Keyframe Animation

Declarative keyframe animation for .NET MAUI — the CSS @keyframes model expressed in XAML, plus a fluent C# timeline API, storyboards, a drawable scene graph, and an optional headless frame exporter.

The thing MAUI’s own Animation class cannot do is seek. Everything here is built around one design constraint: evaluating an animation is a pure function of time. Nothing reads the previous frame. That single property is what makes scrubbing, mid-flight reversal, byte-identical export, and non-flaky timing tests possible rather than merely approximable.

MAUI only

There is no Blazor counterpart, and there won’t be — the web already has @keyframes natively. The timing engine itself (Shiny.Controls.Keyframe.Shared) is host-neutral and depends only on Microsoft.Maui.Graphics, so it will run anywhere .NET does; it is the XAML surface and the view bindings that are MAUI-specific.

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Frameworks

.NET MAUI

Operating Systems

iOS

Android

Windows

macOS

Packages

Package	What it is	Depends on
Shiny.Controls.Keyframe.Shared	The host-neutral timing engine and scene graph — Timing, Timeline, Storyboard, Track<T>, IInterpolator<T>, Player, the easing curves, KeyframeScene and its layers.	Microsoft.Maui.Graphics
Shiny.Maui.Controls.Keyframe	The XAML surface (Animate.Keyframes, Keyframes / Track / Key), KeyframeView, MauiClock, and the animatable-property registry.	the above + Microsoft.Maui.Controls
Shiny.Maui.Controls.Keyframe.Export	Headless frame export and a pure-managed GIF encoder. Optional — and the only thing in Keyframe that pulls in SkiaSharp.	the shared package + Microsoft.Maui.Graphics.Skia

Install only what you need. Animating views never requires the export package.

Features

• CSS @keyframes semantics in XAML — Duration, Delay, Iterations, Direction, Fill, and per-key easing behave the way the web spec says they do, including Fill="Both" and Direction="Alternate".
• Seekable, reversible playback — SeekProgress(0.35) scrubs, Rate = -1 reverses from wherever the animation currently sits. No rebuilding, no restart.
• CSS easing function syntax — cubic-bezier(0.34, 1.56, 0.64, 1), steps(8), and spring(0.35, 14) parse from a plain string, so a curve copied out of a design tool or browser devtools pastes in verbatim. 38 named curves too.
• Implicit keyframes — omit Value on a key and it resolves to the target’s live value when playback starts, so a re-triggered animation continues from where it is instead of snapping.
• Oklab colour blending by default — sRGB interpolation dips through grey at the midpoint; Oklab doesn’t. ColorInterpolator.Srgb and .LinearRgb remain available.
• Shortest-arc angles — Rotation from 350° to 10° turns forward 20°, not back 340°. Spin is there for when multiple turns are the point.
• Fluent C# timelines and storyboards — TimelineBuilder composes tracks; Storyboard sequences, overlaps and staggers whole timelines on a shared clock, and nests.
• A drawn scene graph — KeyframeScene + KeyframeView run the same timing model against layers on a canvas (the Lottie-shaped lane) rather than views in the visual tree.
• Deterministic offscreen export — sample a scene at exact frame times, lazily, and encode to GIF with no external dependency.
• AOT and trim safe — the property registry is hand-registered delegates, not reflection and not compiled Expression trees, both of which work in the emulator and break on device under Native AOT.
• Weak targets — an infinite animation on a popped page goes inert and is collected, rather than pinning the visual tree.

AI Skill

Claude CodeGitHub Copilot

Step 1 — Add the marketplace:

claude plugin marketplace add shinyorg/skills

Step 2 — Install the plugin:

claude plugin install controls@shiny

Step 1 — Add the marketplace:

copilot plugin marketplace add https://github.com/shinyorg/skills

Step 2 — Install the plugin:

copilot plugin install controls@shiny

View controls Plugin

Installation

dotnet add package Shiny.Maui.Controls.Keyframe

xmlns:kf="http://shiny.net/maui/keyframe"

No builder.Use…() call is needed — there is nothing to register. That one XAML namespace covers the shared timing types as well.

Quick Start

An attached property on any VisualElement:

<Border>
    <kf:Animate.Keyframes>
        <kf:Keyframes Duration="0:0:1.2" Iterations="Infinite" Direction="Alternate" Fill="Both">

            <kf:Track Property="Scale">
                <kf:Key Offset="0"   Value="1" />
                <kf:Key Offset="0.5" Value="1.15" Easing="CubicOut" />
                <kf:Key Offset="1"   Value="1" />
            </kf:Track>

            <kf:Track Property="BackgroundColor">
                <kf:Key Offset="0" Value="#2563EB" />
                <kf:Key Offset="1" Value="#EC4899" />
            </kf:Track>

        </kf:Keyframes>
    </kf:Animate.Keyframes>
</Border>

The same animation in C#:

using Shiny.Controls.Keyframe;
using Shiny.Maui.Controls.Keyframe;

var timeline = TimelineBuilder
    .Create(TimeSpan.FromSeconds(1.2))
    .PingPong()
    .RepeatForever()
    .Fill(FillMode.Both)
    .Animate(box, (v, x) => v.Scale = x, k => k
        .From(1)
        .Key(0.5, 1.15, Easings.CubicOut)
        .To(1))
    .Build();

var player = box.Play(timeline);

Why evaluation is a pure function of time

IAnimationNode.Evaluate(t) computes the state at t from the keyframes alone. It never looks at the previous frame, and it never accumulates. Write code that leans on this rather than working around it:

You want to…	Do this	Not this
Scrub from a Slider or gesture	player.SeekProgress(x), or bind KeyframeView.Progress two-way	Rebuild a timeline at the new position
Reverse mid-flight	player.Rate = -1 (or a negative Speed)	Build a second, reversed timeline
Export frames	Sample at exact frame times — identical bytes every run	Render off a real-time clock and hope
Test timing	Step a ManualClock	Task.Delay and a tolerance

Where to go next

XAML AnimationsAnimate.Keyframes, the Keyframes/Track/Key model, animatable properties, and registering your own.

Easing Curves38 named curves, CSS function syntax, and custom curves.

Timelines & PlaybackTimelineBuilder, Player, seeking, reversing, and storyboards.

Drawn ScenesKeyframeScene, KeyframeView, and the layer tree.

Offscreen ExportDeterministic frame export and the GIF encoder.

Limits worth knowing up front

• Everything ticks in managed code on the UI thread. Transform and opacity tracks map 1:1 onto CAKeyframeAnimation / ObjectAnimator / ScalarKeyFrameAnimation, so native compositor offload is the design’s biggest remaining performance win — but it isn’t implemented yet.
• Layout-affecting properties cost a measure/arrange every frame. WidthRequest, HeightRequest, Margin, and Padding all work and are flagged by AnimatableProperty.InvalidatesLayout, but prefer transform and opacity where you have the choice.
• There is no Lottie parser. KeyframeScene is the scene graph one would need, but nothing reads a Lottie JSON file today.
• MP4/video export is out of scope — that needs a real codec. Pipe FrameExporter.Frames() to ffmpeg’s stdin instead. APNG and WebP aren’t implemented either.