fix: Prevent dropdown misplacement in iOS

src/internal/components/dropdown/__tests__/dropdown-position.test.ts

@@ -0,0 +1,91 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { applyDropdownPositionRelativeToViewport } from '../../../../../lib/components/internal/components/dropdown/dropdown-position';
+
+describe('applyDropdownPositionRelativeToViewport', () => {
+  const triggerRect = {
+    blockSize: 50,
+    inlineSize: 100,
+    insetBlockStart: 100,
+    insetInlineStart: 100,
+    insetBlockEnd: 150,
+    insetInlineEnd: 200,
+  };
+
+  const baseDropdownPosition = {
+    blockSize: '100px',
+    inlineSize: '100px',
+    insetInlineStart: '100px',
+    dropBlockStart: false,
+    dropInlineStart: false,
+  };
+
+  test("sets block end when the dropdown is anchored to the trigger's block start (expands up)", () => {
+    const dropdownElement = document.createElement('div');
+    applyDropdownPositionRelativeToViewport({
+      dropdownElement,
+      triggerRect,
+      position: { ...baseDropdownPosition, dropBlockStart: true },
+      isMobile: false,
+    });
+    expect(dropdownElement.style.insetBlockEnd).toBeTruthy();
+    expect(dropdownElement.style.insetBlockStart).toBeFalsy();
+  });
+
+  test("aligns block start with the trigger's block end when the dropdown is anchored to the trigger's block end (expands down)", () => {
+    const dropdownElement = document.createElement('div');
+    applyDropdownPositionRelativeToViewport({
+      dropdownElement,
+      triggerRect,
+      position: baseDropdownPosition,
+      isMobile: false,
+    });
+    expect(dropdownElement.style.insetBlockEnd).toBeFalsy();
+    expect(dropdownElement.style.insetBlockStart).toEqual(`${triggerRect.insetBlockEnd}px`);
+  });
+
+  test("aligns inline start with the trigger's inline start when the dropdown is anchored to the trigger's inline start (anchored from the left in LTR)", () => {
+    const dropdownElement = document.createElement('div');
+    applyDropdownPositionRelativeToViewport({
+      dropdownElement,
+      triggerRect,
+      position: baseDropdownPosition,
+      isMobile: false,
+    });
+    expect(dropdownElement.style.insetInlineStart).toEqual(`${triggerRect.insetInlineStart}px`);
+  });
+
+  test("sets inline end when the dropdown is anchored to the trigger's inline start (anchored from the right in LTR)", () => {
+    const dropdownElement = document.createElement('div');
+    applyDropdownPositionRelativeToViewport({
+      dropdownElement,
+      triggerRect,
+      position: { ...baseDropdownPosition, dropInlineStart: true },
+      isMobile: false,
+    });
+    expect(dropdownElement.style.insetInlineStart).toBeTruthy();
+  });
+
+  test('uses fixed position on desktop', () => {
+    const dropdownElement = document.createElement('div');
+    applyDropdownPositionRelativeToViewport({
+      dropdownElement,
+      triggerRect,
+      position: baseDropdownPosition,
+      isMobile: false,
+    });
+    expect(dropdownElement.style.position).toEqual('fixed');
+  });
+
+  test('uses absolute position on mobile', () => {
+    const dropdownElement = document.createElement('div');
+    applyDropdownPositionRelativeToViewport({
+      dropdownElement,
+      triggerRect,
+      position: baseDropdownPosition,
+      isMobile: true,
+    });
+    expect(dropdownElement.style.position).toEqual('absolute');
+  });
+});

src/internal/components/dropdown/dropdown-fit-handler.ts

@@ -4,6 +4,7 @@ import { getLogicalBoundingClientRect } from '@cloudscape-design/component-toolk
 
 import { getBreakpointValue } from '../../breakpoints';
 import { BoundingBox, getOverflowParentDimensions, getOverflowParents } from '../../utils/scrollable-containers';
+import { LogicalDOMRect } from './dropdown-position';
 
 import styles from './styles.css.js';
 
@@ -361,7 +362,7 @@ export const calculatePosition = (
   isMobile: boolean,
   minWidth?: number,
   stretchBeyondTriggerWidth?: boolean
-): [DropdownPosition, DOMRect] => {
+): [DropdownPosition, LogicalDOMRect] => {
   // cleaning previously assigned values,
   // so that they are not reused in case of screen resize and similar events
   verticalContainerElement.style.maxBlockSize = '';
@@ -393,6 +394,6 @@ export const calculatePosition = (
         isMobile,
         stretchBeyondTriggerWidth,
       });
-  const triggerBox = triggerElement.getBoundingClientRect();
+  const triggerBox = getLogicalBoundingClientRect(triggerElement);
   return [position, triggerBox];
 };

src/internal/components/dropdown/dropdown-position.ts

@@ -0,0 +1,49 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { DropdownPosition } from './dropdown-fit-handler';
+
+export interface LogicalDOMRect {
+  blockSize: number;
+  inlineSize: number;
+  insetBlockStart: number;
+  insetBlockEnd: number;
+  insetInlineStart: number;
+  insetInlineEnd: number;
+}
+
+// Applies its position to the dropdown element when expandToViewport is set to true.
+export function applyDropdownPositionRelativeToViewport({
+  position,
+  dropdownElement,
+  triggerRect,
+  isMobile,
+}: {
+  position: DropdownPosition;
+  dropdownElement: HTMLElement;
+  triggerRect: LogicalDOMRect;
+  isMobile: boolean;
+}) {
+  // Fixed positions is not respected in iOS when the virtual keyboard is being displayed.
+  // For this reason we use absolute positioning in mobile.
+  const useAbsolutePositioning = isMobile;
+
+  // Since when using expandToViewport=true the dropdown is attached to the root of the body,
+  // the same coordinates can be used for fixed or absolute position,
+  // except when using absolute position we need to take into account the scroll position of the body itself.
+  const verticalScrollOffset = useAbsolutePositioning ? document.documentElement.scrollTop : 0;
+  const horizontalScrollOffset = useAbsolutePositioning ? document.documentElement.scrollLeft : 0;
+
+  dropdownElement.style.position = useAbsolutePositioning ? 'absolute' : 'fixed';
+
+  if (position.dropBlockStart) {
+    dropdownElement.style.insetBlockEnd = `calc(100% - ${verticalScrollOffset + triggerRect.insetBlockStart}px)`;
+  } else {
+    dropdownElement.style.insetBlockStart = `${verticalScrollOffset + triggerRect.insetBlockEnd}px`;
+  }
+  if (position.dropInlineStart) {
+    dropdownElement.style.insetInlineStart = `calc(${horizontalScrollOffset + triggerRect.insetInlineEnd}px - ${position.inlineSize})`;
+  } else {
+    dropdownElement.style.insetInlineStart = `${horizontalScrollOffset + triggerRect.insetInlineStart}px`;
+  }
+}

src/internal/components/dropdown/index.tsx

@@ -26,6 +26,7 @@ import {
   hasEnoughSpaceToStretchBeyondTriggerWidth,
   InteriorDropdownPosition,
 } from './dropdown-fit-handler';
+import { applyDropdownPositionRelativeToViewport, LogicalDOMRect } from './dropdown-position';
 import { DropdownProps } from './interfaces';
 
 import styles from './styles.css.js';
@@ -196,7 +197,7 @@ const Dropdown = ({
 
   const setDropdownPosition = (
     position: DropdownPosition | InteriorDropdownPosition,
-    triggerBox: DOMRect,
+    triggerBox: LogicalDOMRect,
     target: HTMLDivElement,
     verticalContainer: HTMLDivElement
   ) => {
@@ -233,17 +234,12 @@ const Dropdown = ({
 
     // Position normal overflow dropdowns with fixed positioning relative to viewport
     if (expandToViewport && !interior) {
-      target.style.position = 'fixed';
-      if (position.dropBlockStart) {
-        target.style.insetBlockEnd = `calc(100% - ${triggerBox.top}px)`;
-      } else {
-        target.style.insetBlockStart = `${triggerBox.bottom}px`;
-      }
-      if (position.dropInlineStart) {
-        target.style.insetInlineStart = `calc(${triggerBox.right}px - ${position.inlineSize})`;
-      } else {
-        target.style.insetInlineStart = `${triggerBox.left}px`;
-      }
+      applyDropdownPositionRelativeToViewport({
+        position,
+        dropdownElement: target,
+        triggerRect: triggerBox,
+        isMobile,
+      });
       // Keep track of the initial dropdown position and direction.
       // Dropdown direction doesn't need to change as the user scrolls, just needs to stay attached to the trigger.
       fixedPosition.current = position;
@@ -390,21 +386,13 @@ const Dropdown = ({
       return;
     }
     const updateDropdownPosition = () => {
-      if (triggerRef.current && dropdownRef.current && verticalContainerRef.current) {
-        const triggerRect = getLogicalBoundingClientRect(triggerRef.current);
-        const target = dropdownRef.current;
-        if (fixedPosition.current) {
-          if (fixedPosition.current.dropBlockStart) {
-            dropdownRef.current.style.insetBlockEnd = `calc(100% - ${triggerRect.insetBlockStart}px)`;
-          } else {
-            target.style.insetBlockStart = `${triggerRect.insetBlockEnd}px`;
-          }
-          if (fixedPosition.current.dropInlineStart) {
-            target.style.insetInlineStart = `calc(${triggerRect.insetInlineEnd}px - ${fixedPosition.current.inlineSize})`;
-          } else {
-            target.style.insetInlineStart = `${triggerRect.insetInlineStart}px`;
-          }
-        }
+      if (triggerRef.current && dropdownRef.current && verticalContainerRef.current && fixedPosition.current) {
+        applyDropdownPositionRelativeToViewport({
+          position: fixedPosition.current,
+          dropdownElement: dropdownRef.current,
+          triggerRect: getLogicalBoundingClientRect(triggerRef.current),
+          isMobile,
+        });
       }
     };
 
@@ -416,7 +404,7 @@ const Dropdown = ({
     return () => {
       controller.abort();
     };
-  }, [open, expandToViewport]);
+  }, [open, expandToViewport, isMobile]);
 
   const referrerId = useUniqueId();