Example

The following code fragments present a group graphic (TMyGroup) and shows what happens when a call to TMyGroup::Draw occurs. The TMyGroup class is created for the purpose of illustration. In most cases, you can just instantiate a TGraphicGroup and call its Draw function to get the functionality shown in this example.

TMyGroup::Draw function implementation

  TMyGroup::Draw( TGrafPort& parentPort )
  {
      TLinkedBundlePort bundlePort( &parentPort, fBundle );
      TLinkedModelMatrixPort matrixPort( &bundlePort, &fModelMatrixState )
      TMyGroupIterator iterator;
      for( MGraphic* child = iterator.First(); child != NIL; child = iterator.Next; )
          child>Draw( matrixPort );
}
      TLinkedModelMatrixPort matrixPort( &bundlePort, &fModelMatrixState )

The constructor to TLinkedModelMatrixPort takes a reference to a port and a model matrix. It establishes a link to the model matrix so that the model matrix supplied in the constructor can be concatenated to the graphic state. The destructor deletes the link.

      for( MGraphic* child = iterator.First(); child != NIL; child = iterator.Next; )
          child>Draw( matrixPort );

The child>Draw call in the for loop iterates the TMyGroup children and calls the Draw function for each child graphic. For example, if the group contains a customized polygon, the TMyPolygon::Draw function is called.

TMyPolygon::Draw function

  TMyPolygon::Draw( TGrafPort& parent )
  {   
      parent.Draw( *this );
  }

The TMyPolygon::Draw function calls TGrafPort::Draw, which gets the device from the drawing port, and calls the TGrafDevice::RenderPolygon function. The RenderPolygon function in the TGrafPort::Draw function has a graphics device.

TSomeGrafDevice::Draw function

  TSomeGrafDevice::Draw(  const TGPolygon& p, 
                          const TGrafState& grafState, 
                          TGrafCache& grafCache )
  {
      grafState.GetAttributeState()>GetAntialiasing();
      grafState.GetModelMatrixState()>GetMatrix();
  }

The grafState.GetModelMatrixState function returns the model matrix stored in the TLinkedViewMatrixPort instance.

The grafState.GetModelMatrixState>GetMatrix function returns the matrix in the matrix state object.

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