html - In angular7, how do I change the height of a mat-select when shows the list of items?

Question

In Angular7, how can I increase the height of a mat-select when it is showing the items? I have the following component file:

import { Component, ViewEncapsulation } from "@angular/core";
import { FormControl } from "@angular/forms";

/** @title Select with multiple selection */
@Component({
  selector: "select-multiple-example",
  templateUrl: "select-multiple-example.html",
  styleUrls: ["select-multiple-example.css"],
  encapsulation: ViewEncapsulation.None
})
export class SelectMultipleExample {
  toppings = new FormControl();
  toppingList: string[] = [
    "Extra cheese",
    "Mushroom",
    "Onion",
    "Pepperoni",
    "Sausage",
    "Tomato",
    "CBFnTQcZ79AeYrdq",
    "1KiYwRjeqdqjNzVb",
    "TeLvgGl7t3yHDrZE",
    "s3ivzgLZO9qDNovJ",
    "QOOH2MCNRRXVJNwD",
    "1RWqdyPpu8yHSDoO",
    "d3aAOYIWYJE695Lf",
    "JoXDWP6zKSrZTIUc",
    "hpxQKFJsJcgVey5A",
    "UMI0akuHn2M5BaAP",
    "LRnQgNNjpqZwpdzj",
    "ZDIgw68mQyNLtxob",
    "Q6HY6tcqFcySJqD9",
    "WVFSg4TKeEqqoF1g",
    "ka4ORT9rUW8EPaPd",
    "ingfHsjBXAmt7yvo",
    "G3MY6MowhI7s0fN9",
    "ZlWqSoRnlhXQCbYz",
    "gerR70hrO5alwsOR",
    "dk0xrarQzfH6HAdl",
    "D1WCkB9jhhPMiuv7",
    "zPMj4g6Iu52jXqwq",
    "P4OEXKI2FZfFVqVn",
    "xMcOFx5m92d9oGQz",
    "dkyWq0tLJ8wQknaA",
    "iJZUeyjyyn3qQaCT",
    "5KhUjwEJK8wIYkoa",
    "YB3rEUkE12Pf9hcO",
    "qzrzSvzDXukVXvZi",
    "Hr1lccIcJZurLKiL",
    "noQo0pUMBeuQGpcf",
    "Tw4ACNCyDbpMI5MQ",
    "kK3QMSqyrNAwo3J0",
    "lvXP7qEm3biOpVbu",
    "gzy7bHaW2Qq6StN0",
    "GjXJAaRovr5CwHaO",
    "7CfVdILE7RhaVDvI",
    "8i5j8nlokIdkPEoO",
    "XpSWhgdwON3XFI15",
    "w5R5JfrDnuCzhqN7",
    "azhjvfD5geZaKjfc",
    "6y1Zdt18KSRNMdxx",
    "kd5ou8n6Ae5sILpj",
    "2p0YQKWdOvpXo4cD",
    "XfmEOsiIpq4C0PVc",
    "qYIzI8y3vOdx2KJ6",
    "6MzPKWHOn1oFOHpd",
    "tJgyk3p4UIDEj985",
    "RXwLNofzoJHUYgOf"
  ];
}

Where I am able to set the width with the following CSS and html:

CSS:

 .myFilter .mat-select-trigger {
  min-width: 80vw;
}

HTML:

<mat-form-field>
  <mat-select class="myFilter" placeholder="Pizza Stuff" [formControl]="toppings" multiple>
    <mat-option *ngFor="let topping of toppingList" [value]="topping">{{topping}}</mat-option>
  </mat-select>
</mat-form-field>

Which is fine, but I want to be able to set the height not the width. If I try and change the CSS to this:

.myFilter .mat-select-trigger {
  max-height: 80vh;
}

then the height of the box increases and not the actual list of items. Assuming that I am somehow able to do that, how can I then ensure that the list doesn't extend beyond the number of items in the toppingList array if, for example, the data contained within it is updated to

toppingList: string[] = [
    "Extra cheese",
    "Mushroom",
    "Onion",
    "Pepperoni",
    "Sausage",
    "Tomato",
    "CBFnTQcZ79AeYrdq",
    "1KiYwRjeqdqjNzVb",
    "TeLvgGl7t3yHDrZE",
    "s3ivzgLZO9qDNovJ",
    "QOOH2MCNRRXVJNwD",
    "1RWqdyPpu8yHSDoO",
    "d3aAOYIWYJE695Lf",
    "JoXDWP6zKSrZTIUc",
    "hpxQKFJsJcgVey5A"
  ];

In other words, if the list is reduced, how can I show all items and remove the scrollbar? Thanks in advance.

UPDATE:

So I have made the following changes: CSS:

.myFilter {
  background-color: yellow; /* Added this to check it was working*/
  min-height: 85vh;
}

HTML:

<mat-form-field>
  <mat-select [panelClass]="'myFilter'" placeholder="Pizza Stuff" [formControl]="toppings" multiple>
    <mat-option *ngFor="let topping of toppingList" [value]="topping">{{topping}}</mat-option>
  </mat-select>
</mat-form-field>

Which has changed the height to 85vh but if I have only 5 items I want the list shorter.

Answer 1

Like this helpful answer to a similar question already states there are a couple of ways you can solve this problem and which one you choose depends on whether you want to apply your rules globally or locally. None of the following examples require you to change the ViewEncapsulation type of your component.

Local override

Using ::ng-deep you can simply override the styles of both the trigger and the panel that are being rendered in child components of your component. Important: ::ng-deep has been marked as deprecated and while it still works there is no guarantee it will do so in future.

select-multiple-example.component.css

::ng-deep .mat-select-trigger {
  min-width: 80vw;
}

::ng-deep .mat-select-panel {
  max-height: 80vh !important;
}

select-multiple-example.component.html

<mat-form-field>
  <mat-select placeholder="ITEMS" multiple>
    <mat-option *ngFor="let item of items" [value]="topping">{{item}}</mat-option>
  </mat-select>
</mat-form-field>

DEMO (I edited your code for the purpose of the demo)

---

Global override

This will apply your overrides to all triggers or panels within your application.

styles.css

.mat-select-trigger {
  min-width: 80vw;
}

.mat-select-panel {
  max-height: 80vh !important;
}

DEMO (overrides can be found in /assets/styles/material-override.scss)

---

Flexible override

Using the @Input pannelClass on your MatSelect (mat-select) will allow you to apply different overrides depending on your use case and independent from other selects in your app.

styles.css

.panel-override {
  max-height: 80vh !important;
}

.panel-override-2 {
  max-height: 100px !important;
}

select-multiple-example.component.html

<mat-form-field>
  <mat-select placeholder="ITEMS" multiple [panelClass]="applyPanelOverride2 ? 'panel-override-2' : 'panel-override'">
    <mat-option *ngFor="let item of items" [value]="item">{{item}}</mat-option>
  </mat-select>
</mat-form-field>

DEMO (note the checkbox in the toolbar)