@polymer/paper-dropdown-menu
Version:
An element that works similarly to a native browser select
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JavaScript
/**
@license
Copyright (c) 2016 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
*/
import '@polymer/polymer/polymer-legacy.js';
import '@polymer/iron-a11y-keys-behavior/iron-a11y-keys-behavior.js';
import '@polymer/iron-icon/iron-icon.js';
import '@polymer/paper-menu-button/paper-menu-button.js';
import '@polymer/paper-styles/default-theme.js';
import './paper-dropdown-menu-icons.js';
import './paper-dropdown-menu-shared-styles.js';
import {IronButtonState} from '@polymer/iron-behaviors/iron-button-state.js';
import {IronControlState} from '@polymer/iron-behaviors/iron-control-state.js';
import {IronFormElementBehavior} from '@polymer/iron-form-element-behavior/iron-form-element-behavior.js';
import {IronValidatableBehavior} from '@polymer/iron-validatable-behavior/iron-validatable-behavior.js';
import {PaperRippleBehavior} from '@polymer/paper-behaviors/paper-ripple-behavior.js';
import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
import {Polymer} from '@polymer/polymer/lib/legacy/polymer-fn.js';
import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
import * as gestures from '@polymer/polymer/lib/utils/gestures.js';
import {html} from '@polymer/polymer/lib/utils/html-tag.js';
import {wrap} from '@polymer/polymer/lib/utils/wrap.js';
// LegacyElementMixin dedupes and this is the base class for elements created
// with the `Polymer` function, so this is only a cache lookup.
// https://github.com/Polymer/polymer/blob/640bc80ac7177b761d46b2fa9c455c318f2b85c6/lib/legacy/class.js#L533-L534
const LegacyPolymerElementBase = LegacyElementMixin(HTMLElement);
/**
Material design: [Dropdown
menus](https://www.google.com/design/spec/components/buttons.html#buttons-dropdown-buttons)
This is a faster, lighter version of `paper-dropdown-menu`, that does not
use a `<paper-input>` internally. Use this element if you're concerned about
the performance of this element, i.e., if you plan on using many dropdowns on
the same page. Note that this element has a slightly different styling API
than `paper-dropdown-menu`.
`paper-dropdown-menu-light` is similar to a native browser select element.
`paper-dropdown-menu-light` works with selectable content. The currently
selected item is displayed in the control. If no item is selected, the `label`
is displayed instead.
Example:
<paper-dropdown-menu-light label="Your favourite pastry">
<paper-listbox slot="dropdown-content">
<paper-item>Croissant</paper-item>
<paper-item>Donut</paper-item>
<paper-item>Financier</paper-item>
<paper-item>Madeleine</paper-item>
</paper-listbox>
</paper-dropdown-menu-light>
This example renders a dropdown menu with 4 options.
The child element with the slot `dropdown-content` is used as the dropdown
menu. This can be a [`paper-listbox`](paper-listbox), or any other or
element that acts like an [`iron-selector`](iron-selector).
Specifically, the menu child must fire an
[`iron-select`](iron-selector#event-iron-select) event when one of its
children is selected, and an
[`iron-deselect`](iron-selector#event-iron-deselect) event when a child is
deselected. The selected or deselected item must be passed as the event's
`detail.item` property.
Applications can listen for the `iron-select` and `iron-deselect` events
to react when options are selected and deselected.
### Styling
The following custom properties and mixins are also available for styling:
Custom property | Description | Default
----------------|-------------|----------
`--paper-dropdown-menu` | A mixin that is applied to the element host | `{}`
`--paper-dropdown-menu-disabled` | A mixin that is applied to the element host when disabled | `{}`
`--paper-dropdown-menu-ripple` | A mixin that is applied to the internal ripple | `{}`
`--paper-dropdown-menu-button` | A mixin that is applied to the internal menu button | `{}`
`--paper-dropdown-menu-icon` | A mixin that is applied to the internal icon | `{}`
`--paper-dropdown-menu-disabled-opacity` | The opacity of the dropdown when disabled | `0.33`
`--paper-dropdown-menu-color` | The color of the input/label/underline when the dropdown is unfocused | `--primary-text-color`
`--paper-dropdown-menu-focus-color` | The color of the label/underline when the dropdown is focused | `--primary-color`
`--paper-dropdown-error-color` | The color of the label/underline when the dropdown is invalid | `--error-color`
`--paper-dropdown-menu-label` | Mixin applied to the label | `{}`
`--paper-dropdown-menu-input` | Mixin applied to the input | `{}`
`--paper-dropdown-menu-underline-focus` | Mixin applied to the focus underline | `{}`
Note that in this element, the underline is just the bottom border of the
"input". To style it:
<style is=custom-style>
paper-dropdown-menu-light.custom {
--paper-dropdown-menu-input: {
border-bottom: 2px dashed lavender;
};
</style>
@element paper-dropdown-menu-light
@demo demo/index.html
*/
Polymer({
/** @override */
_template: html`
<style include="paper-dropdown-menu-shared-styles">
:host {
width: 200px; /* Default size of an <input> */
}
/**
* All of these styles below are for styling the fake-input display
*/
[slot="dropdown-trigger"] {
box-sizing: border-box;
position: relative;
width: 100%;
padding: 16px 0 8px 0;
}
[slot="dropdown-trigger"]:focus {
outline: none;
}
:host([disabled]) [slot="dropdown-trigger"] {
pointer-events: none;
opacity: var(--paper-dropdown-menu-disabled-opacity, 0.33);
}
:host([no-label-float]) [slot="dropdown-trigger"] {
padding-top: 8px; /* If there's no label, we need less space up top. */
}
#input {
@apply --paper-font-subhead;
@apply --paper-font-common-nowrap;
line-height: 1.5;
border-bottom: 1px solid var(--paper-dropdown-menu-color, var(--secondary-text-color));
color: var(--paper-dropdown-menu-color, var(--primary-text-color));
width: 100%;
box-sizing: border-box;
padding: 12px 20px 0 0; /* Right padding so that text doesn't overlap the icon */
outline: none;
@apply --paper-dropdown-menu-input;
}
#input:dir(rtl) {
padding-right: 0px;
padding-left: 20px;
}
:host([disabled]) #input {
border-bottom: 1px dashed var(--paper-dropdown-menu-color, var(--secondary-text-color));
}
:host([invalid]) #input {
border-bottom: 2px solid var(--paper-dropdown-error-color, var(--error-color));
}
:host([no-label-float]) #input {
padding-top: 0; /* If there's no label, we need less space up top. */
}
label {
@apply --paper-font-subhead;
@apply --paper-font-common-nowrap;
display: block;
position: absolute;
bottom: 0;
left: 0;
right: 0;
/**
* The container has a 16px top padding, and there's 12px of padding
* between the input and the label (from the input's padding-top)
*/
top: 28px;
box-sizing: border-box;
width: 100%;
padding-right: 20px; /* Right padding so that text doesn't overlap the icon */
text-align: left;
transition-duration: .2s;
transition-timing-function: cubic-bezier(.4,0,.2,1);
color: var(--paper-dropdown-menu-color, var(--secondary-text-color));
@apply --paper-dropdown-menu-label;
}
label:dir(rtl) {
padding-right: 0px;
padding-left: 20px;
text-align: right;
}
:host([no-label-float]) label {
top: 8px;
/* Since the label doesn't need to float, remove the animation duration
which slows down visibility changes (i.e. when a selection is made) */
transition-duration: 0s;
}
label.label-is-floating {
font-size: 12px;
top: 8px;
}
label.label-is-hidden {
visibility: hidden;
}
:host([focused]) label.label-is-floating {
color: var(--paper-dropdown-menu-focus-color, var(--primary-color));
}
:host([invalid]) label.label-is-floating {
color: var(--paper-dropdown-error-color, var(--error-color));
}
/**
* Sets up the focused underline. It's initially hidden, and becomes
* visible when it's focused.
*/
label:after {
background-color: var(--paper-dropdown-menu-focus-color, var(--primary-color));
bottom: 7px; /* The container has an 8px bottom padding */
content: '';
height: 2px;
left: 45%;
position: absolute;
transition-duration: .2s;
transition-timing-function: cubic-bezier(.4,0,.2,1);
visibility: hidden;
width: 8px;
z-index: 10;
@apply --paper-dropdown-menu-underline-focus;
}
:host([invalid]) label:after {
background-color: var(--paper-dropdown-error-color, var(--error-color));
}
:host([no-label-float]) label:after {
bottom: 7px; /* The container has a 8px bottom padding */
}
:host([focused]:not([disabled])) label:after {
left: 0;
visibility: visible;
width: 100%;
}
iron-icon {
position: absolute;
right: 0px;
bottom: 8px; /* The container has an 8px bottom padding */
@apply --paper-font-subhead;
color: var(--disabled-text-color);
@apply --paper-dropdown-menu-icon;
}
iron-icon:dir(rtl) {
left: 0;
right: auto;
}
:host([no-label-float]) iron-icon {
margin-top: 0px;
}
.error {
display: inline-block;
visibility: hidden;
color: var(--paper-dropdown-error-color, var(--error-color));
@apply --paper-font-caption;
position: absolute;
left:0;
right:0;
bottom: -12px;
}
:host([invalid]) .error {
visibility: visible;
}
</style>
<paper-menu-button id="menuButton" vertical-align="[[verticalAlign]]" horizontal-align="[[horizontalAlign]]" vertical-offset="[[_computeMenuVerticalOffset(noLabelFloat, verticalOffset)]]" disabled="[[disabled]]" no-animations="[[noAnimations]]" on-iron-select="_onIronSelect" on-iron-deselect="_onIronDeselect" opened="{{opened}}" close-on-activate allow-outside-scroll="[[allowOutsideScroll]]">
<!-- support hybrid mode: user might be using paper-menu-button 1.x which distributes via <content> -->
<div id="dropdown-trigger" class="dropdown-trigger" slot="dropdown-trigger" role="button" tabindex="0" aria-haspopup="listbox">
<label class$="[[_computeLabelClass(noLabelFloat,alwaysFloatLabel,hasContent)]]">
[[label]]
</label>
<div id="input" tabindex="-1"> </div>
<iron-icon icon="paper-dropdown-menu:arrow-drop-down"></iron-icon>
<span class="error">[[errorMessage]]</span>
</div>
<slot id="content" name="dropdown-content" slot="dropdown-content"></slot>
</paper-menu-button>
`,
is: 'paper-dropdown-menu-light',
behaviors: [
IronButtonState,
IronControlState,
PaperRippleBehavior,
IronFormElementBehavior,
IronValidatableBehavior
],
properties: {
/**
* The derived "label" of the currently selected item. This value
* is the `label` property on the selected item if set, or else the
* trimmed text content of the selected item.
*/
selectedItemLabel: {type: String, notify: true, readOnly: true},
/**
* The last selected item. An item is selected if the dropdown menu has
* a child with class `dropdown-content`, and that child triggers an
* `iron-select` event with the selected `item` in the `detail`.
*
* @type {?Object}
*/
selectedItem: {type: Object, notify: true, readOnly: true},
/**
* The value for this element that will be used when submitting in
* a form. It reflects the value of `selectedItemLabel`. If set directly,
* it will not update the `selectedItemLabel` value.
*/
value: {
type: String,
notify: true,
observer: '_valueChanged',
},
/**
* The label for the dropdown.
*/
label: {type: String},
/**
* The placeholder for the dropdown.
*/
placeholder: {type: String},
/**
* True if the dropdown is open. Otherwise, false.
*/
opened:
{type: Boolean, notify: true, value: false, observer: '_openedChanged'},
/**
* By default, the dropdown will constrain scrolling on the page
* to itself when opened.
* Set to true in order to prevent scroll from being constrained
* to the dropdown when it opens.
*/
allowOutsideScroll: {type: Boolean, value: false},
/**
* Set to true to disable the floating label. Bind this to the
* `<paper-input-container>`'s `noLabelFloat` property.
*/
noLabelFloat: {type: Boolean, value: false, reflectToAttribute: true},
/**
* Set to true to always float the label. Bind this to the
* `<paper-input-container>`'s `alwaysFloatLabel` property.
*/
alwaysFloatLabel: {type: Boolean, value: false},
/**
* Set to true to disable animations when opening and closing the
* dropdown.
*/
noAnimations: {type: Boolean, value: false},
/**
* The orientation against which to align the menu dropdown
* horizontally relative to the dropdown trigger.
*/
horizontalAlign: {type: String, value: 'right'},
/**
* The orientation against which to align the menu dropdown
* vertically relative to the dropdown trigger.
*/
verticalAlign: {type: String, value: 'top'},
/**
* Overrides the vertical offset computed in
* _computeMenuVerticalOffset.
*/
verticalOffset: Number,
hasContent: {type: Boolean, readOnly: true}
},
listeners: {'tap': '_onTap'},
/**
* @type {!Object}
*/
keyBindings: {'up down': 'open', 'esc': 'close'},
observers: ['_selectedItemChanged(selectedItem)'],
/**
* Override `_attachDom` so that we can pass `delegatesFocus`. The overridden
* implementation of `_attachDom` specifically skips the steps performed here
* if the node already hosts a shadow root:
* https://github.com/Polymer/polymer/blob/640bc80ac7177b761d46b2fa9c455c318f2b85c6/lib/mixins/element-mixin.js#L691-L694
* @override
*/
_attachDom(dom) {
const wrappedThis = wrap(this);
wrappedThis.attachShadow({
mode: 'open',
delegatesFocus: true,
shadyUpgradeFragment: dom,
});
wrappedThis.shadowRoot.appendChild(dom);
return LegacyPolymerElementBase.prototype._attachDom.call(this, dom);
},
/** @override */
focus() {
// When using Shady DOM and in browsers that don't support
// `delegatesFocus`, attempting to focus this element with the browser's
// native `HTMLElement#focus` will cause focus to be lost because this
// element isn't focusable in those situations. To work around this, the
// element in the shadow root that this element intends to delegate focus
// to is manually focused instead.
this.$['dropdown-trigger'].focus();
},
/** @override */
attached: function() {
// NOTE(cdata): Due to timing, a preselected value in a `IronSelectable`
// child will cause an `iron-select` event to fire while the element is
// still in a `DocumentFragment`. This has the effect of causing
// handlers not to fire. So, we double check this value on attached:
var contentElement = this.contentElement;
if (contentElement && contentElement.selectedItem) {
this._setSelectedItem(contentElement.selectedItem);
}
},
/**
* The content element that is contained by the dropdown menu, if any.
*/
get contentElement() {
// Polymer 2.x returns slot.assignedNodes which can contain text nodes.
var nodes = dom(this.$.content).getDistributedNodes();
for (var i = 0, l = nodes.length; i < l; i++) {
if (nodes[i].nodeType === Node.ELEMENT_NODE) {
return nodes[i];
}
}
},
/**
* Show the dropdown content.
*/
open: function() {
this.$.menuButton.open();
},
/**
* Hide the dropdown content.
*/
close: function() {
this.$.menuButton.close();
},
/**
* A handler that is called when `iron-select` is fired.
*
* @param {CustomEvent} event An `iron-select` event.
*/
_onIronSelect: function(event) {
this._setSelectedItem(event.detail.item);
},
/**
* A handler that is called when `iron-deselect` is fired.
*
* @param {CustomEvent} event An `iron-deselect` event.
*/
_onIronDeselect: function(event) {
this._setSelectedItem(null);
},
/**
* A handler that is called when the dropdown is tapped.
*
* @param {CustomEvent} event A tap event.
*/
_onTap: function(event) {
if (gestures.findOriginalTarget(event) === this) {
this.open();
}
},
/**
* Compute the label for the dropdown given a selected item.
*
* @param {Element} selectedItem A selected Element item, with an
* optional `label` property.
*/
_selectedItemChanged: function(selectedItem) {
var value = '';
if (!selectedItem) {
value = '';
} else {
value = selectedItem.label || selectedItem.getAttribute('label') ||
selectedItem.textContent.trim();
}
this.value = value;
this._setSelectedItemLabel(value);
},
/**
* Compute the vertical offset of the menu based on the value of
* `noLabelFloat`.
*
* @param {boolean} noLabelFloat True if the label should not float
* @param {number=} opt_verticalOffset Optional offset from the user
* above the input, otherwise false.
*/
_computeMenuVerticalOffset: function(noLabelFloat, opt_verticalOffset) {
// Override offset if it's passed from the user.
if (opt_verticalOffset) {
return opt_verticalOffset;
}
// NOTE(cdata): These numbers are somewhat magical because they are
// derived from the metrics of elements internal to `paper-input`'s
// template. The metrics will change depending on whether or not the
// input has a floating label.
return noLabelFloat ? -4 : 8;
},
/**
* Returns false if the element is required and does not have a selection,
* and true otherwise.
* @param {*=} _value Ignored.
* @return {boolean} true if `required` is false, or if `required` is true
* and the element has a valid selection.
*/
_getValidity: function(_value) {
return this.disabled || !this.required || (this.required && !!this.value);
},
_openedChanged: function() {
var openState = this.opened ? 'true' : 'false';
var e = this.contentElement;
if (e) {
e.setAttribute('aria-expanded', openState);
}
},
_computeLabelClass: function(noLabelFloat, alwaysFloatLabel, hasContent) {
var cls = '';
if (noLabelFloat === true) {
return hasContent ? 'label-is-hidden' : '';
}
if (hasContent || alwaysFloatLabel === true) {
cls += ' label-is-floating';
}
return cls;
},
_valueChanged: function() {
// Only update if it's actually different.
if (this.$.input && this.$.input.textContent !== this.value) {
this.$.input.textContent = this.value;
}
this._setHasContent(!!this.value);
if (!this.hasContent) {
// If there is no content then reset to ' ', which is required
// for the input height to be correct. Uses 'xa0' instead of ' ' to
// avoid innerHTML.
this.$.input.textContent = '\xa0';
}
}
});