To explore the capabilities of the Shiny toolkit, we will build another complete graphical application. As the development of Shiny has been focused on the lower layer of graphical APIs, an application such as GoMail would involve the creation of many custom widgets. Instead, we will look at a more graphically-oriented application—an image viewer.
To get an idea of how the image viewer should look, we will make a rough design that we can follow. The online tool Balsamiq (balsamiq.com) is a good way to rapidly create wireframes that will suit this purpose. Take a look at the following export. It includes a navigation bar along the top, a directory listing on the left, and a full-size image view on the right:
A mockup of the GoImages application using the Balsamiq tool
Clearly, this image has a far lower level of detail than the design tool we used in Chapter 4, Walk – Building Graphical Windows Applications (back at the beginning of Section 2, Toolkits Using Existing...