Add mirrorStream support to ParticipantVideo for video mirroring

[rahul-lohra]

Goal

We currently do not provide any API to mirror participant video streams. This limitation was raised in Stream Video Android Issue #1657

Mirroring is a common requirement, especially for:

• front camera preview parity (self-view)
• UI consistency across platforms

Implementation

This PR introduces a new parameter mirrorStream in ParticipantVideo, allowing developers to control horizontal mirroring of the rendered video stream.

The mirroring is applied at the rendering layer using the underlying WebRTC renderer, ensuring minimal performance overhead.

Usage

CallContent(
    videoRenderer = { modifier, call, participant, style ->
        ParticipantVideo(mirrorStream = (participant.sessionId != me?.sessionId)..)
     }
} 

Notes

• Mirroring is handled at the renderer level (not via UI transforms), avoiding additional composition cost.
• Defaults are preserved; existing behavior remains unchanged unless explicitly enabled.
• Provides flexibility without exposing rendering internals to the UI layer.

🎨 UI Changes

None

Testing

Join a video call with 2 people, see that the other user is not mirrored

Summary by CodeRabbit

• New Features
  • Improved video participant rendering with enhanced mirroring behavior. Remote participants' video streams are now properly mirrored for optimal display orientation, while local participant video is rendered appropriately without unnecessary mirroring adjustments in video calls.

[github-actions]

PR checklist ✅

All required conditions are satisfied:

• Title length is OK (or ignored by label).
• At least one pr: label exists.
• Sections ### Goal, ### Implementation, and ### Testing are filled.

🎉 Great job! This PR is ready for review.

[coderabbitai]

Walkthrough

A mirrorStream boolean parameter is added to video rendering components, computed by comparing each participant's session ID against the local user's session ID to conditionally mirror non-local participant video streams.

Changes

Cohort / File(s)	Summary
Video Mirror Parameter Addition stream-video-android-ui-compose/src/main/kotlin/io/getstream/video/android/compose/ui/components/call/renderer/ParticipantVideo.kt, demo-app/src/main/kotlin/io/getstream/video/android/ui/call/CallScreen.kt	Introduces mirrorStream: Boolean = false parameter to ParticipantVideo and ParticipantVideoRenderer composables. Parameter is computed in CallScreen by comparing participant session ID to local user session ID and forwarded to the renderer where it affects the mirror state calculation.
Public API Signature Updates stream-video-android-ui-compose/api/stream-video-android-ui-compose.api	Updates method signatures for ParticipantVideo and ParticipantVideoRenderer to include the new boolean mirrorStream parameter after VideoScalingType; removes previous overload signatures without this parameter.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Whiskers twitch with glee,
Session IDs dance and see,
Local stays true, remote gets flipped,
Mirror logic, deftly scripted!
Participants now face the right way, ✨

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	❓ Inconclusive	The PR description covers Goal, Implementation, and Testing sections. However, it lacks UI Changes screenshots/videos, contributor/reviewer checklists, and changelog updates required by the template.	Complete the contributor checklist, include changelog updates, and verify all required documentation sections are addressed. The description lacks formal structure adherence.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding mirrorStream support to ParticipantVideo for video mirroring. It is clear, concise, and directly reflects the primary feature introduced.
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.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/rahullohra/expose-video-renderer-modifier

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In
`@stream-video-android-ui-compose/src/main/kotlin/io/getstream/video/android/compose/ui/components/call/renderer/ParticipantVideo.kt`:
- Around line 268-271: The memoized `mirror` state uses remember with keys
(cameraDirection, mirrorStream) but reads `me?.sessionId` and
`participant.sessionId`, causing stale values when `me` changes; instead remove
the remember/mutableStateOf and compute `mirror` as a derived (immutable) value
directly from `mirrorStream`, `cameraDirection`, `me?.sessionId`, and
`participant.sessionId` (i.e., replace the remembered mutableState logic around
`mirror` with a plain val expression that uses those symbols).

🪄 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: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: ea5c9d74-bd58-4a1e-b216-c9e16570c816

📥 Commits

Reviewing files that changed from the base of the PR and between 1d744dc and 5ad6bbe.

📒 Files selected for processing (3)

• demo-app/src/main/kotlin/io/getstream/video/android/ui/call/CallScreen.kt
• stream-video-android-ui-compose/api/stream-video-android-ui-compose.api
• stream-video-android-ui-compose/src/main/kotlin/io/getstream/video/android/compose/ui/components/call/renderer/ParticipantVideo.kt

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-video-android-core	12.02 MB	12.02 MB	0.00 MB	🟢
stream-video-android-ui-xml	5.68 MB	5.68 MB	0.00 MB	🟢
stream-video-android-ui-compose	6.28 MB	6.28 MB	0.00 MB	🟢

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
27.8% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud