fix: overhaul text lookup

Rewrite text lookup to be more thorough and robust.

Fixes #990.

Also improves performance and allows looking up `user-select: all` text
in Firefox.

CHANGELOG.md

@@ -8,6 +8,9 @@ app.
 
 ## [Unreleased]
 
+- Rewrote text lookup to better handle cases of hidden content (including
+  `user-select: all` content), avoid lingering popups, and improve performance
+  (Fixes [#990](https://github.com/birchill/10ten-ja-reader/issues/990)).
 - (Chrome, Edge) Migrated to Manifest version 3.
 - (Chrome, Edge, Safari) Fixed a bug where overlays would be broken on
   [MangaDex](https://mangadex.org/)

src/content/gdocs-canvas.ts

@@ -2,7 +2,7 @@ import { HighlightStyle } from '../common/content-config-params';
 import { empty, SVG_NS } from '../utils/dom-utils';
 import { Point, Rect } from '../utils/geometry';
 
-import { CursorPosition } from './get-text';
+import { CursorPosition } from './get-cursor-position';
 
 export function injectGdocsStyles() {
   removeGdocsStyles();