Unit Plot;
Interface
uses ViewPort, Color, Basic, Graph;
type
  tPoint = object
    x,y: Real;
    end;
  tPlot = object
    cRegionLL, cRegionUR: tPoint;  {which region to display}
    cWindow00, cWindowDim: tPoint; {window position on the screen}
    procedure SetRegion( px1, px2, py1, py2: Real );
      {minimal and maximal x, minimal and maximal y}
    procedure SetWindow( px0, py0, pxd, pyd: Real );
      {coordinates of lower left corner + width and height of a window}
    procedure Axis( pColor: tColor );
      {draw axis}
    procedure Line( px1, py1, px2, py2: Real; pColor: tColor );
    {private}
    function _VirtualToReal( px, py: Real; var pXOut, pYOut: Real ): Boolean;
      {true if point is inside selected region}
    end;

Implementation
procedure tPlot.SetRegion( px1, px2, py1, py2: Real );
begin
  cRegionLL.x := px1;
  cRegionLL.y := py1;
  cRegionUR.x := px2;
  cRegionUR.y := py2;
end;
procedure tPlot.SetWindow( px0, py0, pxd, pyd: Real );
begin
  cWindow00.x := px0;
  cWindow00.y := py0;
  cWindowDim.x := pxd;
  cWindowDim.y := pyd;
end;
procedure tPlot.Axis( pColor: tColor );
var sLabel: String;
  p1, p2: tPoint;
begin
  with Scr do
    begin
    move( cWindow00, p1, sizeof( p1 ) );
    move( cWindow00, p2, sizeof( p2 ) );
    p2.x := p2.x + cWindowDim.x;
    p2.y := p2.y + cWindowDim.y;
    line( p1.x-0.5, p1.y, p2.x, p1.y, pColor );
    line( p1.x, p1.y-0.5, p1.x, p2.y, pColor );
    line( p2.x, p1.y-0.5, p2.x, p1.y, pColor );
    line( p1.x-0.5, p2.y, p1.x, p2.y, pColor );
    TextFg( pColor.cData[1] );
    sLabel := RealToStr( cRegionLL.x, 4 );
    CellWriteXY( p1.x+0.5, p1.y-0.5, sLabel );
    sLabel := RealToStr( cRegionLL.y, 4 );
    CellWriteXY( p1.x+0.5, p1.y+CellY, sLabel );
    sLabel := RealToStr( cRegionUR.x, 4 );
    CellWriteXY( p2.x-length(sLabel)*CellX, p1.y-0.5, sLabel );
    sLabel := RealToStr( cRegionUR.y, 4 );
    CellWriteXY( p1.x+0.5, p2.y, sLabel );
    {    line( cWindow00.x+cWindowDim.x, cWindow00.y, cWindow00.x+cWindowDim.x,
          cWindow00.y+cWindowDim.y, pColor );
        line( cWindow00.x, cWindow00.y+cWindowDim.y, cWindow00.x+cWindowDim.x,
          cWindow00.y+cWindowDim.y, pColor );
        TextFg( Red );
        sLabel := '[' + RealToStr( cRegionLL.x, 4 ) + ','
          + RealToStr( cRegionLL.y, 4 ) + ']';
        CellWriteXY( cWindow00.x, cWindow00.y+CellY, sLabel );
        CellWriteXY( cWindow00.x+cWindowDim.x, cWindow00.y-0.5,
          RealToStr( cRegionUR.x, 4 ) );
        CellWriteXY( cWindow00.x, cWindow00.y+cWindowDim.y,
          RealToStr( cRegionUR.y, 4 ) );
        sLabel := '[' + RealToStr( cRegionUR.x, 4 ) + ','
          + RealToStr( cRegionUR.y, 4 ) + ']';
        CellWriteXY( cWindow00.x+cWindowDim.x-length(sLabel)*CellX,
          cWindow00.y+cWindowDim.y-0.5, sLabel );
    }
    end;
end;
procedure tPlot.Line( px1, py1, px2, py2: Real; pColor: tColor );
var x1, y1, x2, y2: Real;
begin
  if _VirtualToReal( px1, py1, x1, y1 ) and _VirtualToReal( px2, py2, x2, y2 ) then
    Scr.Line( x1, y1, x2, y2, pColor );
end;
function tPlot._VirtualToReal( px, py: Real; var pXOut, pYOut: Real ): Boolean;
begin
  if (px >= cRegionLL.x) and (px <= cRegionUR.x)
      and (py >= cRegionLL.y) and (py <= cRegionUR.y) then
    begin
    pXOut := ( cWindow00.x+(px-cRegionLL.x)/(cRegionUR.x-cRegionLL.x)
      *(cWindowDim.x) );
    pYOut := ( cWindow00.y+(py-cRegionLL.y)/(cRegionUR.y-cRegionLL.y)
      *(cWindowDim.y) );
    _VirtualToReal := True;
    end
  else
    _VirtualToReal := False;
end;


begin
end.