The object on the right side of the panel is a ``scrollable list'' item. Its entries are the sequence of programs that IPE will execute. The default sequence is as shown in Figure 1. ``Input'' means read in a dataset. ``Taplot'' is an SEP program that converts a floating point dataset to single bytes. ``Ta2vplot'' is a program that takes byte data and produces a raster plot of the data in vplot format. Finally ``Xvpen'' is a program that displays the vplot result under X Windows. (It is a new vplot output filter, also written by me using XView.) IPE's power lies partly in the fact that this sequence can be modified. Programs can be added, replaced, or deleted using the buttons on the left panel.
Notice that one of the buttons in the scrollable list has its name boxed. (this is ``Taplot'' in the example of Figure 1). The box indicates that this is the ``current'' program. When you select a program from this list, it is boxed and a pop-up panel appears with the parameters for the current program. In Figure 2 I show the popup panel for the program Taplot. Parameters can be implemented as any of the following three types, all shown in Figure 2:
Figure 2 highlights one other feature of IPE not yet mentioned. On the parameter panel for Taplot are buttons named Load from parfile and Save to parfile as well as a text field for the specification of a parameter file name. These buttons appear on every parameter panel. SEP programs receive parameters either as command-line arguments or as values in a parameter file. IPE makes use of the latter method. For each program, IPE constructs a parameter file, and writes all the values entered on the panel to this file. This file is passed to the program. In addition to saving to a file, IPE can also load parameters from a file. Thus you can save a particularly useful set of parameters in a file so that you use them again later, without having to re-enter them. The ``Save to parfile'' buttons loads the parameters in, adjusting the sliders and other items automatically.
The left side of the main panel in Figure 1 contains buttons that perform various tasks in IPE. I've already alluded to the buttons Replace, Insert Before, Insert After, and Delete. These buttons add or remove programs from the processing sequence. The insert functions act relative to the ``current'' program, which is indicated by the box, while Replace and Delete act on the current program.
Use of the Replace, Insert Before, and Insert After buttons may initially be confusing. Buttons typically perform an action when the left mouse button is pressed while the cursor is pointed at them. These buttons behave differently. If I position the cursor on any of these buttons and hold down the right mouse button, a menu of available programs comes up, as shown in Figure 3. I select from the menu the program I want to add to the processing sequence. The presence of the pull-down menus attached to these buttons in indicated in XView by the arrow next to the button name.
The button Save/Load is used to save or load in an entire processing sequence, so that you can exit an IPE session, then come back later and pick up where you left off. For example, suppose I use IPE to filter some data. I build the processing sequence, set all the parameters, make some tests, and then leave IPE. I'd like to avoid having to do all that work again when I re-enter IPE. Above I showed how to save the parameters for any one program to a file. The Save/Load button lets you save the entire processing sequence - the sequence of programs, and the name of the parameter file associated with each - to another file. If you exit IPE and come back later, you can use Save/Load to quickly get back to the same point in your work.
The DOIT button causes the processing sequence that you have built to actually be run. Only when DOIT is pressed will results appear.
Finally, the Quit button exits from IPE.