8.2 Using the Message Window

The Message window allows you to monitor the progress of a visual program as it executes. It displays information, warning and error messages from the executive and output from the Print and Echo modules (if you include them in your visual program).

You can use the Print module, for example, to print the contents of an object. See Print in IBM Visualization Data Explorer User's Reference for more information. You can use the Echo module to print values or strings. See Echo in IBM Visualization Data Explorer User's Reference.

To open the Message window, select the Open Message Window option from the Windows pull-down menu of either the Image window or the VPE window. The Message window consists of a text window and various pull-down menus. When a visual program is running, any information, warnings, or errors sent by the server to the user interface are shown in the display area. (See also "Error Messages".)

The Message window allows users to save the contents of the text window in two different ways. The Save As... command of the Message window's File menu brings up a File Selection dialog box that allows the user to designate a file to which the current contents of text window are to be saved. Alternatively, the Log... command of the File menu brings up a File Selection dialog box that allows the user to designate a file that will receive all subsequent messages displayed in the text window.

The Message window provides a number of techniques to help the user locate the source of errors and warnings. Before each successful execution of the visual program, the string "Begin execution" is placed in the text window. This allows the user to more easily determine whether messages are the result of the most recent execution. Also, any line in the text window can be highlighted before execution. Highlighted lines remain highlighted over executions, making it easy to locate a marker indicating the beginning of execution. This technique is particularly useful when a large amount of information (from Print or Echo) is being displayed in the Message window. Alternatively, the contents of the text window can be removed with the Clear option of the Message window's Edit menu.

When an error occurs during the execution of a module, the errant module can be located in the VPE by double-clicking on the line in the Message window's text window containing the error message. This selection causes the VPE's canvas to shift so that the indicated module is within the canvas's scrolled viewing area. Errors for the last execution can also be located using the Next Error and Previous Error commands of the Message window's Edit menu. These commands expose and highlight errors that occurred before or after the currently highlighted error. If no error is currently highlighted, then Previous Error indicates the last error during execution and Next Error indicates the first error.

The Message window can be configured so that it does not display certain message types in the text window (by using the Error Messages, Warning Messages, and Information Messages buttons in the Message window's Options pull-down menu). If a toggle button is activated (colored), the corresponding message type is displayed. The default behavior is to display all error, warning, and information messages. You can change this default behavior with the infoEnabled, warningEnabled, and errorEnabled configuration options described in Appendix D. "User Interface Configuration". By default, the Message window pops up when an error is displayed in the text window and does not automatically pop up when information or warning messages are displayed. You can also change this default behavior with the infoOpensMessage, warningOpensMessage, and errorOpensMessage configuration options described in Appendix D. "User Interface Configuration".

Lastly, when connected to the server, the Execute Script Command... command of the Message window's Options menu allows commands to be issued directly to the server. However, only advanced users should use this feature, as the results of the commands entered can upset the state of the visual program. This command brings up the Execute Script Command dialog box, which will accept a single command in a 1-line text window. Any messages that result from this command appear in the Message window's text window.