Document the behavior of local and global grabs on macOS.

1 files changed, 10 insertions, 0 deletions

diff --git a/doc/grab.n b/doc/grab.n
index a6d0d19..c45e26a 100644
--- a/doc/grab.n
+++ b/doc/grab.n
@@ -61,6 +61,16 @@ The \fBfocus\fR command is still used to determine which window in the
 application receives the keyboard events.
 The keyboard grab is released when the grab is released.
 .PP
+On macOS a global grab affects all windows created by one Tk process.
+No window in that process other than the grab window can even be
+focused, hence no other window receives key or mouse events.  A local
+grab on macOS affects all windows created by one Tcl interpreter.  It
+is possible to focus any window belonging to the Tk process during a
+local grab but the grab window is the only window created by its
+interpreter which receives key or mouse events.  Windows belonging to the
+same process but created by different interpreters continue to receive
+key and mouse events normally.
+.PP
 Grabs apply to particular displays.  If an application has windows
 on multiple displays then it can establish a separate grab on each
 display.