• Add Workspace component, for layouts of tabsets that users can rearrange by dragging tabs: between tabsets, within a tabset's list of tabs, or onto the edge of a tabset to split it. Tabsets can also be resized and maximized. The layout is described by a serializable model, and tab content is not remounted when a tab is moved. - #780
  • Tabsets can be customized with the renderTab, renderTabsetToolbar, and renderEmptyTabset props (and the TabCloseButton component), and styled with the classNames and styles props.
  • Workspaces are uncontrolled (like Group); the useWorkspaceRef and useWorkspaceCallbackRef hooks return its imperative API.
  • Content within a workspace can use the useParentWorkspace, useParentTabset, useParentTabsetState, useParentTab, and useParentTabState hooks.
  • The content of tabs that aren't selected can stay mounted (default), be unmounted, or be rendered within a hidden React <Activity> (hiddenTabBehavior), and selected tabs' content can opt into server rendering (serverRenderTabContent).
  • Supports mouse, touch, and keyboard interaction.
• Fix separators (and grid gridlines) moving farther or less far than the pointer when an ancestor has CSS zoom or a scale transform (e.g. twice as far within zoom: 2). Pointer movements are now converted from screen pixels to layout pixels before resizing. - #780
• Fix separators staying in their "hover" state when the pointer moves onto an iframe within a Group rendered into another window (e.g. a popup). The iframe check no longer uses instanceof HTMLIFrameElement, which is false for iframes from another window. - #778
• Fix the separator resize preview (resizePreviewMode="separator") missing the separator's styles when its element was created by another window's document (e.g. by a popup's opener). - #781