In its current development state, the Morphic implementation of Squeak does not support an extensible mechanism that allows visually appealing transitions whenever a morph's state changes, e.g., positon, rotation, color.

This project provides such an extension to Morphic with the following key-features:

  • respect timeliness no matter how high the cpu load is
  • support any property of a morph that has an accessor like #position:
  • allow graphic transitions even without the need to change the state of a morph

How to Install

4.1, 4.2 Alpha
4.0.2 (Win), ? (Mac)

Just load the Animations package into your Squeak image.

Warning: Once installed, unloading will probably cause your image to stop rendering, which means it will hang. That is because some very important messages (like WorldState>>doOneCycleFor:) were overridden and could get lost on unloading.

There are the following sub-packages:

  • Animations-Core ... core implementation
  • Animations-Canvas ... canvases to be used in graphics animations
  • Animations-Animations ... some example graphics animations
  • Animations-Tests ... tests for all packages

How to Use

Simple Example

Open a workspace and create a new morph:

| myMorph |
myMorph := Morph new topLeft: 100@100; extent: 400@400; openInWorld.

Now let this morph disappear. Try the close all unnecessary morphs for performance reasons:

myMorph fadeOut.

It's gone! Now get it back:

myMorph fadeIn.

This animation is about 200 milliseconds. If your Squeak image is quite busy it will be not that smooth.

Basic Animation Concept

In principle, an animation is a timer that has a duration and can run several times to produce loops.

AnimAnimation new
   duration: 500; "milliseconds"

You may inspect this animation and look at #currentTime but nothing will change. There are no extra processes involved to keep the animation running. You need to call #updateCurrentTime: with an increasing time value frequently to achieve this.

Animations were designed to be used in the Squeak UI process. Therefore, the best reference time to be used is:

WorldState lastCycleTime.

One possibility (there is a better one) could be to use morph's stepping or a custom process:

"Using morph stepping."
   ^ 16 "60 steps per second"

   myAnimations do: [:anim | anim updateCurrentTime].

"Using an extra process."
   myAnimations do: [:anim | anim updateCurrentTime].
   (Delay forMilliseconds: 16) wait. "Avoid high load. Get 60 cycles per second."
] fork.

Having this, the animation AnimAnimation handles just simple time interpretation. You can control the animation with #start, #stop, #pause, #resume. Here are some other examples:

   duration: 500; "Always needed!"
   loopCount: 5;
   direction: #backward; "Not used in base class."

   duration: 1000;
   loopCount: -1; "Infinite."
   start: #keepWhenFinished. "Memory management. Not needed for infinite animations. 
                              Not used in base class."

You can perform an action after the animation is finished using a block:

   duration: 500;
   finishBlock: [Transcript cr; show: 'Animation finished!'];

Variant Animations

Variant animations add value interpolation behaviour to animations. There is a start and an end value. During one animation loop #currentValue changes in this range including the start and the end value itself.

AnimVariantAnimation new
   duration: 500;
   startValue: 1;
   endValue: 10;

Having #updateCurrentTime: called frequently somehow, #updateCurrentValue can be called frequently too to trigger a callback that allows variant animations to change their internal state or perform other operations:

MyVariantAnimation>>updateCurrentValue: newValue
   Transcript cr; show: newValue asString.

The value interpolation uses an easing curve that maps a value between 0.0 and 1.0 to another value between 0.0 and 1.0 or maybe more. This can be used to modify the normal linear interpolation and get some more pleasing effects. Overshooting is possible but 1.0 should map to 1.0 because the loop ends there. Here is an example for a custom easing curve:

MyEasingCurve>>valueForProgress: aFloat
   ^ aFloat * aFloat

AnimVariantAnimation new
   duration: 500;
   startValue: 1;
   endValue: 10;
   easingCurve: MyEasingCurve new;

Variant animations make use of the #direction attribute which means the value goes from #endValue to #startValue if backwards. An offset can be specified to allow relative value changes:

AnimVariantAnimation new
   duration: 500;
   startValue: 1@1;
   endValue: 10@10;
   offsetBlock: [ActiveHand position]; "or just #offset:"

Property Animations

Property animations are variant animations that are bound to an object and a property. The #updateCurrentValue: callback will try to send a keyword message to the object with one argument using the property name:

AnimPropertyAnimation new
   duration: 500;
   target: myMorph;
   property: #position; "There should be a message called #position:."
   startValue: 10@10;
   endValue: 100@100;

Let them run! — How to register Animations

Animations are meant to be used in the Squeak UI process. There is a reference time called WorldState class>>lastCycleTime and some animations can use the world's main loop to keep themselves running. This is achieved by registering the animation in the AnimAnimationRegistry:

AnimPropertyAnimation new
   duration: 500;
   target: myMorph;
   property: #position;
   startValue: 10@10;
   endValue: 100@100;
   start: #deleteWhenFinished; "Automatic registry clean-up. No need to unregister."
   register. "Add to animation registry."

Only AnimPropertyAnimation and AnimGraphicsAnimation can be registered.

If you want to keep animations after they finished, you need to unregister them manually, e.g., if it has stopped:

myAnimation isStopped
   ifTrue: [myAnimation unregister].

Using Processes

The animation registry is thread-safe which means that #register and #unregister operations are secured and can be called from within any process. However, that process should have a higher priority than the Squeak UI process. Otherwise it could be problematic to acquire the mutex because every world cycle needs it too.

Graphics Animations

Graphics animations are variant animations that modify the visual appearance of a morph and all its submorphs doing simple color mappings. Graphic animations need to be registered.

AnimAlphaBlendAnimation new
   morph: myMorph;
   duration: 500;
   startValue: 0.0;
   endValue: 1.0;
   register. "Always needed for graphics animations!"

There is no need to reimplement #updateCurrentValue: but #transformedCanvas: which returns a custom AnimColorMappingCanvas to be used during the drawing routine of morphs:

MyAlphaBlendingAnimation>>transformedCanvas: aCanvas
   ^ (MyAlphaBlendingCanvas
      on: aCanvas)
      alpha: self currentValue "Interpolated alpha value."

Having this, a simple fade-out animation for morphs can be implemented as follows:

   AnimAlphaBlendAnimation new
      morph: self;
      startValue: 1.0; "totally visible"
      endValue: 0.0; "invisible"
      duration: 200;
      finishBlock: [self hide]; "Executed when animation finished."
      start: #deleteWhenFinished.

Color mappings apply to all submorphs in a morph. To prevent a morph from being color-mapped by its owner use the property #ignoresColorMappings.

If you want to hold a certain color mapping state, you must not delete an animation when it has finished. Otherwise the color mapping will disappear. An example would be to gray-out or darken a morph using AnimBrightnessAnimation or AnimGrayscaleAnimation.

How to Extend

Take a look at:

  • memory management of AnimAnimationRegistry
    • #garbageCollect
  • Morph>>#fullDrawOn:
  • WorldState>>#doOneCycleFor:


The Animations package was inspired by the animation framework in the Nokia Qt Framework.

To date the following people contributed to this project:

  • Marcel Taeumel
Last modified 5 years ago Last modified on 11/11/2012 05:38:33 PM