Kernel/VTerm - Fix scroll-on-write code (scroll before writing, not after)

diff --git a/KernelLand/Kernel/drv/vterm_termbuf.c b/KernelLand/Kernel/drv/vterm_termbuf.c
index cb0de74..6869ec7 100644 (file)
--- a/KernelLand/Kernel/drv/vterm_termbuf.c
+++ b/KernelLand/Kernel/drv/vterm_termbuf.c
@@ -78,9 +78,42 @@ void VT_int_PutChar(tVTerm *Term, Uint32 Ch)
                write_pos = Term->WritePos;
                limit = Term->TextHeight*(giVT_Scrollback+1) * Term->TextWidth;
        }
-       
-       // TODO: Can the write position be equal to the end of screen?
-       ASSERTC(write_pos, <, limit);
+
+       ASSERTC(write_pos, >=, 0);
+
+       // Scroll entire buffer (about to write outside limit)
+       if( write_pos >= limit )
+       {
+               ASSERTC(write_pos, <, limit + Term->TextWidth);
+               VT_int_ScrollText(Term, 1);
+               write_pos -= Term->TextWidth;
+       }
+
+       // Bring written cell into view
+       if( !(Term->Flags & VT_FLAG_ALTBUF) )
+       {
+               size_t  onescreen = Term->TextWidth*Term->TextHeight;
+               if( write_pos >= Term->ViewPos + onescreen )
+               {
+                       size_t  new_pos = write_pos - (write_pos % Term->TextWidth) - onescreen + Term->TextWidth;
+                       size_t  count = (new_pos - Term->ViewPos) / Term->TextWidth;
+                       VT_int_ScrollFramebuffer(Term, count);
+                       //Debug("VT_int_PutChar: VScroll down to %i", new_pos/Term->TextWidth);
+                       Term->ViewPos = new_pos;
+               }
+               else if( write_pos < Term->ViewPos )
+               {
+                       size_t  new_pos = write_pos - (write_pos % Term->TextWidth);
+                       size_t  count = (Term->ViewPos - new_pos) / Term->TextWidth;
+                       VT_int_ScrollFramebuffer(Term, -count);
+                       //Debug("VT_int_PutChar: VScroll up to %i", new_pos/Term->TextWidth);
+                       Term->ViewPos = new_pos;
+               }
+               else
+               {
+                       // no action, cell is visible
+               }
+       }
        
        switch(Ch)
        {
@@ -89,6 +122,7 @@ void VT_int_PutChar(tVTerm *Term, Uint32 Ch)
        case '\n':
                VT_int_UpdateScreen( Term, 0 ); // Update the line before newlining
                write_pos += Term->TextWidth;
+               // TODO: Scroll display down if needed
        case '\r':
                write_pos -= write_pos % Term->TextWidth;
                break;
@@ -135,42 +169,14 @@ void VT_int_PutChar(tVTerm *Term, Uint32 Ch)
                break;
        }
        
+       ASSERTC(write_pos, <=, limit);
        if(Term->Flags & VT_FLAG_ALTBUF)
        {
                Term->AltWritePos = write_pos;
-               
-               if(Term->AltWritePos >= limit)
-               {
-                       Term->AltWritePos -= Term->TextWidth;
-                       VT_int_ScrollText(Term, 1);
-               }
        }
        else
        {
                Term->WritePos = write_pos;
-               // Move Screen
-               // - Check if we need to scroll the entire scrollback buffer
-               if(Term->WritePos >= limit)
-               {
-                        int    base;
-                       
-                       // Update view position
-                       base = Term->TextWidth*Term->TextHeight*(giVT_Scrollback);
-                       if(Term->ViewPos < base)
-                               Term->ViewPos += Term->Width;
-                       if(Term->ViewPos > base)
-                               Term->ViewPos = base;
-                       
-                       VT_int_ScrollText(Term, 1);
-                       Term->WritePos -= Term->TextWidth;
-               }
-               // Ok, so we only need to scroll the screen
-               else if(Term->WritePos >= Term->ViewPos + Term->TextWidth*Term->TextHeight)
-               {
-                       VT_int_ScrollFramebuffer( Term, 1 );
-                       
-                       Term->ViewPos += Term->TextWidth;
-               }
        }
 
        HEAP_VALIDATE();