Individualize your apps

May 3, 2001, 06:26 PM —  Unix Insider — 

Are you ready for more pizzazz in your GUI applications? Most GUI toolkits provide several ways to configure such widget characteristics as color, font, and size. For the first installment of this three-column series, we look specifically at the Tk toolkit and its option database.

Tk is quite portable, so the examples here work under Mac OS, Unix, and Windows, among other operating systems. What's more, although these examples are coded in Tcl/Tk, each one can be adapted immediately for the related PerlTk, Tkinter (Python), TkLua, and other Tk-derived bindings.

Many successful Tk programmers are barely aware of the option database. Recent books by John Grayson, Nancy Walsh, and Chris Nelson have only a couple of pages each on this subject, although all three of these books capture the essentials accurately. This continues a tradition begun by Tk's author, John Ousterhout, who wrote in his 1994 book:

The option database shouldn't be needed very often in Tk applications because widgets have reasonable default values.... The option database exists primarily to provide cultural compatibility with other X toolkits; I suggest that you use it as little as possible.

Tk does indeed "have reasonable default values"; even beginners can build quite useful GUIs with Tk. After this column, though, you'll have a better grasp of how to advance beyond that level.

Not a database to fear

Don't be afraid of the option database. It's really just a small, flat configuration file. In other words, you can examine and update it as a simple text file, without the structural and transactional overhead of more formal databases. Here's a minimal example of an option database: a file in your Unix $HOME directory called .Xdefaults with contents:


     *background: blue

In English, this says, "Make the default background color for all my widgets in all my X applications, including Tk applications, blue." The format and interpretation of option databases are portable to Mac OS, OpenVMS, and Windows; the next installment will provide a few platform-specific tips to help start you off right if you're not using Unix.

More generally, an option database is a file that lists key-value pairs. With it, you can customize the appearance of an application without making any changes to the code for that application. A common example is a specification that cranks up the font size for widgets. Suppose you create a Tk-based application and deliver copies to hundreds of users. Everything's going great, until a couple of users complain that the text is too tiny. The option database answers their need with no requirement to alter your application, pass it through

I like it!
Post a comment
The content of this field is kept private and will not be shown publicly.
  • Allowed HTML tags: <a> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd>
  • Lines and paragraphs break automatically.
Free books

Build your tech library with our book giveaways.

Windows PowerShell 2.0 Unleashed
By Tyson Kopczynski, Pete Handley, Marco Shaw; Published by Sams

Windows PowerShell Unleashed will not only give you deep mastery over PowerShell but also a greater understanding of the features being introduced in PowerShell 2.0–and show you how to use it to solve your challenges in your production environment. Enter now!

 

Ubuntu Server Administration
By Michael Jang; Published by McGraw-Hill Osborne Media

Realize a dynamic, stable, and secure Ubuntu Server environment with expert guidance, tips, and techniques from a Linux professional. Ubuntu Server Administration covers every facet of system management -- from users and file systems to performance tuning and troubleshooting. Enter now!

Featured Sponsor

AISO founders envisioned a Web hosting company that was environmentally friendly. While the company employed energy-efficient innovations like solar panels, its infrastructure produced unacceptable power and cooling requirements. Find out how AISO leveraged AMD technology to overcome their challenge in this case study white paper.

In this whitepaper, Scalar explores the opportunity to change the landscape with respect to mission critical databases built around Oracle. Leveraging technologies such as Linux, high-end commodity processing power and Oracle RAC technology to architect, design, build and maintain database infrastructure that delivers maximum availability, reliability and performance at a fraction of traditional cost.

On a typical day, weather.com, the Web site for The Weather Channel in Atlanta, serves up between 15 million and 20 million page views. But in September 2004, when back-to-back hurricanes ransacked Florida, the peak traffic on one day more than tripled: over 70 million page views by more than 7 million unique visitors. Read the full success story now.

More Resources