Instance Method


Tells the delegate that the window is about to show a sheet at the specified location, giving it the opportunity to return a custom location for the attachment of the sheet to the window.


optional func window(_ window: NSWindow, willPositionSheet sheet: NSWindow, using rect: NSRect) -> NSRect



The window containing the sheet to be animated.


The sheet to be shown.


The default sheet location, just under the title bar of the window, aligned with the left and right edges of the window.

Return Value

The custom location specified.


This method is also called whenever the user resizes window while sheet is attached.

This method is useful in many situations. If your window has a toolbar, for example, you can specify a location for the sheet that is just below it. If you want the sheet associated with a certain control or view, you could position the sheet so that it appears to originate from the object (through animation) or is positioned next to it.

Neither the rect parameter nor the returned NSRect value define the boundary of the sheet. They indicate where the top-left edge of the sheet is attached to the window. The origin is expressed in window coordinates; the default origin.y value is the height of the content view and the default origin.x value is 0. The size.width value indicates the width and behavior of the initial animation; if size.width is narrower than the sheet, the sheet genies out from the specified location, and if size.width is wider than the sheet, the sheet slides out. You cannot affect the size of the sheet through the size.width and size.height fields. It is recommended that you specify zero for the size.height value as this field may have additional meaning in a future release.

See Also

Managing Sheets

func windowWillBeginSheet(Notification)

Notifies the delegate that the window is about to open a sheet.

func windowDidEndSheet(Notification)

Tells the delegate that the window has closed a sheet.