From 1fb608842df69dccf6255a50e1952889c64b5068 Mon Sep 17 00:00:00 2001
From: TJ Egan <tw15egan@gmail.com>
Date: Mon, 12 Feb 2024 12:20:39 -0500
Subject: [PATCH] refactor(Modal): use mask-image for overflow indicator

---
 .../ComposedModal/ComposedModal.tsx           | 19 +++---
 packages/react/src/components/Modal/Modal.tsx |  3 -
 .../styles/scss/components/modal/_modal.scss  | 58 ++++---------------
 3 files changed, 17 insertions(+), 63 deletions(-)

diff --git a/packages/react/src/components/ComposedModal/ComposedModal.tsx b/packages/react/src/components/ComposedModal/ComposedModal.tsx
index 35d3f4ab4dfe..d77d54658c13 100644
--- a/packages/react/src/components/ComposedModal/ComposedModal.tsx
+++ b/packages/react/src/components/ComposedModal/ComposedModal.tsx
@@ -62,18 +62,13 @@ export const ModalBody = React.forwardRef<HTMLDivElement, ModalBodyProps>(
       : {};
 
     return (
-      <>
-        <div
-          className={contentClass}
-          {...hasScrollingContentProps}
-          {...rest}
-          ref={ref}>
-          {children}
-        </div>
-        {hasScrollingContent && (
-          <div className={`${prefix}--modal-content--overflow-indicator`} />
-        )}
-      </>
+      <div
+        className={contentClass}
+        {...hasScrollingContentProps}
+        {...rest}
+        ref={ref}>
+        {children}
+      </div>
     );
   }
 );
diff --git a/packages/react/src/components/Modal/Modal.tsx b/packages/react/src/components/Modal/Modal.tsx
index 33b3cf03e808..0af0f7b8f80f 100644
--- a/packages/react/src/components/Modal/Modal.tsx
+++ b/packages/react/src/components/Modal/Modal.tsx
@@ -488,9 +488,6 @@ const Modal = React.forwardRef(function Modal(
         {...hasScrollingContentProps}>
         {children}
       </div>
-      {hasScrollingContent && (
-        <div className={`${prefix}--modal-content--overflow-indicator`} />
-      )}
       {!passiveModal && (
         <ButtonSet className={footerClasses} aria-busy={loadingActive}>
           {Array.isArray(secondaryButtons) && secondaryButtons.length <= 2
diff --git a/packages/styles/scss/components/modal/_modal.scss b/packages/styles/scss/components/modal/_modal.scss
index 3deba95eb14e..f9194d6a7575 100644
--- a/packages/styles/scss/components/modal/_modal.scss
+++ b/packages/styles/scss/components/modal/_modal.scss
@@ -350,60 +350,22 @@
   .#{$prefix}--modal-scroll-content {
     // Required to accommodate focus outline's negative offset when scrolling in Chrome
     border-block-end: 2px solid transparent;
+    mask-image: linear-gradient(
+        to bottom,
+        $layer calc(100% - 80px),
+        transparent calc(100% - 48px),
+        transparent 100%
+      ),
+      linear-gradient(to left, $layer 0, 16px, transparent 16px),
+      linear-gradient(to right, $layer 0, 2px, transparent 2px),
+      linear-gradient(to top, $layer 0, 2px, transparent 2px);
   }
+
   // Required so overflow-indicator disappears at end of content
   .#{$prefix}--modal-scroll-content > *:last-child {
     padding-block-end: $spacing-06;
   }
 
-  .#{$prefix}--modal-content--overflow-indicator {
-    position: absolute;
-    background: $layer;
-    block-size: convert.to-rem(48px);
-    grid-column: 1/-1;
-    grid-row: 2/-2;
-    inline-size: calc(100% - $spacing-05);
-    inset-block-end: 0;
-    inset-inline-start: 0;
-    pointer-events: none;
-
-    &::before {
-      position: absolute;
-      background-image: linear-gradient(to bottom, transparent, $layer);
-      block-size: convert.to-rem(32px);
-      content: '';
-      inline-size: 100%;
-      inset-block-start: -32px;
-      pointer-events: none;
-    }
-  }
-
-  // Safari-only media query
-  // won't appear correctly with CSS custom properties
-  // see: code snippet and tabs overflow indicators
-  @media not all and (min-resolution >= 0.001dpcm) {
-    @supports (-webkit-appearance: none) and (stroke-color: transparent) {
-      .#{$prefix}--modal-content--overflow-indicator {
-        background-image: linear-gradient(to bottom, rgba($layer, 0), $layer);
-      }
-    }
-  }
-
-  .#{$prefix}--modal-content:focus
-    ~ .#{$prefix}--modal-content--overflow-indicator {
-    margin: 0 2px 2px;
-  }
-
-  @media screen and (-ms-high-contrast: active) {
-    .#{$prefix}--modal-scroll-content > *:last-child {
-      padding-block-end: 0;
-    }
-
-    .#{$prefix}--modal-content--overflow-indicator {
-      display: none;
-    }
-  }
-
   // -----------------------------
   // Modal footer
   // -----------------------------