Re: Redisplay issue

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 29 Nov 2015 15:35:04 -0800
> From: Yuan MEI <yuan.mei.list@gmail.com>
> Cc: emacs-devel <emacs-devel@gnu.org>
> 
> This is when redisplay works normally:
> 
> >>> right after window exposure
> 
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> expose_frame (0, 0, 170, 1026)
> expose_window (1, 1, 168, 1024)
> expose_window (1, 0, 168, 0)
> expose_window (1, 0, 168, 0)
> expose_frame (0, 0, 818, 1026)
> expose_window (1, 17, 816, 992)
> expose_window (1, 1009, 816, 16)
> expose_window (1, 16, 816, 0)
> expose_window (1, 0, 816, 16)
> 
> >>> some time pause here, although nothing else (mouse is outside of Emacs, no mouse movement or key press)
> 
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> 
> This is when partial redraw happened:
> 
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> expose_frame (0, 0, 170, 1026)
> expose_window (1, 1, 168, 1024)
> expose_window (1, 0, 168, 0)
> expose_window (1, 0, 168, 0)
> expose_frame (0, 0, 818, 1026)
> expose_window (1, 17, 816, 992)
> expose_window (1, 1009, 816, 16)
> expose_window (1, 16, 816, 0)
> expose_window (1, 0, 816, 16)
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> 
> >>> I switched to another virtual desktop then came back, redraw remained incorrect but the following showed up in the log
> 
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> expose_frame (0, 0, 170, 1026)
> expose_window (1, 1, 168, 1024)
> expose_window (1, 0, 168, 0)
> expose_window (1, 0, 168, 0)
> expose_frame (0, 0, 818, 1026)
> expose_window (1, 17, 816, 992)
> expose_window (1, 1009, 816, 16)
> expose_window (1, 16, 816, 0)
> expose_window (1, 0, 816, 16)
> 
> >>> switched out and back again, finding the entire frame showing only the background color, no menu or status bar
> 
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> expose_frame (0, 0, 170, 1026)
> expose_window (1, 1, 168, 1024)
> expose_window (1, 0, 168, 0)
> expose_window (1, 0, 168, 0)
> expose_frame (0, 0, 818, 1026)
> expose_window (1, 17, 816, 992)
> expose_window (1, 1009, 816, 16)
> expose_window (1, 16, 816, 0)
> expose_window (1, 0, 816, 16)
> 
> >>> a few seconds of time pause, then a few glyphs showed up in the status bar
> 
> redisplay_preserve_echo_area (8)
> redisplay_internal 0
> 0x299e030 ( SPEEDBAR): same window start
> 0x299e030 ( SPEEDBAR): 1
> 0x1383e60 (*GNU Emacs*): same window start
> 0x1383e60 (*GNU Emacs*): 1
> redisplay_preserve_echo_area (9)
> redisplay_internal 0
> 
> Any ideas?

The "good" and the "bad" traces are completely identical!

Can you add 2 more traces as in the diffs below, recompile, and repeat
the experiment?  I'd like to be sure that the traces are identical
down to the screen line level.

Thanks.

diff --git a/src/xdisp.c b/src/xdisp.c
index 50c5518..1e52d31 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -30580,6 +30580,9 @@ expose_window (struct window *w, XRectangle *fr)
 		}
 
 	      row->clip = fr;
+
+	      TRACE ((stderr, "expose_line %d: (%d, %d, %d, %d)\n",
+		      row->y, r.x, r.y, r.width, r.height));
 	      if (expose_line (w, row, &r))
 		mouse_face_overwritten_p = true;
 	      row->clip = NULL;
@@ -30607,6 +30610,9 @@ expose_window (struct window *w, XRectangle *fr)
 	      row->enabled_p)
 	  && row->y < r_bottom)
 	{
+
+	  TRACE ((stderr, "expose_line %d: (%d, %d, %d, %d)\n",
+		  row->y, r.x, r.y, r.width, r.height));
 	  if (expose_line (w, row, &r))
 	    mouse_face_overwritten_p = true;
 	}