Support for (box . SIZE) 'cursor-type'

This allows control of the minimum size of a masked image under
which the box cursor becomes hollow.
* buffer.c (cursor-type): Add commentary about (box . SIZE)
'cursor-type'.
* xdisp.c (get_specified_cursor_type): Check for 'cursor-type'
of the form (box . SIZE).
(get_window_cursor_type): Check masked image size for
(box . SIZE) 'cursor-type'.

* doc/emacs/display.texi (Cursor Display):
* doc/emacs/display.texi (Cursor Parameters): Add description
of (box . SIZE) 'cursor-type'.

* etc/NEWS: Mention the new (box . SIZE) 'cursor-type'.

1 files changed, 3 insertions, 0 deletions

diff --git a/doc/lispref/frames.texi b/doc/lispref/frames.texi
index 2bb505c1c7a..70ebe2e87d7 100644
--- a/doc/lispref/frames.texi
+++ b/doc/lispref/frames.texi
@@ -2220,6 +2220,9 @@ How to display the cursor.  Legitimate values are:
 @table @code
 @item box
 Display a filled box.  (This is the default.)
+@item (box . @var{SIZE})
+Display a filled box.  However, display it as a hollow box if point is
+under masked image larger than @var{SIZE} pixels in either dimension.
 @item hollow
 Display a hollow box.
 @item nil