fix: scrollbar gutters and dialog scrolling on open

src/internal/scroll.ts

@@ -33,6 +33,13 @@ export function lockBodyScrolling(lockingEl: HTMLElement) {
   if (!document.documentElement.classList.contains('sl-scroll-lock')) {
     /** Scrollbar width + body padding calculation can go away once Safari has scrollbar-gutter support. */
     const scrollbarWidth = getScrollbarWidth() + getExistingBodyPadding(); // must be measured before the `sl-scroll-lock` class is applied
+
+    let scrollbarGutterProperty = "stable"
+    if (scrollbarWidth <= 0) {
+      // if there's no scrollbar, just set it to "revert" so whatever the user has set gets used.
+      scrollbarGutterProperty = "revert";
+    }
+    document.documentElement.style.setProperty("--sl-scroll-lock-gutter", scrollbarGutterProperty)
     document.documentElement.classList.add('sl-scroll-lock');
     document.documentElement.style.setProperty('--sl-scroll-lock-size', `${scrollbarWidth}px`);
   }

src/themes/_utility.css

@@ -6,7 +6,10 @@
 
 @supports (scrollbar-gutter: stable) {
   .sl-scroll-lock {
-    scrollbar-gutter: stable !important;
+    scrollbar-gutter: var(--sl-scroll-lock-gutter) !important;
+  }
+
+  .sl-scroll-lock body {
     overflow: hidden !important;
   }
 }