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Widget

Et2Widget Mixin

Overview

Et2Widget is the mixin every eTemplate widget is built from. It is what turns a plain Lit⁠ element into something an eTemplate can create, address, fill with content and destroy - so almost everything in the Properties table below appears on every widget in this reference, and is documented here rather than repeated on all of them. 

export class Et2Example extends Et2Widget(LitElement) { … }

An input additionally uses Et2InputWidget, which layers value handling and validation on top of this.

What it provides

Identity. id is the widget’s name inside its template, and is what the server sends values back under. dom_id is the resulting DOM id, which is namespaced by the template so two templates on one page cannot collide.

Content binding. A widget does not usually carry its own value in the template - it names one, and the surrounding content supplies it. getArrayMgr() and the array managers reachable from it are how a widget resolves @-references and ${row} expressions against the content, the select options, the modifications and the validation errors the server sent.

Beware the namespace rule: putting an id on a container opens a namespace for everything inside it, so children resolve their references relative to that id. Giving a layout box an id it does not need silently starves its whole subtree - references go falsy and auto-repeating grids stop repeating, with nothing logged.

The widget tree. getChildren(), getRoot(), getPath() and getInstanceManager() navigate the eTemplate structure, which is not the same as the DOM tree - a row widget in a datagrid, for instance, has no widget-tree parent at all.

Construction from XML. loadFromXML(), createElementFromNode() and parseXMLAttrs() are how a .xet template becomes live widgets. You call these only when building something that hosts its own template; ordinary widgets get them for free.

Presentation. label, class, statustext (the tooltip), align, accesskey and hidden.

Actions. actions attaches the egw action system - context menus, drag and drop, keyboard shortcuts.

disabled is not what you expect

Et2Widget’s own style is:

:host([disabled]) { display: none; }

Only Et2InputWidget puts that back to display: initial. So on an input, disabled greys the widget out as you would expect - but on anything else, a box, a groupbox, et2-details, a tab, disabled removes the widget from the page entirely and is indistinguishable from hidden.

Use hidden when you mean “not visible”, so the template says what it means. See Disabled vs Readonly vs Hidden.

Lifecycle

loadingFinished() runs once the widget and its children are constructed and bound to content - it is the point at which the widget tree is complete, and the right place for work that needs to see siblings. destroy() tears the widget down and detaches it from its parent.

For the standard Lit lifecycle underneath this - connectedCallback, willUpdate, firstUpdated, updated - see Lit’s own documentation⁠. A practical consequence worth knowing: a widget is constructed as soon as it is inserted into the document, but its render root does not exist until the first update, so anything reaching into a widget from outside has to wait for updateComplete.

Writing one

See Creating a widget for a worked example, and Web Component Authoring for the conventions this codebase expects - including how to document what you write.

Used by

This mixin is applied by the following widgets.

Properties

Name Description Type Default
accesskey Accesskey provides a hint for generating a keyboard shortcut for the current element. The attribute value must consist of a single printable character. string -
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 string -
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 string -
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. boolean false
dom_id Get the actual DOM ID, which has been prefixed to make sure it’s unique. string -
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. boolean -
id Get the ID of the widget string -
label The label of the widget This is usually displayed in some way. It’s also important for accessability. This is defined in the parent somewhere, and re-defining it causes labels to disappear string -
noLang Disable any translations for the widget boolean -
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 string -
styles WebComponent * - -
options Get property-values as object
use widget methods 		object -
supportedWidgetClasses et2_widget compatability
Legacy compatability. Some legacy widgets check their parent to see whats allowed 		array []

Methods

Name Description Arguments
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. _parent: et2_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. _node: , _name:
getArrayMgr() Returns the array manager object for the given part managed_array_type: string
getArrayMgrs() Returns an associative array containing the top-most array managers. _mgrs: object
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() Loads the widget tree from an XML node _node:
loadingFinished() Needed for legacy compatability. promises: Promise[]
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. _attrsObj: , _target: object, _proto: et2_widget
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 value: string
setArrayMgr() Sets the array manager for the given part _part: string, _mgr: object
setArrayMgrs() Sets all array manager objects - this function can be used to set the root array managers of the container object. _mgrs: 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 manager: etemplate2
_handleClick() Click handler calling custom handler set via onclick attribute to this.onclick _ev: MouseEvent
destroy() et2_widget compatability
true 		-
set_class() Set the widget class
Use this.class or this.classList instead 		new_class: string
set_disabled() Wrapper on this.disabled because legacy had it.
Use widget.disabled for visually disabled, widget.hidden for visually hidden. Disabled vs Readonly vs Hidden 		value: boolean
set_statustext() supports legacy set_statustext
use this.statustext 		value: string