[Qemu-devel] [Bug 1239008] [NEW] qemu fails to scroll screen on ^Vidmem output

[rjasmin]

Public bug reported:

Pascal uses ^Vidmem for B800 console output. The terminal does not
oblige the Pascal OS code to scroll the output. Virtualbox emulation
works, so this must be a qemu bug. Using QEMU in KVM mode as Ubuntu LTS.

Source line to trip bug(in theory pushes VideoMem up one line):

procedure Scroll;
//this is whats causing crashes. FIXME:Virtualbox not affected.QEMU BUG?
begin
  if scrolldisabled then exit;
      if (CursorPosY >= 24) then begin  //in case called before end of screen
    blank:= $20 or (TextAttr shl 8);
    Move((VidMem+(2*80))^,VidMem^,24*(2*80));
    // Empty last line
    FillWord((VidMem+(24*2*80))^,80,Blank);
    CursorPosX:=1;
    CursorPosY:=23;
    update_cursor;
  end;
end;

** Affects: qemu
     Importance: Undecided
         Status: New

** Affects: kvm (Ubuntu)
     Importance: Undecided
         Status: New

** Also affects: kvm (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1239008

Title:
  qemu fails to scroll screen on ^Vidmem output

Status in QEMU:
  New
Status in “kvm” package in Ubuntu:
  New

Bug description:
  Pascal uses ^Vidmem for B800 console output. The terminal does not
  oblige the Pascal OS code to scroll the output. Virtualbox emulation
  works, so this must be a qemu bug. Using QEMU in KVM mode as Ubuntu
  LTS.

  Source line to trip bug(in theory pushes VideoMem up one line):

  procedure Scroll;
  //this is whats causing crashes. FIXME:Virtualbox not affected.QEMU BUG?
  begin
    if scrolldisabled then exit;
        if (CursorPosY >= 24) then begin  //in case called before end of screen
      blank:= $20 or (TextAttr shl 8);
      Move((VidMem+(2*80))^,VidMem^,24*(2*80));
      // Empty last line
      FillWord((VidMem+(24*2*80))^,80,Blank);
      CursorPosX:=1;
      CursorPosY:=23;
      update_cursor;
    end;
  end;

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