Codechange: make creating temporary StringParameters easier

[rubidium42]

Motivation / Problem

The repetitiveness of:

int64 args_array[] = { this->index };
StringParameters tmp_params(args_array);

Description

Introduce a sub class of StringParameters that has its own buffer.
Introduce a templated method that can accept any number of arguments that creates and fills the appropriate "StringParameters" instance.
Use that templated function instead, so the above code becomes auto tmp_params = MakeParameters(this->index);.

As added bonus, stuff like:

int64 args_array[] = {(int64)(size_t)e->name.c_str()};
StringParameters tmp_params(args_array);

becomes auto tmp_params = MakeParameters(e->name);, by implementing SetParam for const std::string& and const char *.

Limitations

None I can think of, except that there are a few other places where this new class could be used. However, those are for a later PR.

String pointers/references are still cast to size_t and then uint64_t. Solving that is, again, for a later PR.

I would have liked to use std::array and rely on copy-elision. That does work with GCC, but neither Clang nor MSVC does copy-elision for MakeParameters making that route troublesome. So, I've gone with std::vector so it can just move a pointer around.

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker

[LordAro]

Is there any particular reason all the AllocatedStringParameters variables can't be marked as const?

[rubidium42]

Is there any particular reason all the AllocatedStringParameters variables can't be marked as const?

Most places require StringParameters &, because either they run GetInt64 which updates the offset variable within StringParameters or run SetParam which also updates the object.