Drop obsolete symbol SF-VALUE
Search the ChangeLogs to see this symbol has gradually been eliminated from scripts in GIMP repo.
There are only two scripts left using it. One, grid-system.scm should be obsoleted also (see forthcoming issue.) The other would be improved by substituting SF-ADJUSTMENT for SF-VALUE.
Now is the time to eliminate support for SF-VALUE in the ScriptFu machinery. It clutters the code, is technical debt.
The symbol is ancient, from the earliest ScriptFu. It was long ago replaced by the better alternative SF-ADJUSTMENT.
Following is the section of a document for script authors, explaining the issue better...
SF-VALUE kind of argument is obsolete
The symbol SF-VALUE is obsolete. You can edit v2 scripts and replace that symbol.
In v2, SF-VALUE declared a formal argument that is an unquoted, arbitrary string. Usually, SF-VALUE was used for an integer valued argument. In the dialog for a script, ScriptFu showed a text entry widget. Usually the widget showed a default integer literal, but the widget let you enter any text into the string.
You usually will replace it with a SF-ADJUSTMENT kind of formal argument, where the "digits" field of the SF-ADJUSTMENT is 0, meaning: no decimal places, i.e. integer valued. You must also add the other fields, e.g. the lower and upper limits.
A script that has been edited to replace SF-VALUE with SF-ADJUSTMENT will remain compatible with GIMP 2.
Example:
SF-VALUE "Font size (pixels)" "50"
=>
SF-ADJUSTMENT "Font size (pixels)" '(50 1 1000 1 10 0 SF-SPINNER)
Here, in the seven-tuple, the 0 denotes: no decimal places.
Another example, where you formerly used SF-VALUE to declare a formal argument that is float valued:
SF-VALUE "Lighting (degrees)" "45.0"
=>
SF-ADJUSTMENT "Lighting (degrees)" '(45.0 0 360 5 10 1 SF-SLIDER)
Here, the 1 denotes: show 1 decimal place, for example "45.0", in the dialog widget.
A SF-VALUE argument let a user enter executable Scheme code, say "'(1 g 1)", which is a list literal, to be injected into a Scheme call to a plugin. That use is no longer possible. If you must do that, use SF-STRING to get a string, and then your plugin can eval the string.
Rationale
A SF-VALUE argument let a user enter garbage for an argument, so that the script subsequently has an error. SF-ADJUSTMENT is more user-friendly.