Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/hooks/usePositioning.ts

@@ -0,0 +1,62 @@
+import { useSelector } from "react-redux";
+
+import { useSidebar } from "~/contexts/Sidebar";
+import {
+  SidebarAlignmentEnum,
+  SidebarPlacementEnum,
+  SidebarPositionInfo,
+} from "~/subApps/sheet/components/Sidebar/types";
+import { SheetPositioningInfo } from "~/tools/js/CharacterSheet/typings";
+import { appEnvSelectors } from "~/tools/js/Shared/selectors";
+
+export const usePositioning = () => {
+  const {
+    sidebar: { isVisible, placement, alignment, width },
+  } = useSidebar();
+
+  const getSheetPositioning = (): SheetPositioningInfo => {
+    let offset: number = 0;
+    if (!isVisible) {
+      return { offset, left: offset };
+    }
+
+    if (placement === SidebarPlacementEnum.FIXED) {
+      offset = width / 2;
+    }
+
+    return {
+      offset,
+      left: alignment === SidebarAlignmentEnum.LEFT ? offset : -1 * offset,
+    };
+  };
+
+  const getSidebarPositioning = (): SidebarPositionInfo => {
+    const sheetDimensions = useSelector(appEnvSelectors.getDimensions);
+    const sheetPosition = getSheetPositioning();
+
+    const { sheet, window } = sheetDimensions;
+
+    let posX: number = 0;
+    let sidebarGutter: number = 15;
+    let screenGutterSize: number = (window.width - sheet.width) / 2;
+
+    if (placement === SidebarPlacementEnum.FIXED) {
+      posX = screenGutterSize + sheetPosition.offset - sidebarGutter - width;
+    } else {
+      screenGutterSize -= sidebarGutter;
+      let overflowOffset: number =
+        width > screenGutterSize ? width - screenGutterSize : 0;
+      posX = screenGutterSize - width + overflowOffset;
+    }
+
+    return {
+      left: alignment === SidebarAlignmentEnum.LEFT ? posX : "auto",
+      right: alignment === SidebarAlignmentEnum.RIGHT ? posX : "auto",
+    };
+  };
+
+  return {
+    getSheetPositioning,
+    getSidebarPositioning,
+  };
+};