Development: Decompose PDF Preview components

src/main/webapp/app/lecture/pdf-preview/pdf-preview-enlarged-canvas/pdf-preview-enlarged-canvas.component.html

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+<div #enlargedContainer class="enlarged-container" (click)="closeIfOutside($event)">
+    @if (isEnlargedCanvasLoading()) {
+        <div class="d-flex justify-content-center position-absolute">
+            <div class="spinner-border" role="status">
+                <span class="sr-only" jhiTranslate="loading"></span>
+            </div>
+        </div>
+    }
+    <canvas #enlargedCanvas></canvas>
+    <button class="btn btn-close" (click)="closeEnlargedView($event)"></button>
+    @if (currentPage() !== 1) {
+        <button class="btn btn-secondary nav-button left" (click)="handleNavigation('prev', $event)" aria-label="Previous page">←</button>
+    }
+    @if (currentPage() !== totalPages()) {
+        <button class="btn btn-secondary nav-button right" (click)="handleNavigation('next', $event)" aria-label="Next page">→</button>
+    }
+    <div class="page-number-display">{{ currentPage() }}</div>
+</div>

src/main/webapp/app/lecture/pdf-preview/pdf-preview-enlarged-canvas/pdf-preview-enlarged-canvas.component.scss

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+.enlarged-container {
+    position: absolute;
+    width: 100%;
+    height: 100%;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    background-color: var(--pdf-preview-enlarged-container-overlay);
+    z-index: 5;
+
+    .btn-close {
+        position: absolute;
+        top: 10px;
+        right: 10px;
+        cursor: pointer;
+        color: var(--bs-body-color);
+    }
+}
+
+.nav-button {
+    position: absolute;
+    transform: translateY(-50%);
+    cursor: pointer;
+    border-radius: 50%;
+    width: 30px;
+    height: 30px;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    font-size: 20px;
+    z-index: 3;
+}
+
+.nav-button.left {
+    left: calc(5% + 10px);
+
+    @media (max-width: 1200px) {
+        left: 10px;
+    }
+}
+
+.nav-button.right {
+    right: calc(5% + 10px);
+
+    @media (max-width: 1200px) {
+        right: 10px;
+    }
+}
+
+.page-number-display {
+    position: absolute;
+    bottom: 10px;
+    right: calc(5% + 10px);
+    font-size: 18px;
+    color: var(--bs-body-color);
+    z-index: 2;
+    text-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
+
+    @media (max-width: 1200px) {
+        right: 10px;
+    }
+}

src/main/webapp/app/lecture/pdf-preview/pdf-preview-enlarged-canvas/pdf-preview-enlarged-canvas.component.ts

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+import { Component, ElementRef, HostListener, effect, input, output, signal, viewChild } from '@angular/core';
+import { ArtemisSharedModule } from 'app/shared/shared.module';
+
+type NavigationDirection = 'next' | 'prev';
+
+@Component({
+    selector: 'jhi-pdf-preview-enlarged-canvas-component',
+    templateUrl: './pdf-preview-enlarged-canvas.component.html',
+    styleUrls: ['./pdf-preview-enlarged-canvas.component.scss'],
+    standalone: true,
+    imports: [ArtemisSharedModule],
+})
+export class PdfPreviewEnlargedCanvasComponent {
+    enlargedContainer = viewChild.required<ElementRef<HTMLDivElement>>('enlargedContainer');
+    enlargedCanvas = viewChild.required<ElementRef<HTMLCanvasElement>>('enlargedCanvas');
+
+    readonly DEFAULT_ENLARGED_SLIDE_HEIGHT = 800;
+
+    // Inputs
+    pdfContainer = input.required<HTMLDivElement>();
+    originalCanvas = input<HTMLCanvasElement>();
+    totalPages = input<number>(0);
+
+    // Signals
+    currentPage = signal<number>(1);
+    isEnlargedCanvasLoading = signal<boolean>(false);
+
+    //Outputs
+    isEnlargedViewOutput = output<boolean>();
+
+    constructor() {
+        effect(
+            () => {
+                this.enlargedContainer().nativeElement.style.top = `${this.pdfContainer().scrollTop}px`;
+                this.displayEnlargedCanvas(this.originalCanvas()!);
+            },
+            { allowSignalWrites: true },
+        );
+    }
+
+    /**
+     * Handles navigation within the PDF viewer using keyboard arrow keys.
+     * @param event - The keyboard event captured for navigation.
+     */
+    @HostListener('document:keydown', ['$event'])
+    handleKeyboardEvents(event: KeyboardEvent) {
+        if (event.key === 'ArrowRight' && this.currentPage() < this.totalPages()) {
+            this.navigatePages('next');
+        } else if (event.key === 'ArrowLeft' && this.currentPage() > 1) {
+            this.navigatePages('prev');
+        }
+    }
+
+    /**
+     * Adjusts the canvas size based on the window resize event to ensure proper display.
+     */
+    @HostListener('window:resize')
+    resizeCanvasBasedOnContainer() {
+        this.adjustCanvasSize();
+    }
+
+    /**
+     * Dynamically updates the canvas size within an enlarged view based on the viewport.
+     */
+    adjustCanvasSize = () => {
+        const canvasElements = this.pdfContainer().querySelectorAll('.pdf-canvas-container canvas');
+        if (this.currentPage() - 1 < canvasElements.length) {
+            const canvas = canvasElements[this.currentPage() - 1] as HTMLCanvasElement;
+            this.updateEnlargedCanvas(canvas);
+        }
+    };
+
+    displayEnlargedCanvas(originalCanvas: HTMLCanvasElement) {
+        this.isEnlargedCanvasLoading.set(true);
+        this.currentPage.set(Number(originalCanvas.id));
+        this.toggleBodyScroll(true);
+        setTimeout(() => {
+            this.updateEnlargedCanvas(originalCanvas);
+        }, 500);
+    }
+
+    /**
+     * Updates the enlarged canvas dimensions to optimize PDF page display within the current viewport.
+     * This method dynamically adjusts the size, position, and scale of the canvas to maintain the aspect ratio,
+     * ensuring the content is centered and displayed appropriately within the available space.
+     * It is called within an animation frame to synchronize updates with the browser's render cycle for smooth visuals.
+     *
+     * @param originalCanvas - The source canvas element used to extract image data for resizing and redrawing.
+     */
+    updateEnlargedCanvas(originalCanvas: HTMLCanvasElement) {
+        requestAnimationFrame(() => {
+            const isVertical = originalCanvas.height > originalCanvas.width;
+            this.adjustPdfContainerSize(isVertical);
+
+            const scaleFactor = this.calculateScaleFactor(originalCanvas);
+            this.resizeCanvas(originalCanvas, scaleFactor);
+            this.redrawCanvas(originalCanvas);
+            this.isEnlargedCanvasLoading.set(false);
+        });
+    }
+
+    /**
+     * Calculates the scaling factor to adjust the canvas size based on the dimensions of the container.
+     * This method ensures that the canvas is scaled to fit within the container without altering the aspect ratio.
+     *
+     * @param originalCanvas - The original canvas element representing the PDF page.
+     * @returns The scaling factor used to resize the original canvas to fit within the container dimensions.
+     */
+    calculateScaleFactor(originalCanvas: HTMLCanvasElement): number {
+        const containerWidth = this.pdfContainer().clientWidth;
+        const containerHeight = this.pdfContainer().clientHeight;
+
+        let scaleX, scaleY;
+
+        if (originalCanvas.height > originalCanvas.width) {
+            // Vertical slide
+            const fixedHeight = this.DEFAULT_ENLARGED_SLIDE_HEIGHT;
+            scaleY = fixedHeight / originalCanvas.height;
+            scaleX = containerWidth / originalCanvas.width;
+        } else {
+            // Horizontal slide
+            scaleX = containerWidth / originalCanvas.width;
+            scaleY = containerHeight / originalCanvas.height;
+        }
+
+        return Math.min(scaleX, scaleY);
+    }
+
+    /**
+     * Resizes the canvas according to the computed scale factor.
+     * This method updates the dimensions of the enlarged canvas element to ensure that the entire PDF page
+     * is visible and properly scaled within the viewer.
+     *
+     * @param originalCanvas - The canvas element from which the image is scaled.
+     * @param scaleFactor - The factor by which the canvas is resized.
+     */
+    resizeCanvas(originalCanvas: HTMLCanvasElement, scaleFactor: number): void {
+        const enlargedCanvas = this.enlargedCanvas().nativeElement;
+        enlargedCanvas.width = originalCanvas.width * scaleFactor;
+        enlargedCanvas.height = originalCanvas.height * scaleFactor;
+    }
+
+    /**
+     * Redraws the original canvas content onto the enlarged canvas at the updated scale.
+     * This method ensures that the image is rendered clearly and correctly positioned on the enlarged canvas.
+     *
+     * @param originalCanvas - The original canvas containing the image to be redrawn.
+     */
+    redrawCanvas(originalCanvas: HTMLCanvasElement): void {
+        const enlargedCanvas = this.enlargedCanvas().nativeElement;
+        const context = enlargedCanvas.getContext('2d');
+        context!.clearRect(0, 0, enlargedCanvas.width, enlargedCanvas.height);
+        context!.drawImage(originalCanvas, 0, 0, enlargedCanvas.width, enlargedCanvas.height);
+    }
+
+    /**
+     * Adjusts the size of the PDF container based on whether the enlarged view is active or not.
+     * If the enlarged view is active, the container's size is reduced to focus on the enlarged content.
+     * If the enlarged view is closed, the container returns to its original size.
+     *
+     * @param isVertical A boolean flag indicating whether to enlarge or reset the container size.
+     */
+    adjustPdfContainerSize(isVertical: boolean): void {
+        const pdfContainer = this.pdfContainer();
+        if (isVertical) {
+            pdfContainer.style.height = `${this.DEFAULT_ENLARGED_SLIDE_HEIGHT}px`;
+        } else {
+            pdfContainer.style.height = '60vh';
+        }
+    }
+
+    /**
+     * Toggles the ability to scroll through the PDF container.
+     * @param disable A boolean flag indicating whether scrolling should be disabled (`true`) or enabled (`false`).
+     */
+    toggleBodyScroll(disable: boolean): void {
+        this.pdfContainer().style.overflow = disable ? 'hidden' : 'auto';
+    }
+
+    /**
+     * Closes the enlarged view of the PDF and re-enables scrolling in the PDF container.
+     */
+    closeEnlargedView(event: MouseEvent) {
+        this.isEnlargedViewOutput.emit(false);
+        this.adjustPdfContainerSize(false);
+        this.toggleBodyScroll(false);
+        event.stopPropagation();
+    }
+
+    /**
+     * Closes the enlarged view if a click event occurs outside the actual canvas area but within the enlarged container.
+     * @param event The mouse event captured, used to determine the location of the click.
+     */
+    closeIfOutside(event: MouseEvent): void {
+        const target = event.target as HTMLElement;
+        const enlargedCanvas = this.enlargedCanvas().nativeElement;
+
+        if (target.classList.contains('enlarged-container') && target !== enlargedCanvas) {
+            this.closeEnlargedView(event);
+        }
+    }
+
+    /**
+     * Handles navigation between PDF pages and stops event propagation to prevent unwanted side effects.
+     * @param direction The direction to navigate.
+     * @param event The MouseEvent to be stopped.
+     */
+    handleNavigation(direction: NavigationDirection, event: MouseEvent): void {
+        event.stopPropagation();
+        this.navigatePages(direction);
+    }
+
+    /**
+     * Navigates to a specific page in the PDF based on the direction relative to the current page.
+     * @param direction The navigation direction (next or previous).
+     */
+    navigatePages(direction: NavigationDirection) {
+        const nextPageIndex = direction === 'next' ? this.currentPage() + 1 : this.currentPage() - 1;
+        if (nextPageIndex > 0 && nextPageIndex <= this.totalPages()) {
+            this.currentPage.set(nextPageIndex);
+            const canvas = this.pdfContainer().querySelectorAll('.pdf-canvas-container canvas')[this.currentPage() - 1] as HTMLCanvasElement;
+            this.updateEnlargedCanvas(canvas);
+        }
+    }
+}

src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.html

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+<div class="pdf-container" #pdfContainer>
+    @if (isEnlargedView()) {
+        <jhi-pdf-preview-enlarged-canvas-component
+            class="enlarged-canvas"
+            [pdfContainer]="pdfContainer"
+            [totalPages]="totalPages()"
+            [originalCanvas]="originalCanvas()"
+            (isEnlargedViewOutput)="isEnlargedView.set($event)"
+        />
+    }
+</div>

src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.scss

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+.pdf-container {
+    position: relative;
+    display: grid;
+    grid-template-columns: repeat(auto-fill, minmax(270px, 1fr));
+    gap: 10px;
+    height: 60vh;
+    overflow-y: auto;
+    border: 1px solid var(--border-color);
+    padding: 10px;
+    margin: 10px 0;
+    width: 100%;
+    box-shadow: 0 2px 5px var(--pdf-preview-pdf-container-shadow);
+    z-index: 0;
+
+    @media (max-width: 800px) {
+        grid-template-columns: repeat(auto-fit, minmax(270px, 1fr));
+    }
+
+    @media (max-width: 500px) {
+        grid-template-columns: 1fr;
+    }
+}
+
+.enlarged-canvas {
+    display: contents;
+}