Created by Olivier Selliez | olivier.selliez.dev@gmail.com
A lightweight, class-based animation engine for Windows Forms in PowerShell. This library implements Robert Penner's easing equations to provide smooth, non-linear transitions for UI elements.
The library is modularized into four core components:
| File | Role |
|---|---|
Tweens.ps1 |
Data Models: Defines the PowerShel 5.1 classes for different animation types. |
TweensVariables.ps1 |
Constants: Defines the string identifiers for the easing algorithms (e.g., $easeBounceOut). |
TweensMovement.ps1 |
Logic: Contains the mathematical functions (Easing) and the specific property update logic. |
TweensUpdater.ps1 |
Engine: Manages the System.Windows.Forms.Timer and the global update loop. |
To integrate the library into your project, follow these steps:
Import the library files at the start of your script:
. "$PSScriptRoot\Tweens\TweensVariables.ps1"
. "$PSScriptRoot\Tweens\Tweens.ps1"
. "$PSScriptRoot\Tweens\TweensUpdater.ps1"
. "$PSScriptRoot\Tweens\TweensMovement.ps1"Initialize the required global variables and the timer:
# Set target framerate
$Script:refreshRate = 60
# Initialize the animation queue
$Script:listToAnimate = New-Object System.Collections.ArrayList
# Start the timer when the form is shown
$mainForm.Add_Shown({ $timer.Start() })
# CRITICAL: Dispose the timer on close to prevent memory leaks in the PowerShell session
$mainForm.Add_Closing({ $timer.Dispose() })All animations inherit from the base Tween class, which tracks nbTicks (progress) and duration (total length in frames).
Animates the Location property (X, Y) of a control.
- Constructor:
[TweenMoveTo]::new($Control, $DestPoint, $DurationSec, $Easing, $Callback) - Example:
[TweenMoveTo]::new($btn, [System.Drawing.Point]::new(100, 100), 2.0, $easeExpoOut, $null)
Transitions a control's color channels (Alpha, Red, Green, Blue).
- Constructor:
[TweenColorARGB]::new($Control, $Property, $StartColor, $EndColor, $DurationSec, $Easing, $Callback) - Property: Use
"ForeColor"or"BackColor". - Example:
[TweenColorARGB]::new($label, "ForeColor", [Color]::Black, [Color]::Red, 1.5, $easeLinear, $null)
Animates a numeric value inside a control's Text property.
- Constructor:
[TweenNumericString]::new($Control, $Type, $StartVal, $EndVal, $DurationSec, $Easing, $Callback) - Type:
"int"(rounds down) or"double"(rounds to 2 decimals).
Animates the Value property of a System.Windows.Forms.ProgressBar.
- Constructor:
[TweenProgressBar]::new($ProgressBar, $StartVal, $EndVal, $DurationSec, $Easing, $Callback)
Easing functions determine the "feel" of the animation. Each algorithm (except Linear) supports four modes: In, Out, InOut, and OutIn. For visual demonstrations and previews of these curves, visit easings.net.
| Type | Description |
|---|---|
| Linear | Constant speed transition. |
| Quad / Cubic / Quart / Quint | Increasingly aggressive power-based curves. |
| Expo | Exponential growth/decay; very snappy. |
| Sine | Smooth, organic sinusoidal transition. |
| Circ | Circular curve transition. |
| Back | Retracts slightly before moving or overshoots the target at the end. |
| Elastic | An oscillating "spring" effect. |
| Bounce | A realistic bouncing effect at the start or end. |
Access these using the script-scoped variables: $Script:easeBounceOut, $Script:easeElasticInOut, etc.
The Update function in TweensUpdater.ps1 runs every tick. It iterates through $Script:listToAnimate. When a tween reaches its duration, it is automatically removed from the list.
The duration is calculated as $DurationInSeconds * $refreshRate. If the UI thread is heavily blocked, the animation might appear slower because ticks are skipped, but the library ensures the final destination is reached.
Since Windows Forms is single-threaded (STA), the animations run on the same thread as the UI. Avoid long-running synchronous tasks during animations to prevent stuttering.
# Move a button to (200, 200) over 3 seconds with a bounce effect
$destination = [System.Drawing.Point]::new(200, 200)
# Passing a scriptblock as a callback
$myTween = [TweenMoveTo]::new($btnSubmit, $destination, 3.0, $Script:easeBounceOut, { [System.Windows.Forms.MessageBox]::Show("Animation Done!") })
# Add to the engine
$Script:listToAnimate.Add($myTween)Documentation generated for the PowerShell Tweens project.
