Tutorial: Angular

Angular

Using AUX with Angular

AUX can be integrated into an Angular project simply by installing it as a dependency. AUX Widgets are exposed as WebComponents using the v1 WebComponents API, which is supported in modern browser. To import all AUX Components into an Angular project add a global import to the top level module.

import '@deutschesoft/a.ux';

Importing the standard AUX CSS theme can be done by adding node_modules/@deuso/aux/styles/main.css to the styles list in the angular.json configuration file.

In order to use WebComponents inside of Angular templates, the corresponding Angular module needs to have the CUSTOM_ELEMENTS_SCHEMA. Once that is set up, AUX Components should work within Angular templates.

Setting options

All options of AUX Widgets are available via usual tag attributes and can be set from within the template.

<aux-fader min=-96 max=6></aux-fader>

In order to set attributes on WebComponents dynamically, a special Angular syntax needs to be used.

<aux-fader min=-96 max=6 [attr.value]="myValue"></aux-fader>

A cleaner pattern is to avoid using attributes for dynamic options and instead set the property on the DOM object directy. They are mapped onto AUX Widget options automatically.

<aux-fader min=-96 max=6 [value]="myValue"></aux-fader>

Subscribing to events

All AUX Widget events are available via standard DOM custom events. Unlike DOM events, AUX Widget events have a list of arguments. They are available in the CustomEvent object as ev.detail.args.

For instance, for option changes triggered by user interaction, AUX widgets define one standard event called useraction. It has two events, the option name and the new value. The following event handler would call the method onValueChanged with a two element array.

<aux-fader min=-96 max=6 (useraction)="onValueChanged($event.detail.args)">
</aux-fader>

AUX Angular Directives

The AUX repository contains implementations of several Angular directives which aim to make bindings between AUX Widget options and Angular components simpler and more performant than relying on custom DOM events. The implementation of those Angular Directives can be found in the angular subdirectory. They can be added to an Angular application by importing them

import { AuxDirectivesModule } from '@deuso/aux/angular/aux-directives.module';

and adding them to the imports list of the @NgModule declaration.

In addition is is necessary to add all typescript files for the AUX Angular directives into the "include" entry in tsconfig.app.json to allow the typescript compiler to find them:

"include": [
  "src/**/*.ts",
  "node_modules/@deuso/aux/angular/*.ts"
],

Observing value changes

This group of directives can be used to observe changes of AUX Widget options. These directives can be used to subscribe to changes to any number of options. They expect an Object as argument with options names as keys. The values can either be a function or an object implementing a next() method, such as Subject or the more general Observer interface of RxJS. The directives will automatically manage subscriptions and notify the subscriber when values change.

Note that when supplying a method to one of these directives as a handler, it needs to be bound to the component. This can be achieved by using myMethod.bind(this). Otherwise the callback will not be executed in the scope of the component.

The auxObserve directive

The auxObserve directive reacts to value changes triggered by user interaction. It will not trigger when the corresponding options is set programmatically. It is a good way to transfer value changes to a back end.

<aux-fader min=-96 max=6 [auxObserve]="{ value: value_subject }">
</aux-fader>

The auxObserveAll directive

The auxObserveAll directive reacts to all changes to an option. This means that it will also trigger when the option has been changed programmatically, e.g. by setting the corresponding property. It will also emit the current value of the option initially, similarly to how BehaviorSubject or ReplaySubject work in RxJS.

It can be useful when synchronizing options between several widgets regardless of whether the change was made by the user.

<aux-fader min=-96 max=6 [auxObserveAll]="{ value: value_subject }">
</aux-fader>

The auxIntercept directive

The auxIntercept directive reacts to changes to an option triggered by a user and prevents it being applied to the widget. This makes it possible to e.g. externally check if a parameter is valid before feeding it back into the widget.

<aux-fader min=-96 max=6 [auxIntercept]="{ value: clip_value }">
</aux-fader>

Observing AUX Widget events

The auxSubscribe directive

The auxSubscribe directive can be used to subscribe to a number of AUX Widget events. As with the value observe directives it expects an object which contain either functions or observers. Functions are called with the AUX event arguments. Observers receive the array of arguments as the value.

Using auxSubscribe can be more convenient when working with Subjects than using the DOM custom events as described above. It is also more efficient because it avoids the translation to and from DOM events.

Binding options using auxBind

Binding backend values to AUX widget options can be done simply by setting the property. However, when doing this while a user is interacting with the widget leads to very poor user experience. For instance, a fader value would jump while being dragged if the back end connection has network delay.

The auxBind can be used to prevent such issues when binding options to backend data. It internally uses the DebounceBinding class which is part of AUX. It delays received values

  • while the interacting option is true on a widget or
  • for a certain number of milliseconds after the option was changed by user action.

The delay used in the auxBind option is 250 milliseconds.

Similar to all other directives, the arguments of the auxBind is an object containing several options. If the value is a object which implements the Observable interface it uses the emitted values, otherwise it passes the value itself.

<aux-fader min=-96 max=6 [auxBind]="{ value: value_observable }">
</aux-fader>

Notifying widgets of resize events

Some widgets need to be redrawn when their size changes. This applies for instance to those widgets which contain scales. Other examples are charts with grids and similar. Widgets automatically react to the size of the browser window changing, however they do not detect if the widget has changed its size for some other reason. Some modern browsers support an API called ResizeObserver, however, it is not broadly enough supported, yet, to be relied upon. In order to notify a widget that a resize happened, the trigger_resize() method needs to be called. This can be done using the directive auxResize. Its argument is an observable.

In future versions when ResizeObserver is supported more broadly, this directive will become a no-op.

Caveats

Order of options

In principle the order of options should not matter. However, there are currently some exceptions to this rule. For instance, the value option is usually clipped to the range min .. max when being set. For these situations it is important to make sure that options such as min and max are set before setting the value. When using standard WebComponents with attributes, the set of initial options is set at once on creation of the Widget. However, when using WebComponents in Angular, the attributes are not applied on creation but afterwards separately. They are currently added in the order in which they appear in the template. It is therefore advisable to apply min, max and similar options at the beginning. Example:

<aux-fader min=-96 max=6 value=3></aux-fader>