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Slate React Android marked inserts must not replay raw old-leaf selection

docs/solutions/ui-bugs/2026-05-23-slate-react-android-marked-inserts-must-not-replay-raw-old-leaf-selection.md

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Original Source

Slate React Android marked inserts must not replay raw old-leaf selection

Problem

Android marked typing can be model-correct while the caret is still wrong. When collapsed typing with active marks splits the current text leaf, any delayed selection restoration based on the old DOM point must be normalized onto the new marked leaf before it reaches the editor.

Symptoms

  • Text insertion produces the expected split text: { text: "a" }, { text: "w", bold: true }.
  • Selection incorrectly lands at raw [0,0]@2, outside the original leaf's length, instead of [0,1]@1.
  • The upstream Android issue shows keyboard dismissal and cursor jumps after toggling bold on a collapsed selection.

What Didn't Work

  • Asserting only document text and marks. The text tree was correct while selection still pointed at the old leaf.
  • Treating a package test as raw Android closure. It can prove the Slate input manager contract, not keyboard visibility or IME stability.

Solution

Keep the Android manager's scheduled action so pending text diffs still flush, but let the existing at normalization own selection placement. Do not run a second raw selection write after performAction() normalizes the point.

ts
scheduleAction(() => {}, {
  at: newPoint,
  preserveInsertPositionHint: true,
})

The focused contract belongs beside the Android input manager tests:

ts
Editor.select(editor, range(1))
Editor.addMark(editor, 'bold', true)
EDITOR_TO_PENDING_INSERTION_MARKS.set(editor, { bold: true })

manager.handleDOMBeforeInput(beforeInputEvent('insertText', 'w'))
manager.flush()

expect(Editor.getSnapshot(editor).selection).toEqual({
  anchor: { path: [0, 1], offset: 1 },
  focus: { path: [0, 1], offset: 1 },
})

Why This Works

performAction() already normalizes pending points through normalizePoint(editor, action.at). For old point [0,0]@2, normalization walks past the old one-character leaf and lands on the inserted marked sibling at [0,1]@1.

The previous scheduled action then immediately overwrote that normalized selection by calling tx.selection.set(...) with the raw old point. Removing that second write preserves the correct normalized result and keeps the flush timing behavior.

Prevention

  • For Android/input-manager tests, assert both document text and selection.
  • When a pending point is based on pre-diff DOM state, normalize once at the runtime owner and avoid later raw selection.set(...) writes.
  • Do not promote this kind of package proof to Android issue closure without a raw Android Chrome/WebView lane for keyboard visibility and follow-up typing.