paper-tabs.html

<!--
@license
Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->

<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-flex-layout/iron-flex-layout.html">
<link rel="import" href="../iron-icon/iron-icon.html">
<link rel="import" href="../iron-menu-behavior/iron-menubar-behavior.html">
<link rel="import" href="../iron-resizable-behavior/iron-resizable-behavior.html">
<link rel="import" href="../paper-icon-button/paper-icon-button.html">
<link rel="import" href="../paper-styles/color.html">
<link rel="import" href="paper-tabs-icons.html">
<link rel="import" href="paper-tab.html">

<!--
Material design: [Tabs](https://www.google.com/design/spec/components/tabs.html)

`paper-tabs` makes it easy to explore and switch between different views or functional aspects of
an app, or to browse categorized data sets.

Use `selected` property to get or set the selected tab.

Example:

    <paper-tabs selected="0">
      <paper-tab>TAB 1</paper-tab>
      <paper-tab>TAB 2</paper-tab>
      <paper-tab>TAB 3</paper-tab>
    </paper-tabs>

See <a href="?active=paper-tab">paper-tab</a> for more information about
`paper-tab`.

A common usage for `paper-tabs` is to use it along with `iron-pages` to switch
between different views.

    <paper-tabs selected="{{selected}}">
      <paper-tab>Tab 1</paper-tab>
      <paper-tab>Tab 2</paper-tab>
      <paper-tab>Tab 3</paper-tab>
    </paper-tabs>

    <iron-pages selected="{{selected}}">
      <div>Page 1</div>
      <div>Page 2</div>
      <div>Page 3</div>
    </iron-pages>


To use links in tabs, add `link` attribute to `paper-tab` and put an `<a>`
element in `paper-tab` with a `tabindex` of -1.

Example:

<pre><code>
&lt;style is="custom-style">
  .link {
    &#64;apply --layout-horizontal;
    &#64;apply --layout-center-center;
  }
&lt;/style>

&lt;paper-tabs selected="0">
  &lt;paper-tab link>
    &lt;a href="#link1" class="link" tabindex="-1">TAB ONE&lt;/a>
  &lt;/paper-tab>
  &lt;paper-tab link>
    &lt;a href="#link2" class="link" tabindex="-1">TAB TWO&lt;/a>
  &lt;/paper-tab>
  &lt;paper-tab link>
    &lt;a href="#link3" class="link" tabindex="-1">TAB THREE&lt;/a>
  &lt;/paper-tab>
&lt;/paper-tabs>
</code></pre>

### Styling

The following custom properties and mixins are available for styling:

Custom property | Description | Default
----------------|-------------|----------
`--paper-tabs-selection-bar-color` | Color for the selection bar | `--paper-yellow-a100`
`--paper-tabs-selection-bar` | Mixin applied to the selection bar | `{}`
`--paper-tabs` | Mixin applied to the tabs | `{}`
`--paper-tabs-content` | Mixin applied to the content container of tabs | `{}`
`--paper-tabs-container` | Mixin applied to the layout container of tabs | `{}`
`--paper-tabs-scroll-buttons` | Mixin applied to the scroll buttons | `{}`
`--paper-tabs-scroll-button-left` | Mixin applied to the left scroll button | `{}`
`--paper-tabs-scroll-button-right` | Mixin applied to the right scroll button | `{}`

@hero hero.svg
@demo demo/index.html
-->

<dom-module id="paper-tabs">
  <template>
    <style>
      :host {
        @apply --layout;
        @apply --layout-center;

        height: 48px;
        font-size: 14px;
        font-weight: 500;
        overflow: hidden;
        -moz-user-select: none;
        -ms-user-select: none;
        -webkit-user-select: none;
        user-select: none;

        /* NOTE: Both values are needed, since some phones require the value to be `transparent`. */
        -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
        -webkit-tap-highlight-color: transparent;

        @apply --paper-tabs;
      }

      :host-context([dir=rtl]) {
        @apply --layout-horizontal-reverse;
      }

      #tabsContainer {
        position: relative;
        height: 100%;
        white-space: nowrap;
        overflow: hidden;
        @apply --layout-flex-auto;
        @apply --paper-tabs-container;
      }

      #tabsContent {
        height: 100%;
        -moz-flex-basis: auto;
        -ms-flex-basis: auto;
        flex-basis: auto;
        @apply --paper-tabs-content;
      }

      #tabsContent.scrollable {
        position: absolute;
        white-space: nowrap;
      }

      #tabsContent:not(.scrollable),
      #tabsContent.scrollable.fit-container {
        @apply --layout-horizontal;
      }

      #tabsContent.scrollable.fit-container {
        min-width: 100%;
      }

      #tabsContent.scrollable.fit-container > ::slotted(*) {
        /* IE - prevent tabs from compressing when they should scroll. */
        -ms-flex: 1 0 auto;
        -webkit-flex: 1 0 auto;
        flex: 1 0 auto;
      }

      .hidden {
        display: none;
      }

      .not-visible {
        opacity: 0;
        cursor: default;
      }

      paper-icon-button {
        width: 48px;
        height: 48px;
        padding: 12px;
        margin: 0 4px;
      }

      #selectionBar {
        position: absolute;
        height: 0;
        bottom: 0;
        left: 0;
        right: 0;
        border-bottom: 2px solid var(--paper-tabs-selection-bar-color, var(--paper-yellow-a100));
          -webkit-transform: scale(0);
        transform: scale(0);
          -webkit-transform-origin: left center;
        transform-origin: left center;
          transition: -webkit-transform;
        transition: transform;

        @apply --paper-tabs-selection-bar;
      }

      #selectionBar.align-bottom {
        top: 0;
        bottom: auto;
      }

      #selectionBar.expand {
        transition-duration: 0.15s;
        transition-timing-function: cubic-bezier(0.4, 0.0, 1, 1);
      }

      #selectionBar.contract {
        transition-duration: 0.18s;
        transition-timing-function: cubic-bezier(0.0, 0.0, 0.2, 1);
      }

      #tabsContent > ::slotted(:not(#selectionBar)) {
        height: 100%;
      }

      paper-icon-button {
        @apply --paper-tabs-scroll-buttons;
      }

      #scroll-button-left {
        @apply --paper-tabs-scroll-button-left;
      }

      #scroll-button-right {
        @apply --paper-tabs-scroll-button-right;
      }
    </style>

    <paper-icon-button id="scroll-button-left" icon="paper-tabs:chevron-left" class$="[[_computeScrollButtonClass(_leftHidden, scrollable, hideScrollButtons)]]" on-up="_onScrollButtonUp" on-down="_onLeftScrollButtonDown" tabindex="-1"></paper-icon-button>

    <div id="tabsContainer" on-track="_scroll" on-down="_down">
      <div id="tabsContent" class$="[[_computeTabsContentClass(scrollable, fitContainer)]]">
        <div id="selectionBar" class$="[[_computeSelectionBarClass(noBar, alignBottom)]]"
            on-transitionend="_onBarTransitionEnd"></div>
        <slot></slot>
      </div>
    </div>

    <paper-icon-button id="scroll-button-right" icon="paper-tabs:chevron-right" class$="[[_computeScrollButtonClass(_rightHidden, scrollable, hideScrollButtons)]]" on-up="_onScrollButtonUp" on-down="_onRightScrollButtonDown" tabindex="-1"></paper-icon-button>

  </template>

  <script>
    Polymer({
      is: 'paper-tabs',

      behaviors: [
        Polymer.IronResizableBehavior,
        Polymer.IronMenubarBehavior
      ],

      properties: {
        /**
         * If true, ink ripple effect is disabled. When this property is changed,
         * all descendant `<paper-tab>` elements have their `noink` property
         * changed to the new value as well.
         */
        noink: {
          type: Boolean,
          value: false,
          observer: '_noinkChanged'
        },

        /**
         * If true, the bottom bar to indicate the selected tab will not be shown.
         */
        noBar: {
          type: Boolean,
          value: false
        },

        /**
         * If true, the slide effect for the bottom bar is disabled.
         */
        noSlide: {
          type: Boolean,
          value: false
        },

        /**
         * If true, tabs are scrollable and the tab width is based on the label width.
         */
        scrollable: {
          type: Boolean,
          value: false
        },

        /**
         * If true, tabs expand to fit their container. This currently only applies when
         * scrollable is true.
         */
        fitContainer: {
          type: Boolean,
          value: false
        },

        /**
         * If true, dragging on the tabs to scroll is disabled.
         */
        disableDrag: {
          type: Boolean,
          value: false
        },

        /**
         * If true, scroll buttons (left/right arrow) will be hidden for scrollable tabs.
         */
        hideScrollButtons: {
          type: Boolean,
          value: false
        },

        /**
         * If true, the tabs are aligned to bottom (the selection bar appears at the top).
         */
        alignBottom: {
          type: Boolean,
          value: false
        },

        selectable: {
          type: String,
          value: 'paper-tab'
        },

        /**
         * If true, tabs are automatically selected when focused using the
         * keyboard.
         */
        autoselect: {
          type: Boolean,
          value: false
        },

        /**
         * The delay (in milliseconds) between when the user stops interacting
         * with the tabs through the keyboard and when the focused item is
         * automatically selected (if `autoselect` is true).
         */
        autoselectDelay: {
          type: Number,
          value: 0
        },

        _step: {
          type: Number,
          value: 10
        },

        _holdDelay: {
          type: Number,
          value: 1
        },

        _leftHidden: {
          type: Boolean,
          value: false
        },

        _rightHidden: {
          type: Boolean,
          value: false
        },

        _previousTab: {
          type: Object
        }
      },

      hostAttributes: {
        role: 'tablist'
      },

      listeners: {
        'iron-resize': '_onTabSizingChanged',
        'iron-items-changed': '_onTabSizingChanged',
        'iron-select': '_onIronSelect',
        'iron-deselect': '_onIronDeselect'
      },

      keyBindings: {
        'left:keyup right:keyup': '_onArrowKeyup'
      },

      created: function() {
        this._holdJob = null;
        this._pendingActivationItem = undefined;
        this._pendingActivationTimeout = undefined;
        this._bindDelayedActivationHandler = this._delayedActivationHandler.bind(this);
        this.addEventListener('blur', this._onBlurCapture.bind(this), true);
      },

      ready: function() {
        this.setScrollDirection('y', this.$.tabsContainer);
      },

      detached: function() {
        this._cancelPendingActivation();
      },

      _noinkChanged: function(noink) {
        var childTabs = Polymer.dom(this).querySelectorAll('paper-tab');
        childTabs.forEach(noink ? this._setNoinkAttribute : this._removeNoinkAttribute);
      },

      _setNoinkAttribute: function(element) {
        element.setAttribute('noink', '');
      },

      _removeNoinkAttribute: function(element) {
        element.removeAttribute('noink');
      },

      _computeScrollButtonClass: function(hideThisButton, scrollable, hideScrollButtons) {
        if (!scrollable || hideScrollButtons) {
          return 'hidden';
        }

        if (hideThisButton) {
          return 'not-visible';
        }

        return '';
      },

      _computeTabsContentClass: function(scrollable, fitContainer) {
        return scrollable ? 'scrollable' + (fitContainer ? ' fit-container' : '') : ' fit-container';
      },

      _computeSelectionBarClass: function(noBar, alignBottom) {
        if (noBar) {
          return 'hidden';
        } else if (alignBottom) {
          return 'align-bottom';
        }

        return '';
      },

      // TODO(cdata): Add `track` response back in when gesture lands.

      _onTabSizingChanged: function() {
        this.debounce('_onTabSizingChanged', function() {
          this._scroll();
          this._tabChanged(this.selectedItem);
        }, 10);
      },

      _onIronSelect: function(event) {
        this._tabChanged(event.detail.item, this._previousTab);
        this._previousTab = event.detail.item;
        this.cancelDebouncer('tab-changed');
      },

      _onIronDeselect: function(event) {
        this.debounce('tab-changed', function() {
          this._tabChanged(null, this._previousTab);
          this._previousTab = null;
        // See polymer/polymer#1305
        }, 1);
      },

      _activateHandler: function() {
        // Cancel item activations scheduled by keyboard events when any other
        // action causes an item to be activated (e.g. clicks).
        this._cancelPendingActivation();

        Polymer.IronMenuBehaviorImpl._activateHandler.apply(this, arguments);
      },

      /**
       * Activates an item after a delay (in milliseconds).
       */
      _scheduleActivation: function(item, delay) {
        this._pendingActivationItem = item;
        this._pendingActivationTimeout = this.async(
            this._bindDelayedActivationHandler, delay);
      },

      /**
       * Activates the last item given to `_scheduleActivation`.
       */
      _delayedActivationHandler: function() {
        var item = this._pendingActivationItem;
        this._pendingActivationItem = undefined;
        this._pendingActivationTimeout = undefined;
        item.fire(this.activateEvent, null, {
          bubbles: true,
          cancelable: true
        });
      },

      /**
       * Cancels a previously scheduled item activation made with
       * `_scheduleActivation`.
       */
      _cancelPendingActivation: function() {
        if (this._pendingActivationTimeout !== undefined) {
          this.cancelAsync(this._pendingActivationTimeout);
          this._pendingActivationItem = undefined;
          this._pendingActivationTimeout = undefined;
        }
      },

      _onArrowKeyup: function(event) {
        if (this.autoselect) {
          this._scheduleActivation(this.focusedItem, this.autoselectDelay);
        }
      },

      _onBlurCapture: function(event) {
        // Cancel a scheduled item activation (if any) when that item is
        // blurred.
        if (event.target === this._pendingActivationItem) {
          this._cancelPendingActivation();
        }
      },

      get _tabContainerScrollSize () {
        return Math.max(
          0,
          this.$.tabsContainer.scrollWidth -
            this.$.tabsContainer.offsetWidth
        );
      },

      _scroll: function(e, detail) {
        if (!this.scrollable) {
          return;
        }

        var ddx = (detail && -detail.ddx) || 0;
        this._affectScroll(ddx);
      },

      _down: function(e) {
        // go one beat async to defeat IronMenuBehavior
        // autorefocus-on-no-selection timeout
        this.async(function() {
          if (this._defaultFocusAsync) {
            this.cancelAsync(this._defaultFocusAsync);
            this._defaultFocusAsync = null;
          }
        }, 1);
      },

      _affectScroll: function(dx) {
        this.$.tabsContainer.scrollLeft += dx;

        var scrollLeft = this.$.tabsContainer.scrollLeft;

        this._leftHidden = scrollLeft === 0;
        this._rightHidden = scrollLeft === this._tabContainerScrollSize;
      },

      _onLeftScrollButtonDown: function() {
        this._scrollToLeft();
        this._holdJob = setInterval(this._scrollToLeft.bind(this), this._holdDelay);
      },

      _onRightScrollButtonDown: function() {
        this._scrollToRight();
        this._holdJob = setInterval(this._scrollToRight.bind(this), this._holdDelay);
      },

      _onScrollButtonUp: function() {
        clearInterval(this._holdJob);
        this._holdJob = null;
      },

      _scrollToLeft: function() {
        this._affectScroll(-this._step);
      },

      _scrollToRight: function() {
        this._affectScroll(this._step);
      },

      _tabChanged: function(tab, old) {
        if (!tab) {
          // Remove the bar without animation.
          this.$.selectionBar.classList.remove('expand');
          this.$.selectionBar.classList.remove('contract');
          this._positionBar(0, 0);
          return;
        }

        var r = this.$.tabsContent.getBoundingClientRect();
        var w = r.width;
        var tabRect = tab.getBoundingClientRect();
        var tabOffsetLeft = tabRect.left - r.left;

        this._pos = {
          width: this._calcPercent(tabRect.width, w),
          left: this._calcPercent(tabOffsetLeft, w)
        };

        if (this.noSlide || old == null) {
          // Position the bar without animation.
          this.$.selectionBar.classList.remove('expand');
          this.$.selectionBar.classList.remove('contract');
          this._positionBar(this._pos.width, this._pos.left);
          return;
        }

        var oldRect = old.getBoundingClientRect();
        var oldIndex = this.items.indexOf(old);
        var index = this.items.indexOf(tab);
        var m = 5;

        // bar animation: expand
        this.$.selectionBar.classList.add('expand');

        var moveRight = oldIndex < index;
        var isRTL = this._isRTL;
        if (isRTL) {
          moveRight = !moveRight;
        }

        if (moveRight) {
          this._positionBar(this._calcPercent(tabRect.left + tabRect.width - oldRect.left, w) - m,
              this._left);
        } else {
          this._positionBar(this._calcPercent(oldRect.left + oldRect.width - tabRect.left, w) - m,
              this._calcPercent(tabOffsetLeft, w) + m);
        }

        if (this.scrollable) {
          this._scrollToSelectedIfNeeded(tabRect.width, tabOffsetLeft);
        }
      },

      _scrollToSelectedIfNeeded: function(tabWidth, tabOffsetLeft) {
        var l = tabOffsetLeft - this.$.tabsContainer.scrollLeft;
        if (l < 0) {
          this.$.tabsContainer.scrollLeft += l;
        } else {
          l += (tabWidth - this.$.tabsContainer.offsetWidth);
          if (l > 0) {
            this.$.tabsContainer.scrollLeft += l;
          }
        }
      },

      _calcPercent: function(w, w0) {
        return 100 * w / w0;
      },

      _positionBar: function(width, left) {
        width = width || 0;
        left = left || 0;

        this._width = width;
        this._left = left;
        this.transform(
            'translateX(' + left + '%) scaleX(' + (width / 100) + ')',
            this.$.selectionBar);
      },

      _onBarTransitionEnd: function(e) {
        var cl = this.$.selectionBar.classList;
        // bar animation: expand -> contract
        if (cl.contains('expand')) {
          cl.remove('expand');
          cl.add('contract');
          this._positionBar(this._pos.width, this._pos.left);
        // bar animation done
        } else if (cl.contains('contract')) {
          cl.remove('contract');
        }
      }
    });
  </script>
</dom-module>