Add AnimationSpeed property to SKLottieView by Copilot · Pull Request #331 · mono/SkiaSharp.Extended

Copilot · 2026-02-05T03:10:33Z

Summary

Adds an AnimationSpeed property to SKLottieView to control Lottie animation playback speed, with comprehensive fixes for edge cases discovered through multi-model code review.

Features

AnimationSpeed property - Control playback speed (default 1.0)
- Values > 1.0 speed up animation
- Values 0-1.0 slow down animation
- Value 0 pauses animation
- Negative values reverse playback direction

Bug Fixes

Fix	Description
Negative speed on load	Animation now initializes at Duration when speed < 0
Source race condition	Added CancellationTokenSource to cancel in-flight loads
Memory leak	CancellationTokenSource now properly disposed
Reset order	Added `isResetting` guard to prevent spurious AnimationCompleted
Reverse + negative speed	Fixed flip logic to consider effective direction
Reverse → Restart switch	Fixed animation getting stuck at 0 when switching modes

Code Quality

Renamed playForwards → isInForwardPhase for clarity
Added XML documentation to AnimationSpeed property
Added overflow protection for NaN/Infinity/extreme speed values

Demo App Enhancements

AnimationSpeed slider (-2x to 2x)
Speed preset buttons (-1x, 0.5x, 1x, 2x)
RepeatMode picker (Restart/Reverse)
RepeatCount input field

Tests

Added 18+ new tests covering:

Positive/negative/zero speed scenarios
Speed changes mid-playback
RepeatMode interactions
Edge cases (NaN, Infinity, extreme values)
Mode switching scenarios

Total: 140 MAUI tests passing

API Naming Research

Library	Property Name
lottie-android	`speed`
lottie-ios	`animationSpeed`
lottie-web	`setSpeed()`
This PR	`AnimationSpeed`

Follows iOS convention for .NET clarity.

mattleibow · 2026-02-05T03:39:51Z

/azp run

Copilot

Pull request overview

This PR adds an AnimationSpeed property to SKLottieView to control Lottie animation playback speed, addressing issue #281. The implementation allows users to speed up, slow down, or pause animations by multiplying the frame delta time by a speed factor. The default speed is 1.0 (normal playback).

Changes:

Added AnimationSpeed bindable property with type double and default value 1.0
Modified Update() method to apply the speed multiplier to deltaTime before processing
Added comprehensive unit tests covering default value, speed variations (2x, 0.5x, 0), and dynamic speed changes

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
source/SkiaSharp.Extended.UI.Maui/Controls/Lottie/SKLottieView.shared.cs	Adds `AnimationSpeed` bindable property and applies speed multiplier in `Update()` method
tests/SkiaSharp.Extended.UI.Maui.Tests/Controls/Lottie/SKLottieViewTest.cs	Adds 5 test methods covering default value, speed variations, and dynamic changes

source/SkiaSharp.Extended.UI.Maui/Controls/Lottie/SKLottieView.shared.cs

tests/SkiaSharp.Extended.UI.Maui.Tests/Controls/Lottie/SKLottieViewTest.cs

Co-authored-by: mattleibow <1096616+mattleibow@users.noreply.github.com>

- Add XML documentation explaining AnimationSpeed behavior including negative values - Rename playForwards to isInForwardPhase for clarity - Add overflow protection for extreme speed values - Add tests for negative AnimationSpeed (reverse playback) - Add test for AnimationSpeed with RepeatMode.Reverse - Add test for dynamically changing AnimationSpeed

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Fixes identified by 5-model code review: - Fix overflow protection for NaN, Infinity, and edge cases - Fix negative AnimationSpeed not triggering completion or repeats - Fix restart position for negative speed (restarts at Duration) Changes: - Use effective direction (movingForward) based on AnimationSpeed sign - Update boundary detection to work with negative speeds - Update restart logic to reset to correct position based on speed - Add 6 new tests for negative speed scenarios

Tests added based on 5-model code review: - AnimationCompletedEventFiresOnlyOnce - ManualProgressSetDoesNotIncrementRepeatCount - SwitchingRepeatModeFromReverseToRestartMidAnimation - ProgressOutOfBoundsIsAccepted - ChangingAnimationSpeedToNegativeMidPlayback - ZeroAnimationSpeedPausesAnimation All 257 tests passing (120 base + 137 MAUI)

Fix 1: Negative AnimationSpeed now correctly initializes Progress to Duration - Animation loads at correct starting position for reverse playback - No longer requires manual Progress = Duration workaround Fix 2: Source race condition fixed with CancellationTokenSource - Changing Source cancels any in-flight load - Prevents wrong animation from displaying on rapid source changes Tests added: - NegativeSpeedAnimationStartsAtDurationOnLoad - SourceChangeCancellsPreviousLoad - Updated NegativeAnimationSpeedFromStartClampsToZero -> NegativeAnimationSpeedStartsAtDuration All 259 tests passing (139 MAUI + 120 base)

Fixes from 5-model code review: - Fix Reset() order causing spurious AnimationCompleted on load (isResetting guard) - Fix CancellationTokenSource memory leak (dispose before recreating) - Fix Reverse mode with negative speed (proper flip logic) Demo app enhancements: - Add AnimationSpeed slider (-2x to 2x) with preset buttons - Add RepeatMode picker (Restart/Reverse) - Add RepeatCount input field

mattleibow · 2026-02-06T01:14:03Z

/azp run

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

Copilot · 2026-02-06T01:17:41Z

samples/SkiaSharpDemo/Demos/Lottie/LottiePage.xaml.cs

 		IsPlaying = !IsPlaying;

+	private void OnSetSpeed(string speed) =>
+		AnimationSpeed = double.Parse(speed);


Using double.Parse without culture or error handling could throw FormatException if the command parameter is malformed. Consider using double.TryParse with InvariantCulture, or add try-catch error handling to prevent the app from crashing if an invalid value is passed.

Copilot · 2026-02-06T01:17:42Z

tests/SkiaSharp.Extended.UI.Maui.Tests/Controls/Lottie/SKLottieViewTest.cs

+		// (Duration differs between trophy.json and lolo.json)
+		Assert.NotEqual(TimeSpan.Zero, lottie.Duration);
+	}
 }


The PR description mentions adding tests for NaN and Infinity edge cases, but there are no tests covering AnimationSpeed set to double.NaN, double.PositiveInfinity, or double.NegativeInfinity. While the overflow protection code handles these cases (lines 140-141), tests should verify this behavior to ensure the protection works correctly and prevent regressions.

Copilot · 2026-02-06T01:17:42Z

source/SkiaSharp.Extended.UI.Maui/Controls/Lottie/SKLottieView.shared.cs

+		const long SafeMax = long.MaxValue - 1;  // Avoid overflow when casting from double
+		const long SafeMin = long.MinValue + 2;  // Avoid overflow when negating TimeSpan
+		if (!double.IsFinite(scaledTicks))
+			scaledTicks = double.IsNaN(scaledTicks) || scaledTicks < 0 ? SafeMin : SafeMax;


The logic condition "scaledTicks < 0" on line 141 is redundant when double.IsFinite already returned false. By the time this condition is evaluated, we already know !double.IsFinite(scaledTicks) is true, meaning the value is either NaN, PositiveInfinity, or NegativeInfinity. For NaN, the comparison "scaledTicks < 0" always returns false in C#. For infinities, NegativeInfinity < 0 is true and PositiveInfinity < 0 is false. The comment says "Handle NaN and Infinity explicitly" but the logic mixes them. Consider simplifying to: if (double.IsNaN(scaledTicks)) scaledTicks = 0; else if (double.IsNegativeInfinity(scaledTicks)) scaledTicks = SafeMin; else if (double.IsPositiveInfinity(scaledTicks)) scaledTicks = SafeMax;

Suggested change

scaledTicks = double.IsNaN(scaledTicks) || scaledTicks < 0 ? SafeMin : SafeMax;

{

if (double.IsNaN(scaledTicks))

scaledTicks = 0;

else if (double.IsNegativeInfinity(scaledTicks))

scaledTicks = SafeMin;

else if (double.IsPositiveInfinity(scaledTicks))

scaledTicks = SafeMax;

}

Copilot · 2026-02-06T01:17:42Z

source/SkiaSharp.Extended.UI.Maui/Controls/Lottie/SKLottieView.shared.cs

 	int repeatsCompleted = 0;
+	CancellationTokenSource? loadCancellation;
+	bool isResetting;



The CancellationTokenSource field 'loadCancellation' is never disposed when the control itself is disposed or finalized. This could lead to a memory leak if the control is created and destroyed repeatedly (e.g., in navigation scenarios). Consider implementing IDisposable on SKLottieView or overriding an appropriate cleanup method to dispose of loadCancellation when the control is no longer needed.

Suggested change

~SKLottieView()

{

DisposeLoadCancellation();

}

private void DisposeLoadCancellation()

{

if (loadCancellation != null)

{

try

{

loadCancellation.Cancel();

}

catch

{

// Ignore exceptions on cancel during finalization.

}

loadCancellation.Dispose();

loadCancellation = null;

}

}

Copilot AI assigned Copilot and mattleibow Feb 5, 2026

Copilot started work on behalf of mattleibow February 5, 2026 03:10 View session

Copilot AI changed the title ~~[WIP] Add property to set animation speed in SKLottieView~~ Add AnimationSpeed property to SKLottieView Feb 5, 2026

Copilot AI requested a review from mattleibow February 5, 2026 03:17

Copilot finished work on behalf of mattleibow February 5, 2026 03:17

mattleibow approved these changes Feb 5, 2026

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mattleibow marked this pull request as ready for review February 5, 2026 03:39

mattleibow requested a review from Copilot February 5, 2026 21:43

Copilot started reviewing on behalf of mattleibow February 5, 2026 21:44 View session

Copilot AI reviewed Feb 5, 2026

View reviewed changes

Copilot AI and others added 4 commits February 6, 2026 01:24

Initial plan

d864e3a

Add AnimationSpeed property to SKLottieView with tests

598818b

Co-authored-by: mattleibow <1096616+mattleibow@users.noreply.github.com>

Fix test method name grammatical error

ebb8e94

Co-authored-by: mattleibow <1096616+mattleibow@users.noreply.github.com>

mattleibow force-pushed the copilot/add-animation-speed-property branch from 4128657 to 2d0e369 Compare February 5, 2026 23:25

mattleibow requested a review from Copilot February 5, 2026 23:31

Copilot started reviewing on behalf of mattleibow February 5, 2026 23:31 View session

Copilot AI reviewed Feb 5, 2026

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mattleibow added 4 commits February 6, 2026 01:50

mattleibow requested a review from Copilot February 6, 2026 01:13

Copilot started reviewing on behalf of mattleibow February 6, 2026 01:14 View session

Copilot AI reviewed Feb 6, 2026

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Add AnimationSpeed property to SKLottieView#331

Add AnimationSpeed property to SKLottieView#331
Copilot wants to merge 8 commits intomainfrom
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Copilot AI commented Feb 5, 2026 •

edited by mattleibow

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-			scaledTicks = double.IsNaN(scaledTicks) || scaledTicks < 0 ? SafeMin : SafeMax;
+		{
+			if (double.IsNaN(scaledTicks))
+				scaledTicks = 0;
+			else if (double.IsNegativeInfinity(scaledTicks))
+				scaledTicks = SafeMin;
+			else if (double.IsPositiveInfinity(scaledTicks))
+				scaledTicks = SafeMax;
+		}

+	~SKLottieView()
+	{
+		DisposeLoadCancellation();
+	}
+	private void DisposeLoadCancellation()
+	{
+		if (loadCancellation != null)
+		{
+			try
+			{
+				loadCancellation.Cancel();
+			}
+			catch
+			{
+				// Ignore exceptions on cancel during finalization.
+			}
+			loadCancellation.Dispose();
+			loadCancellation = null;
+		}
+	}

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Summary

Features

Bug Fixes

Code Quality

Demo App Enhancements

Tests

API Naming Research

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Copilot AI commented Feb 5, 2026 •

edited by mattleibow

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