Chrome-style tabs across several windows, built on nativeapi's WindowDragSession and WindowManager.getWindowAtPoint. Every tab's page is a live Flutter subtree that keeps its state (edited address, like count, scroll position, and a running timer) wherever the tab goes.

Flutter's multi-window API is experimental. This example is written against the stable channel (checked with Flutter 3.50.0). Stable does not offer flutter config --enable-windowing, so main() turns the API on itself by setting Flutter's internal isWindowingEnabled before the binding starts.

flutter channel stable && flutter upgrade
flutter run -d macos   # or windows, linux

This example is excluded from the repository's melos scripts because CI pins an older stable release.

Two browser windows open, with four and two tabs.

• Reorder: drag a tab along its strip; the other tabs slide out of the way.
• Tear off: drag a tab more than 28 px above or below the strip. It becomes a new window of the same size, with the tab still under the cursor. If it was the window's only tab, the whole window moves instead.
• Merge: drag a torn-off tab over another window's strip. It joins that strip at the cursor right away, while you are still dragging, and you can keep reordering or pull it out again.
• Move a window: drag the empty part of a strip.
• + adds a tab; closing a window's last tab closes the window; the app quits with the last window.

Each page shows Page state #n · … · moved between windows k×; n never changes for a tab, because its State is never recreated.

• TabsController (lib/src/tabs_controller.dart) owns the windows and their tab lists. On a press it starts a pointer-only WindowDragSession; from then on every step is driven by the session's cursor position, including reordering: after a merge the target window never saw the press, so Flutter has no pointer to report there.
  • in a strip: the dragged tab's left edge follows the cursor and its index is updated as it crosses its neighbours;
  • leaving the strip vertically: a new WindowController gets the tab, and start(newWindow, anchor) keeps the grabbed point of the tab under the cursor (the only tab: start(sourceWindow, anchor));
  • while a window follows the cursor: getWindowAtPoint(cursor, draggedId) plus the strips' screen rects find a strip to merge into; merging retargets the session to pointer-only, closes the dragged window, and carries on as a drag along the new strip.
• TabLayout (lib/src/tab_layout.dart) is the strip geometry shared by the widgets and the controller; test/tab_layout_test.dart covers it.
• All windows live in one ViewCollection, and each page is built under its tab's GlobalKey, so moving a tab between windows reparents the page instead of rebuilding it.
• NativeDragDetector cancels the Flutter pointer once the native session takes over; the press may belong to a window whose content moves away and that never sees the release.
• The UI is DazzUI through the shared dazzui_host package, one Host per window. The tab strip is the subject of the example, so it is drawn by hand (in the theme's colours); the toolbar, buttons and address field are DazzUI's, and each tab's marker colour is one of the theme's ramps.

• The strip replaces the title bar. On macOS that is setContentUnderTitleBar(true): the traffic lights stay on a transparent bar and the strip leaves room for them. Elsewhere that call returns false and the strip falls back to titleBarStyle = hidden, which takes the window buttons with it, so the strip carries its own close button.
• With a hidden title bar the content owns the title bar area: nativeapi keeps macOS from moving the window for drags there (it otherwise would, even over the Flutter content), so the strip moves windows itself.
• macOS, Windows, and Linux on X11 are supported by the native session. On Wayland applications cannot read the global cursor position, so dragging does not work there.