Practical Programming in Tcl & Tk, Third Edition By Brent B. Welch
Table of Contents
Chapter 28. The Resource Database
Often it is sufficient to just set up the database and let the widget implementations use the values. However, it is also possible to record application-specific information in the database. To fetch a resource value, use option get:
option get window name class
The window is a Tk widget pathname. The name is a resource name. In this case, it is not a pattern or a full name. Instead, it is the resource name as specified in the tables in this book. Similarly, the class is a simple class name. It is possible to specify a null name or class. If there is no matching database entry, option get returns the empty string.
It is not possible to enumerate the database, nor can you detect the difference between a value that is the empty string and the absence of a value. You can work around this by introducing well-known resource names that list other resources. This trick is used in the next section.
