Fix tooltip placement bugs by upgrading Popper

ts/util/popperUtil.ts

@@ -0,0 +1,33 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { Modifier } from '@popperjs/core';
+import type { OffsetModifier } from '@popperjs/core/lib/modifiers/offset';
+
+/**
+ * Shorthand for the [offset modifier][0] when you just wanna set the distance.
+ *
+ * [0]: https://popper.js.org/docs/v2/modifiers/offset/
+ */
+export const offsetDistanceModifier = (
+  distance: number
+): Partial<OffsetModifier> => ({
+  name: 'offset',
+  options: { offset: [undefined, distance] },
+});
+
+/**
+ * Make the popper element the same width as the reference, even when you resize.
+ *
+ * Should probably be used with the "top-start", "top-end", "bottom-start", or
+ * "bottom-end" placement.
+ */
+export const sameWidthModifier: Modifier<'sameWidth', unknown> = {
+  name: 'sameWidth',
+  enabled: true,
+  phase: 'write',
+  fn({ state }) {
+    // eslint-disable-next-line no-param-reassign
+    state.elements.popper.style.width = `${state.rects.reference.width}px`;
+  },
+};