MOBILE-3833 style: Shadow on collapsible footer only if not at bottom

src/addons/messages/pages/discussion/discussion.page.ts

@@ -445,13 +445,9 @@ export class AddonMessagesDiscussionPage implements OnInit, OnDestroy, AfterView
             return;
         }
 
-        // Don't use domUtils.getScrollHeight because it gives an outdated value after receiving a new message.
-        const scrollHeight = this.scrollElement ? this.scrollElement.scrollHeight : 0;
-
         // Check if we are at the bottom to scroll it after render.
         // Use a 5px error margin because in iOS there is 1px difference for some reason.
-        this.scrollBottom = Math.abs(scrollHeight - (this.scrollElement?.scrollTop || 0) -
+        this.scrollBottom = CoreDom.scrollIsBottom(this.scrollElement, 5);
-            (this.scrollElement?.clientHeight || 0)) < 5;
 
         if (this.messagesBeingSent > 0) {
             // Ignore polling due to a race condition.
@@ -510,10 +506,11 @@ export class AddonMessagesDiscussionPage implements OnInit, OnDestroy, AfterView
      * The scroll was moved. Update new messages count.
      */
     scrollFunction(): void {
-        if (this.newMessages > 0) {
+        if (this.newMessages == 0) {
-            const scrollBottom = (this.scrollElement?.scrollTop || 0) + (this.scrollElement?.clientHeight || 0);
+            return;
-            const scrollHeight = (this.scrollElement?.scrollHeight || 0);
+        }
-            if (scrollBottom > scrollHeight - 40) {
+
+        if (CoreDom.scrollIsBottom(this.scrollElement, 40)) {
             // At the bottom, reset.
             this.setNewMessagesBadge(0);
 
@@ -544,7 +541,6 @@ export class AddonMessagesDiscussionPage implements OnInit, OnDestroy, AfterView
             this.setNewMessagesBadge(newMessagesUnread);
         }
     }
-    }
 
     /**
      * Get the conversation.

src/app/app.component.ts

@@ -31,6 +31,7 @@ import { CoreUrlUtils } from '@services/utils/url';
 import { CoreConstants } from '@/core/constants';
 import { CoreSitePlugins } from '@features/siteplugins/services/siteplugins';
 import { CoreDomUtils } from '@services/utils/dom';
+import { CoreDom } from '@singletons/dom';
 
 const MOODLE_VERSION_PREFIX = 'version-';
 const MOODLEAPP_VERSION_PREFIX = 'moodleapp-';
@@ -90,9 +91,21 @@ export class AppComponent implements OnInit, AfterViewInit {
         });
 
         // Listen to scroll to add style when scroll is not 0.
-        win.addEventListener('ionScroll', ({ detail, target }: CustomEvent<ScrollDetail>) => {
+        win.addEventListener('ionScroll', async ({ detail, target }: CustomEvent<ScrollDetail>) => {
-            const header = (target as HTMLElement).closest('.ion-page')?.querySelector('ion-header');
+            if ((target as HTMLElement).tagName != 'ION-CONTENT') {
-            header?.classList.toggle('core-header-shadow', detail.scrollTop > 0);
+                return;
+            }
+            const content = (target as HTMLIonContentElement);
+
+            const page = content.closest('.ion-page');
+            if (!page) {
+                return;
+            }
+
+            page.querySelector<HTMLIonHeaderElement>('ion-header')?.classList.toggle('core-header-shadow', detail.scrollTop > 0);
+
+            const scrollElement = await content.getScrollElement();
+            content.classList.toggle('core-footer-shadow', !CoreDom.scrollIsBottom(scrollElement));
         });
 
         // Listen for session expired events.

src/core/directives/collapsible-footer.ts

@@ -126,6 +126,9 @@ export class CoreCollapsibleFooterDirective implements OnInit, OnDestroy {
         const scroll = await this.content.getScrollElement();
         this.content.scrollEvents = true;
 
+        // Init shadow.
+        this.content.classList.toggle('core-footer-shadow', !CoreDom.scrollIsBottom(scroll));
+
         this.content.addEventListener('ionScroll', this.contentScrollListener = (e: CustomEvent<ScrollDetail>): void => {
             if (!this.content) {
                 return;

src/core/singletons/dom.ts

@@ -232,6 +232,21 @@ export class CoreDom {
         return CoreDom.scrollToElement(container, '.core-input-error');
     }
 
+    /**
+     * Has the scroll reached bottom?
+     *
+     * @param scrollElement Scroll Element.
+     * @param marginError Error margin when calculating.
+     * @return Wether the scroll reached the bottom.
+     */
+    static scrollIsBottom(scrollElement?: HTMLElement, marginError = 0): boolean {
+        if (!scrollElement) {
+            return true;
+        }
+
+        return scrollElement.scrollTop + scrollElement.clientHeight >= scrollElement.scrollHeight - marginError;
+    }
+
     /**
      * Move element to content so it can be slotted.
      *

src/theme/theme.base.scss

@@ -1434,8 +1434,11 @@ ion-grid.core-no-grid > ion-row {
     right: 0;
 }
 
-[collapsible-footer] {
+.core-footer-shadow [collapsible-footer] {
     box-shadow: var(--drop-shadow-top, none);
+}
+[collapsible-footer] {
+    transition: box-shadow 0.5s;
     width: 100%;
     bottom: 0;
     z-index: 3;