fix(refresher): refresher is visible with multiple custom scroll targets (#25750)

Resolves #25495

core/src/components.d.ts

@@ -671,6 +671,7 @@ export namespace Components {
           * If `true`, the content will scroll behind the headers and footers. This effect can easily be seen by setting the toolbar to transparent.
          */
         "fullscreen": boolean;
+        "getBackgroundElement": () => Promise<HTMLElement>;
         /**
           * Get the element where the actual scrolling takes place. This element can be used to subscribe to `scroll` events or manually modify `scrollTop`. However, it's recommended to use the API provided by `ion-content`:  i.e. Using `ionScroll`, `ionScrollStart`, `ionScrollEnd` for scrolling events and `scrollToPoint()` to scroll the content into a certain point.
          */

core/src/components/content/content.tsx

@@ -28,6 +28,7 @@ export class Content implements ComponentInterface {
   private cTop = -1;
   private cBottom = -1;
   private scrollEl?: HTMLElement;
+  private backgroundContentEl?: HTMLElement;
   private isMainContent = true;
 
   // Detail is used in a hot loop in the scroll event, by allocating it here
@@ -188,6 +189,18 @@ export class Content implements ComponentInterface {
     return Promise.resolve(this.scrollEl!);
   }
 
+  /**
+   * Returns the background content element.
+   * @internal
+   */
+  @Method()
+  async getBackgroundElement(): Promise<HTMLElement> {
+    if (!this.backgroundContentEl) {
+      await new Promise((resolve) => componentOnReady(this.el, resolve));
+    }
+    return Promise.resolve(this.backgroundContentEl!);
+  }
+
   /**
    * Scroll to the top of the component.
    *
@@ -332,7 +345,7 @@ export class Content implements ComponentInterface {
           '--offset-bottom': `${this.cBottom}px`,
         }}
       >
-        <div id="background-content" part="background"></div>
+        <div ref={(el) => (this.backgroundContentEl = el)} id="background-content" part="background"></div>
         <TagType
           class={{
             'inner-scroll': true,

core/src/components/refresher/refresher.tsx

@@ -443,15 +443,17 @@ export class Refresher implements ComponentInterface {
       console.error('Make sure you use: <ion-refresher slot="fixed">');
       return;
     }
-
     const contentEl = this.el.closest(ION_CONTENT_ELEMENT_SELECTOR);
     if (!contentEl) {
       printIonContentErrorMsg(this.el);
       return;
     }
-
+    /**
+     * Waits for the content to be ready before querying the scroll
+     * or the background content element.
+     */
+    await contentEl.componentOnReady();
     const customScrollTarget = contentEl.querySelector(ION_CONTENT_CLASS_SELECTOR);
-
     /**
      * Query the custom scroll target (if available), first. In refresher implementations,
      * the ion-refresher element will always be a direct child of ion-content (slot="fixed"). By
@@ -459,18 +461,10 @@ export class Refresher implements ComponentInterface {
      * the correct scroll element will be returned by the implementation.
      */
     this.scrollEl = await getScrollElement(customScrollTarget ?? contentEl);
-
     /**
-     * Query the host `ion-content` directly (if it is available), to use its
-     * inner #background-content has the target. Otherwise fallback to the
-     * custom scroll target host.
-     *
-     * This makes it so that implementers do not need to re-create the background content
-     * element and styles.
+     * Query the background content element from the host ion-content element directly.
      */
-    this.backgroundContentEl = getElementRoot(contentEl ?? customScrollTarget).querySelector(
-      '#background-content'
-    ) as HTMLElement;
+    this.backgroundContentEl = await contentEl.getBackgroundElement();
 
     if (await shouldUseNativeRefresher(this.el, getIonMode(this))) {
       this.setupNativeRefresher(contentEl);