Trivial Solutions
                    The LoseThos 64-bit PC Operating System
File:/LT/OSMain/Display.CPZ
This, and all LoseThos files, are public domain.  Do whatever you like.
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LoseThos code compiles with the 64-bit LoseThos compiler/assembler I wrote.
Boot the LoseThos CD and you can compile it.  Not in Kansas anymore!

Click here for preliminary compiler information you need.

Project: OSMain

U0 DrawChar(U64 ch)
{
/* This is for RAW output during boot
before the window manager is running
and for the debugger.

See GrUpdateForegroundOfText for
the normal screen text output routine.

See also GrUpdateScreen().

*/
  static U64 timeout=0;
  static TaskStruct *task=NULL;
  BoolI8 old_preempt=Preempt(OFF);
  I64 i,row,col;
  U8 *ptr,*ptr1,*ptr2;

//Give exclusive access to this task for 8mS,
//so we don't get mixed crash messages.
  while (task!=Fs && GetTimeStamp<timeout)
    Pause;
  task=Fs;
  timeout=GetTimeStamp+time_stamp_freq>>7; //8mS

  if (!(sys_dc_flags&DCF_SHOW_DOLLAR)) {
    if (ch=='$') {
      if (sys_dc_flags&DCF_IN_DOLLAR) {
        sys_dc_flags&=~DCF_IN_DOLLAR;
        if (!(sys_dc_flags & DCF_LAST_DOLLAR)) {
          sys_dc_flags&=~DCF_LAST_DOLLAR;
          return;
        }
      } else {
        sys_dc_flags|=DCF_IN_DOLLAR|DCF_LAST_DOLLAR;
        return;
      }
    }
    sys_dc_flags&=~DCF_LAST_DOLLAR;
    if (sys_dc_flags&DCF_IN_DOLLAR)
      return;
  }
  if (ch==CH_TAB) {
    DrawChar(CH_SPACE);
    while (sys_dc_col & 7)
      DrawChar(CH_SPACE);
  } else if (ch==CH_BACKSPACE) {
    sys_dc_col--;
    DrawChar(CH_SPACE);
    sys_dc_col--;
  } else if (ch==CH_CR) {
    DrawChar(CH_SPACE);
    while (sys_dc_col % text_cols)
      DrawChar(CH_SPACE);

  } else if (Bt(displayable_chars_bitmap,ch)||ch==0x7F) {
    row=sys_dc_col/text_cols%text_rows;
    col=sys_dc_col%text_cols;
    if (text_mode) {
      if (sys_dc_flags&DCF_SCROLL && sys_dc_col && !row && !col) {
        MemCpy(VGA_TEXT_MEM_BASE,VGA_TEXT_MEM_BASE+text_cols,
          text_cols*(text_rows-1)*2);
        MemSet(VGA_TEXT_MEM_BASE+text_cols*(text_rows-1)*2,0,text_cols*2);
        sys_dc_col-=text_cols;
        row=text_rows-1;
      }
      ptr=VGA_TEXT_MEM_BASE+(row*text_cols+col)*2;
      ptr[0]=ch;
      ptr[1]=BLACK<<4+WHITE;
    } else {
      OutU8(VGA_SC_INDEX,VGA_MAP_MASK);
      OutU8(VGA_SC_DATA,0x0F); //All planes -- WHITE
      if (sys_dc_flags&DCF_SCROLL && sys_dc_col && !row && !col) {
      //Scroll cached image
        MemCpy(sys_dc_screen_image,sys_dc_screen_image+gr_width*FONT_HEIGHT>>3,
            gr_width*(gr_height-FONT_HEIGHT)>>3);
        MemSet(sys_dc_screen_image+gr_width*(gr_height-FONT_HEIGHT)>>3,0,gr_width*FONT_HEIGHT>>3);

        MemCpy(VGA_GRAPHIC_MEM_BASE,sys_dc_screen_image,gr_width*gr_height>>3);
        sys_dc_col-=text_cols;
        row=text_rows-1;
      }
      ptr=ptr1=col+row*gr_width;
      ptr+=VGA_GRAPHIC_MEM_BASE;
      ptr1+=sys_dc_screen_image; //Write to cached image as well
      ptr2=&gr_font[ch.u8[0]*FONT_HEIGHT];
      for (i=0;i<FONT_HEIGHT;i++) {
        *ptr=*ptr1=reverse_bits_table[*ptr2++];
        ptr+=gr_width>>3;
        ptr1+=gr_width>>3;
      }
      }
    sys_dc_col++;
  }
  Preempt(old_preempt);
}

U0 WinDerivedValsUpdate(TaskStruct *task=NULL)
{
  if (!task) task=Fs;

  PushFD;
  Cli; //TODO Multiprocessor safe
  task->win_width =task->win_right-task->win_left+1;
  task->win_height=task->win_bottom-task->win_top+1;

//Inside the Border
  task->win_pixel_left  =FONT_WIDTH*task->win_left;
  task->win_pixel_right =FONT_WIDTH*(task->win_right+1)-1;
  task->win_pixel_width =task->win_pixel_right-task->win_pixel_left+1;
  task->win_pixel_top   =FONT_HEIGHT*task->win_top;
  task->win_pixel_bottom=FONT_HEIGHT*(task->win_bottom+1)-1;
  task->win_pixel_height=task->win_pixel_bottom-task->win_pixel_top+1;

//Outside the border
  if (Bt(&task->display_flags,DISPLAYf_NO_BORDER)) {
    task->win_border_pixel_left =task->win_pixel_left;
    task->win_border_pixel_right =task->win_pixel_right;
    task->win_border_pixel_top  =task->win_pixel_top;
    task->win_border_pixel_bottom=task->win_pixel_bottom;
  } else {
    task->win_border_pixel_left =task->win_pixel_left-FONT_WIDTH;
    task->win_border_pixel_right =task->win_pixel_right+FONT_WIDTH;
    task->win_border_pixel_top  =task->win_pixel_top-FONT_HEIGHT;
    task->win_border_pixel_bottom=task->win_pixel_bottom+FONT_HEIGHT;
  }
  PopFD;
}

BoolI64 AKDRawDisplayPutKey(U64 ch,U64 scancode)
{
  nounusedwarn scancode;
  if (IsRaw) {
    DrawChar(ch);
    return TRUE;
  } else
    return FALSE;
}

BoolI64 AKDRawDisplayPutS(U8 *st)
{
  U8 ch;
  if (IsRaw) {
    while (ch=*st++)
      DrawChar(ch);
    return TRUE;
  } else
    return FALSE;
}

U0 TaskWaitLastInputIdle(TaskStruct *task)
{
  TaskCmdStruct *tempc;
  PushFD;
  Cli;
  while (TRUE) {
    tempc=&task->last_input_filter_task->next_servant_cmd;
    if (tempc==*tempc &&
        Bt(&task->last_input_filter_task->task_flags,TASKf_IDLE))
      break;
    Yield;
  }
  PopFD;
}

BoolI64 AKDInputFilterPutKey(U64 ch,U64 scancode)
{
  BoolI8 old_preempt;
  if (Bt(&Fs->task_flags,TASKf_INPUT_FILTER_TASK)) {
    old_preempt=Preempt(OFF);
//This is for nestled autotypes
//more trouble than it's worth
//    TaskWaitLastInputIdle(Fs);
    Msg(MSG_KEY_DOWN,ch,scancode);
    Preempt(old_preempt);
    return TRUE;
  } else
    return FALSE;
}

BoolI64 AKDInputFilterPutS(U8 *st)
{
  U8 ch;
  BoolI8 old_preempt;
  if (Bt(&Fs->task_flags,TASKf_INPUT_FILTER_TASK)) {
    old_preempt=Preempt(OFF);
//This is for nestled autotypes
//more trouble than it's worth
//    TaskWaitLastInputIdle(Fs);
    while (ch=*st++)
      Msg(MSG_KEY_DOWN,ch,0);
    Preempt(old_preempt);
    return TRUE;
  } else
    return FALSE;
}

BoolI64 AKDTaskPutKey(U64 ch,U64 scancode)
{
  BoolI8 old_preempt=Preempt(OFF);
  TaskKeyDevStruct *tempk;
  if (!sys_cur_focus_task) {
    Preempt(old_preempt);
    return FALSE;
  }
  tempk=sys_cur_focus_task->next_key_dev;
  while (tempk!=&sys_cur_focus_task->next_key_dev) {
    if (!(scancode & SCF_KEY_DESC) || tempk->flags & KDF_HAS_DESCS) {
      if (tempk->put_key(tempk->task,tempk->put_data,ch,scancode)) {
        Preempt(old_preempt);
        return TRUE;
      }
    }
    tempk=tempk->next;
  }
  Preempt(old_preempt);
  return FALSE;
}


BoolI64 AKDTaskPutS(U8 *st)
{
  BoolI8 old_preempt=Preempt(OFF);
  TaskKeyDevStruct *tempk;
  if (!sys_cur_focus_task) {
    Preempt(old_preempt);
    return FALSE;
  }
  tempk=sys_cur_focus_task->next_key_dev;
  while (tempk!=&sys_cur_focus_task->next_key_dev) {
    if (tempk->put_s(tempk->task,tempk->put_data,st)) {
      Preempt(old_preempt);
      return TRUE;
    }
    tempk=tempk->next;
  }
  Preempt(old_preempt);
  return FALSE;
}

U0 PutKey(U64 ch,U64 sc)
{ //See PutKeyHandling
  KeyDevStruct *tempp=sys_put_key_root.next;
  if (!Bt(&Fs->display_flags,DISPLAYf_SILENT)) {
    if (sys_cur_scan_code & SCF_SCROLL) {
      if (sys_cur_focus_task==Fs) {
        while (sys_cur_scan_code & SCF_SCROLL)
          Yield;
      }
    }
    while (tempp!=&sys_put_key_root) {
      if (!(sc & SCF_KEY_DESC) || tempp->flags & KDF_HAS_DESCS) {
        if (tempp->put_key(ch,sc))
          break;
      }
      tempp=tempp->next;
    }
  }
}

U0 PutChar(U64 ch)
{
  PutKey(ch,0);
}

U0 PutS(U8 *st)
{ //See PutKeyHandling
  U8 ch,*ptr;
  BoolI8 cont=TRUE;
  if (!st) return;
  KeyDevStruct *tempp=sys_put_key_root.next;
  if (!Bt(&Fs->display_flags,DISPLAYf_SILENT)) {
    if (sys_cur_scan_code & SCF_SCROLL) {
      if (sys_cur_focus_task==Fs) {
        while (sys_cur_scan_code & SCF_SCROLL)
          Yield;
      }
    }
    while (cont && tempp!=&sys_put_key_root) {
      if (tempp->put_s) {
        if (tempp->put_s(st))
          break;
      } else {
        ptr=st;
        while (ch=*ptr++)
          if (tempp->put_key(ch,0))
            cont=FALSE;
      }
      tempp=tempp->next;
    }
  }
}

U0 SetKeyDesc(U8 *fmt,...)
{
  I64 i;
  U8 *buf=SPrintFJoin(NULL,fmt,argc,argv);
  StrCpy(key_desc,buf);
  key_handler=Caller;
  Free(buf);
  for (i=0;i<5;i++)
    Yield;  //This makes KeyMap work better
}

U0 SetCtrlAltLetCB(U8 ch,U0 (*fp_handler)(U64 sc),U8 *desc,BoolI8 in_irq=FALSE)
{
  ch=ToUpper(ch)-'A';
  if (ch<26) {
    fp_ctrl_alt_let_cbs[ch]=fp_handler;
    Free(ctrl_alt_let_descs[ch]);
    ctrl_alt_let_descs[ch]=AStrNew(desc);
    BEqu(&ctrl_alt_let_in_irq_flags,ch,in_irq);
  }
}

KeyDevStruct *KeyDevAdd(BoolI64 (*fp_put_key)(U64 ch,U64 sc),BoolI64 (*fp_puts)(U8 *st),U64 priority,BoolI8 key_descs=FALSE)
//Places hook in StdOut chain
{ //See PutKeyHandling
  BoolI8 old_preempt=Preempt(OFF);
  KeyDevStruct *tempp,*tempp1=sys_put_key_root.last;
  tempp=ACAlloc(sizeof(KeyDevStruct));
  tempp->put_key=fp_put_key;
  tempp->put_s=fp_puts;
  tempp->priority=priority;
  if (key_descs)
    tempp->flags|=KDF_HAS_DESCS;
  while (tempp1->priority>priority)
    tempp1=tempp1->last;
  InsQue(tempp,tempp1);
  Preempt(old_preempt);
  return tempp;
}

U0 KeyDevRem(KeyDevStruct *tempp)
{
  BoolI8 old_preempt=Preempt(OFF);
  RemQue(tempp);
  Preempt(old_preempt);
  Free(tempp);
}

TaskKeyDevStruct *TaskKeyDevAdd(BoolI64 (*fp_put_key)(TaskStruct *task,U0 *data,U64 ch,U64 sc),
  BoolI64 (*fp_puts)(TaskStruct *task,U0 *data,U8 *st),U64 priority,BoolI8 key_descs,TaskStruct *task,U0 *data)
//Places hook in StdOut chain for just a task
{ //See PutKeyHandling
  BoolI8 old_preempt=Preempt(OFF);
  TaskKeyDevStruct *tempk,*tempk1;
  if (!TaskValidate(task)) {
    Preempt(old_preempt);
    return NULL;
  }
  tempk1=task->last_key_dev;
  tempk=CAlloc(sizeof(TaskKeyDevStruct),task);
  tempk->task=task;
  tempk->put_data=data;
  tempk->put_key=fp_put_key;
  tempk->put_s=fp_puts;
  tempk->priority=priority;
  if (key_descs)
    tempk->flags|=KDF_HAS_DESCS;
  while (tempk1->priority>priority)
    tempk1=tempk1->last;
  InsQue(tempk,tempk1);
  Preempt(old_preempt);
  return tempk;
}

U0 TaskKeyDevRem(TaskKeyDevStruct *tempk)
{
  BoolI8 old_preempt=Preempt(OFF);
  RemQue(tempk);
  Preempt(old_preempt);
  Free(tempk);
}