Re: Normal mode patch

[Gianluca Guida]

On Wed, Jan 07, 2004 at 02:07:29PM +0100, Yoshinori K. Okuji wrote:
>
> On Wednesday 31 December 2003 18:24, Marco Gerards wrote:
> > gianluca (I don't remember his real name) told me on IRC that it
> > crashes whenever the console scrolls.  I was able to reproduce this.
> > It is not clear what still needs to be done to get the graphics
> > console to work.  If it is not a lot of work I can do that, I have
> > quite some experience with VGA programming.
> 
> You are right. There is a big problem when scrolling the menu. Probably 
> it is due to a wrong calculation of a memory pointer, but I'm not sure 
> where it is. As you see, the code is a bit ugly, so it might be better 
> to clean up the code more or less before diving into the problem 
> seriously.
> 

As Marco Gerards made me note, the problem in vga.c was due to a wrong
check to ypos value for scrolling (TEXT_HEIGHT instead of TEXT_HEIGHT-1).

After fixing this, however, I've experienced another problem: the
scrolling itself doesn't work. It clears the screen instead of moving
it. I am not at all a VGA expert, and as long as my brain works at late
night it seems that when using pupa_memmove the memory is read as 
zero-valued.

I've then implemented a slow but simple and working function that
rebuilds completely the screen using textbuf info. I've called it
screen_update(). Under bochs runned on a Pentium MMX (;-)) it showed
slow, but on real hardware (Pentium III 600Mhz) its speed was acceptable.

I think that as long as what we want do is to scroll some hundreds of
characters, no one will complain too much about this rude patch.

Gianluca

? vga_patch
Index: vga.c
===================================================================
RCS file: /cvsroot/pupa/pupa/term/i386/pc/vga.c,v
retrieving revision 1.1
diff -u -p -r1.1 vga.c
--- vga.c       25 Sep 2003 20:15:52 -0000      1.1
+++ vga.c       9 Jan 2004 01:49:54 -0000
@@ -279,14 +279,34 @@ write_cursor (void)
 }
 
 static void
+screen_update (void)
+{
+  int oldxpos, oldypos;
+  int i,j;
+  
+  oldxpos=xpos; oldypos=ypos;
+  for (j=0; j<TEXT_HEIGHT; j++)
+    {
+      ypos=j;
+   
+      for(i=0; i<TEXT_WIDTH; i++)
+        {
+          xpos=i;
+          write_char();
+        }
+     }
+}
+  
+static void
 scroll_up (void)
 {
   unsigned i;
   unsigned plane;
+ 
   
   pupa_memmove (text_buf, text_buf + TEXT_WIDTH,
                sizeof (struct colored_char) * TEXT_WIDTH * (TEXT_HEIGHT - 1));
-      
+
   for (i = TEXT_WIDTH * (TEXT_HEIGHT - 1); i < TEXT_WIDTH * TEXT_HEIGHT; i++)
     {
       text_buf[i].code = ' ';
@@ -296,16 +316,7 @@ scroll_up (void)
       text_buf[i].index = 0;
     }
 
-  for (plane = 0x1; plane <= 0x8; plane <<= 1)
-    {
-      set_map_mask (plane);
-      pupa_memmove (VGA_MEM, VGA_MEM + VGA_WIDTH * CHAR_HEIGHT / 8,
-                   VGA_WIDTH * (VGA_HEIGHT - CHAR_HEIGHT) / 8);
-    }
-
-  set_map_mask (0x0f);
-  pupa_memset (VGA_MEM + VGA_WIDTH * (VGA_HEIGHT - CHAR_HEIGHT) / 8, 0,
-              VGA_WIDTH * CHAR_HEIGHT / 8);
+  screen_update();
 }
 
 static void
@@ -331,7 +342,7 @@ pupa_vga_putchar (pupa_uint32_t c)
          break;
          
        case '\n':
-         if (ypos >= TEXT_HEIGHT)
+         if (ypos >= TEXT_HEIGHT - 1)
            scroll_up ();
          else
            ypos++;
@@ -381,7 +392,7 @@ pupa_vga_putchar (pupa_uint32_t c)
        {
          xpos = 0;
          
-         if (ypos >= TEXT_HEIGHT)
+         if (ypos >= TEXT_HEIGHT - 1)
            scroll_up ();
          else
            ypos++;