminal as XTerm } from "@xterm/xterm";
+
+export interface CellDimensions {
+  width: number;
+  height: number;
+}
+
+// Cache to avoid repeated DOM measurements (invalidated on resize)
+let cachedDims: CellDimensions | null = null;
+let cachedTermId: number = 0;
+let termIdCounter = 0;
+const termIdMap = new WeakMap<XTerm, number>();
+
+function getTermId(term: XTerm): number {
+  let id = termIdMap.get(term);
+  if (id === undefined) {
+    id = ++termIdCounter;
+    termIdMap.set(term, id);
+  }
+  return id;
+}
+
+/**
+ * Get cell dimensions (width/height in CSS pixels) from an xterm instance.
+ * Tries the internal renderer API first (fast path), falls back to DOM measurement.
+ */
+export function getXTermCellDimensions(term: XTerm): CellDimensions {
+  // Try xterm core renderer API (fast path)
+  const coreAccess = term as XTerm & {
+    _core?: { _renderService?: { dimensions?: { css?: { cell?: CellDimensions } } } };
+  };
+  const coreDims = coreAccess._core?._renderService?.dimensions?.css?.cell;
+  if (coreDims && coreDims.width > 0 && coreDims.height > 0) {
+    // Update cache while we have a good value
+    const id = getTermId(term);
+    cachedDims = { width: coreDims.width, height: coreDims.height };
+    cachedTermId = id;
+    return cachedDims;
+  }
+
+  // Check cache (same terminal instance)
+  const id = getTermId(term);
+  if (cachedDims && cachedTermId === id) {
+    return cachedDims;
+  }
+
+  // Fallback: measure from DOM (triggers single reflow)
+  const dims = measureCellFromDOM(term);
+  cachedDims = dims;
+  cachedTermId = id;
+  return dims;
+}
+
+/**
+ * Measure cell dimensions by inserting a temporary span into the terminal element.
+ * Triggers a single reflow (reading offsetWidth + offsetHeight).
+ */
+function measureCellFromDOM(term: XTerm): CellDimensions {
+  const element = term.element;
+  if (!element) return { width: 8, height: 16 };
+
+  const span = document.createElement("span");
+  span.textContent = "W";
+  Object.assign(span.style, {
+    position: "absolute",
+    visibility: "hidden",
+    fontFamily: term.options.fontFamily || "monospace",
+    fontSize: `${term.options.fontSize}px`,
+    lineHeight: "normal",
+  });
+  element.appendChild(span);
+  const width = span.offsetWidth || 8;
+  const height = span.offsetHeight || 16;
+  span.remove();
+  return { width, height };
+}
+
+/**
+ * Invalidate the cached cell dimensions (call on terminal resize).
+ */
+export function invalidateCellDimensionCache(): void {
+  cachedDims = null;
+}