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HP Data Entry and Forms Management System (VPLUS) Reference Manual: HP 3000 MPE/iX Computer Systems > Chapter 6 USING VPLUS INTRINSICS
HOW INTRINSICS ARE USED |
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The VPLUS intrinsics control the interface between forms stored in a forms file, a terminal screen, data entered on a form, and an application. Table 6-1 “Summary of VPLUS Intrinsics” illustrates the relation between the VPLUS intrinsics, terminal, forms file, application, data file or optional batch file, and the buffer areas in memory used by the intrinsics. The intrinsics use a buffer area in memory for the form definition and another buffer area for the data. A third area in memory is used as a buffer for the window area, the line on the form to which error and other messages are sent. User-defined function key labels also reside in a buffer area while they are active. There is a buffer area for global labels and another for form-specific labels. These buffer areas are managed by VPLUS and are in addition to any buffers the application may define. A form displayed on the terminal screen consists of protected areas (headings, labels, titles, display-only fields) and the unprotected areas (fields) into which data can be entered by a user. Any form written to the terminal screen by VSHOWFORM already resides as a form image in memory. It may also be stored in terminal local form storage. The form image contains the description of all the protected areas on the form, except for "display only" fields. It also contains the visual enhancements for all fields, protected and unprotected. The form image can be loaded from the forms file into local form storage by VLOADFORMS. Or the form image is read from the forms file into memory by a call to VGETNEXTFORM. Then it is written to the terminal screen or loaded into local form storage depending on options that can be set in VREADFIELDS or VSHOWFORM. Associated with each form is a set of data specifications — field attributes and processing specifications defined in FORMSPEC. These specifications are read from the forms file by VGETNEXTFORM and reside in memory during execution of the form. The field attributes can be dynamically altered using VCHANGEFIELD. Besides the form definition, there is a data buffer area in memory that contains data for all the fields (unprotected and display only) defined for the form. These fields reside in the buffer in the order they are defined on the screen, from left to right, top to bottom. When ENTER is pressed at the terminal, VREADFIELDS transfers the user-entered data from the screen to the data buffer. Before data is entered, if there are any initializations, VINITFORM sets the appropriate fields in the buffer to initial values. In the field phase, VFIELDEDITS verifies and possibly modifies the user-entered data in the data buffer according to any edit specifications defined for the fields. VFINISHFORM performs any final form modifications specified in the "finish" phase. Data for display-only fields may be written to the buffer by VINITFORM, VFIELDEDITS, or VFINISHFORM. Any changes to the data buffer are displayed at the terminal by the next VSHOWFORM. An application can send data to the buffer with VPUTBUFFER or to a single field in the buffer with VPUTFIELD or VPUTtype. Conversely, the data buffer can be copied to an application with VGETBUFFER, or a single field can be copied with VGETFIELD or VGETtype. As is done in ENTRY, during data collection, data in the data buffer can be written to the batch file by VWRITEBATCH. The data in the batch file can be read from the batch file to the data buffer by VREADBATCH. Typically, data is read from the batch file for display at the terminal during browse and modify operations. If the field editing specifications detect an error in data entry or data movement, an error flag is set for the field. When called, VERRMSG returns the message associated with the error, and VPUTWINDOW puts the message into the window. If an error is detected by an application, VSETERROR may be used to set the error flag, and also to put any message associated with the error into the window. Any non-error messages generated by an application are put in the window by VPUTWINDOW. A subsequent call to VSHOWFORM displays the contents of the window at the terminal. If there are user-defined function key labels, these labels are transferred to the key label area of memory. There is a key label area for global function key labels and another area for current form labels (global labels are associated with a forms file; form labels are associated only with the current form). Labels may be defined with FORMSPEC. Alternately, VSETKEYLABEL or VSETKEYLABELS may be used to override existing labels with labels from the application. Global labels defined with FORMSPEC are transferred to the global key label area when the forms file is opened by VOPENFORMF. Form labels defined by FORMSPEC are transferred to the form key label area by VGETNEXTFORM. A global or current form label specified by VSETKEYLABEL is copied into the appropriate key label area from an application. VSETKEYLABELS functions in the same manner for multiple label definitions. Labels are displayed on HP terminals by a call to VSHOWFORM. |
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