From 89133062b10d39c94a0f86e6b0da0d262ce14de6 Mon Sep 17 00:00:00 2001
From: Dmitry Lavrinovich <52966626+dmlvr@users.noreply.github.com>
Date: Mon, 25 May 2026 10:31:01 +0300
Subject: [PATCH] T1328375 - Web Dashboard: "Uncaught TypeError: Cannot read
 properties of null (reading 'hide')" error is thrown on attempt to scroll
 above the Bar column (#33686)

Signed-off-by: Dmitry Lavrinovich <52966626+dmlvr@users.noreply.github.com>
Co-authored-by: Andrei Kharitonov <andrei.kharitonov@devexpress.com>
---
 .../viz/sparklines/base_sparkline.ts          |  1 +
 .../baseSparklineTooltipEvents.tests.js       | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/packages/devextreme/js/__internal/viz/sparklines/base_sparkline.ts b/packages/devextreme/js/__internal/viz/sparklines/base_sparkline.ts
index 006189610986..1cddaca89ae5 100644
--- a/packages/devextreme/js/__internal/viz/sparklines/base_sparkline.ts
+++ b/packages/devextreme/js/__internal/viz/sparklines/base_sparkline.ts
@@ -275,6 +275,7 @@ const _disposeTooltip = BaseSparkline.prototype._disposeTooltip;
 BaseSparkline.prototype._disposeTooltip = function () {
   if (this._tooltip) {
     _disposeTooltip.apply(this, arguments);
+    this._tooltipShown = false;
   }
 };
 BaseSparkline.prototype._setTooltipRendererOptions = function () {
diff --git a/packages/devextreme/testing/tests/DevExpress.viz.sparklines/baseSparklineTooltipEvents.tests.js b/packages/devextreme/testing/tests/DevExpress.viz.sparklines/baseSparklineTooltipEvents.tests.js
index 0fddab370329..6eaa14b4626b 100644
--- a/packages/devextreme/testing/tests/DevExpress.viz.sparklines/baseSparklineTooltipEvents.tests.js
+++ b/packages/devextreme/testing/tests/DevExpress.viz.sparklines/baseSparklineTooltipEvents.tests.js
@@ -149,3 +149,31 @@ QUnit.test('Tooltip should not hide if in the canvas with margins', function(ass
     assert.strictEqual(tooltipShown.callCount, 1);
     assert.strictEqual(tooltipHidden.callCount, 0);
 });
+
+QUnit.test('No errors after dispose and manual _hideTooltip call (T1328375)', function(assert) {
+    const bullet = this.createWidget({
+        startScaleValue: 0,
+        endScaleValue: 35,
+        value: 20,
+        tooltip: {
+            enabled: true
+        }
+    });
+
+    const consoleErrorStub = sinon.stub(console, 'error');
+    let caughtError;
+
+    bullet._showTooltip();
+    bullet.dispose();
+
+    try {
+        bullet._hideTooltip();
+    } catch(error) {
+        caughtError = error;
+    } finally {
+        consoleErrorStub.restore();
+    }
+
+    assert.strictEqual(caughtError, undefined, '_hideTooltip should not throw after dispose');
+    assert.strictEqual(consoleErrorStub.callCount, 0, 'console should not contain runtime errors');
+});