[Chat] Split view layout for web (#10258)

src/screens/Messages/components/splitView/context.tsx

@@ -0,0 +1,31 @@
+import {createContext, useContext, useMemo} from 'react'
+
+const SplitViewContext = createContext<{
+  isWithinSplitView: boolean
+  isWithinLeftPanel: boolean
+  isWithinRightPanel: boolean
+}>({
+  isWithinSplitView: false,
+  isWithinLeftPanel: false,
+  isWithinRightPanel: false,
+})
+
+export function SplitViewProvider({
+  children,
+  side,
+}: {
+  children: React.ReactNode
+  side: 'left' | 'right'
+}) {
+  const value = useMemo(
+    () => ({
+      isWithinSplitView: true,
+      isWithinLeftPanel: side === 'left',
+      isWithinRightPanel: side === 'right',
+    }),
+    [side],
+  )
+  return <SplitViewContext value={value}>{children}</SplitViewContext>
+}
+
+export const useIsWithinSplitView = () => useContext(SplitViewContext)