OPEN FORM

Declares a compiled form in the program.

Syntax

OPEN FORM identifier FROM form-file
  1. identifier is an identifier that defines the name of the form object.
  2. form-file defines the name of the compiled form file, without .42f extension.

Usage

In order to use a .42f compiled version of a form specification file, the programs must declare the form with the OPEN FORM instruction and then display the form in the current window by using the DISPLAY FORM instruction.

OPEN FORM / DISPLAY FORM are typically used at the beginning of programs to display the main form in the default SCREEN window:
OPEN FORM custform FROM "customer"
DISPLAY FORM custform

The form identifier does not need to match the name of the form specification files, but it must be unique among form names in the program. Its scope of reference is the entire program.

Important:

The form file name identifies the compiled .42f file to be loaded. The file name may use a .42f extension, but this is not recommended.

The file name can be a simple file name, a relative file path, or an absolute file path.
  • When using a simple file name or a relative path, form files are found relative to several directories in a given order, as described in the FGLRESOURCEPATH reference topic.
  • When specifying an absolute path, FGLRESOURCEPATH (or DBPATH) is not used. On Windows®, an absolute file name must start with a drive letter ( C: ), a backslash ( \ ) or a slash ( / ). If FGLRESOURCEPATH contains a driver letter ( C: ), a form file specified as "/foo/bar" will only be found in "C:/foo/bar", if C: is the current drive.

If you execute an OPEN FORM with the name of an open form, the runtime system first closes the existing form before opening the new form.

The scope of reference of form identifier is the entire program.

When the window is dedicated to the form, use the OPEN WINDOW WITH FORM instruction to create the window and the form object in one statement.

In TUI mode, the form is displayed in the current window at the position defined by the FORM LINE attribute that can be specified in the ATTRIBUTE clause of OPEN WINDOW or as default with the OPTIONS instruction.

After the form is loaded, you can activate the form by executing a CONSTRUCT, DISPLAY ARRAY, INPUT, INPUT ARRAY, or DIALOG statement. When the runtime system executes the OPEN FORM instruction, it allocates resources and loads the form into memory. To release the allocated resources when the form is no longer needed, the program must execute the CLOSE FORM instruction. This is a memory-management feature to recover memory from forms that the program no longer displays on the screen. If the form was loaded with a window by using the WITH FORM clause, it is automatically closed when the window is closed with a CLOSE WINDOW instruction.

Example

MAIN
  OPEN FORM f1 FROM "customer"
  DISPLAY FORM f1
  CALL input_customer()
  CLOSE FORM f1
  OPEN FORM f2 FROM "custlist"
  DISPLAY FORM f2
  CALL input_custlist()
  CLOSE FORM f2
END MAIN