feat(viewer): Add smooth zoom and scroll animations to viewer

changelog.md

@@ -1,5 +1,14 @@
 # Changelog
 
+## 2025-12-11 - 2.1.0 - feat(viewer)
+Add smooth zoom and scroll animations to viewer
+
+- Introduce smooth zoom animation: new private animateZoomTo(targetZoom, duration) method and zoomAnimationId to track/cancel running animations
+- Animate transitions for numeric zoom presets and zoom step changes (handleZoomStep now uses animateZoomTo)
+- Cancel ongoing zoom animation when user manipulates the zoom slider
+- Make fit-to-width and fit-to-page calculations optionally animate (calculateFitWidth/ calculateFitPage accept animate flag)
+- Add animated scrolling helper animateScrollTo for smooth page scrolling when requested (used when smooth=true)
+
 ## 2025-12-11 - 2.0.6 - fix(DeDocumentViewer)
 Account for toolbar and padding when calculating Fit Page zoom in viewer
 

ts/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@design.estate/dees-document',
-  version: '2.0.6',
+  version: '2.1.0',
   description: 'A sophisticated framework for dynamically generating and rendering business documents like invoices with modern web technologies, featuring PDF creation, templating, and automation.'
 }

ts_web/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@design.estate/dees-document',
-  version: '2.0.6',
+  version: '2.1.0',
   description: 'A sophisticated framework for dynamically generating and rendering business documents like invoices with modern web technologies, featuring PDF creation, templating, and automation.'
 }

ts_web/elements/viewer.ts

@@ -105,6 +105,9 @@ export class DeDocumentViewer extends DeesElement {
   @state()
   accessor thumbnailPages: number[] = [];
 
+  // Zoom animation
+  private zoomAnimationId: number | null = null;
+
   public static styles = [
     cssManager.defaultStyles,
     css`
@@ -905,31 +908,69 @@ export class DeDocumentViewer extends DeesElement {
       this.updateDisplayZoom();
     } else if (value === "fit-width") {
       // Calculate zoom to fit page width to viewport width
-      this.calculateFitWidth();
+      this.calculateFitWidth(true);
     } else if (value === "fit-page") {
       // Calculate zoom to fit entire page in viewport
-      this.calculateFitPage();
+      this.calculateFitPage(true);
     } else {
-      this.zoomLevel = value;
-      this.displayZoom = value;
+      // Animate to numeric preset
+      this.animateZoomTo(value);
     }
   }
 
   private handleZoomStep(delta: number): void {
     const current = this.zoomLevel ?? this.displayZoom;
     const newZoom = Math.min(400, Math.max(25, current + delta));
-    this.zoomLevel = newZoom;
-    this.displayZoom = newZoom;
+    this.animateZoomTo(newZoom);
     this.zoomMode = newZoom;
   }
 
   private handleZoomSlider(e: Event): void {
+    // Cancel any running animation when user takes manual control
+    if (this.zoomAnimationId !== null) {
+      cancelAnimationFrame(this.zoomAnimationId);
+      this.zoomAnimationId = null;
+    }
     const value = parseInt((e.target as HTMLInputElement).value, 10);
     this.zoomLevel = value;
     this.displayZoom = value;
     this.zoomMode = value;
   }
 
+  /**
+   * Animate zoom level to target value
+   * @param targetZoom - Target zoom percentage
+   * @param duration - Animation duration in ms (default: 200)
+   */
+  private animateZoomTo(targetZoom: number, duration: number = 200): void {
+    // Cancel any existing animation
+    if (this.zoomAnimationId !== null) {
+      cancelAnimationFrame(this.zoomAnimationId);
+    }
+
+    const startZoom = this.zoomLevel ?? this.displayZoom;
+    const startTime = performance.now();
+    const easeOutCubic = (t: number) => 1 - Math.pow(1 - t, 3);
+
+    const animate = (currentTime: number) => {
+      const elapsed = currentTime - startTime;
+      const progress = Math.min(elapsed / duration, 1);
+      const easedProgress = easeOutCubic(progress);
+
+      const currentZoom = startZoom + (targetZoom - startZoom) * easedProgress;
+      this.zoomLevel = Math.round(currentZoom);
+      this.displayZoom = this.zoomLevel;
+
+      if (progress < 1) {
+        this.zoomAnimationId = requestAnimationFrame(animate);
+      } else {
+        this.zoomAnimationId = null;
+      }
+    };
+
+    this.zoomAnimationId = requestAnimationFrame(animate);
+  }
+
   private handleSpacingPreset(value: number): void {
     this.pageGap = value;
   }
@@ -1083,19 +1124,24 @@ export class DeDocumentViewer extends DeesElement {
     setTimeout(cleanup, 100);
   }
 
-  private calculateFitWidth(): void {
+  private calculateFitWidth(animate: boolean = false): void {
     const viewport = this.shadowRoot?.querySelector(".viewport");
     if (!viewport) return;
 
     // Account for padding and scrollbar width
     const viewportWidth = viewport.clientWidth - 32 - 16;
     const scale = viewportWidth / plugins.shared.A4_WIDTH;
+    const targetZoom = Math.round(scale * 100);
 
-    this.zoomLevel = Math.round(scale * 100);
-    this.displayZoom = this.zoomLevel;
+    if (animate) {
+      this.animateZoomTo(targetZoom);
+    } else {
+      this.zoomLevel = targetZoom;
+      this.displayZoom = targetZoom;
+    }
   }
 
-  private calculateFitPage(): void {
+  private calculateFitPage(animate: boolean = false): void {
     const viewport = this.shadowRoot?.querySelector(".viewport");
     if (!viewport) return;
 
@@ -1110,9 +1156,14 @@ export class DeDocumentViewer extends DeesElement {
     const scaleByHeight = viewportHeight / plugins.shared.A4_HEIGHT;
     const scaleByWidth = viewportWidth / plugins.shared.A4_WIDTH;
     const scale = Math.min(scaleByHeight, scaleByWidth);
+    const targetZoom = Math.round(scale * 100);
 
-    this.zoomLevel = Math.round(scale * 100);
-    this.displayZoom = this.zoomLevel;
+    if (animate) {
+      this.animateZoomTo(targetZoom);
+    } else {
+      this.zoomLevel = targetZoom;
+      this.displayZoom = targetZoom;
+    }
   }
 
   private updateDisplayZoom(): void {
@@ -1297,14 +1348,42 @@ export class DeDocumentViewer extends DeesElement {
       const pageRect = targetPage.getBoundingClientRect();
       const pageOffsetFromDoc = pageRect.top - docRect.top;
 
-      // Scroll to the page position
-      viewport.scrollTo({
-        top: pageOffsetFromDoc,
-        behavior: smooth ? "smooth" : "instant",
-      });
+      // Scroll to the page position with fast custom animation
+      if (smooth) {
+        this.animateScrollTo(viewport, pageOffsetFromDoc, 250);
+      } else {
+        viewport.scrollTop = pageOffsetFromDoc;
+      }
     }
   }
 
+  /**
+   * Animate scroll to target position
+   * @param element - The scrollable element
+   * @param targetTop - Target scroll position
+   * @param duration - Animation duration in ms (default: 150)
+   */
+  private animateScrollTo(element: Element, targetTop: number, duration: number = 150): void {
+    const startTop = element.scrollTop;
+    const distance = targetTop - startTop;
+    const startTime = performance.now();
+    const easeOutCubic = (t: number) => 1 - Math.pow(1 - t, 3);
+
+    const step = (currentTime: number) => {
+      const elapsed = currentTime - startTime;
+      const progress = Math.min(elapsed / duration, 1);
+      const easedProgress = easeOutCubic(progress);
+
+      element.scrollTop = startTop + distance * easedProgress;
+
+      if (progress < 1) {
+        requestAnimationFrame(step);
+      }
+    };
+
+    requestAnimationFrame(step);
+  }
+
   /**
    * Trigger the print dialog
    */