Allow printers to hard-wire values of options

[andreas-gruenbacher]

I'm looking for a reasonable way to hard-wire the value of an option for a specific printer. For example, with the following shortened definition, I can define the default value of the option:

<option type="enum" id="opt/Resolution">
  <arg_longname><en>Resolution</en></arg_longname>
  <arg_shortname><en>Resolution</en></arg_shortname>
  <arg_execution> ... </arg_execution>
  <constraints>
    <constraint sense="true">
      <driver>driver</driver>
      <printer>printer</printer>
      <arg_defval>ev/300dpi</arg_defval>
    </constraint>
  </constraints>
  <enum_vals>
    <enum_val id="ev/300dpi">
      <ev_driverval>300</ev_driverval>
      ...
    </enum_val>
    <enum_val id="ev/600dpi">
      <ev_driverval>600</ev_driverval>
      ...
    </enum_val>
  </enum_vals>
</option>

If I add constraints on the enum_vals so that only a single option remains available for a printer, the option will disappear fro user interfaces and it will effectively be hard-wired.

However, for options that always have exactly one value for each supported printers, this still requires adding an enum for each possible choice, and some boilerplate code. It obviously doesn't work at all for options that have free values.

What I'd ideally like to do is to directly define the driverval, so something like <arg_val>300</arg_val> instead of <arg_defval>ev/300dpi</arg_defval>. Is there a way to do that already?