Virtual Select component for Angular Material Form Field

Table of contents

• Description
• Getting started
• Examples
• Customization
• API
  • NgxVirtualSelectFieldComponent
  • NgxVirtualSelectFieldOptionComponent
  • NgxVirtualSelectFieldOptionSelectionChangeEvent
  • NgxVirtualSelectFieldTriggerComponent
  • NgxVirtualSelectFieldOptionForDirective
  • NgxVirtualSelectFieldOptionModel
  • NGX_VIRTUAL_SELECT_FIELD_CONFIG
  • NgxVirtualSelectFieldConfig
  • CSS variables

Description

This package replicates the Angular Material Select component with virtual scroll capabilities with help of cdk-virtual-scroll. It provides most major features of the original Angular Material Select component. The goal of this package is to provide similar api and features as the original Angular Material Select component but with virtual scroll capabilities. One major difference is that this package does not support option groups at the moment. Also, this requires own structural directive to be used for options in order to provide virtual scroll capabilities and custom template.

Features:

• Virtual scroll
• Multi select
• Single select
• Integrates with Angular Material Form Field
• Custom trigger template
• Custom option template
• Keyboard navigation and shortcuts
• Theming trough css variables

Not Supported Features for now:

• Animations
• Custom Error state mather
• Custom scroll strategy
• Accessibility
• Option groups

Demo

Getting started

1. Install package

   npm install ngx-virtual-select-field

2. Import bundle into your component

   import { NgxVirtualSelectFieldBundle } from 'ngx-virtual-select-field';
   ...
   @Component({
     imports: [
       NgxVirtualSelectFieldBundle,
       ...
     ],
     ...
   })

3. Create options collection in component. Options collection should be an array of objects with value and label properties. Optionally, you can add disabled property to disable specific options and getLabel() fot type ahead search.

   ...
   protected options: NgxVirtualSelectFieldOptionModel<number>[]
   
   constructor() {
     this.options = new Array(100000)
       .fill(null)
       .map((_, index) => ({
         value: index,
         label: `${index} Option`,
         disabled: index % 5 === 0,
       }));
   }

4. Setup template markup. ngxVirtualSelectFieldOptionFor directive should be user to pass options collection to the component and provide custom option template.

   <mat-form-field>
     <mat-label>Virtual Select Field Example</mat-label>
     <ngx-virtual-select-field [value]="value">
       <ngx-virtual-select-field-option 
        *ngxVirtualSelectFieldOptionFor="let option of options" 
        [value]="option.value"
        [disabled]="option.disabled"> 
        {{ option.label }}
      </ngx-virtual-select-field-option>
     </ngx-virtual-select-field>
   </mat-form-field>

5. Include theme styles. You can define your own theme with help of CSS variables or inherit from material theme.

   @use 'ngx-virtual-select-field/theme' as theme;
   
   @include theme.inherit-material-theme(); // this will inherit css variables from material theme

Examples

Basic setup with value input and output binding

<mat-form-field>
  <mat-label>Example</mat-label>
  <ngx-virtual-select-field [value]="value" (valueChange)="onValueChange($event)">
    <ngx-virtual-select-field-option 
      *ngxVirtualSelectFieldOptionFor="let option of options" [value]="option.value"> 
      {{ option.label }} 
    </ngx-virtual-select-field-option>
  </ngx-virtual-select-field>
</mat-form-field>

Form control integration

<mat-form-field>
  <mat-label>Form Control Example</mat-label>
  <ngx-virtual-select-field [formControl]="formControl">
    <ngx-virtual-select-field-option 
      *ngxVirtualSelectFieldOptionFor="let option of options" [value]="option.value">
        {{ option.label }}
    </ngx-virtual-select-field-option>
  </ngx-virtual-select-field>
</mat-form-field>

Multi select

<mat-form-field>
  <mat-label>Multi Select Example</mat-label>
  <ngx-virtual-select-field [value]="value" multiple (valueChange)="onValueChange($event)">
    <ngx-virtual-select-field-option 
      *ngxVirtualSelectFieldOptionFor="let option of options" 
      [value]="option.value"> 
      {{ option.label }} 
    </ngx-virtual-select-field-option>
  </ngx-virtual-select-field>
</mat-form-field>

Custom trigger template

<mat-form-field class="field">
  <mat-label>Custom Trigger Example</mat-label>
  <ngx-virtual-select-field multiple [(value)]="value">
    <ngx-virtual-select-field-trigger> 
      {{ value.length }} selected 
    </ngx-virtual-select-field-trigger>
    <ngx-virtual-select-field-option 
      *ngxVirtualSelectFieldOptionFor="let option of options" 
      [value]="option.value"> 
      {{ option.label }} 
    </ngx-virtual-select-field-option>
  </ngx-virtual-select-field>
</mat-form-field>

Customization

Components supports custom templates for trigger and option elements. You can use ngx-virtual-select-field-trigger and ngx-virtual-select-field-option components to define custom templates.

There are number of input parameters available to specify specific behavior of the component.

Injection tokens might be used to customize all component instances

All styles are defined with css variables, so you can easily override them in your own styles.

See more in API section below.

API

NgxVirtualSelectFieldComponent

selector: ngx-virtual-select-field
Component to define select field

| Input | Type | Default | Description | | ------------------------- | ---------------------------- | ------- | ------------------------------------------------------------------------------ | | panelWidth | string\|number \|null | auto | Width for overlay panel | | optionHeight | number | 48 | Height for an option element | | panelViewportPageSize | number | 8 | Amount of visible items in list | | multiple | boolean | false | Enable multiple selection | | tabIndex | number | 0 | Tab index for keyboard navigation | | typeaheadDebounceInterval | number | 300 | Milliseconds to wait before navigating to active element after keyboard search | | panelClass | string \| string[] \| null | null | CSS class to be added to the panel element | | value | TValue[] \| TValue \| null | null | Value of the select field | | placeholder | string | none | Placeholder for the select field | | required | boolean | false | Define if fields is required | | disabled | boolean | false | Define if fields is disabled |

| Output | Type | Description | | ----------- | -------------------- | -------------------------- | | valueChange | TValue \| TValue[] | Value change event emitter |

NgxVirtualSelectFieldOptionComponent

selector: ngx-virtual-select-field-option
Component to define option element

| Input | Type | Default | Description | | ---------------- | --------- | ------- | ------------------------------ | | value (required) | TValue | | Value of the option | | disabled | boolean | false | Whether the option is disabled |

| Output | Type | Description | | -------------- | --------------------------------------------------------- | ---------------------------- | | selectedChange | NgxVirtualSelectFieldOptionSelectionChangeEvent<TValue> | Option selected value change |

NgxVirtualSelectFieldOptionSelectionChangeEvent

Interface to define option selection change event contract
Properties: | Name | Type | Description | |----------|-----------------------------------------------------------|----------------------------| | source | NgxVirtualSelectFieldOptionComponent<TValue> | Option component instance | | value | TValue | Value of the option | | selected | boolean | Whether the option is selected |

NgxVirtualSelectFieldTriggerComponent

selector: ngx-virtual-select-field-trigger
Directive to define custom trigger template

NgxVirtualSelectFieldOptionForDirective

selector: *ngxVirtualSelectFieldOptionFor
Directive to define custom option template and iterate over options | Input | Type | Description | |----------------------------------|----------------------------------------------|---------------------| | of (required) | NgxVirtualSelectFieldOptionModel<TValue>[] | Options collection |

NgxVirtualSelectFieldOptionModel

Interface to define option model contract
Properties: | Name | Type | Description | |-----------------------|----------------------------------------------------------------|----------------------------| | value | TValue | Value of the option | | label | string | Label of the option | | disabled? | boolean | Whether the option is disabled | | getLabel() optional | (option: NgxVirtualSelectFieldOptionModel<TValue>) => string | Function to get label of the option |

NGX_VIRTUAL_SELECT_FIELD_CONFIG

Injection token to define global configuration for all instances of the component Config see in NgxVirtualSelectFieldConfig interface

NgxVirtualSelectFieldConfig

Interface to define global configuration contract Properties: | Name | Type | Description | |-----------------------|--------------------------------------------|----------------------------| | panelWidth | string\|number | Width for overlay panel | | overlayPanelClass | string \| string[] | CSS class to be added to the panel element| | optionHeight | number | Height for an option element | | panelViewportPageSize | number | Amount of visible items in list |

CSS variables

All styles are defined with css variables, so you can easily override them in your own styles. CSS variables for main component:

:root {
  --ngx-virtual-select-field-trigger-text-color: ...;
  --ngx-virtual-select-field-trigger-text-color--disabled: ...;
  --ngx-virtual-select-field-trigger-font-family: ...;
  --ngx-virtual-select-field-trigger-line-height: ...;
  --ngx-virtual-select-field-trigger-font-size: ...;
  --ngx-virtual-select-field-trigger-font-weight: ...;
  --ngx-virtual-select-field-trigger-letter-spacing: ...;

  --ngx-virtual-select-field-placeholder-text-color: ...;
  --ngx-virtual-select-field-placeholder-transition: ...;

  --ngx-virtual-select-field-arrow-size: ...;
  --ngx-virtual-select-field-arrow-color--enabled: ...;
  --ngx-virtual-select-field-arrow-color--focused: ...;
  --ngx-virtual-select-field-arrow-color--invalid: ...;
  --ngx-virtual-select-field-arrow-color--disabled: ...;

  --ngx-virtual-select-field-panel-background: ...;
  --ngx-virtual-select-field-panel-box-shadow: ...;
  --ngx-virtual-select-field-panel-list-wrapper-padding: ...;
}

CSS variables for option component:

:root {
  --ngx-virtual-select-field-option-color: ...;
  --ngx-virtual-select-field-option-font-family: ...;
  --ngx-virtual-select-field-option-line-height: ...;
  --ngx-virtual-select-field-option-font-size: ...;
  --ngx-virtual-select-field-option-letter-spacing: ...;
  --ngx-virtual-select-field-option-font-weight: ...;

  --ngx-virtual-select-field-option-selected-state-label-text-color: ...;
  --ngx-virtual-select-field-option-background-color--active: ...;
  --ngx-virtual-select-field-option-background-color--hover: ...;
  --ngx-virtual-select-field-option-background-color--selected: ...;

  --ngx-virtual-select-field-option-disabled-state-opacity: ...;
  --ngx-virtual-select-field-option-gap: ...;
  --ngx-virtual-select-field-option-padding: ...;
}