HP OpenVMS Systems Documentation

Common Desktop Environment: Programmer's Guide

1 Basic Application Integration

Contents of Chapter:

Basic Integration Features

Organization of Basic Integration Information

Basic Integration Tasks

Levels of Printing
Complete Print Integration
Partial Print Integration
Nonintegrated Printing
Creating a Registration Package for Your Application

Basic application integration is a set of highly recommended tasks you should perform.

Basic integration does not involve extensive use of the desktop application programmer's interface (API). Therefore, it does not provide other interaction with the desktop, such as drag and drop, session management, ToolTalk messaging, and programmatic access to the actions and data-typing database.

A few of the integration tasks covered in this chapter require source code modification. They are optional, and are discussed here because they are closely related to basic integration tasks.

Basic Integration Features

Basic application integration provides these features for end users:

A graphical way to locate and start your application on the desktop
Your application will provide a desktop registration package, and your installation script will automatically register your application.
Registration creates an application group at the top level of Application Manager. The application group contains an icon the user double-clicks to start the application.
The ability to recognize and manipulate your application's data files
Your application will provide data types for its data files.
Data typing configures data files to use a unique icon to help users identify them. The data files also have meaningful desktop behavior. For example, the user can start your application by double-clicking a data file; dropping a data file on a desktop printer drop zone prints the file using the appropriate print command.
Easy font and color selection using Style Manager
Your application will change interface fonts and background, foreground, and shadow colors dynamically.
The desktop defines general interface font and color resources that are used if no corresponding application-specific resources exist.

Basic integration provides these advantages to system administrators:

Easy installation and registration
Upon installation, the application is automatically registered. The system administrator has little or no additional work to do.
Easy ongoing administration
All the desktop's configuration files are gathered in one location. Furthermore, the application can easily be unregistered if, for example, the administrator wants to update it or to move it to a different application server.

Organization of Basic Integration Information

Most of the tasks involved in basic integration are also performed by system administrators who are integrating an existing application into the desktop. Therefore, most basic integration documentation is located in the chapter "Registering an Application" in the CDE Advanced User's and System Administrator's Guide.

This chapter guides you to that information and contains additional information specific to application programming.

Basic Integration Tasks

These are the general tasks involved in basic integration:

Modify any application resources that set fonts and colors. This allows users to change the application's interface fonts and colors using Style Manager.
See the section on modifying font and color resources in the chapter "Registering an Application" in the CDE Advanced User's and System Administrator's Guide.
Create the registration package for your application.
See the text "Creating a Registration Package for Your Application" and "Registering an Application" in the CDE Advanced User's and System Administrator's Guide.
Modify your application's installation script to install the registration package files and perform the registration procedure.
See the section on registering the application using dtappintegrate in the chapter "Registering an Application" in the CDE Advanced User's and System Administrator's Guide.
Print application data files on networked and local printers. The desktop printer model provides a graphical way for users to print and is built on top of the native networking capabilities of the UNIX lp service.

Levels of Printing

The printing functionality available to the user depends on the level of integration you use. There are three levels of print integration:

Complete print integration. See "Complete Print Integration."
You should do complete integration if you have the ability to modify the application's source code.
When you do complete print integration, users can print data files on various printers by dropping them on printer drop zones (the Front Panel Printer control and printer icons in Print Manager). Certain other desktop behaviors are also implemented (see "Desktop Printing Environment Variables").
Partial print integration. See "Partial Print Integration."
You should do partial integration if you do not have the ability to modify the application's source code, but you do have the ability to invoke printing by way of an action.
When you do partial integration, your application provides a subset of full-integration functionality. For example, by using the LPDEST environment variable, your application's printing mechanism will obtain the print destination from the drop zone.
No print integration. See "Nonintegrated Printing."
If an application cannot supply a print action for its data files, you should configure the data files to display an error dialog box when users drop the files on printer drop zones.

Complete Print Integration

To do complete print integration, your application must:

Provide a print action
Use the four desktop printing environment variables

Desktop Printing Environment Variables

To have fully integrated printing, your application must use the values of the following four environment variables. The LPDEST variable is particularly important. It provides the ability for the user to choose the print destination by using a particular printer drop zone.

Printing Variable: Description
LPDEST: Uses the specified value as the printer destination for the file. If the variable is not set, the default printing device for your application should be used.
DTPRINTUSERFILENAME: Specifies the name of the file as it should appear in the Print dialog or print output. If the variable is not set, the actual file name should be used.
DTPRINTSILENT: Specifies whether to display a Print dialog box. When the variable is set to True, the Print dialog should not be displayed. If the variable is not set, the dialog box should be displayed.
DTPRINTFILEREMOVE: When the variable is set to True, the file should be removed after it is printed. This functionality is intended for temporary files that don't need to be retained after printing is complete. If the variable is not set, the file should not be removed.

A Fully Integrated Print Action

The print action is usually defined in a configuration file, app_root/dt/appconfig/types/<language>/name.dt.

If your print action starts a program that dereferences the four environment variables indicated in "Desktop Printing Environment Variables." then your data type is fully integrated. The print action must be written to be specific for the application's data type and should accept only a single file.

For example, the following print action is specific for a data type named ThisAppData:

ACTION Print
{
   ARG_TYPE             ThisAppData
   EXEC_STRING          print_command -file %(file)Arg_1%
}

If your application handles the ToolTalk Media message set Print request, then your print action could send a variant of it with the following actions.

ACTION Print { ARG_TYPE ThisAppData ARG_CLASS FILE ARG_COUNT 1 TYPE TT_MSG TT_CLASS TT_REQUEST TT_SCOPE TT_SESSION TT_OPERATION Print TT_FILE %Arg_1% TT_ARG0_ MODE TT_IN TT_ARG0_ VTYPE %Arg_1% TT_ARG1_ MODE TT_IN TT_ARG1_ VTYPE LPDEST TT_ARG1_VALUE $LPDEST TT_ARG2_MODE TT_IN TT_ARG2_VTYPE DTPRINTUSERFILENAME TT_ARG2_VALUE $DTPRINTUSERFILENAME TT_ARG3_MODE TT_IN TT_ARG3_VTYPE DTPRINTSILENT TT_ARG3_VALUE $DTPRINTSILENT TT_ARG4_MODE TT_IN TT_ARG4_VTYPE DTPRINTFILEREMOVE TT_ARG4_VALUE $DTPRINTFILEREMOVE }

ACTION Print { ARG_TYPE ThisAppData ARG_CLASS BUFFER ARG_COUNT 1 TYPE TT_MSG TT_CLASS TT_REQUEST TT_SCOPE TT_SESSION TT_OPERATION Print TT_ARG0_MODE TT_IN TT_ARG0_VTYPE %Arg_1% TT_ARG0_VALUE %Arg_1% TT_ARG1_MODE TT_IN TT_ARG1_VTYPE LPDEST TT_ARG1_VALUE $LPDEST TT_ARG2_MODE TT_IN TT_ARG2_VTYPE DTPRINTUSERFILENAME TT_ARG2_VALUE $DTPRINTUSERFILENAME TT_ARG3_MODE TT_IN TT_ARG3_VTYPE DTPRINTSILENT TT_ARG3_VALUE $DTPRINTSILENT TT_ARG4_MODE TT_IN TT_ARG4_VTYPE DTPRINTFILEREMOVE TT_ARG4_VALUE false }

If any of the four environment variables are not set, the corresponding message argument will be null. When the message argument is null, refer to "Desktop Printing Environment Variables" for the default interpretation.

Creating Print Actions for Filtered Data or Data Ready to Print

The desktop print utility /usr/dt/dtlp provides functionality on top of the lp subsystem. It gathers lp print options and prints the specified file.

Your application can use dtlp if either of the following conditions is true:

The data files do not need to be processed before they are sent to a printer.
Or, your application provides a filter for converting its data files to a ready-to-print form.

For more information about dtlp, see the dtlp(1) man page.

If the file is ready to print, the Print action runs dtlp in the EXEC_STRING. For example:

ACTION Print { ARG_TYPE ThisAppData EXEC_STRING dtlp %Arg_1% }

If the application provides a conversion filter, the filter must be run before running dtlp. For example:

ACTION Print
{
   ARG_TYPE             MyAppData
   EXEC_STRING          /bin/sh `cat %Arg_1%| filter_name | dtlp`
}

where filter_name is the name of the print filter.

Partial Print Integration

To do partial print integration, your application must provide a print action. The extent to which printing is integrated depends on which, if any, of the printing environment variables are handled by the action

Providing the Print Command for Partial Integration

To provide partial print integration, your application must provide a print command line of the form:

print_command [options]-file filename

where options provides a mechanism for dereferencing none, some, or all of the printing environment variables (see "Desktop Printing Environment Variables").

The simplest form of this print command line omits options.

print_command -file filename

This command line lets users print your application's data files using the desktop printer drop zones. However, printing destination is not set by the drop zone. In addition, other print behaviors set by the environment variables are not implemented. For example, the desktop may not be able to direct silent printing or remove temporary files.

If your print command line provides additional command-line options that correspond to the desktop printing environment variables, you can provide additional integration.

For example, the following command line provides the ability to dereference LPDEST:

print_command [-d destination] [-file filename]

where:

destination is the destination printer.

The next print command line provides options for dereferencing all four variables:

print_command [-d destination] [-u user_file_name] [-s] [-e] -file filename

where:

user_file_name: Indicates the file name as seen by the user.
-s: Printing is silent (no Print dialog box is displayed).
-e: Removes the file after it is printed.

The dereferencing occurs in the action definition. See the section, "Desktop Printing Environment Variables" for more information.

Turning Environment Variables into Command-Line Switches

If your action is not capable of dereferencing the four environment variables, but it is capable of taking corresponding command-line options, this subsection explains how to turn the environment variable values into command-line options.

For example, this is a simple print action that deferences LPDEST:

ACTION Print
{
   ARG_TYPE             data_type
   EXEC_STRING          print_command -d $LPDEST -file %(file)Arg_1%
}

However, this print action may create unpredictable behavior if LPDEST is
not set.

One way to create a Print action that provides proper behavior when variables are not set is to create a shell script that is used by the Print action.

For example, the following action and the script it uses properly handle all four environment variables:

ACTION Print
{
   ARG_TYPE            data_type
   EXEC_STRING         app_root/bin/envprint %(File)Arg_1%
}

The contents of the envprint script follow:

#!/bin/sh
# envprint - sample print script
DEST=""
USERFILENAME=""
REMOVE=""
SILENT=""

if [ $LPDEST ] ; then
    DEST="-d $LPDEST"
fi

if [ $DTPRINTUSERFILENAME ] ; then
    USERFILENAME="-u $DTPRINTUSERFILENAME"
fi

DTPRINTFILEREMOVE=echo $DTPRINTFILEREMOVE | tr "[:upper:]" "[:lower:]"`
if [ "$DTPRINTFILEREMOVE" = "true" ] ; then
    REMOVE="-e"
fi

DTPRINTSILENT=`echo $DTPRINTSILENT | tr "[:upper:]" "[:lower:]"`
if [ "$DTPRINTSILENT" = "true" ] ; then
    SILENT="-s"
fi

print_command $DEST $USERFILENAME $REMOVE $SILENT -file $1

Nonintegrated Printing

If your application does not integrate printing with the desktop, users must open your application to properly print data files.

Nevertheless, you should provide a print action that runs when users drop your application's data files on a printer drop zone. Otherwise, the desktop may assume that the file contains text data, and the print output will be garbled.

The desktop provides a print action for this purpose named NoPrint. The NoPrint action displays a dialog box telling users that the data files cannot be printed using the printer drop zones.

The NoPrint action displays the Unable to Print dialog box shown in Figure 1-1.

Figure 1-1 Dialog box displayed by the built-in NoPrint action

To use the Unable to Print dialog box, create a print action specific to your data type that maps to the NoPrint action. For example, suppose the data type for your application is:

DATA_ATTRIBUTES MySpreadSheet_Data1
{
   -
}

The following Print action maps to the NoPrint for this data type:

ACTION Print { ARG_TYPE MySpreadSheet_Data1 TYPE MAP MAP_ACTION NoPrint }

Creating a Registration Package for Your Application

The desktop registration package you create for an application should become part of the application's installation package. The procedures for creating a registration package are also performed by system administrators integrating existing applications into the desktop. These procedures and a detailed example are documented in the chapter "Registering an Application" in the CDE Advanced User's and System Administrator's Guide.