Simplify clasp text output customization.

[BenKaufmann]

• Update clasp and simplify CustomTextOutput

[BenKaufmann]

However, I think it is not quite the same. This would break systems, which want to print something after clasp printed its model. Now they can only print something before if they want to use the default printer. Systems like clingcon or clingo-lpx won't be affected because there I took over printing completely but it is still a break.

Hm, I'm obviously missing something then.

From my understanding, both versions should do the same.

• Both the old and the new code only use CustomTextOutput if there is a printer, i.e. app_->has_printer() is true.
• In the old code, CustomTextOutput directly replaced the base classe's printModel() function (with a nearly verbatim copy) and:
  1. only forwarded to the base version if there's no control object. Otherwise,
  2. checked whether the model should be printed and if so first invoked the printer and then afterwards in the (optionally invoked) callback forwarded to printValues() of the base class.
  3. Finally and only if x == optQ(), printMeta() of the base class was invoked
• In the new code, the base class TextOutput gained a new virtual function printModelValues(), which is called from TextOutput::printModel() only after the "should we print this model" check returned true.
  1. CustomTextOutput` overrides this function and again first invokes the printer.
  2. Only if the printer invokes the callback, CustomTextOutput then calls printModelValues() of the base class, which (as previously) calls printValues().
  3. Finally and only if x == optQ(), printMeta() is invoked from the base class implementation of printModel().

Could you please help me figure out where I went wrong?

[BenKaufmann]

@rkaminsk Sorry for the noise. Postponing the call to printModelValues() to after the callback has finished is already a breaking change :disappointed:

EDIT: I updated the PR. Does this address your concern?

[rkaminsk]

Now it looks like it was before sans the copied code. I think it can be merged like this.