Improves all-day event header animation performance

Optimizes all-day event header animation by caching DOM elements.

This change avoids redundant DOM queries during animation,
resulting in smoother transitions when adding or removing all-day
events. It also introduces a destroy method for proper cleanup
of cached elements.

src/renderers/HeaderRenderer.ts

@@ -19,14 +19,76 @@ export interface HeaderRenderer {
  * Base class with shared addToAllDay implementation
  */
 export abstract class BaseHeaderRenderer implements HeaderRenderer {
+  // Cached DOM elements to avoid redundant queries
+  private cachedCalendarHeader: HTMLElement | null = null;
+  private cachedAllDayContainer: HTMLElement | null = null;
+  private cachedHeaderSpacer: HTMLElement | null = null;
+  
   abstract render(calendarHeader: HTMLElement, context: HeaderRenderContext): void;
 
+  /**
+   * Get cached calendar header element
+   */
+  private getCalendarHeader(): HTMLElement | null {
+    if (!this.cachedCalendarHeader) {
+      this.cachedCalendarHeader = document.querySelector('swp-calendar-header');
+    }
+    return this.cachedCalendarHeader;
+  }
+
+  /**
+   * Get cached all-day container element
+   */
+  private getAllDayContainer(): HTMLElement | null {
+    if (!this.cachedAllDayContainer) {
+      const calendarHeader = this.getCalendarHeader();
+      if (calendarHeader) {
+        this.cachedAllDayContainer = calendarHeader.querySelector('swp-allday-container');
+      }
+    }
+    return this.cachedAllDayContainer;
+  }
+
+  /**
+   * Get cached header spacer element
+   */
+  private getHeaderSpacer(): HTMLElement | null {
+    if (!this.cachedHeaderSpacer) {
+      this.cachedHeaderSpacer = document.querySelector('swp-header-spacer');
+    }
+    return this.cachedHeaderSpacer;
+  }
+
+  /**
+   * Calculate all-day height based on number of rows
+   */
+  private calculateAllDayHeight(targetRows: number): {
+    targetHeight: number;
+    currentHeight: number;
+    heightDifference: number;
+  } {
+    const root = document.documentElement;
+    const targetHeight = targetRows * ALL_DAY_CONSTANTS.SINGLE_ROW_HEIGHT;
+    const currentHeight = parseInt(getComputedStyle(root).getPropertyValue('--all-day-row-height') || '0');
+    const heightDifference = targetHeight - currentHeight;
+    
+    return { targetHeight, currentHeight, heightDifference };
+  }
+
+  /**
+   * Clear cached DOM elements (call when DOM structure changes)
+   */
+  private clearCache(): void {
+    this.cachedCalendarHeader = null;
+    this.cachedAllDayContainer = null;
+    this.cachedHeaderSpacer = null;
+  }
+
   /**
    * Expand header to show all-day row
    */
   addToAllDay(dayHeader: HTMLElement): void {
-    const root = document.documentElement;
+    const { currentHeight } = this.calculateAllDayHeight(0);
-    const currentHeight = parseInt(getComputedStyle(root).getPropertyValue('--all-day-row-height') || '0');
     
     if (currentHeight === 0) {
       // Find the calendar header element to animate
@@ -47,7 +109,7 @@ export abstract class BaseHeaderRenderer implements HeaderRenderer {
   }
 
   checkAndAnimateAllDayHeight(): void {
-    const container = document.querySelector('swp-allday-container');
+    const container = this.getAllDayContainer();
     if (!container) return;
     
     const allDayEvents = container.querySelectorAll('swp-allday-event');
@@ -100,24 +162,21 @@ export abstract class BaseHeaderRenderer implements HeaderRenderer {
    * Animate all-day container to specific number of rows
    */
   animateToRows(targetRows: number): void {
-    const root = document.documentElement;
+    const { targetHeight, currentHeight, heightDifference } = this.calculateAllDayHeight(targetRows);
-    const targetHeight = targetRows * ALL_DAY_CONSTANTS.SINGLE_ROW_HEIGHT;
-    const currentHeight = parseInt(getComputedStyle(root).getPropertyValue('--all-day-row-height') || '0');
     
     if (targetHeight === currentHeight) return; // No animation needed
     
     console.log(`🎬 All-day height animation starting: ${currentHeight}px → ${targetHeight}px (${Math.ceil(currentHeight / ALL_DAY_CONSTANTS.SINGLE_ROW_HEIGHT)} → ${targetRows} rows)`);
     
-    // Find elements to animate
+    // Get cached elements
-    const calendarHeader = document.querySelector('swp-calendar-header') as HTMLElement;
+    const calendarHeader = this.getCalendarHeader();
-    const headerSpacer = document.querySelector('swp-header-spacer') as HTMLElement;
+    const headerSpacer = this.getHeaderSpacer();
-    const allDayContainer = calendarHeader?.querySelector('swp-allday-container') as HTMLElement;
+    const allDayContainer = this.getAllDayContainer();
     
     if (!calendarHeader || !allDayContainer) return;
     
     // Get current parent height for animation
     const currentParentHeight = parseFloat(getComputedStyle(calendarHeader).height);
-    const heightDifference = targetHeight - currentHeight;
     const targetParentHeight = currentParentHeight + heightDifference;
     
     const animations = [
@@ -133,6 +192,7 @@ export abstract class BaseHeaderRenderer implements HeaderRenderer {
     
     // Add spacer animation if spacer exists
     if (headerSpacer) {
+      const root = document.documentElement;
       const currentSpacerHeight = parseInt(getComputedStyle(root).getPropertyValue('--header-height')) + currentHeight;
       const targetSpacerHeight = parseInt(getComputedStyle(root).getPropertyValue('--header-height')) + targetHeight;
       
@@ -150,6 +210,7 @@ export abstract class BaseHeaderRenderer implements HeaderRenderer {
     
     // Update CSS variable after animation
     Promise.all(animations.map(anim => anim.finished)).then(() => {
+      const root = document.documentElement;
       root.style.setProperty('--all-day-row-height', `${targetHeight}px`);
       eventBus.emit('header:height-changed');
     });
@@ -163,9 +224,17 @@ export abstract class BaseHeaderRenderer implements HeaderRenderer {
       // Create simple all-day container (initially hidden)
       container = document.createElement('swp-allday-container');
       calendarHeader.appendChild(container);
-    } else {
+      // Clear cache since DOM structure changed
+      this.clearCache();
     }
   }
+
+  /**
+   * Public cleanup method for cached elements
+   */
+  public destroy(): void {
+    this.clearCache();
+  }
 }
 
 /**