fix(modal): fixing footer pinnning after dragging content, fixing multiple footer support

Author: ShaneK

core/src/components/modal/gestures/sheet.ts

@@ -84,7 +84,7 @@ export const createSheetGesture = (
   let offset = 0;
   let canDismissBlocksGesture = false;
   let cachedScrollEl: HTMLElement | null = null;
-  let cachedFooterEl: HTMLIonFooterElement | null = null;
+  let cachedFooterEls: HTMLIonFooterElement[] | null = null;
   let cachedFooterYPosition: number | null = null;
   let currentFooterState: 'moving' | 'stationary' | null = null;
   const canDismissMaxStep = 0.95;
@@ -126,9 +126,9 @@ export const createSheetGesture = (
    * @param newPosition Whether the footer is in a moving or stationary position.
    */
   const swapFooterPosition = (newPosition: 'moving' | 'stationary') => {
-    if (!cachedFooterEl) {
-      cachedFooterEl = baseEl.querySelector('ion-footer') as HTMLIonFooterElement | null;
-      if (!cachedFooterEl) {
+    if (!cachedFooterEls) {
+      cachedFooterEls = Array.from(baseEl.querySelectorAll('ion-footer'));
+      if (!cachedFooterEls.length) {
         return;
       }
     }
@@ -137,57 +137,80 @@ export const createSheetGesture = (
 
     currentFooterState = newPosition;
     if (newPosition === 'stationary') {
-      // Reset positioning styles to allow normal document flow
-      cachedFooterEl.classList.remove('modal-footer-moving');
-      cachedFooterEl.style.removeProperty('position');
-      cachedFooterEl.style.removeProperty('width');
-      cachedFooterEl.style.removeProperty('height');
-      cachedFooterEl.style.removeProperty('top');
-      cachedFooterEl.style.removeProperty('left');
-      page?.style.removeProperty('padding-bottom');
-
-      // Move to page
-      page?.appendChild(cachedFooterEl);
+      cachedFooterEls.forEach((cachedFooterEl) => {
+        // Reset positioning styles to allow normal document flow
+        cachedFooterEl.classList.remove('modal-footer-moving');
+        cachedFooterEl.style.removeProperty('position');
+        cachedFooterEl.style.removeProperty('width');
+        cachedFooterEl.style.removeProperty('height');
+        cachedFooterEl.style.removeProperty('top');
+        cachedFooterEl.style.removeProperty('left');
+        page?.style.removeProperty('padding-bottom');
+
+        // Move to page
+        page?.appendChild(cachedFooterEl);
+      });
     } else {
-      // Get both the footer and document body positions
-      const cachedFooterElRect = cachedFooterEl.getBoundingClientRect();
-      const bodyRect = document.body.getBoundingClientRect();
-
-      // Add padding to the parent element to prevent content from being hidden
-      // when the footer is positioned absolutely. This has to be done before we
-      // make the footer absolutely positioned or we may accidentally cause the
-      // sheet to scroll.
-      const footerHeight = cachedFooterEl.clientHeight;
-      page?.style.setProperty('padding-bottom', `${footerHeight}px`);
-
-      // Apply positioning styles to keep footer at bottom
-      cachedFooterEl.classList.add('modal-footer-moving');
-
-      // Calculate absolute position relative to body
-      // We need to subtract the body's offsetTop to get true position within document.body
-      const absoluteTop = cachedFooterElRect.top - bodyRect.top;
-      const absoluteLeft = cachedFooterElRect.left - bodyRect.left;
-
-      // Capture the footer's current dimensions and hard code them during the drag
-      cachedFooterEl.style.setProperty('position', 'absolute');
-      cachedFooterEl.style.setProperty('width', `${cachedFooterEl.clientWidth}px`);
-      cachedFooterEl.style.setProperty('height', `${cachedFooterEl.clientHeight}px`);
-      cachedFooterEl.style.setProperty('top', `${absoluteTop}px`);
-      cachedFooterEl.style.setProperty('left', `${absoluteLeft}px`);
-
-      // Also cache the footer Y position, which we use to determine if the
-      // sheet has been moved below the footer. When that happens, we need to swap
-      // the position back so it will collapse correctly.
-      cachedFooterYPosition = absoluteTop;
-      // If there's a toolbar, we need to combine the toolbar height with the footer position
-      // because the toolbar moves with the drag handle, so when it starts overlapping the footer,
-      // we need to account for that.
-      const toolbar = baseEl.querySelector('ion-toolbar') as HTMLIonToolbarElement | null;
-      if (toolbar) {
-        cachedFooterYPosition -= toolbar.clientHeight;
-      }
-
-      document.body.appendChild(cachedFooterEl);
+      let footerHeights = 0;
+      cachedFooterEls.forEach((cachedFooterEl, index) => {
+        // Get both the footer and document body positions
+        const cachedFooterElRect = cachedFooterEl.getBoundingClientRect();
+        const bodyRect = document.body.getBoundingClientRect();
+
+        // Calculate the total height of all footers
+        // so we can add padding to the page element
+        footerHeights += cachedFooterEl.clientHeight;
+
+        // Calculate absolute position relative to body
+        // We need to subtract the body's offsetTop to get true position within document.body
+        const absoluteTop = cachedFooterElRect.top - bodyRect.top;
+        const absoluteLeft = cachedFooterElRect.left - bodyRect.left;
+
+        // Capture the footer's current dimensions and store them in CSS variables for
+        // later use when applying absolute positioning.
+        cachedFooterEl.style.setProperty('--pinned-width', `${cachedFooterEl.clientWidth}px`);
+        cachedFooterEl.style.setProperty('--pinned-height', `${cachedFooterEl.clientHeight}px`);
+        cachedFooterEl.style.setProperty('--pinned-top', `${absoluteTop}px`);
+        cachedFooterEl.style.setProperty('--pinned-left', `${absoluteLeft}px`);
+
+        // Only cache the first footer's Y position
+        // This is used to determine if the sheet has been moved below the footer
+        // and needs to be swapped back to stationary so it collapses correctly.
+        if (index === 0) {
+          cachedFooterYPosition = absoluteTop;
+          // If there's a toolbar, we need to combine the toolbar height with the footer position
+          // because the toolbar moves with the drag handle, so when it starts overlapping the footer,
+          // we need to account for that.
+          const toolbar = baseEl.querySelector('ion-toolbar') as HTMLIonToolbarElement | null;
+          if (toolbar) {
+            cachedFooterYPosition -= toolbar.clientHeight;
+          }
+        }
+      });
+
+      // Apply the pinning of styles after we've calculated everything
+      // so that we don't cause layouts to shift while calculating the footer positions.
+      // Otherwise, with multiple footers we'll end up capturing the wrong positions.
+      cachedFooterEls.forEach((cachedFooterEl) => {
+        // Add padding to the parent element to prevent content from being hidden
+        // when the footer is positioned absolutely. This has to be done before we
+        // make the footer absolutely positioned or we may accidentally cause the
+        // sheet to scroll.
+        page?.style.setProperty('padding-bottom', `${footerHeights}px`);
+
+        // Apply positioning styles to keep footer at bottom
+        cachedFooterEl.classList.add('modal-footer-moving');
+
+        // Apply our preserved styles to pin the footer
+        cachedFooterEl.style.setProperty('position', 'absolute');
+        cachedFooterEl.style.setProperty('width', 'var(--pinned-width)');
+        cachedFooterEl.style.setProperty('height', 'var(--pinned-height)');
+        cachedFooterEl.style.setProperty('top', 'var(--pinned-top)');
+        cachedFooterEl.style.setProperty('left', 'var(--pinned-left)');
+
+        // Move the element to the body when everything else is done
+        document.body.appendChild(cachedFooterEl);
+      });
     }
   };
 
@@ -400,6 +423,16 @@ export const createSheetGesture = (
      * is not scrolled to the top.
      */
     if (!expandToScroll && detail.deltaY <= 0 && cachedScrollEl && cachedScrollEl.scrollTop > 0) {
+      /**
+       * If expand to scroll is disabled, we need to make sure we swap the footer position
+       * back to stationary so that it will collapse correctly if the modal is dismissed without
+       * dragging (e.g. through a dismiss button).
+       * This can cause issues if the user has a modal with content that can be dragged, as we'll
+       * swap to moving on drag and if we don't swap back here then the footer will get stuck.
+       */
+      if (!expandToScroll) {
+        swapFooterPosition('stationary');
+      }
       return;
     }