Per-buffer window counters.

* buffer.h (struct buffer): New member window_count.
(buffer_window_count): New function.
* buffer.c (Fget_buffer_create, Fmake_indirect_buffer):
Initialize window_count.
(Fkill_buffer): Verify window_count for the buffer being killed.
(modify_overlay): Do not force redisplay if buffer is not shown
in any window.
(init_buffer_once): Initialize window_count for buffer_defaults
and buffer_local_symbols.
* window.h (buffer_shared): Remove declaration.
(wset_buffer): Convert from inline ...
* window.c (wset_buffer): ... to an ordinary function.
(adjust_window_count): New function.
(make_parent_window): Use it.
* xdisp.c (buffer_shared): Remove.
(redisplay_internal, redisplay_window): Adjust users.
(buffer_shared_and_changed): Use per-buffer window counter.

1 files changed, 17 insertions, 2 deletions

diff --git a/src/buffer.h b/src/buffer.h
index 1129840bd47..d838d3767ef 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -770,11 +770,15 @@ struct buffer
      In an ordinary buffer, it is 0.  */
   struct buffer *base_buffer;
 
-  /* In an indirect buffer, this is -1. In an ordinary buffer,
+  /* In an indirect buffer, this is -1.  In an ordinary buffer,
      it's the number of indirect buffers that share our text;
      zero means that we're the only owner of this text.  */
   int indirections;
 
+  /* Number of windows showing this buffer.  Always -1 for
+     an indirect buffer since it counts as its base buffer.  */
+  int window_count;
+
   /* A non-zero value in slot IDX means that per-buffer variable
      with index IDX has a local value in this buffer.  The index IDX
      for a buffer-local variable is stored in that variable's slot
@@ -1173,7 +1177,18 @@ BUF_FETCH_MULTIBYTE_CHAR (struct buffer *buf, ptrdiff_t pos)
        + pos + BUF_BEG_ADDR (buf) - BEG_BYTE);
   return STRING_CHAR (p);
 }
-
+
+/* Return number of windows showing B.  */
+
+BUFFER_INLINE int
+buffer_window_count (struct buffer *b)
+{
+  if (b->base_buffer)
+    b = b->base_buffer;
+  eassert (b->window_count >= 0);
+  return b->window_count;
+}
+
 /* Overlays */
 
 /* Return the marker that stands for where OV starts in the buffer.  */