Adding height animation to multi-panel

src/components/compress/custom-els/MultiPanel/index.ts

@@ -1,4 +1,5 @@
 import * as style from './styles.css';
+import { transitionHeight } from '../../../../lib/util';
 
 interface CloseAllOptions {
   exceptFirst?: boolean;
@@ -6,15 +7,44 @@ interface CloseAllOptions {
 
 const openOneOnlyAttr = 'open-one-only';
 
-function getClosestHeading(el: Element) {
+function getClosestHeading(el: Element): HTMLElement | undefined {
   // Look for the child of multi-panel, but stop at interactive elements like links & buttons
   const closestEl = el.closest('multi-panel > *, a, button');
   if (closestEl && closestEl.classList.contains(style.panelHeading)) {
-    return closestEl;
+    return closestEl as HTMLElement;
   }
   return undefined;
 }
 
+async function close(content: HTMLElement) {
+  const from = content.getBoundingClientRect().height;
+
+  content.removeAttribute('expanded');
+  content.setAttribute('aria-expanded', 'false');
+
+  await transitionHeight(content, {
+    from,
+    to: 0,
+    duration: 300,
+  });
+
+  content.style.height = '';
+}
+
+async function open(content: HTMLElement) {
+  const from = content.getBoundingClientRect().height;
+
+  content.setAttribute('expanded', '');
+  content.setAttribute('aria-expanded', 'true');
+
+  await transitionHeight(content, {
+    from,
+    duration: 300,
+  });
+
+  content.style.height = '';
+}
+
 /**
  * A multi-panel view that the user can add any number of 'panels'.
  * 'a panel' consists of two elements. Even index element becomes heading,
@@ -47,7 +77,7 @@ export default class MultiPanel extends HTMLElement {
 
   // Click event handler
   private _onClick(event: MouseEvent) {
-    const el = event.target as Element;
+    const el = event.target as HTMLElement;
     const heading = getClosestHeading(el);
     if (!heading) return;
     this._toggle(heading);
@@ -108,41 +138,36 @@ export default class MultiPanel extends HTMLElement {
     }
   }
 
-  private _toggle(heading: Element) {
+  private _toggle(heading: HTMLElement) {
     if (!heading) return;
-    const content = heading.nextElementSibling;
+    const content = heading.nextElementSibling as HTMLElement;
 
     // if there is no content, nothing to expand
     if (!content) return;
 
     // toggle expanded and aria-expanded attributes
     if (content.hasAttribute('expanded')) {
-      content.removeAttribute('expanded');
-      content.setAttribute('aria-expanded', 'false');
+      close(content);
     } else {
       if (this.openOneOnly) this._closeAll();
-      content.setAttribute('expanded', '');
-      content.setAttribute('aria-expanded', 'true');
+      open(content);
     }
   }
 
   private _closeAll(options: CloseAllOptions = {}): void {
     const { exceptFirst = false } = options;
-    let els = [...this.children].filter(el => el.matches('[expanded]'));
+    let els = [...this.children].filter(el => el.matches('[expanded]')) as HTMLElement[];
 
     if (exceptFirst) {
       els = els.slice(1);
     }
 
-    for (const el of els) {
-      el.removeAttribute('expanded');
-      el.setAttribute('aria-expanded', 'false');
-    }
+    for (const el of els) close(el);
   }
 
   // children of multi-panel should always be even number (heading/content pair)
   private _childrenChange() {
-    let preserveTabIndex : boolean = false;
+    let preserveTabIndex = false;
     let heading = this.firstElementChild;
 
     while (heading) {

src/components/compress/custom-els/MultiPanel/styles.css

@@ -1,11 +1,10 @@
 .panel-heading {
-  background:gray;
+  background: gray;
 }
 .panel-content {
-  height:0px;
-  overflow:scroll;
-  transition: height 1s;
+  height: 0px;
+  overflow: auto;
 }
 .panel-content[expanded] {
-  height:auto;
+  height: auto;
 }

src/components/compress/style.scss

@@ -9,10 +9,6 @@
 
   @media (min-width: 600px) {
     grid-template-columns: 1fr auto;
-    grid-template-rows: calc(100% - 75px);
-  }
-
-  @media (min-width: 860px) {
     grid-template-rows: 100%;
   }
 }
@@ -21,19 +17,23 @@
   color: #fff;
   opacity: 0.9;
   font-size: 1.2rem;
-  max-height: 100%;
   display: flex;
   flex-flow: column;
   max-width: 400px;
   margin: 0 auto;
   width: calc(100% - 60px);
   max-height: calc(100% - 143px);
+  overflow: hidden;
 
   @media (min-width: 600px) {
-    max-height: none;
+    max-height: calc(100% - 75px);
     width: 300px;
     margin: 0;
   }
+
+  @media (min-width: 860px) {
+    max-height: none;
+  }
 }
 
 .multi-panel {

src/components/expander/index.tsx

@@ -1,6 +1,6 @@
 import { h, Component, ComponentChild, ComponentChildren } from 'preact';
 import * as style from './style.scss';
-import { linkRef } from '../../lib/initial-util';
+import { transitionHeight } from '../../lib/util';
 
 interface Props {
   children: ComponentChildren;
@@ -13,7 +13,6 @@ export default class Expander extends Component<Props, State> {
   state: State = {
     outgoingChildren: [],
   };
-  private el?: HTMLDivElement;
   private lastElHeight: number = 0;
 
   componentWillReceiveProps(nextProps: Props) {
@@ -32,10 +31,10 @@ export default class Expander extends Component<Props, State> {
 
     // Only interested if going from empty to not-empty, or not-empty to empty.
     if ((children[0] && nextChildren[0]) || (!children[0] && !nextChildren[0])) return;
-    this.lastElHeight = this.el!.getBoundingClientRect().height;
+    this.lastElHeight = this.base!.getBoundingClientRect().height;
   }
 
-  componentDidUpdate(previousProps: Props) {
+  async componentDidUpdate(previousProps: Props) {
     const children = this.props.children as ComponentChild[];
     const previousChildren = previousProps.children as ComponentChild[];
 
@@ -43,37 +42,20 @@ export default class Expander extends Component<Props, State> {
     if ((children[0] && previousChildren[0]) || (!children[0] && !previousChildren[0])) return;
 
     // What height do we need to transition to?
-    this.el!.style.transition = 'none';
-    this.el!.style.height = '';
-    const newHeight = children[0] ? this.el!.getBoundingClientRect().height : 0;
+    this.base!.style.height = '';
+    this.base!.style.overflow = 'hidden';
+    const newHeight = children[0] ? this.base!.getBoundingClientRect().height : 0;
 
-    if (this.lastElHeight === newHeight) {
-      this.el!.style.transition = '';
-      return;
-    }
+    await transitionHeight(this.base!, {
+      duration: 300,
+      from: this.lastElHeight,
+      to: newHeight,
+    });
 
-    // Set the currently rendered height absolutely.
-    this.el!.style.height = this.lastElHeight + 'px';
-    this.el!.style.transition = '';
-    this.el!.style.overflow = 'hidden';
-    // Force a style calc so the browser picks up the start value.
-    getComputedStyle(this.el!).height;
-    // Animate to the new height.
-    this.el!.style.height = newHeight + 'px';
-
-    const listener = () => {
-      // Unset the height & overflow, so element changes do the right thing.
-      this.el!.style.height = '';
-      this.el!.style.overflow = '';
-      this.el!.removeEventListener('transitionend', listener);
-      this.el!.removeEventListener('transitioncancel', listener);
-      if (this.state.outgoingChildren[0]) {
-        this.setState({ outgoingChildren: [] });
-      }
-    };
-
-    this.el!.addEventListener('transitionend', listener);
-    this.el!.addEventListener('transitioncancel', listener);
+    // Unset the height & overflow, so element changes do the right thing.
+    this.base!.style.height = '';
+    this.base!.style.overflow = '';
+    if (this.state.outgoingChildren[0]) this.setState({ outgoingChildren: [] });
   }
 
   render(props: Props, { outgoingChildren }: State) {
@@ -81,10 +63,7 @@ export default class Expander extends Component<Props, State> {
     const childrenExiting = !children[0] && outgoingChildren[0];
 
     return (
-      <div
-        ref={linkRef(this, 'el')}
-        class={`${style.expander} ${childrenExiting ? style.childrenExiting : ''}`}
-      >
+      <div class={childrenExiting ? style.childrenExiting : ''}>
         {children[0] ? children : outgoingChildren}
       </div>
     );

src/components/expander/style.scss

@@ -1,7 +1,3 @@
-.expander {
-  transition: height 200ms ease-in-out;
-}
-
 .children-exiting {
   & > * {
     pointer-events: none;

src/lib/util.ts

@@ -258,3 +258,43 @@ export function konami(): Promise<void> {
     window.addEventListener('keydown', listener);
   });
 }
+
+interface TransitionOptions {
+  from?: number;
+  to?: number;
+  duration?: number;
+  easing?: string;
+}
+
+export async function transitionHeight(el: HTMLElement, opts: TransitionOptions): Promise<void> {
+  const {
+    from = el.getBoundingClientRect().height,
+    to = el.getBoundingClientRect().height,
+    duration = 1000,
+    easing = 'ease-in-out',
+  } = opts;
+
+  if (from === to || duration === 0) {
+    el.style.height = to + 'px';
+    return;
+  }
+
+  el.style.height = from + 'px';
+  el.style.transition = `height ${duration}ms ${easing}`;
+  // Force a style calc so the browser picks up the start value.
+  getComputedStyle(el).height;
+  el.style.height = to + 'px';
+
+  return new Promise<void>((resolve) => {
+    const listener = (event: Event) => {
+      if (event.target !== el) return;
+      el.style.transition = '';
+      el.removeEventListener('transitionend', listener);
+      el.removeEventListener('transitioncancel', listener);
+      resolve();
+    };
+
+    el.addEventListener('transitionend', listener);
+    el.addEventListener('transitioncancel', listener);
+  });
+}