Restrictions and Limitations (UNIX and VMS Environments)
When defining function, control, and arrow keys, beware of the following restrictions and limitations:
• The FRS has the following internal limitations: 40 function keys (PFn or Fn), 40 FRS keys, and 25 menu items.
• The FRS imposes no restrictions on which function, control, or arrow keys can be mapped or remapped; however, certain control keys can be captured by the operating system before they reach the FRS. For example, the operating system reserves: Control-C, Control-O, Control-Q, Control-S, Control-T, Control-X, Control-Y.
• FRS commands cannot be mapped to a FRS key. This is syntactically illegal because FRS commands and FRS keys both appear on the left side of the equals sign in the mapping statement.
• TERM_INGRES cannot be reset dynamically by the application once the Forms System has been initialized.
• Positional menu item mapping cannot be turned off. In the vt100i termcap description, the application key pad is assigned by default to positional menu items. 1 on the key pad is assigned to the first menu item. You can see this if you look at the mapping file, for example:
menuitem1 = pf13
If you assign a FRS key to an activation block, that key's label appears on the menu line in place of the default key's label. The default key, however, still works.
"Go", key frskey5 =
begin
... [first menu item]
end;
In the above example, both 1 and whatever is mapped to frskey5 triggers the Go operation, even though you only see the frskey5's label. To deactivate this, you must assign another FRS function to the PF key now assigned to menuitem1:
frskey10 = pf13
Normally, you must use an unused FRS key for this function.
• Currently, map files are the only way to turn off a function, control, or arrow key (for example, controlV = off). Keys cannot be turned off by the 4GL or embedded query language set command.
• Keyboard review for the DEC VT series:
• On a VT220, F1 through F6 are reserved by the terminal. These cannot be mapped in map files.
• Escape is considered reserved for vt100, vt220, and all other terminals that use Escape sequences to define function keys.
Last modified date: 01/30/2023