fix: Scrolling along edges breaks text editing (#135)

Existing Gutenberg `preventFocusCapture` logic relies upon `pointerdown`
and `pointerup` events for temporarily disabling all text blocks
`contenteditable` status. This is down to mitigate issues with block
selection for `flex` elements.

However, `pointerup` events are not always triggered on touch devices
when a touch turns into a swipe. When you scroll with your finger
outside of the block canvas, the `pointerup` callback is never invoked.
Scrolling twice or more leads to a stale `value` in the callback, and a
state where `contenteditable` is perpetually disabled.

Author: dcalhoun

patches/@wordpress+rich-text+7.22.0.patch

@@ -0,0 +1,16 @@
+diff --git a/node_modules/@wordpress/rich-text/build-module/component/event-listeners/prevent-focus-capture.js b/node_modules/@wordpress/rich-text/build-module/component/event-listeners/prevent-focus-capture.js
+index 3b885f5..c2ea3d0 100644
+--- a/node_modules/@wordpress/rich-text/build-module/component/event-listeners/prevent-focus-capture.js
++++ b/node_modules/@wordpress/rich-text/build-module/component/event-listeners/prevent-focus-capture.js
+@@ -36,9 +36,11 @@ export function preventFocusCapture() {
+     }
+     defaultView.addEventListener('pointerdown', onPointerDown);
+     defaultView.addEventListener('pointerup', onPointerUp);
++    defaultView.addEventListener('pointercancel', onPointerUp);
+     return () => {
+       defaultView.removeEventListener('pointerdown', onPointerDown);
+       defaultView.removeEventListener('pointerup', onPointerUp);
++      defaultView.removeEventListener('pointercancel', onPointerUp);
+     };
+   };
+ }

patches/README.md

@@ -10,3 +10,7 @@ Existing patches should be described and justified here.
 
 -   Expose an `open` prop on the `Inserter` component, allowing toggling the inserter visibility via the quick inserter's "Browse all" button.
 -   Disable `stripExperimentalSettings` in the `BlockEditorProvider` component so that the Patterns and Media inserter tabs function.
+
+### `@wordpress/rich-text`
+
+-   Fix `preventFocusCapture` causing uneditable text blocks on touch devices when scrolling by swiping outside of the block canvas--e.g., along the edge of the screen.