experiment: add list-box base styles and visual tests (#9186)

Author: web-padawan

packages/list-box/package.json

@@ -21,6 +21,8 @@
   "type": "module",
   "files": [
     "src",
+    "!src/*-base-styles.d.ts",
+    "!src/*-base-styles.js",
     "theme",
     "vaadin-*.d.ts",
     "vaadin-*.js",

packages/list-box/src/vaadin-list-box-base-styles.d.ts

@@ -0,0 +1,8 @@
+/**
+ * @license
+ * Copyright (c) 2017 - 2025 Vaadin Ltd.
+ * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
+ */
+import type { CSSResult } from 'lit';
+
+export const listBoxStyles: CSSResult;

packages/list-box/src/vaadin-list-box-base-styles.js

@@ -0,0 +1,33 @@
+/**
+ * @license
+ * Copyright (c) 2017 - 2025 Vaadin Ltd.
+ * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
+ */
+import '@vaadin/component-base/src/style-props.js';
+import { css } from 'lit';
+
+export const listBoxStyles = css`
+  :host {
+    --vaadin-item-checkmark-display: block;
+    display: flex;
+  }
+
+  :host([hidden]) {
+    display: none !important;
+  }
+
+  [part='items'] {
+    height: 100%;
+    overflow-y: auto;
+    width: 100%;
+  }
+
+  [part='items'] ::slotted(hr) {
+    border-color: var(--vaadin-divider-color, var(--_vaadin-border-color));
+    border-width: 0 0 1px;
+    margin: 4px 8px;
+    margin-inline-start: calc(
+      var(--vaadin-icon-size, 1lh) + var(--vaadin-item-gap, var(--_vaadin-gap-container-inline)) + 8px
+    );
+  }
+`;

packages/list-box/src/vaadin-list-box-core-styles.d.ts

@@ -0,0 +1,8 @@
+/**
+ * @license
+ * Copyright (c) 2017 - 2025 Vaadin Ltd.
+ * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
+ */
+import type { CSSResult } from 'lit';
+
+export const listBoxStyles: CSSResult;

packages/list-box/src/vaadin-list-box-core-styles.js

@@ -0,0 +1,23 @@
+/**
+ * @license
+ * Copyright (c) 2017 - 2025 Vaadin Ltd.
+ * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
+ */
+import { css } from 'lit';
+
+export const listBoxStyles = css`
+  :host {
+    display: flex;
+  }
+
+  :host([hidden]) {
+    display: none !important;
+  }
+
+  [part='items'] {
+    height: 100%;
+    width: 100%;
+    overflow-y: auto;
+    -webkit-overflow-scrolling: touch;
+  }
+`;

packages/list-box/src/vaadin-list-box.js

@@ -8,9 +8,12 @@ import { ControllerMixin } from '@vaadin/component-base/src/controller-mixin.js'
 import { defineCustomElement } from '@vaadin/component-base/src/define.js';
 import { ElementMixin } from '@vaadin/component-base/src/element-mixin.js';
 import { TooltipController } from '@vaadin/component-base/src/tooltip-controller.js';
-import { ThemableMixin } from '@vaadin/vaadin-themable-mixin/vaadin-themable-mixin.js';
+import { registerStyles, ThemableMixin } from '@vaadin/vaadin-themable-mixin/vaadin-themable-mixin.js';
+import { listBoxStyles } from './vaadin-list-box-core-styles.js';
 import { MultiSelectListMixin } from './vaadin-multi-select-list-mixin.js';
 
+registerStyles('vaadin-list-box', listBoxStyles, { moduleId: 'vaadin-list-box-styles' });
+
 /**
  * `<vaadin-list-box>` is a Web Component for creating menus.
  *
@@ -47,22 +50,6 @@ import { MultiSelectListMixin } from './vaadin-multi-select-list-mixin.js';
 class ListBox extends ElementMixin(MultiSelectListMixin(ThemableMixin(ControllerMixin(PolymerElement)))) {
   static get template() {
     return html`
-      <style>
-        :host {
-          display: flex;
-        }
-
-        :host([hidden]) {
-          display: none !important;
-        }
-
-        [part='items'] {
-          height: 100%;
-          width: 100%;
-          overflow-y: auto;
-          -webkit-overflow-scrolling: touch;
-        }
-      </style>
       <div part="items">
         <slot></slot>
       </div>

packages/list-box/src/vaadin-lit-list-box.js

@@ -3,12 +3,13 @@
  * Copyright (c) 2017 - 2025 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css, html, LitElement } from 'lit';
+import { html, LitElement } from 'lit';
 import { defineCustomElement } from '@vaadin/component-base/src/define.js';
 import { ElementMixin } from '@vaadin/component-base/src/element-mixin.js';
 import { PolylitMixin } from '@vaadin/component-base/src/polylit-mixin.js';
 import { TooltipController } from '@vaadin/component-base/src/tooltip-controller.js';
 import { ThemableMixin } from '@vaadin/vaadin-themable-mixin/vaadin-themable-mixin.js';
+import { listBoxStyles } from './vaadin-list-box-core-styles.js';
 import { MultiSelectListMixin } from './vaadin-multi-select-list-mixin.js';
 
 /**
@@ -26,22 +27,7 @@ class ListBox extends ElementMixin(MultiSelectListMixin(ThemableMixin(PolylitMix
   }
 
   static get styles() {
-    return css`
-      :host {
-        display: flex;
-      }
-
-      :host([hidden]) {
-        display: none !important;
-      }
-
-      [part='items'] {
-        height: 100%;
-        width: 100%;
-        overflow-y: auto;
-        -webkit-overflow-scrolling: touch;
-      }
-    `;
+    return listBoxStyles;
   }
 
   static get properties() {

packages/list-box/test/visual/base/list-box.test.js

@@ -0,0 +1,51 @@
+import { fixtureSync } from '@vaadin/testing-helpers/dist/fixture.js';
+import { visualDiff } from '@web/test-runner-visual-regression';
+import '@vaadin/item/src/vaadin-item.js';
+import '../../../src/vaadin-list-box.js';
+
+describe('list-box', () => {
+  let div, element;
+
+  beforeEach(() => {
+    div = document.createElement('div');
+    div.style.display = 'inline-block';
+    div.style.padding = '10px';
+
+    element = fixtureSync(
+      `
+        <vaadin-list-box>
+          <vaadin-item focused>Item 0</vaadin-item>
+          <vaadin-item>Item 1</vaadin-item>
+          <vaadin-item>Item 2</vaadin-item>
+          <vaadin-item disabled>Item 3</vaadin-item>
+          <hr>
+          <vaadin-item>Item 4</vaadin-item>
+        </vaadin-list-box>
+      `,
+      div,
+    );
+  });
+
+  ['ltr', 'rtl'].forEach((dir) => {
+    describe(dir, () => {
+      before(() => {
+        document.documentElement.setAttribute('dir', dir);
+      });
+
+      after(() => {
+        document.documentElement.removeAttribute('dir');
+      });
+
+      it('basic', async () => {
+        element.selected = 2;
+        await visualDiff(div, `${dir}-basic`);
+      });
+
+      it('multiple', async () => {
+        element.multiple = true;
+        element.selectedValues = [1, 2];
+        await visualDiff(div, `${dir}-multiple`);
+      });
+    });
+  });
+});