fixes #1805 (#1821)

docs/pages/resources/changelog.md

@@ -23,6 +23,7 @@ New versions of Shoelace are released as-needed and generally occur when a criti
 - Fixed a bug in `<sl-input>` and `<sl-textarea>` that made it work differently from `<input>` and `<textarea>` when using defaults [#1746]
 - Fixed a bug in `<sl-select>` that prevented it from closing when tabbing to another select inside a shadow root [#1763]
 - Fixed a bug in `<sl-spinner>` that caused the animation to appear strange in certain circumstances [#1787]
+- Fixed a bug that caused modal scroll locking to conflict with the `scrollbar-gutter` property [#1805]
 - Fixed a bug in `<sl-option>` that caused slotted content to show up when calling `getTextLabel()` [#1730]
 - Improved the accessibility of `<sl-tooltip>` so they persist when hovering over the tooltip and dismiss when pressing [[Esc]] [#1734]
 

src/themes/_utility.css

@@ -4,9 +4,18 @@
  * to reduce the possibility of collisions.
  */
 
-.sl-scroll-lock {
-  padding-right: var(--sl-scroll-lock-size) !important;
-  overflow: hidden !important;
+@supports (scrollbar-gutter: stable) {
+  .sl-scroll-lock {
+    scrollbar-gutter: stable !important;
+    overflow: hidden !important;
+  }
+}
+
+@supports not (scrollbar-gutter: stable) {
+  .sl-scroll-lock {
+    padding-right: var(--sl-scroll-lock-size) !important;
+    overflow: hidden !important;
+  }
 }
 
 .sl-toast-stack {