text: /*
   * Copyright (c) 2020 TK Chia
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   *   * Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the following disclaimer.
   *   * Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in the
   *     documentation and/or other materials provided with the distribution.
   *   * Neither the name of the developer(s) nor the names of its
   *     contributors may be used to endorse or promote products derived from
   *     this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
   * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #define _LIBI86_COMPILING_
  #include <stdint.h>
  #include "libi86/internal/graph.h"
  
  void
  _scrolltextwindow (short rows)
  {
    unsigned char x1z, x2z, y1z, y2z;
    short hm1;
    bool scroll_up_p;
  
  #ifndef __GNUC__
    __libi86_vid_state_init ();
  #endif
  
    if (! rows)
      return;
  
    x1z = __libi86_vid_state.x1z;
    y1z = __libi86_vid_state.y1z;
    x2z = __libi86_vid_state.x2z;
    y2z = __libi86_vid_state.y2z;
  
    hm1 = y2z - y1z;  /* window height minus 1 */
    if (rows > 0)
      {
        scroll_up_p = true;
        if (rows > hm1)
  	rows = 0;
      }
    else
      {
        scroll_up_p = false;
        if (rows < -hm1)
  	rows = 0;
        else
  	rows = -rows;
      }
  
    __libi86_vid_scroll (x1z, y1z, x2z, y2z, rows, scroll_up_p);
  }
  