Date: Sun, 21 Dec 1997 14:01:44 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Nate Eldredge <eldredge AT ap DOT net>
cc: djgpp AT delorie DOT com
Subject: Re: Emacs bug: Doesn't restore display settings
In-Reply-To: <199712201834.KAA17092@adit.ap.net>
Message-ID: <Pine.SUN.3.91.971221140125.8399W-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Precedence: bulk


On Sat, 20 Dec 1997, Nate Eldredge wrote:

> There is a minor bug in Emacs. Apparently it changes the display attributes
> so that text with the `blink' bit set ends up with an intense background
> instead. This is all fine, but it doesn't change it back when it finishes.

This was fixed a long time ago.  Are you using the original Emacs
binary from em1934b.zip distributed about a year ago?  If so, get the
latest binary from SimTel.NET, it shouldn't have this problem.

If you have Emacs sources on your machine, here's the source-level
patch that fixed this for me:

*** src/msdos.c~5	Mon Dec 23 18:15:20 1996
--- src/msdos.c	Mon Jan  6 19:19:18 1997
*************** Boston, MA 02111-1307, USA.  */
*** 62,67 ****
--- 62,71 ----
  #define _USE_LFN 0
  #endif
  
+ #ifndef _dos_ds
+ #define _dos_ds _go32_info_block.selector_for_linear_memory
+ #endif
+ 
  #if __DJGPP__ > 1
  
  #include <signal.h>
*************** ScreenVisualBell (void)
*** 370,386 ****
--- 374,412 ----
  
  #ifndef HAVE_X_WINDOWS
  
+ static int blink_bit = -1;	/* the state of the blink bit at startup */
+ 
  /* Enable bright background colors.  */
  static void
  bright_bg (void)
  {
    union REGS regs;
  
+   /* Remember the original state of the blink/bright-background bit.
+      It is stored at 0040:0065h in the BIOS data area.  */
+   if (blink_bit == -1)
+     blink_bit = (_farpeekb (_dos_ds, 0x465) & 0x20) == 0x20;
+ 
    regs.h.bl = 0;
    regs.x.ax = 0x1003;
    int86 (0x10, &regs, &regs);
  }
  
+ /* Disable bright background colors (and enable blinking) if we found
+    the video system in that state at startup.  */
+ static void
+ maybe_enable_blinking (void)
+ {
+   if (blink_bit == 1)
+     {
+       union REGS regs;
+ 
+       regs.h.bl = 1;
+       regs.x.ax = 0x1003;
+       int86 (0x10, &regs, &regs);
+     }
+ }
+ 
  /* Set the screen dimensions so that it can show no less than
     ROWS x COLS frame.  */
  
*************** IT_reset_terminal_modes (void)
*** 868,873 ****
--- 894,903 ----
      return;
    
    mouse_off ();
+ 
+   /* Leave the video system in the same state as we found it,
+      as far as the blink/bright-background bit is concerned.  */
+   maybe_enable_blinking ();
   
    /* We have a situation here.
       We cannot just do ScreenUpdate(startup_screen_buffer) because
*************** run_msdos_command (argv, dir, tempin, te
*** 3009,3014 ****
--- 3039,3049 ----
        mouse_init ();
        mouse_moveto (x, y);
      }
+ 
+   /* Some programs might change the meaning of the highest bit of the
+      text attribute byte, so we get blinking characters instead of the
+      bright background colors.  Restore that.  */
+   bright_bg ();
    
   done:
    chdir (oldwd);