/**
@page usage Usage
@section cmd Command Line Interface
To use the application on the command line check 'gds-render `--`help'.

Usage:
  gds-render [OPTION…]  FILE - Convert GDS file `<FILE>` to graphic

Help Options:  
  -h, `--`help                          Show help options  
  `--`help-all                          Show all help options  
  `--`help-gtk                          Show GTK+ Options  
  
Application Options:  
  -v, `--`version                       Print version  
  -r, `--`renderer=pdf|svg|tikz|ext     Renderer to use  
  -s, `--`scale=`<SCALE>`                 Divide output coordinates by `<SCALE>`  
  -o, `--`output-file=PATH              Output file path  
  -m, `--`mapping=PATH                  Path for Layer Mapping File  
  -c, `--`cell=NAME                     Cell to render  
  -a, `--`tex-standalone                Create standalone PDF  
  -l, `--`tex-layers                    Create PDF Layers (OCG)  
  -P, `--`custom-render-lib=PATH        Path to a custom shared object, that implements the render_cell_to_file function  
  `--`display=DISPLAY                   X display to use  


@section gui Graphical User Interface

The graphical user interface (GUI) can be used to open GDS Files, configure the layer rendering (colors, order, transparency etc.), and convert cells.

It is possible to export the layer configurations so they can be used later on. Even in the @ref cmd 

@image html gui.png
@image latex gui.png

The cell selector on the left shows the GDS Libraries and Cells. The cells are marked green if all references inside the cell could be found. If not all references could be found, the cell is marked orange. This doens't show if child cells have missing childs. Only one level of the hierarchy is checked in order to make it easier to spot an errorneous cell. Cells with missing child cells are still renderable but `--` obviously `--` faulty. If a cell or any sub-cell contains a reference loop, the cell is marked red. In this case it can't be selected for rendering.

In the above image one cell is green; so everything is okay. And the other one is red, which indicates a reference loop. This cell cannot be selected for rendering!
*/