Implement blink rendering

Fixes #944

src/browser/renderer/shared/TextBlinkStateManager.ts

@@ -0,0 +1,62 @@
+/**
+ * Copyright (c) 2026 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { ICoreBrowserService } from 'browser/services/Services';
+import { Disposable, toDisposable } from 'common/Lifecycle';
+
+export class TextBlinkStateManager extends Disposable {
+  private _intervalDuration: number = 0;
+  private _interval: number | undefined;
+  private _blinkOn: boolean = true;
+
+  constructor(
+    private readonly _renderCallback: () => void,
+    private readonly _coreBrowserService: ICoreBrowserService
+  ) {
+    super();
+    this._register(toDisposable(() => this._clearInterval()));
+  }
+
+  public get isBlinkOn(): boolean {
+    return this._blinkOn;
+  }
+
+  public get isEnabled(): boolean {
+    return this._intervalDuration > 0;
+  }
+
+  public setIntervalDuration(duration: number): void {
+    if (duration === this._intervalDuration) {
+      return;
+    }
+
+    this._intervalDuration = duration;
+    this._clearInterval();
+
+    const wasBlinkOn = this._blinkOn;
+    if (duration > 0) {
+      this._blinkOn = true;
+      this._interval = this._coreBrowserService.window.setInterval(() => {
+        this._blinkOn = !this._blinkOn;
+        this._renderCallback();
+      }, duration);
+      if (!wasBlinkOn) {
+        this._renderCallback();
+      }
+    } else {
+      this._blinkOn = true;
+      if (!wasBlinkOn) {
+        this._renderCallback();
+      }
+    }
+  }
+
+  private _clearInterval(): void {
+    if (this._interval !== undefined) {
+      this._coreBrowserService.window.clearInterval(this._interval);
+      this._interval = undefined;
+    }
+  }
+}