feat(undo): add optional undo/redo history size limit and disable buttons when unavailable`

[rleisti]

Context

When editing segmentations, each labelmap edit records an undo memo that holds full labelmap buffers. Over a long session the undo/redo history can therefore grow large enough to cause memory pressure / out-of-memory or buffer-allocation failures, especially with large volumes.

Today the history size is fixed at Cornerstone's internal default and cannot be tuned by a deployment. This PR adds an optional maxUndoRedoCacheSize app config so integrators working with large data can bound the history. It is opt-in: when the option is not set, Cornerstone's existing default is used, so there is no behavior change for current users.

While in this area, it also fixes a small UX papercut: the header Undo/Redo buttons were always clickable, so clicking them with an empty history did nothing and made the app feel broken.

This contribution has been donated by the University of Calgary.

Changes & Results

• New app config option maxUndoRedoCacheSize (platform/core/src/types/AppTypes.ts): optional number on AppTypes.Config. When unset, the Cornerstone default is used.
• Apply the option on startup (extensions/cornerstone/src/init.tsx): when appConfig.maxUndoRedoCacheSize is provided, set csUtilities.HistoryMemo.DefaultHistoryMemo.size accordingly.
• Disable the header Undo/Redo buttons when nothing is available (extensions/default/src/ViewerLayout/ViewerHeader.tsx): the buttons are now disabled (greyed out) based on canUndo / canRedo.
• New useUndoRedoState hook (extensions/default/src/ViewerLayout/useUndoRedoState.ts): tracks DefaultHistoryMemo.canUndo/canRedo and re-evaluates on the relevant Cornerstone events (HISTORY_UNDO/HISTORY_REDO, plus ANNOTATION_COMPLETED/ANNOTATION_REMOVED/SEGMENTATION_DATA_MODIFIED, since a new memo can be pushed without emitting a history event).
• Docs (platform/docs/docs/configuration/configurationFiles.md): document the new maxUndoRedoCacheSize option.

Effects:

• Before: undo/redo history size was not configurable; Undo/Redo buttons were always enabled even with an empty history.
• After: deployments can optionally cap the history via config; Undo/Redo buttons grey out when there is nothing to undo/redo. No change to default behavior when the option is unset.

Testing

The Undo button and the Redo button (no configuration):

1. Open a study in the viewer.
2. Make sure that the Undo button and the Redo button in the header are disabled (grey).
3. Draw a measurement, or paint a segmentation. Make sure that the Undo button becomes enabled.
4. Click Undo until the history is empty. Make sure that the Undo button becomes disabled and the Redo button becomes enabled.
5. Draw a new measurement. Make sure that the Redo button becomes disabled.
6. Drag a handle of an existing measurement, and release the mouse button. Make sure that the Undo button is enabled and the Redo button is disabled.

The history size limit (optional):

The dev servers (pnpm dev, pnpm dev:fast) load platform/app/public/config/dev.js. A production build loads config/default.js. To use a different file, set APP_CONFIG, for example APP_CONFIG=config/default.js pnpm dev:fast.

The viewer applies the value when a mode opens. Therefore, open a study before each check in the console.

1. In config/dev.js, add this entry to the customizationService array (the legacy form):

   { 'cornerstone.maxUndoRedoCacheSize': { $set: 5 } },

2. Reload the viewer, and open a study. In the console, make sure that window.cornerstone.utilities.HistoryMemo.DefaultHistoryMemo.size returns 5.
3. Do 6 or more edits, then click Undo until the Undo button becomes disabled. Make sure that only the 5 most recent edits undo.
4. Replace the customizationService array with the phased form. Then do step 2 again:

   customizationService: {
     global: {
       'cornerstone.maxUndoRedoCacheSize': { $set: 5 },
     },
   },

5. Set the value to 0. Reload the viewer, and open a study. Make sure that DefaultHistoryMemo.size returns 50.
6. Set the value to 10.5. Reload the viewer, and open a study. Make sure that the console shows RangeError: Invalid array length. The mode entry throws this error for an invalid value.
7. Remove the customization, reload the viewer, and open a study. Make sure that DefaultHistoryMemo.size returns 50, the Cornerstone default. This result shows that the default behavior does not change.

The test steps do not use window.config.maxUndoRedoCacheSize. The option is a customization, and it is not a top-level appConfig key.

Checklist

PR

• My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• My code has been well-documented (function documentation, inline comments,
  etc.)

Public Documentation Updates

• The documentation page has been updated as necessary for any public API
  additions or removals.

Tested Environment

• OS: Ubuntu 22.04.5 LTS
• Node version: 22.22.2
• Browser: Firefox 140.12.0esr (64-bit)

Summary by CodeRabbit

• New Features
  • Undo and Redo controls now reflect whether undo/redo is available, with improved accessibility labeling.
  • Undo/redo button state updates automatically as editing history changes.
  • Added opt-in configurability for undo/redo history retention via cornerstone.maxUndoRedoCacheSize.
• Bug Fixes
  • Invalid or non-finite history cache settings are ignored to preserve default behavior.
• Documentation
  • Documented the cornerstone.maxUndoRedoCacheSize configuration option and what happens when it’s unset.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

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[rleisti]

@wayfarer3130 @jbocce please review if you have time

[coderabbitai]

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📝 Walkthrough

Walkthrough

Undo/redo history size is now configurable through Cornerstone customizations. A React hook tracks history availability, and the viewer header disables unavailable Undo and Redo controls while adding accessible labels.

Changes

Undo/redo history controls

Layer / File(s)	Summary
History size configuration extensions/cornerstone/src/types/AppTypes.ts, extensions/cornerstone/src/init.tsx, platform/docs/docs/configuration/configurationFiles.md	Adds the typed cornerstone.maxUndoRedoCacheSize customization, applies valid non-negative numeric values during initialization, and documents the option.
History availability synchronization extensions/default/src/ViewerLayout/useUndoRedoState.ts	Adds a hook that reads DefaultHistoryMemo, synchronizes after relevant tool events, defers reads until updates settle, and cleans up listeners and timers.
Undo and Redo header controls extensions/default/src/ViewerLayout/ViewerHeader.tsx	Uses the hook to disable unavailable actions and adds aria-label attributes to both controls.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant CornerstoneToolEvents
  participant useUndoRedoState
  participant DefaultHistoryMemo
  participant ViewerHeader
  CornerstoneToolEvents->>useUndoRedoState: notify history-changing event
  useUndoRedoState->>DefaultHistoryMemo: read availability after timeout
  DefaultHistoryMemo-->>useUndoRedoState: return canUndo and canRedo
  useUndoRedoState-->>ViewerHeader: provide undo/redo state

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Possibly related PRs

• OHIF/Viewers#6133: Adds typed customization-service access used by the new Cornerstone customization key.

Suggested reviewers: sedghi, wayfarer3130

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly describes the two main changes and follows the semantic-release format.
Description check	✅ Passed	The description includes all required sections, explains the motivation and effects, documents testing steps, and completes the checklist. It contains minor inaccuracies about the configuration type a…

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[wayfarer3130]

Just appConfig.maxUndoRedoCacheSize >=0

[wayfarer3130]

This should be a customization now rather than a config item - it is still possible to set as a config item, but through the customization values.

[wayfarer3130]

Can you make maxUndoRedoCacheSize a customization setting?

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@extensions/cornerstone/src/init.tsx`:
- Around line 162-171: Update the validation guarding the assignment to
csUtilities.HistoryMemo.DefaultHistoryMemo.size in the maxUndoRedoCacheSize
configuration flow. Accept only finite, non-negative integer values, rejecting
Infinity, NaN, and fractional values before mutating the history size.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: d89a251e-4669-4484-a0b6-65ed38534dfa

📥 Commits

Reviewing files that changed from the base of the PR and between daccaea and fc8fac1.

📒 Files selected for processing (3)

• extensions/cornerstone/src/init.tsx
• extensions/cornerstone/src/types/AppTypes.ts
• platform/docs/docs/configuration/configurationFiles.md

[wayfarer3130]

The merge of master

I merged origin/master into this branch, and I pushed the merge. The merge had one conflict, and I resolved that conflict.

The conflict is in extensions/default/src/ViewerLayout/ViewerHeader.tsx. The master branch moved the undo button and the redo button out of ViewerHeader.tsx. The two buttons are now in extensions/default/src/ViewerLayout/HeaderUndoRedo.tsx, and the new ohif.headerRightSide customization renders that component.

I kept the structure of master, and I moved the changes of this branch into HeaderUndoRedo.tsx:

• the useUndoRedoState hook;
• the disabled property on each button;
• the aria-label property on each button;
• the cursor-pointer class, which moves from the wrapper element to each button.

Please check this resolution. The resolution is a design decision, and the resolution is not a text merge.

The review findings

1. The documented configuration does not work

extensions/cornerstone/src/init.tsx reads the customization in preRegistration.

platform/app/src/appInit.js calls loadAndApplyBootstrapCustomizations at line 121. platform/app/src/appInit.js calls registerExtensions at line 123. platform/app/src/appInit.js calls applyGlobalCustomizations() at line 129.

preRegistration runs during registerExtensions. Therefore getCustomization('cornerstone.maxUndoRedoCacheSize') returns undefined for a value in the global phase, and the limit never applies. Only the bootstrap phase gives a value to preRegistration. A mode customizations map also gives a value to preRegistration.

2. A bad value stops the start of the application

The test in extensions/cornerstone/src/init.tsx is Number.isFinite(maxUndoRedoCacheSize) && maxUndoRedoCacheSize >= 0. That test accepts three values that damage the setter.

The setter of DefaultHistoryMemo.size in @cornerstonejs/core runs this.ring = new Array(newSize):

• The value 10.5 makes new Array throw RangeError: Invalid array length.
• The value 1e10 makes new Array throw the same RangeError, because the maximum length of an array is 4294967295.
• The value 0 makes position become NaN in the push method, because push computes (this.position + 1) % this._size. The line this.ring[this.position] = memo then writes to the property NaN. One labelmap buffer stays in memory forever, and canUndo stays false.

preRegistration throws the RangeError, and the application does not start. Please use Number.isInteger(value) && value >= 1, and please add a maximum value.

3. A drag of a measurement does not update the buttons

HISTORY_CHANGING_EVENTS in extensions/default/src/ViewerLayout/useUndoRedoState.ts does not contain ANNOTATION_MODIFIED.

A user drags an existing measurement. The tool pushes a memo, and the tool fires only ANNOTATION_MODIFIED. triggerAnnotationCompleted runs only for a new annotation. Therefore the undo button stays grey after the drag, and the redo button stays enabled although redoAvailable is 0.

4. The documentation puts the option in the wrong list

platform/docs/docs/configuration/configurationFiles.md adds the bullet to the list of the top-level appConfig keys. The option is a customization identifier, and the option is not a top-level key. No code reads a top-level maxUndoRedoCacheSize.

The test steps of this pull request set maxUndoRedoCacheSize at the top level, and the test steps read window.config.maxUndoRedoCacheSize. Those test steps do not test the code of this pull request.

5. The new labels have no translation keys

HeaderUndoRedo.tsx uses t('Header:Undo') and t('Header:Redo'). platform/i18n/src/locales/en-US/Header.json contains neither key. i18next returns the name of the key, so English shows the correct word. A different language also shows the English word.

A note on the findings

Finding 1, finding 2 and finding 4 all concern the same configuration path. One change can correct all three findings.

What I checked, and found correct

• The size setter exists on DefaultHistoryMemo, and the setter is writable.
• The deferred read with setTimeout(0) handles the brush correctly. applyActiveStrategy fires SEGMENTATION_DATA_MODIFIED before doneEditMemo() pushes the memo.
• The labelmap memo, the annotation memo, the tracking-state memo and the segment-index memo each carry an id. Therefore undo() dispatches HISTORY_UNDO.
• The Button component supports disabled, with disabled:opacity-50 and disabled:pointer-events-none.
• The click methods of the Playwright page object wait for the button to become actionable.

🤖 Generated with Claude Code

[cypress]

Viewers    Run #6776

Run Properties:   Passed #6776  •  806b62ac9e: Merge remote-tracking branch 'origin/master' into feat/undo-redo-limit

Project	Viewers
Branch Review	feat/undo-redo-limit
Run status	Passed #6776
Run duration	01m 47s
Commit	806b62ac9e: Merge remote-tracking branch 'origin/master' into feat/undo-redo-limit
Committer	Bill Wallace
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