<code-movie-runtime> - Web runtime for Code.Movie

Convenient wrapper for Code.Movie animations that provides a basic high-level UI and DOM API via the custom element <code-movie-runtime>.

Setup

You can install the library as @codemovie/code-movie-runtime from NPM, download the latest release from GitHub or just grab dist/index.js from the source code. The library exports the component class and auto-registers the tag name code-movie-runtime. You can throw the module into any web page without doing anything else and it will just work.

The element works by slotting another element (the animation) and switching classes on it. The element is extremely basic and meant to be used by other tools or hacked and extended by you, the user.

HTML API

General usage

The element <code-movie-runtime> is a custom HTML element with several slots, attributes, and DOM properties for customization. To get it working, just load dist/index.js as module in your web page! A minimal example:

<script type="module" src="dist/index.js"></script>
<code-movie-runtime controls keyframes="0 1 2 3">
  <div>Switch classes on me!</div>
</code-movie-runtime>

This will cycle classes on the div element wrapped by the custom elements from frame0 to frame1 to frame2 to frame3. The keyframes are defined as a whitespace-separated list of numbers in the keyframes attribute while the existence of the controls attribute provides basic forwards/backwards buttons.

Attribute summary:

• controls: Boolean attribute. When present, shows controls UI (by default just a pair of forwards/backwards buttons). Reflected by the DOM property controls.
• keyframes: Defines the list of keyframes with a value of whitespace-separated positive integers. Values that are anything but a list of whitespace-separated integers are equal to the attribute missing (eg. there are no keyframes at all in this case). The list of keyframes is internally sorted in ascending order and cleared of any duplicates or non-numbers. Negative numbers are interpreted as positive numbers.
• current: Indicates the current frame. Can be changed to change the current frame. Reflected by the DOM property current. Values that are anything but a positive integer are treated as 0.

Custom controls

The default control UI for the element is basic and ugly. There are three options to remedy this:

1. Wrap the element

You can wrap a <code-movie-runtime> element without a controls attribute and add your own custom logic that uses the JavaScript API described below. This is probably the way to go for integration in frameworks like React.

2. Style the controls

If you just want to reposition and re-style the existing controls, you can use the following CSS ::part() selectors:

• code-movie-runtime::part(controls): The container element for the buttons
• code-movie-runtime::part(controls-prevBtn): The "previous" buttons
• code-movie-runtime::part(controls-nextBtn): The "next" buttons

The buttons are <button> elements with <span> elements inside.

3. Replace the controls

The default controls are actually just fallback content for a shadow DOM slot. This means that you can very easily add your own:

<code-movie-runtime controls keyframes="0 1 2 3">
  <div>Switch classes on me!</div>
  <div slot="controls">
    <div data-command="prev">Back</div>
    <div data-command="next">Next</div>
  </div>
</code-movie-runtime>

All you need to do to make your custom buttons (in this case, <div> elements) work is to add the attributes data-command="prev" and data-command="next" respectively. You can also build up your custom controls to do way more than just provide two buttons. See demo/index.html for an example.

4. Hack the element

The element's shadow root is open and most of the private properties on the CodeMovieRuntime class are not actually private. Go and mess with them!

JavaScript API

Instances of <code-movie-runtime> implement the following DOM APIs:

getter/setter controls (boolean)

Reflects the HTML attribute controls. Setting this property to a falsy value removes the attribute and makes the control UI invisible. Note that this also affects custom control UI that has been slotted.

getter/setter current (number)

Reflects and sets the current keyframe. The setter can be used to navigate to a specific keyframe. It coerces and rounds values to integers and clamps them to the range of available keyframes.

getter nextCurrent (number | null)

Reflects the keyframe the element is about to switch to during an cm-beforeframechange event. This property is only set during this event and returns null at any other time. The property can be inspected when handling a cm-beforeframechange and its value can be used to decide if the event should be canceled.

getter maxFrame (number)

Returns the last keyframe.

getter/setter keyframes (Array<number>)

Reflects the HTML attribute keyframes. Setting this property to anything but an array is equal to setting the property to an empty array. Non-numeric array contents is coerced to positive integers if possible and discarded otherwise.

methods next() and prev()

Go to the next or previous keyframe respectively, unless the corresponding cm-beforeframechange event gets cancelled. Returns a number indicating the new keyframe.

method go(value: number): number

Sets the current keyframe to the specified value just like the setter for current does. Coerces and rounds input values to integers and clamps them to the range of available keyframes. Returns the current keyframe.

Event cm-beforeframechange (bubbles, cancelable, not composed)

Fires before a frame change occurs. Call preventDefault() on the event to stop the frame change from happening. You can inspect the event target's current property to figure out the current frame and the event target's nextCurrent property to see what the next frame is going to be and then decide whether or not you want to to stop the frame change.

Event cm-afterframechange (bubbles, not cancelable, not composed)

As the name suggests, this is fired after a frame change has occurred.

Notes

Neither dom properties nor HTML attributes for the events cm-beforeframechange and cm-afterframechange are implemented! You must use addEventListener(), attributes or properties like onCmAfterframechange = ... are not supported.

Integrations

TypeScript

The module provides types for the element's class CodeMovieRuntime and adds its declarations into HTMLElementTagNameMap. This ensures that built-ins like document.createElement() know how to handle the new tag name code-movie-runtime. Unless you want to use another tag name or integrate with special HTML snowflakes like React, you don't have to do anything.