Functions for drawing node-and-edge graphs that have been laid out by 'graphviz'. This provides an alternative rendering to that provided by the 'Rgraphviz' package, with two main advantages: the rendering provided by 'gridGraphviz' should be more similar to what 'graphviz' itself would draw; and rendering with 'grid' allows for post-hoc customisations using the named viewports and grobs that 'gridGraphviz' produces.