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/src/buffer.c b/src/buffer.c
index 5c65d4d4d19..cc7d4e4817c 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -6247,6 +6247,9 @@ Values are interpreted as follows:
   t               use the cursor specified for the frame
   nil             don't display a cursor
   box             display a filled box cursor
+  (box . SIZE)    display a filled box cursor, but make it
+                  hollow if cursor is under masked image larger than
+                  SIZE pixels in either dimension.
   hollow          display a hollow box cursor
   bar             display a vertical bar cursor with default width
   (bar . WIDTH)   display a vertical bar cursor with width WIDTH