The ToolTalk Desktop Services Message Set allows an application to integrate and control other applications without user intervention. This section presents two scenarios ("The Smart Desktop" and "Integrated Toolsets") that show how the Desktop Services Message Set might be implemented.
The scenario in this section is intended to illustrate how the ToolTalk service can be used in an application-level program that interprets user requests; it is not intended to illustrate how the Common Desktop Environment product implements the ToolTalk service to interpret user requests.
A common user requirement for a graphic user interface (GUI) front-end is the ability to have data files be aware (or "know") of their applications. To do this, an application-level program is needed to interpret the user's requests. Examples of application-level programs (known as smart desktops) are the Apple Macintosh finder, Microsoft Windows File Manager, and the Common Desktop Desktop File Manager. The key common requirements for smart desktops are:
Takes a file
Determines its application
Invokes the application
The ToolTalk Service provides additional flexibility by allowing classes of tools to edit a specific data type. The following scenario illustrates how the Desktop Services Message Set might be implemented as a smart desktop transparent to the end-user.
Diane double-clicks on the File Manager icon.
The File Manager opens and displays the files in Diane's current directory.
Diane double-clicks on an icon for a data file.
The File Manager requests that the file represented by the icon be displayed. The File Manager encodes the file type in the display message.
The ToolTalk session manager matches the pattern in the display message to a registered application (in this case, the Icon Editor), and finds an instance of the application running on Diane's desktop.
If the ToolTalk session manager does not find a running instance of the application, it checks the statically-defined process types (ptypes) and starts an application that best matches the pattern in the message. If none of the ptypes matches, the session manager returns failure to the File Manager application.
The Icon Editor accepts the display message, de-iconifies itself, and raises itself to the top of the display.
Diane manually edits the file.
Another significant application for which the Desktop Services Message Set can be implemented is integrated toolsets. These environments can be applied in vertical applications (such as a CASE developer toolset) or in horizontal environments (such as compound documents). Common to both of these applications is the premise that the overall solution is built from specialized applications designed to perform one particular task well. Examples of integrated toolset applications are text editors, drawing packages, video or audio display tools, compiler front-ends, and debuggers. The integrated toolset environment requires applications to interact by calling on each other to handle user requests. For example, to display video, an editor calls a video display program; or to check a block of completed code, an editor calls a compiler.
The following scenario shows how the Desktop Services Message Set might be implemented as an integrated toolset:
Bruce is working on a compound document using his favorite editor.
He decides to change the some of the source code text.
Bruce double-clicks on the source code text.
The Document Editor first determines the text represents source code and then determines which file contains the source code.
The Document Editor sends an edit message request, using the file name as a parameter for the message.
The ToolTalk session manager matches the pattern in the edit message to a registered application (in this case, the Source Code Editor), and finds an instance of the application running on Bruce's desktop.
If the ToolTalk session manager does not find a running instance of the application, it checks the statically-defined ptypes and starts an application that best matches the pattern in the message. If none of the ptypes matches, the session manager returns failure to the Document Editor application.
The Source Code Editor accepts the edit message request.
The Source Code Editor determines that the source code file is under configuration control, and sends a message to check out the file.
The Source Code Control application accepts the message and creates a read-write copy of the requested file. It then passes the name of the file back to the Source Code Editor.
The Source Code Editor opens a window that contains the source file.
Bruce edits the source code text.