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Dropdown Button

<et2-dropdown-button> | Et2DropdownButton

Overview

A split button - a button with a dropdown list

There are several parts to the button UI:

  • Container: This is what is percieved as the dropdown button, the whole package together
    • Button: The part on the left that can be clicked
    • Arrow: The button to display the choices
    • Menu: The list of choices

Menu options are passed via the select_options. They are normally the same as for a select box, but the title can also be full HTML if needed.

Examples

A split button: a button on the left that does the currently selected thing, and an arrow on the right that opens the list of the other things it could do. Use it when there is an obvious default action with a handful of near-identical variations - “Save” with “Save & New” and “Save & Reset” behind it - and a row of separate buttons would be noise.

The choices come from select_options, the same shape a select takes. In a template that is usually <option> children or server-side sel_options; in javascript it is an array of {value, label}.

Options

change fires when a menu entry is picked; click on the main button fires with whatever is currently selected.

Selected: save_new

<et2-dropdown-button id="dropdown-example" label="Save &amp; New"></et2-dropdown-button>
<p>Selected: <span id="dropdown-output">save_new</span></p>
<script>
    const dropdown = document.getElementById("dropdown-example");
    const output = document.getElementById("dropdown-output");
    customElements.whenDefined("et2-dropdown-button").then(() =>
    {
        dropdown.select_options = [
            {value: "save_new", label: "Save & New"},
            {value: "save_reset", label: "Save & Reset"},
            {value: "save_close", label: "Save & Close"}
        ];
    });
    dropdown.addEventListener("change", () => {output.textContent = dropdown.value;});
</script>

Note that picking an option only changes the selection - it does not run the action. The main button is what the user clicks to do the thing, which is why the label follows the selection.

Icons on the options

An option can carry an icon, and a color that tints its row in the menu.

<et2-dropdown-button id="dropdown-icon-example" label="Export"></et2-dropdown-button>
<script>
    const iconDropdown = document.getElementById("dropdown-icon-example");
    customElements.whenDefined("et2-dropdown-button").then(() =>
    {
        iconDropdown.select_options = [
            {value: "csv", label: "Export as CSV", icon: "filetype-csv"},
            {value: "pdf", label: "Export as PDF", icon: "filetype-pdf"},
            {value: "print", label: "Print", icon: "printer"}
        ];
    });
</script>

Icon only

iconOnly drops the text from the main button and shows the selected option’s own icon instead. Useful in a toolbar where the row of buttons has to stay narrow.

It needs something to be selected, or there is nothing to draw and the main button comes up empty. Marking an option default: true is not enough on its own - that flag is only read when defaultPreference is set (see below) - so give the widget a value as well. 

<et2-dropdown-button id="dropdown-icononly-example" iconOnly></et2-dropdown-button>
<script>
    const iconOnlyDropdown = document.getElementById("dropdown-icononly-example");
    customElements.whenDefined("et2-dropdown-button").then(() =>
    {
        iconOnlyDropdown.select_options = [
            {value: "list", label: "List", icon: "list-ul"},
            {value: "grid", label: "Grid", icon: "grid-3x2-gap"},
            {value: "calendar", label: "Calendar", icon: "calendar3"}
        ];
        iconOnlyDropdown.value = "list";
    });
</script>

Remembering the choice

defaultPreference names a preference to store the selection in. The stored value is preselected on the next load, and every pick is written back - so the main button becomes “whatever you did last time” rather than doing nothing useful until the user has opened the menu once. An option marked default: true is the fallback for a user who has never picked anything. 

<et2-dropdown-button id="save_split" defaultPreference="save_new" onclick="app.myapp.save_action" onchange="app.myapp.save_action">
    <option value="save_new" default="save_new">Save &amp; New</option>
    <option value="save_reset">Save &amp; Reset</option>
</et2-dropdown-button>

This one is not a live preview: storing a preference is a round-trip to the server.

Placement

placement moves the menu, for a button near the bottom or the right edge of a dialog. It defaults to bottom-end. 

<et2-dropdown-button id="dropdown-placement-example" label="Menu on top" placement="top-start"></et2-dropdown-button>
<script>
    const placementDropdown = document.getElementById("dropdown-placement-example");
    customElements.whenDefined("et2-dropdown-button").then(() =>
    {
        placementDropdown.select_options = [
            {value: "one", label: "First choice"},
            {value: "two", label: "Second choice"}
        ];
    });
</script>

Disabled

disabled greys out both halves.

<et2-dropdown-button id="dropdown-disabled-example" label="Nothing to save" disabled></et2-dropdown-button>
<script>
    const disabledDropdown = document.getElementById("dropdown-disabled-example");
    customElements.whenDefined("et2-dropdown-button").then(() =>
    {
        disabledDropdown.select_options = [{value: "one", label: "First choice"}];
    });
</script>

readonly renders nothing at all - there is no value worth showing when the actions are gone.

Slots

Name Description
prefix Content placed before the main button’s label
suffix Content placed after the main button’s label

Learn more about using slots.

Properties

Name Description Reflects Type Default
defaultPreference Name of a preference to read/store the default selected option in. When set, the option matching the stored preference value (falling back to whichever option is marked default: true) is preselected on load, and every user selection is written back to the same preference - so the main/left part of the button becomes a quick-action for “whatever was last picked”, instead of doing nothing until the user has opened the menu at least once. string ""
iconOnly Show only the selected option’s icon on the main button, not its text label boolean false

Learn more about attributes and properties.

Inherited properties (25)

Et2Widget

Name Description
accesskey Accesskey provides a hint for generating a keyboard shortcut for the current element. The attribute value must consist of a single printable character.
actions Set Actions on the widget Each action is defined as an object: move: { type: “drop”, acceptedTypes: “mail”, icon: “move”, caption: “Move to” onExecute: javascript:mail_move” } This will turn the widget into a drop target for “mail” drag types. When “mail” drag types are dropped, the global function mail_move(egwAction action, egwActionObject sender) will be called. The ID of the dragged “mail” will be in sender.id, some information about the sender will be in sender.context. The etemplate2 widget involved can typically be found in action.parent.data.widget, so your handler can operate in the widget context easily. The location varies depending on your action though. It might be action.parent.parent.data.widget To customise how the actions are handled for a particular widget, override _link_actions(). It handles the more widget-specific parts.
align Used by Et2Box to determine alignment. Allowed values are left, right
class CSS Class. This class is applied to the outside, on the web component itself. Due to how WebComponents work, this might not change anything inside the component.
data Set the dataset from a CSV
deferredProperties Any attribute that refers to row content cannot be resolved immediately, but some like booleans cannot stay a string because it’s a boolean attribute. We store them for later, and parse when they’re fully in their row. If you are creating a widget that can go in a nextmatch row, and it has boolean attributes that can change for each row, add those attributes into deferredProperties
disabled Defines whether this widget is visibly disabled. The widget is still visible, but clearly cannot be interacted with. Widgets disabled in the template will not return a value to the application code, even if re-enabled via javascript before submitting. To allow a disabled widget to be re-enabled and return a value, disable via javascript in the app’s et2_ready() instead of an attribute in the template file.
dom_id Get the actual DOM ID, which has been prefixed to make sure it’s unique.
hidden The widget is not visible. As far as the user is concerned, the widget does not exist. Widgets hidden with an attribute in the template may not be created in the DOM, and will not return a value. Widgets can be hidden after creation, and they may return a value if hidden this way.
id Get the ID of the widget
label The label of the widget Legacy support for labels with %s that get wrapped around the widget Not the best way go with webComponents - shouldn’t modify their DOM like this
noLang Disable any translations for the widget
parentId Parent is different than what is specified in the template / hierarchy. Widget ID of another node to insert this node into instead of the normal location
statustext Tooltip which is shown for this element on hover
styles WebComponent *
options Get property-values as object
supportedWidgetClasses et2_widget compatability

Et2InputWidget

Name Description
autofocus Have browser focus this input on load. Overrides etemplate2.focusOnFirstInput(), use only once per page https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#attributes
hasFeedbackFor Get a list of feedback types
translate List of properties that get translated
needed Compatibility for deprecated name “needed”

Et2WidgetWithSelectMixin

Name Description
emptyLabel Textual label for first row, eg: ‘All’ or ‘None’. It’s value will be ″
select_options Select box options Will be found automatically based on ID and type, or can be set explicitly in the template using
_optionTargetNode Get the node where we’re putting the options If this were a normal selectbox, this would be just the

LitElement

Name Description
updateComplete A read-only promise that resolves when the component has finished updating.

Events

Name Description Event Detail
change Missing description Event

Learn more about events.

Inherited methods (32)

Et2Widget

Name Description
checkCreateNamespace() Checks whether a namespace exists for this element in the content array. If yes, an own perspective of the content array is created. If not, the parent content manager is used. Constructor attributes are passed in case a child needs to make decisions
clone() Creates a copy of this widget.
createElementFromNode() Create a et2_widget from an XML node. First the type and attributes are read from the node. Then the readonly & modifications arrays are checked for changes specific to the loaded data. Then the appropriate constructor is called. After the constructor returns, the widget has a chance to further initialize itself from the XML node when the widget’s loadFromXML() method is called with the node.
getArrayMgr() Returns the array manager object for the given part
getArrayMgrs() Returns an associative array containing the top-most array managers.
getChildren() Get child widgets Use .children to get web component children
getInstanceManager() Returns the instance manager
getPath() Returns the path into the data array. By default, array manager takes care of this, but some extensions need to override this
getRoot() Returns the base widget Usually this is the same as getInstanceManager().widgetContainer
loadFromXML() Load extra stuff from the template node. In particular, we’re looking for any
loadingFinished() Needed for legacy compatability.
parseXMLAttrs() The parseXMLAttrs function takes an XML DOM attributes object and adds the given attributes to the _target associative array. This function also parses the legacyOptions. N.B. This is only used for legacy widgets. WebComponents use transformAttributes() and do their own handling of attributes.
set_label() NOT the setter, since we cannot add to the DOM before connectedCallback() TODO: This is not best practice. Should just set property, DOM modification should be done in render https://lit-element.polymer-project.org/guide/templates#design-a-performant-template
setArrayMgr() Sets the array manager for the given part
setArrayMgrs() Sets all array manager objects - this function can be used to set the root array managers of the container object.
setInstanceManager() Set the instance manager Normally this is not needed as it’s set on the top-level container, and we just return that reference
_handleClick() Click handler calling custom handler set via onclick attribute to this.onclick
destroy() et2_widget compatability
set_class() Set the widget class
set_disabled() Wrapper on this.disabled because legacy had it.
set_statustext() supports legacy set_statustext

Et2InputWidget

Name Description
et2HandleBlur() If the value is unchanged, put any held validation messages back Named et2HandleBlur to avoid overwriting handleBlur() in Shoelace components
et2HandleFocus() When input receives focus, clear any validation errors. If the value is the same on blur, we’ll put them back The ones from the server (ManualMessage) can interfere with submitting. Named et2HandleFocus to avoid overwriting handleFocus() in Shoelace components
getInputNode() Get input to e.g. set aria-attributes
handleSlChange() Handle sl-change event from Shoelace components and dispatch a change event so anything listening for change events can react to it instead of having to listen for both sl-change and change.
isValid() Used by etemplate2 to determine if we can submit or not
submit() Called whenever the template gets submitted. We return false if the widget is not valid, which cancels the submission.
validate() Massively simplified validate, as compared to what ValidatorMixin gives us, since ValidatorMixin extends FormControlMixin which breaks SlSelect’s render() We take all validators for the widget, and if there’s a value (or field is required) we check the value with each validator. For array values we check each element with each validator. If the value does not pass the validator, we collect the message and display feedback to the user. We handle validation errors from the server with ManualMessages, which always “fail”. If the value is empty, we only validate if the field is required.
_oldChange() Change handler calling custom handler set via onchange attribute

Et2WidgetWithSelectMixin

Name Description
optionSearch() Search options for a given value, returning the first matching option
_emptyLabelTemplate() Render the “empty label”, used when the selectbox does not currently have a value
set_select_options() Set select options