MOBILE-3320 core: Add format text placeholder when loading

src/core/directives/format-text.ts

@@ -72,6 +72,7 @@ export class CoreFormatTextDirective implements OnChanges {
     @Input() wsNotFiltered?: boolean | string; // If true it means the WS didn't filter the text for some reason.
     @Input() captureLinks?: boolean; // Whether links should tried to be opened inside the app. Defaults to true.
     @Input() openLinksInApp?: boolean; // Whether links should be opened in InAppBrowser.
+    @Input() hideIfEmpty = false; // If true, the tag will contain nothing if text is empty.
 
     /**
      * Max height in pixels to render the content box. It should be 50 at least to make sense.
@@ -86,6 +87,8 @@ export class CoreFormatTextDirective implements OnChanges {
     protected element: HTMLElement;
     protected showMoreDisplayed = false;
     protected loadingChangedListener?: CoreEventObserver;
+    protected emptyText = '';
+    protected contentSpan: HTMLElement;
 
     constructor(
         element: ElementRef,
@@ -93,9 +96,20 @@ export class CoreFormatTextDirective implements OnChanges {
         protected viewContainerRef: ViewContainerRef,
         protected sanitizer: DomSanitizer,
     ) {
-
         this.element = element.nativeElement;
-        this.element.classList.add('opacity-hide'); // Hide contents until they're treated.
+        this.element.classList.add('core-format-text-loading'); // Hide contents until they're treated.
+
+        const placeholder = document.createElement('span');
+        placeholder.classList.add('core-format-text-loader');
+        this.element.appendChild(placeholder);
+
+        this.contentSpan = document.createElement('span');
+        this.contentSpan.classList.add('core-format-text-content');
+        this.element.appendChild(this.contentSpan);
+
+        this.emptyText = this.hideIfEmpty ? '' : ' ';
+        this.contentSpan.innerHTML = this.emptyText;
+
         this.afterRender = new EventEmitter<void>();
 
         this.element.addEventListener('click', this.elementClicked.bind(this));
@@ -183,7 +197,7 @@ export class CoreFormatTextDirective implements OnChanges {
      * Add magnifying glass icons to view adapted images at full size.
      */
     addMagnifyingGlasses(): void {
-        const imgs = Array.from(this.element.querySelectorAll('.core-adapted-img-container > img'));
+        const imgs = Array.from(this.contentSpan.querySelectorAll('.core-adapted-img-container > img'));
         if (!imgs.length) {
             return;
         }
@@ -339,7 +353,7 @@ export class CoreFormatTextDirective implements OnChanges {
      */
     protected finishRender(): void {
         // Show the element again.
-        this.element.classList.remove('opacity-hide');
+        this.element.classList.remove('core-format-text-loading');
         // Emit the afterRender output.
         this.afterRender.emit();
     }
@@ -349,7 +363,7 @@ export class CoreFormatTextDirective implements OnChanges {
      */
     protected async formatAndRenderContents(): Promise<void> {
         if (!this.text) {
-            this.element.innerHTML = ''; // Remove current contents.
+            this.contentSpan.innerHTML = this.emptyText; // Remove current contents.
             this.finishRender();
 
             return;
@@ -370,12 +384,12 @@ export class CoreFormatTextDirective implements OnChanges {
         // Disable media adapt to correctly calculate the height.
         this.element.classList.add('core-disable-media-adapt');
 
-        this.element.innerHTML = ''; // Remove current contents.
+        this.contentSpan.innerHTML = ''; // Remove current contents.
         if (this.maxHeight && result.div.innerHTML != '' &&
                 (this.fullOnClick || (window.innerWidth < 576 || window.innerHeight < 576))) { // Don't collapse in big screens.
 
             // Move the children to the current element to be able to calculate the height.
-            CoreDomUtils.moveChildren(result.div, this.element);
+            CoreDomUtils.moveChildren(result.div, this.contentSpan);
 
             // Calculate the height now.
             this.calculateHeight();
@@ -396,7 +410,7 @@ export class CoreFormatTextDirective implements OnChanges {
                     });
             }
         } else {
-            CoreDomUtils.moveChildren(result.div, this.element);
+            CoreDomUtils.moveChildren(result.div, this.contentSpan);
 
             // Add magnifying glasses to images.
             this.addMagnifyingGlasses();
@@ -405,7 +419,7 @@ export class CoreFormatTextDirective implements OnChanges {
         if (result.options.filter) {
             // Let filters handle HTML. We do it here because we don't want them to block the render of the text.
             CoreFilterDelegate.handleHtml(
-                this.element,
+                this.contentSpan,
                 result.filters,
                 this.viewContainerRef,
                 result.options,

src/core/directives/tests/format-text.test.ts

@@ -66,7 +66,7 @@ describe('CoreFormatTextDirective', () => {
         );
 
         // Assert
-        const text = fixture.nativeElement.querySelector('core-format-text');
+        const text = fixture.nativeElement.querySelector('core-format-text .core-format-text-content');
         expect(text).not.toBeNull();
         expect(text.innerHTML).toEqual(sentence);
     });

src/core/features/course/components/format/core-course-format.html

@@ -142,7 +142,10 @@
         </ion-item-divider>
 
         <ion-item class="ion-text-wrap" *ngIf="section.summary">
-            <core-format-text [text]="section.summary" contextLevel="course" [contextInstanceId]="course?.id"></core-format-text>
+            <ion-label>
+                <core-format-text [text]="section.summary" contextLevel="course" [contextInstanceId]="course?.id">
+                </core-format-text>
+            </ion-label>
         </ion-item>
 
         <ng-container *ngFor="let module of section.modules">

src/theme/bootstrap.scss

@@ -9,6 +9,7 @@
     clip: rect(0, 0, 0, 0);
     white-space: nowrap;
     border: 0;
+    display: block !important;
 }
 
 .sr-only-focusable:active, .sr-only-focusable:focus {

src/theme/components/format-text.scss

@@ -2,22 +2,70 @@
 /** Styles of elements inside the directive should be placed in format-text.scss */
 @import "~theme/globals";
 
-:root {
+core-format-text {
-    --background: var(--background, #{$ion-item-background});
+    --core-format-text-background: var(--background, #{$ion-item-background});
-    --background-gradient-rgb: var(--background-rgb, #{color-to-rgb-list($ion-item-background)});
+    --core-format-text-background-gradient-rgb: var(--background-rgb, #{color-to-rgb-list($ion-item-background)});
-    --viewer-icon-background: rgba(255, 255, 255, .5);
+    --core-format-text-viewer-icon-background: rgba(255, 255, 255, .5);
+    --core-format-text-loader-shine: 251,251,251;
 }
 
-:root body.dark {
+body.dark core-format-text {
-    --background: var(--background, #{$ion-item-background-dark});
+    --core-format-text-background: var(--background, #{$ion-item-background-dark});
-    --background-gradient-rgb: var(--background-rgb, #{color-to-rgb-list($ion-item-background-dark)});
+    --core-format-text-background-gradient-rgb: var(--background-rgb, #{color-to-rgb-list($ion-item-background-dark)});
-    --viewer-icon-background: rgba(0, 0, 0, .5);
+    --core-format-text-viewer-icon-background: rgba(0, 0, 0, .5);
+    --core-format-text-loader-shine: 90,90,90;
 }
 
 core-format-text {
+    display: contents;
+
+    .core-format-text-loader {
+        opacity: 0;
+        @include core-transition(opacity, 200ms);
+        display: contents;
+    }
+
+    &.core-format-text-loading {
+        position: relative;
+        width: 100%;
+        height: 100%;
+        opacity: 1;
+        background-color: rgba(0,0,0,.1);
+        overflow: hidden;
+        border-radius: 5px;
+        display: block;
+
+        .core-format-text-loader {
+            position: absolute;
+            left: -45%;
+            height: 100%;
+            width: 45%;
+            background-image: -webkit-linear-gradient(to left, rgba(var(--core-format-text-loader-shine), .05), rgba(var(--core-format-text-loader-shine), .3), rgba(var(--core-format-text-loader-shine), .6), rgba(var(--core-format-text-loader-shine), .3), rgba(var(--core-format-text-loader-shine), .05));
+            background-image: linear-gradient(to left, rgba(var(--core-format-text-loader-shine), .05), rgba(var(--core-format-text-loader-shine), .3), rgba(var(--core-format-text-loader-shine), .6), rgba(var(--core-format-text-loader-shine), .3), rgba(var(--core-format-text-loader-shine), .05));
+            animation: loading 1s infinite;
+            opacity: 1;
+            display: inline;
+        }
+
+        .core-format-text-content {
+            opacity: 0;
+            display: inline;
+        }
+
+        .core-show-more {
+            display: none !important;
+        }
+    }
+
+    .core-format-text-content {
+        opacity: 1;
+        @include core-transition(opacity, 200ms);
+
+        display: contents;
         user-select: text;
         word-break: break-word;
         word-wrap: break-word;
+    }
 
     &[maxHeight],
     &[ng-reflect-max-height] {
@@ -57,7 +105,7 @@ core-format-text {
                     position: absolute;
                     @include position(null, 0, 0, null);
                     z-index: 7;
-                    background-color: var(--background);
+                    background-color: var(--core-format-text-background);
                     color: var(--text-color);
                     @include padding(null, null, null, 10px);
                     margin: 0;
@@ -68,10 +116,8 @@ core-format-text {
                     height: 100%;
                     position: absolute;
                     @include position(null, 0, 0, 0);
-                    background: -moz-linear-gradient(top, rgba(var(--background-gradient-rgb), 0) calc(100% - 50px), rgba(var(--background-gradient-rgb), 1) calc(100% - 15px));
+                    background: -webkit-linear-gradient(top, rgba(var(--core-format-text-background-gradient-rgb), 0) calc(100% - 50px), rgba(var(--core-format-text-background-gradient-rgb), 1) calc(100% - 15px));
-                    background: -webkit-gradient(left top, left bottom, color-stop(calc(100% - 50px), rgba(var(--background-gradient-rgb), 0)), color-stop(calc(100% - 15px), rgba(var(--background-gradient-rgb), 1)));
+                    background: linear-gradient(to bottom, rgba(var(--core-format-text-background-gradient-rgb), 0) calc(100% - 50px), rgba(var(--core-format-text-background-gradient-rgb), 1) calc(100% - 15px));
-                    background: -webkit-linear-gradient(top, rgba(var(--background-gradient-rgb), 0) calc(100% - 50px), rgba(var(--background-gradient-rgb), 1) calc(100% - 15px));
-                    background: linear-gradient(to bottom, rgba(var(--background-gradient-rgb), 0) calc(100% - 50px), rgba(var(--background-gradient-rgb), 1) calc(100% - 15px));
                     z-index: 6;
                 }
             }
@@ -115,15 +161,15 @@ core-format-text {
     .core-adapted-img-container {
         position: relative;
         display: inline-block;
-        width: 100%;
+        max-width: 100%;
     }
 
     .core-image-viewer-icon {
         position: absolute;
         @include position(null, 10px, 10px, null);
-        color: var(--black);
+        color: var(--ion-text-color);
         border-radius: 5px;
-        background-color: var(--viewer-icon-background);
+        background-color: var(--core-format-text-viewer-icon-background);
         display: flex;
 
         width: var(--a11y-min-target-size);
@@ -141,3 +187,13 @@ core-format-text {
         }
     }
 }
+
+
+@keyframes loading {
+    0% {
+        left: -45%;
+    }
+    100% {
+        left: 100%;
+    }
+}