Accessing the Data-Typing Database

This chapter describes the data-typing functions and how to use the data-typing database.

• Summary

• Data Criteria and Data Attributes

• Data-Typing Functions

• Registering Objects as Drop Zones

• Example of Using the Data-Typing Database

Summary

Data typing provides an extension to the attributes of files and data beyond what is provided by the traditional UNIX file systems. These extensions consist of attributes, such as icon names, descriptions, and actions, that can be performed on files and data. This information is stored in name/value pairs in the DATA_ATTRIBUTES table (or database). The desktop uses a certain set of DATA_ATTRIBUTES, described in the following paragraphs. The DATA_ATTRIBUTES table is extendable for future and application-specific growth, although extending this table is not recommended because other applications may not check the additions.

Data is matched with a specific file or data entry in a DATA_CRITERIA table. The DATA_CRITERIA table entries are sorted in decreasing order from most specific to least specific. For example, /usr/lib/lib* is more specific than /usr/* and would, therefore, appear first. When a request to type a file or data is made, the table is checked in sequence to find the best match using the information provided either from the file or from the data. When an information and entry match is found, DATA_ATTRIBUTES_NAME is used to find the proper DATA_ATTRIBUTES entry.

If you want your application to present data objects (either files or data buffers) to the user in a manner consistent with the desktop, use the DtDts* API to determine how to display the data object by calling the DtDtsDataTypeToAttributeValue() function for the ICON attribute.

Library and Header Files

To use data typing, you need to link to the libDtSvc library. Actions are usually loaded with the data-typing information. Actions require links to the libXm and libX11 libraries. The header files are Dt/Dts.h and Dt/Dt.h.

Demo Program

A demo program containing an example of how to use the data-typing database is in /usr/dt/examples/dtdts/datatypes/datatyping.c.

Data Criteria and Data Attributes

Data typing consists of two parts:

• A database that stores data criteria and data attributes

• A collection of routines that query the database

The attributes of data criteria, in alphabetical order, are:

• CONTENT

• DATA_ATTRIBUTES_NAME

• LINK_NAME

• LINK_PATH

• MODE

• NAME_PATTERN

• PATH_PATTERN

Table 9-1 describes the data criteria in the order in which you are most likely to use them.

Table 9-1 Data Criteria in Order of Most Likely Use

Some of the more common attributes of data types, in alphabetical order, are:

• ACTIONS

• COPY_TO_ACTION

• DESCRIPTION

• ICON

• INSTANCE_ICON

• IS_EXECUTABLE

• IS_TEXT

• LINK_TO_ACTION

• MEDIA

• MIME_TYPE

• MOVE_TO_ACTION

• NAME_TEMPLATE

• PROPERTIES

• X400_TYPE