Cache current header and mode line height for each window.

* window.h (struct window): New fields mode_line_height
and header_line_height.
* window.c (make_window): Initialize them.
* dispextern.h (CURRENT_MODE_LINE_HEIGHT)
(CURRENT_HEADER_LINE_HEIGHT): Use them.  Adjust comment.
(current_mode_line_height, current_header_line_height):
Remove declaration.
* xdisp.c (current_mode_line_height, current_header_line_height):
Remove.
(pos_visible_p, init_xdisp): Adjust user.
(redisplay_window): Invalidate mode_line_height and
header_line_height if current and desired matrices do not agree.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/window.h b/src/window.h
index efe03737052..f5ae81149b3 100644
--- a/src/window.h
+++ b/src/window.h
@@ -264,6 +264,12 @@ struct window
        A value of -1 means use frame values.  */
     int scroll_bar_width;
 
+    /* Effective height of the mode line, or -1 if not known.  */
+    int mode_line_height;
+
+    /* Effective height of the header line, or -1 if not known.  */
+    int header_line_height;
+
     /* Z - the buffer position of the last glyph in the current
        matrix of W.  Only valid if window_end_valid is nonzero.  */
     ptrdiff_t window_end_pos;