fix(tabs): prevent vertical auto scroll

.circleci/config.yml

@@ -10,7 +10,7 @@ executors:
 parameters:
     current_golden_images_hash:
         type: string
-        default: 019c0496b4ab51e1da329cae280244c60500cb86
+        default: e7fc14cdcd7c7fa2b5bee0ad6cfc51a6302d6b52
     wireit_cache_name:
         type: string
         default: wireit

packages/tabs/src/Tabs.ts

@@ -66,6 +66,38 @@ export const ScaledIndicator = {
     },
 };
 
+/**
+ * Given that the scroll needs to be on the right side of the viewport.
+ * Returns the coordonate x it needs to scroll so that the tab with given index is visible.
+ */
+export function calculateScrollTargetForRightSide(
+    index: number,
+    direction: 'rtl' | 'ltr',
+    tabs: Tab[],
+    container: HTMLDivElement
+): number {
+    const nextIndex = index + (direction === 'rtl' ? -1 : 1);
+    const nextTab = tabs[nextIndex];
+    const viewportEnd = container.scrollLeft + container.offsetWidth;
+    return nextTab ? nextTab.offsetLeft - container.offsetWidth : viewportEnd;
+}
+
+/**
+ * Given that the scroll needs to be on the left side of the viewport.
+ * Returns the coordonate x it needs to scroll so that the tab with given index is visible.
+ */
+export function calculateScrollTargetForLeftSide(
+    index: number,
+    direction: 'rtl' | 'ltr',
+    tabs: Tab[],
+    container: HTMLDivElement
+): number {
+    const prevIndex = index + (direction === 'rtl' ? 1 : -1);
+    const prevTab = tabs[prevIndex];
+    const leftmostElement = direction === 'rtl' ? -container.offsetWidth : 0;
+    return prevTab ? prevTab.offsetLeft + prevTab.offsetWidth : leftmostElement;
+}
+
 /**
  * @element sp-tabs
  *
@@ -245,16 +277,54 @@ export class Tabs extends SizedMixin(Focusable, { noDefaultSize: true }) {
         return complete;
     }
 
+    private getNecessaryAutoScroll(index: number): number {
+        const selectedTab = this.tabs[index];
+        const selectionEnd = selectedTab.offsetLeft + selectedTab.offsetWidth;
+        const viewportEnd = this.tabList.scrollLeft + this.tabList.offsetWidth;
+        const selectionStart = selectedTab.offsetLeft;
+        const viewportStart = this.tabList.scrollLeft;
+
+        if (selectionEnd > viewportEnd) {
+            // Selection is on the right side, not visible.
+            return calculateScrollTargetForRightSide(
+                index,
+                this.dir,
+                this.tabs,
+                this.tabList
+            );
+        } else if (selectionStart < viewportStart) {
+            // Selection is on the left side, not visible.
+            return calculateScrollTargetForLeftSide(
+                index,
+                this.dir,
+                this.tabs,
+                this.tabList
+            );
+        }
+
+        return -1;
+    }
+
     public async scrollToSelection(): Promise<void> {
         if (!this.enableTabsScroll || !this.selected) {
             return;
         }
 
         await this.updateComplete;
-        const selectedTab = this.tabs.find(
+
+        const selectedIndex = this.tabs.findIndex(
             (tab) => tab.value === this.selected
         );
-        selectedTab?.scrollIntoView();
+
+        if (selectedIndex !== -1 && this.tabList) {
+            // We have a selection, calculate the scroll needed to bring it into view
+            const scrollTarget = this.getNecessaryAutoScroll(selectedIndex);
+
+            // scrollTarget = -1 means it is already into view.
+            if (scrollTarget !== -1) {
+                this.tabList.scrollTo({ left: scrollTarget });
+            }
+        }
     }
 
     protected override updated(

packages/tabs/stories/tabs-overflow.stories.ts

@@ -9,7 +9,7 @@ the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTA
 OF ANY KIND, either express or implied. See the License for the specific language
 governing permissions and limitations under the License.
 */
-import { TemplateResult } from '@spectrum-web-components/base';
+import { html, TemplateResult } from '@spectrum-web-components/base';
 import { OverflowProperties, renderTabsOverflowExample } from './index.js';
 
 export default {
@@ -30,3 +30,24 @@ export const autoscroll = (args: OverflowProperties): TemplateResult => {
 autoscroll.args = {
     selected: 15,
 };
+
+// https://github.com/adobe/spectrum-web-components/issues/4590
+export const autoscrollOnlyHorizontally = (
+    args: OverflowProperties
+): TemplateResult => {
+    return html`
+        <style>
+            .container {
+                height: 500px;
+                overflow-y: scroll;
+            }
+        </style>
+        <div class="container">
+            <div style="height: 500px">There are some tabs down here!</div>
+            ${renderTabsOverflowExample(args)}
+        </div>
+    `;
+};
+autoscrollOnlyHorizontally.args = {
+    selected: 15,
+};