Animations

1. How to Install
2. Simple Example
3. Basic Animation Concept
4. Variant Animations
5. Property Animations
6. How to Register Animations
7. Graphics Animations
8. Composite Animations

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 such as #position:
• allow graphic transitions even without the need to change the state of a morph

How to Install

1. Get Squeak 4.5 or later with a recent CogVM for your operating system.
2. If not already integrated, load Metacello. Learn how it works.
3. Finally, load Animations into your Squeak image by executing the following snippet in a workspace:

Metacello new
  baseline: 'Animations';
  repository: 'github://hpi-swa/animations/repository';
  load.
(Smalltalk classNamed: 'AnimMorphicProject') new enter.

You have to enter an AnimMorphicProject so that animations will actually run. A regular Morphic project will skip animations automatically.

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"
   start.

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."
MyMorph>>stepTime
   ^ 16 "60 steps per second"

MyMorph>>step
   myAnimations do: [:anim | anim updateCurrentTime: WorldState lastCycleTime].

"Using an extra process."
[
   myAnimations do: [:anim | anim updateCurrentTime: WorldState lastCycleTime].
   (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:

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

AnimAnimation
   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:

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

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;
   start.

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;
   start.

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:"
   start.

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 an accessor method #position:."
   startValue: 10@10;
   endValue: 100@100;
   start.

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, for example, when 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.

Dynamic Scope

If you want to change the registry used for myAnimation register, you have to set the dynamic scope:

AnimAnimationRegistry
   value: myRegistry
   during: [ "...some code with animations..." ]

Note that this will not work for composite animations that have to register and unregister their parts as time passes. Works good for tests, though.

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;
   start;
   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:

MyMorph>>fadeOut
   AnimAlphaBlendAnimation new
      morph: self;
      startValue: 1.0; "totally visible"
      endValue: 0.0; "invisible"
      duration: 200;
      finishBlock: [self hide]; "Executed when animation finished."
      register;
      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.

Composite Animations

You can compose multiple animations into a sequence to be played one after another automatically:

AnimCompositeAnimation new
   add: (AnimSaturationAnimation new
      morph: myMorph;
      startValue: 1.0;
      endValue: 0.0;
      duration: 250);
   add: (AnimSaturationAnimation new
      morph: myMorph;
      startValue: 0.0;
      endValue: 1.0;
      duration: 250);
   loopCount: 1;
   register;
   start.

Use plain animations to add a delay to the composition:

delay := AnimAnimation new
   duration: 1000; "milliseconds"
   yourself.

You can add composite animations to composite animations to create complex sequences. See Morph >> #pulse for another example.

Considering infinite animations (i.e. loopCount == -1), there is a simple check that tells you to

• avoid more than one infinite animation in a composition
• avoid a regular animation after an infinite animation in a composition

Note that we recommend the use of composite animations instead of finishBlocks if possible.