fix: auto scroll to top in code block

[appflowy]

fix #300 #261

Summary by Sourcery

Prevent editor selection from causing unwanted scroll-to-top jumps in code blocks by customizing the selection scroll behavior.

Bug Fixes:

• Avoid page jumping to the top when the caret moves inside syntax-highlighted code blocks by only scrolling when the cursor is out of view.

Tests:

• Add Playwright end-to-end coverage to assert stable scroll behavior when editing within code blocks.

[sourcery-ai]

Reviewer's Guide

Replaces Slate's default scrollSelectionIntoView behavior with a custom implementation that avoids jump-to-top scrolling in code blocks and wires it into the editor, along with an end-to-end Playwright test for the regression.

Sequence diagram for custom scrollSelectionIntoView behavior

sequenceDiagram
  actor User
  participant EditorEditable
  participant SlateEditable
  participant ReactEditor
  participant scrollSelectionIntoView
  participant DOMRange
  participant ScrollContainer

  User->>EditorEditable: Type in code block
  EditorEditable->>SlateEditable: Render with scrollSelectionIntoView prop
  SlateEditable->>ReactEditor: Update selection
  SlateEditable->>DOMRange: Compute DOM range for selection
  SlateEditable->>scrollSelectionIntoView: scrollSelectionIntoView(editor, domRange)

  scrollSelectionIntoView->>DOMRange: getBoundingClientRect()
  scrollSelectionIntoView->>scrollSelectionIntoView: Validate rangeRect and selection
  scrollSelectionIntoView->>DOMRange: Read startContainer.parentElement as leafEl
  scrollSelectionIntoView->>ScrollContainer: leafEl.closest(appflowy-scroll-container)
  alt Cursor already visible
    scrollSelectionIntoView-->>SlateEditable: Return without scrolling
  else Cursor out of view
    scrollSelectionIntoView->>leafEl: Override getBoundingClientRect
    scrollSelectionIntoView->>leafEl: scrollIntoView(block=nearest)
    scrollSelectionIntoView->>leafEl: Restore getBoundingClientRect
    scrollSelectionIntoView-->>SlateEditable: Return after minimal scroll
  end

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File-Level Changes

Change	Details	Files
Introduce custom scrollSelectionIntoView to prevent jump-to-top behavior when the cursor is in a code block.	Add a scrollSelectionIntoView helper that short-circuits when selection is not collapsed or when the DOM range has an invalid bounding rect. Compute the cursor range rect and the nearest scroll container with the .appflowy-scroll-container selector. Skip scrolling when the cursor is already within the visible vertical bounds of the scroll container. Temporarily override the leaf element’s getBoundingClientRect with the range’s implementation and call scrollIntoView with block: 'nearest', then restore the original behavior.	src/components/editor/Editable.tsx
Wire the custom scrollSelectionIntoView into the Slate Editable component and add e2e coverage for the regression.	Pass the custom scrollSelectionIntoView function as a prop to the EditorEditable’s underlying Slate Editable component. Add a Playwright E2E test that exercises code-block editing and verifies the editor no longer auto-scrolls to the top when syntax highlighting or DOM re-renders occur.	src/components/editor/Editable.tsx playwright/e2e/editor/blocks/code_block_scroll.spec.ts

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#300	Prevent the page from auto-scrolling to the top when pressing Enter inside a code block located lower on the page, keeping the cursor movement within the code block and the current scroll position stable.	✅
#300	Add an automated test to prevent regression of the scroll-jump behavior when editing code blocks.	✅

Possibly linked issues

• [Bug] Page scroll jumps to top when pressing Enter inside a lower code block #300: PR customizes scrollSelectionIntoView to avoid scroll jumps in code blocks, directly fixing the reported issue.

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[sourcery-ai]

Hey - I've left some high level feedback:

• The temporary monkey-patching of leafEl.getBoundingClientRect would be safer if wrapped in a try/finally (or similar guard) so the override is always cleaned up even if scrollIntoView throws, rather than relying on the final delete line executing normally.
• The use of a hard-coded .appflowy-scroll-container selector in scrollSelectionIntoView could be brittle; consider making the scroll container lookup more generic or configurable so the behavior doesn’t silently break if the container class changes or if the editor is rendered in a different scrollable context.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The temporary monkey-patching of `leafEl.getBoundingClientRect` would be safer if wrapped in a try/finally (or similar guard) so the override is always cleaned up even if `scrollIntoView` throws, rather than relying on the final `delete` line executing normally.
- The use of a hard-coded `.appflowy-scroll-container` selector in `scrollSelectionIntoView` could be brittle; consider making the scroll container lookup more generic or configurable so the behavior doesn’t silently break if the container class changes or if the editor is rendered in a different scrollable context.

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