FIX: Misaligned Virtual Cursor when changing resolution (ISXB-1119)

[Darren-Kelly-Unity]

Description

When changing resolution in the virtual cursor sample the virtual cursor ended up misaligned in different resolutions.
https://jira.unity3d.com/browse/ISXB-1119

Testing status & QA

I have tested in multiple resolutions & swapping resolutions at runtime to be sure this is working.

Overall Product Risks

• Complexity: 1
• Halo Effect: 1

Comments to reviewers

Checklist

Before review:

• Changelog entry added.
  • Explains the change in Changed, Fixed, Added sections.
  • For API change contains an example snippet and/or migration example.
  • JIRA ticket linked, example (case %%). If it is a private issue, just add the case ID without a link.
  • Jira port for the next release set as "Resolved".
• Tests added/changed, if applicable.
  • Functional tests Area_CanDoX, Area_CanDoX_EvenIfYIsTheCase, Area_WhenIDoX_AndYHappens_ThisIsTheResult.
  • Performance tests.
  • Integration tests.
• Docs for new/changed API's.
  • Xmldoc cross references are set correctly.
  • Added explanation how the API works.
  • Usage code examples added.
  • The manual is updated, if needed.

During merge:

• Commit message for squash-merge is prefixed with one of the list:
  • NEW: ___.
  • FIX: ___.
  • DOCS: ___.
  • CHANGE: ___.
  • RELEASE: 1.1.0-preview.3.

[u-pr]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪ The change is localized to virtual cursor motion scaling and UI positioning with a small amount of new logic to validate across a few UI configurations.

🏅 Score: 78 The fix is directionally correct but introduces some null-safety and edge-case risks around `Canvas`/`CanvasScaler` availability and scaling math.

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Null Safety m_CanvasScaler is checked for null but m_Canvas is still dereferenced when computing scales; if no Canvas is found (or TryFindCanvas fails due to hierarchy changes), accessing m_Canvas.pixelRect can throw and break virtual cursor motion. var resolutionXScale = 1f; var resolutionYScale = 1f; if (m_CanvasScaler != null) { resolutionXScale = m_Canvas.pixelRect.xMax / m_CanvasScaler.referenceResolution.x; resolutionYScale = m_Canvas.pixelRect.yMax / m_CanvasScaler.referenceResolution.y; } Divide By Zero The resolution scale divides by m_CanvasScaler.referenceResolution.x/y; if either component is zero (misconfigured scaler), this will produce infinities and propagate into delta and anchored positioning. if (m_CanvasScaler != null) { resolutionXScale = m_Canvas.pixelRect.xMax / m_CanvasScaler.referenceResolution.x; resolutionYScale = m_Canvas.pixelRect.yMax / m_CanvasScaler.referenceResolution.y; } var currentTime = InputState.currentTime; if (Mathf.Approximately(0, m_LastStickValue.x) && Mathf.Approximately(0, m_LastStickValue.y)) { // Motion has started. m_LastTime = currentTime; } // Compute delta. var deltaTime = (float)(currentTime - m_LastTime); var delta = new Vector2(m_CursorSpeed * resolutionXScale * stickValue.x * deltaTime, m_CursorSpeed * resolutionYScale * stickValue.y * deltaTime); Coordinate Space Writing anchoredPosition from newPosition assumes compatible coordinate spaces; when using different Canvas render modes or non-default scaling modes, pixelRect space and RectTransform.anchoredPosition space may not map 1:1, so the cursor could still drift/misalign. var pixelRect = m_Canvas.pixelRect; newPosition.x = Mathf.Clamp(newPosition.x, pixelRect.xMin, pixelRect.xMax); newPosition.y = Mathf.Clamp(newPosition.y, pixelRect.yMin, pixelRect.yMax); } ////REVIEW: the fact we have no events on these means that actions won't have an event ID to go by; problem? InputState.Change(m_VirtualMouse.position, newPosition); InputState.Change(m_VirtualMouse.delta, delta); // Update software cursor transform, if any. if (m_CursorTransform != null && (m_CursorMode == CursorMode.SoftwareCursor || (m_CursorMode == CursorMode.HardwareCursorIfAvailable && m_SystemMouse == null))) { m_CursorTransform.anchoredPosition = m_CanvasScaler == null ? newPosition : new Vector2(newPosition.x / resolutionXScale, newPosition.y / resolutionYScale); }

Update review

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[u-pr]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
Possible issue	Fix scaling computation and null-safety Guard against m_Canvas being null when m_CanvasScaler is found, otherwise m_Canvas.pixelRect can throw at runtime. Also avoid using xMax/yMax as “size”; use pixelRect.width/height (or size) to compute scale correctly even if the rect origin is not at (0,0). Packages/com.unity.inputsystem/InputSystem/Plugins/UI/VirtualMouseInput.cs [426-432] var resolutionXScale = 1f; var resolutionYScale = 1f; -if (m_CanvasScaler != null) +if (m_CanvasScaler != null && m_Canvas != null) { - resolutionXScale = m_Canvas.pixelRect.xMax / m_CanvasScaler.referenceResolution.x; - resolutionYScale = m_Canvas.pixelRect.yMax / m_CanvasScaler.referenceResolution.y; + var pixelRect = m_Canvas.pixelRect; + resolutionXScale = pixelRect.width / m_CanvasScaler.referenceResolution.x; + resolutionYScale = pixelRect.height / m_CanvasScaler.referenceResolution.y; } Suggestion importance[1-10]: 7 __ Why: As written, m_Canvas.pixelRect can throw if m_Canvas is null, and using pixelRect.xMax/yMax is incorrect for size when the rect origin is not (0,0); width/height is the right measure. This is a real runtime correctness fix in UpdateMotion.	Medium
	Ensure scaler matches the canvas Prefer finding the CanvasScaler from the same Canvas hierarchy you already resolved to avoid mismatches when nested canvases exist. This prevents using a scaler from a different parent canvas than the one providing pixelRect, which would skew scaling. Packages/com.unity.inputsystem/InputSystem/Plugins/UI/VirtualMouseInput.cs [371-375] private void TryFindCanvas() { m_Canvas = m_CursorGraphic?.GetComponentInParent<Canvas>(); - m_CanvasScaler = m_CursorGraphic?.GetComponentInParent<CanvasScaler>(); + m_CanvasScaler = m_Canvas != null ? m_Canvas.GetComponent<CanvasScaler>() : null; } Suggestion importance[1-10]: 6 __ Why: Resolving CanvasScaler independently from m_CursorGraphic can pick a scaler from a different parent than m_Canvas, causing inconsistent scaling against m_Canvas.pixelRect. Tying m_CanvasScaler lookup to the resolved m_Canvas improves correctness with nested canvases.	Low
More suggestions

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[codecov-github-com]

Codecov Report

Attention: Patch coverage is 73.33333% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...system/InputSystem/Plugins/UI/VirtualMouseInput.cs	73.33%	4 Missing ⚠️

@@           Coverage Diff            @@
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  Coverage    77.95%   77.95%           
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  Files          476      476           
  Lines        97453    97479   +26     
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+ Hits         75971    75994   +23     
- Misses       21482    21485    +3     

Flag	Coverage Δ
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inputsystem_MacOS_6000.4	5.32% <ø> (-0.01%)	⬇️
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inputsystem_MacOS_6000.5	5.32% <ø> (-0.01%)	⬇️
inputsystem_MacOS_6000.5_project	77.37% <73.33%> (+<0.01%)	⬆️
inputsystem_Ubuntu_2022.3	5.54% <ø> (+<0.01%)	⬆️
inputsystem_Ubuntu_2022.3_project	75.27% <73.33%> (+<0.01%)	⬆️
inputsystem_Ubuntu_6000.0	5.32% <ø> (-0.01%)	⬇️
inputsystem_Ubuntu_6000.0_project	77.17% <73.33%> (+0.01%)	⬆️
inputsystem_Ubuntu_6000.3	5.32% <ø> (-0.01%)	⬇️
inputsystem_Ubuntu_6000.3_project	77.17% <73.33%> (+<0.01%)	⬆️
inputsystem_Ubuntu_6000.4	5.33% <ø> (-0.01%)	⬇️
inputsystem_Ubuntu_6000.4_project	77.18% <73.33%> (+<0.01%)	⬆️
inputsystem_Ubuntu_6000.5	5.33% <ø> (-0.01%)	⬇️
inputsystem_Ubuntu_6000.5_project	77.18% <73.33%> (+<0.01%)	⬆️
inputsystem_Windows_2022.3	5.54% <ø> (+<0.01%)	⬆️
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inputsystem_Windows_6000.0	5.32% <ø> (-0.01%)	⬇️
inputsystem_Windows_6000.0_project	77.50% <73.33%> (+<0.01%)	⬆️
inputsystem_Windows_6000.3	5.32% <ø> (-0.01%)	⬇️
inputsystem_Windows_6000.3_project	77.49% <73.33%> (+<0.01%)	⬆️
inputsystem_Windows_6000.4	5.32% <ø> (-0.01%)	⬇️
inputsystem_Windows_6000.4_project	77.50% <73.33%> (+<0.01%)	⬆️
inputsystem_Windows_6000.5	5.32% <ø> (-0.01%)	⬇️
inputsystem_Windows_6000.5_project	77.50% <73.33%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...system/InputSystem/Plugins/UI/VirtualMouseInput.cs	69.11% <73.33%> (+1.16%)	⬆️

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[ekcoh]

I only looked at code changes, but fixing this TODO looks legit, I would recommend adding a CHANGELOG entry though and linking the associated public issue tracker from the changelog.

[ekcoh]

Needs CHANGELOG entry.

[ekcoh]

Thanks for adding the missing CHANGELOG entry.

[Pauliusd01]

@Darren-Kelly-Unity changelog is under the wrong area, should be under unreleased

[Pauliusd01]

/test_plan

[u-pr]

Test Plan

• Test plan approved by PR author
• Test execution in progress
• Test execution complete
• Ready for merge

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Summary of Changes & Risk Assessment

Summary of Changes

This PR fixes an issue where the virtual cursor in the Input System's UI plugin became misaligned or moved at incorrect speeds when the game resolution was changed. It introduces scaling logic in VirtualMouseInput.cs that utilizes the CanvasScaler's reference resolution and the current Canvas pixel rect to normalize cursor movement and positioning.

Risk Assessment

• High Risk Areas: None identified.
• Medium Risk Areas: Null-safety in UpdateMotion (specifically m_Canvas and m_CanvasScaler interactions), potential divide-by-zero if referenceResolution is misconfigured.
• Low Risk Areas: Changes to OnEnable for canvas discovery, Changelog updates.

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Test Scenarios

Functional Testing

• Resolution Consistency: In a scene with VirtualMouseInput and a CanvasScaler (set to "Scale With Screen Size"), verify that the cursor moves across the screen at the same relative speed in 1280x720 vs 1920x1080.
• Boundary Alignment: Move the virtual cursor to the extreme corners of the screen. Switch resolutions at runtime and verify the cursor remains clamped correctly to the new corners.
• Software Cursor Mapping: Ensure the m_CursorTransform.anchoredPosition correctly matches the visual center of the cursor graphic across different aspect ratios (e.g., 16:9 to 21:9).

Regression Testing

• No Scaler Support: Verify that if the Canvas does not have a CanvasScaler component, the virtual cursor still functions with 1:1 pixel movement (as per VirtualMouseInput.cs:L468).
• Hardware Cursor Mode: Verify that CursorMode.HardwareCursorIfAvailable still functions correctly and is not negatively impacted by the new scaling math.

🔍 Regression Deep Dive (additional risks identified)

• Hierarchy Changes: Test disabling and re-enabling the VirtualMouseInput component after moving it to a different Canvas to ensure TryFindCanvas (VirtualMouseInput.cs:L371) picks up the correct scaler.
• Render Mode Verification: Test behavior in both "Screen Space - Overlay" and "Screen Space - Camera" render modes to ensure pixelRect values are consistent.

Edge Cases

• Zero Reference Resolution: Set CanvasScaler.referenceResolution to (0,0) in the Inspector. Verify the code handles this gracefully or at least doesn't crash the editor (check for division by zero risks at VirtualMouseInput.cs:L431).
• Missing References: Verify no NullReferenceException occurs if m_CursorGraphic is unassigned on the component.

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_{💡 This test plan updates automatically when /test_plan is run on new commits. If you have any feedback, please reach out in #ai-qa}

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[Pauliusd01]

The sample is unusable for me, I can't click on any of the buttons or scroll in 1080p and when I switch it to 4K my cursor is locked in an invisible bounding box and cannot even get to the buttons. Were you testing on a Mac? Maybe It's platform specific?
https://github.com/user-attachments/assets/396c46d1-a66c-45fd-b16e-657ec8ee4135

[Pauliusd01]

It could also be a case of our sample being incorrect and not working with the updated code?