Try restoring the site editor animation (#51956)

* Try restoring the site editor animation

* fix header animation

* Remove accidental addition of layout prop

* tidy up formatting

* fix animate presence issue

* Fix animation between sidebar view and distraction free edit view

* Leave sidebar present and maintain canvas to
sidebar animation

The sidebar is necessary for routing on mobile so we have to maintain its presence in the DOM. Just hiding it isn't enough though, as it is still able to be reached with keyboard tabs and screen readers. Using the relatively new `inert` property disables the element from user interaction, so we add that when we don't want the sidebar to be shown.

* Fix mobile view for pattern library

On Mobile, the canvas mode wasn't being set to edit when using the pattern library. This updates it to use the showSidbar value instead, keeping it in sync with the inert setting.

---------

Co-authored-by: Saxon Fletcher <saxonafletcher@gmail.com>
Co-authored-by: Jerry Jones <jones.jeremydavid@gmail.com>

packages/edit-site/src/components/layout/index.js

@@ -224,66 +224,61 @@ export default function Layout() {
 					<AnimatePresence initial={ false }>
 						{ isEditorPage && isEditing && (
 							<NavigableRegion
+								key="header"
 								className="edit-site-layout__header"
 								ariaLabel={ __( 'Editor top bar' ) }
 								as={ motion.div }
 								variants={ {
-									isDistractionFree: { opacity: 0 },
-									isDistractionFreeHovering: { opacity: 1 },
-									view: { opacity: 1 },
-									edit: { opacity: 1 },
+									isDistractionFree: { opacity: 0, y: 0 },
+									isDistractionFreeHovering: {
+										opacity: 1,
+										y: 0,
+									},
+									view: { opacity: 1, y: '-100%' },
+									edit: { opacity: 1, y: 0 },
+								} }
+								exit={ {
+									y: '-100%',
+								} }
+								initial={ {
+									opacity: isDistractionFree ? 1 : 0,
+									y: isDistractionFree ? 0 : '-100%',
 								} }
 								transition={ {
 									type: 'tween',
 									duration: disableMotion ? 0 : 0.2,
 									ease: 'easeOut',
 								} }
 							>
-								{ isEditing && <Header /> }
+								<Header />
 							</NavigableRegion>
 						) }
 					</AnimatePresence>
 				</motion.div>
 
 				<div className="edit-site-layout__content">
-					<AnimatePresence initial={ false }>
-						{
-							<motion.div
-								initial={ {
-									opacity: 0,
-								} }
-								animate={
-									showSidebar
-										? { opacity: 1, display: 'block' }
-										: {
-												opacity: 0,
-												transitionEnd: {
-													display: 'none',
-												},
-										  }
-								}
-								exit={ {
-									opacity: 0,
-								} }
-								transition={ {
-									type: 'tween',
-									duration:
-										// Disable transition in mobile to emulate a full page transition.
-										disableMotion || isMobileViewport
-											? 0
-											: ANIMATION_DURATION,
-									ease: 'easeOut',
-								} }
-								className="edit-site-layout__sidebar"
-							>
-								<NavigableRegion
-									ariaLabel={ __( 'Navigation' ) }
-								>
-									<Sidebar />
-								</NavigableRegion>
-							</motion.div>
-						}
-					</AnimatePresence>
+					<motion.div
+						// The sidebar is needed for routing on mobile
+						// (https://github.com/WordPress/gutenberg/pull/51558/files#r1231763003),
+						// so we can't remove the element entirely. Using `inert` will make
+						// it inaccessible to screen readers and keyboard navigation.
+						inert={ showSidebar ? undefined : 'inert' }
+						animate={ { opacity: showSidebar ? 1 : 0 } }
+						transition={ {
+							type: 'tween',
+							duration:
+								// Disable transition in mobile to emulate a full page transition.
+								disableMotion || isMobileViewport
+									? 0
+									: ANIMATION_DURATION,
+							ease: 'easeOut',
+						} }
+						className="edit-site-layout__sidebar"
+					>
+						<NavigableRegion ariaLabel={ __( 'Navigation' ) }>
+							<Sidebar />
+						</NavigableRegion>
+					</motion.div>
 
 					<SavePanel />