Function DrawTurtle

xgeneral.cpp:2000–2056

// and left 10, which draws a box twice as wide as it is high.

void DrawTurtle(CONST char *sz, int x0, int y0)
{
  int i, x, y, deltax, deltay;
  flag fBlank, fNoupdate;
  char szErr[cchSzDef], chCmd;

  gi.xTurtle = x0; gi.yTurtle = y0;
  while (chCmd = ChCap(*sz)) {
    sz++;

    // 'B' prefixing a command means just move the cursor, and don't draw.

    if (fBlank = (chCmd == 'B')) {
      chCmd = ChCap(*sz);
      sz++;
    }

    // 'N' prefixing a command means don't update cursor when done drawing.

    if (fNoupdate = (chCmd == 'N')) {
      chCmd = ChCap(*sz);
      sz++;
    }

    // Process the eight directional commands.

    switch (chCmd) {
    case 'U': deltax =  0; deltay = -1; break;      // Up
    case 'D': deltax =  0; deltay =  1; break;      // Down
    case 'L': deltax = -1; deltay =  0; break;      // Left
    case 'R': deltax =  1; deltay =  0; break;      // Right
    case 'E': deltax =  1; deltay = -1; break;      // NorthEast
    case 'F': deltax =  1; deltay =  1; break;      // SouthEast
    case 'G': deltax = -1; deltay =  1; break;      // SouthWest
    case 'H': deltax = -1; deltay = -1; break;      // NorthWest
    default:
      deltax = deltay = 0;
      sprintf(szErr, "Bad draw turtle action character: '%c'", chCmd);
      PrintError(szErr);
    }
    x = gi.xTurtle;
    y = gi.yTurtle;
    i = NFromPch(&sz)*gi.nScale;    // Figure out how far to draw.
    if (fBlank) {
      gi.xTurtle += deltax*i;
      gi.yTurtle += deltay*i;
    } else {
      gi.xTurtle += deltax*i;
      gi.yTurtle += deltay*i;
      DrawLine(x, y, gi.xTurtle, gi.yTurtle);
      if (fNoupdate) {
        gi.xTurtle = x;
        gi.yTurtle = y;
      }
    }
  }
}