toolbar: work around tooltip bugs

This works around several bugs where tooltips don't close when expected.

Fixes: https://github.com/pybricks/pybricks-code/issues/275

src/utils/monkey-patch.ts

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2021 The Pybricks Authors
+
+import { Tooltip2 } from '@blueprintjs/popover2';
+import React, { useEffect, useRef } from 'react';
+
+/** Hack to access private members of Popover2. */
+interface Popover2Private {
+    handleTargetBlur: (e: React.FocusEvent<HTMLElement>) => void;
+    handleMouseLeave: (e: React.MouseEvent<HTMLElement>) => void;
+}
+/** Hack to access private members of Tooltip2. */
+interface Tooltip2Private {
+    popover: Popover2Private;
+}
+
+/**
+ * Monkey patch Popover2 blur event handler to make tooltips close when
+ * focus is lost.
+ *
+ * https://github.com/palantir/blueprint/issues/4503
+ *
+ * @returns A React ref to be attached to the Tooltip2 component.
+ */
+export function useTooltip2MonkeyPatch<T>(): React.RefObject<Tooltip2<T>> {
+    const tooltipRef = useRef<Tooltip2<T>>(null);
+
+    useEffect(() => {
+        if (!tooltipRef.current) {
+            return;
+        }
+
+        const tooltip = tooltipRef.current as unknown as Tooltip2Private;
+
+        const oldHandleTargetBlur = tooltip.popover.handleTargetBlur;
+
+        tooltip.popover.handleTargetBlur = (e) => {
+            if (e.relatedTarget) {
+                oldHandleTargetBlur(e);
+            } else {
+                closeTooltip2(tooltipRef);
+            }
+        };
+
+        return () => {
+            tooltip.popover.handleTargetBlur = oldHandleTargetBlur;
+        };
+    }, [tooltipRef]);
+
+    return tooltipRef;
+}
+
+/**
+ * Hack to access private members of Tooltip2 to programmatically close the tooltip.
+ * @param tooltipRef The reference returned from useTooltip2MonkeyPatch()
+ */
+export function closeTooltip2<T>(tooltipRef: React.RefObject<Tooltip2<T>>): void {
+    if (!tooltipRef.current) {
+        return;
+    }
+
+    const tooltip = tooltipRef.current as unknown as Tooltip2Private;
+
+    // Currently, the event arg is not used so it should be safe to pass undefined.
+    tooltip.popover.handleMouseLeave(
+        undefined as unknown as React.MouseEvent<HTMLElement>,
+    );
+}