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Re: How to add the second (or other) languages

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On 16/02/2025 19:59, pozz wrote:
> Il 12/02/2025 20:50, David Brown ha scritto:

>>
>> You don't need a very fancy pre-processor to handle this yourself, if 
>> you are happy to make a few changes to the code.  Have your code use 
>> something like :
>>
>> #define DisplayPrintf(id, desc, args...) \
>>      display_printf(strings[language][string_ ## id], ## x)
>>
>> Use it like :
>>
>>      DisplayPrintf(event_type_on, "Event on", ev->idx);
>>
>>
>> A little Python preprocessor script can chew through all your C files 
>> and identify each call to "DisplayPrintf". 
> 
> Little... yes, it would be little, but not simple, at least for me. How 
> to write a correct C preprocessor in Python?

You don't write a C preprocessor - that's the point.

Tools like gettext have to handle any C code.  That means they need to 
deal with situations with complicated macros, include files, etc.

You don't need to do that when you make your own tools.  You make the 
rules - /you/ decide what limitations you will accept in order to 
simplify the pre-processing script.

So you would typically decide you only put these DisplayPrintf calls in 
C files, not headers, that you ignore all normal C preprocessor stuff, 
and that you keep each call entirely on one line, and that you'll never 
use the sequence "DisplayPrintf" for anything else.  Then your Python 
preprocessor becomes :

	for this_line in open(filename).readlines() :
		if "DisplayPrintf" in line :
			handle(line)

This is /vastly/ simpler than dealing with more general C code, without 
significant restrictions to you as the programmer using the system.

If you /really/ want to handle include files, conditional compilation 
and all rest of it, get the C compiler to handle that - use "gcc -E" and 
use the output of that.  Trying to duplicate that in your own Python 
code would be insane.

> 
> This preprocessor should ingest a C source file after it is preprocessed 
> by the standard C preprocessor for the specific build you are doing.
> 
> For example, you could have a C source file that contains:
> 
> #if BUILD == BUILD_FULL
>    DisplayPrintf(msg, "Press (1) for simple process, (2) for advanced 
> process");
>    x = wait_keypress();
>    if (x == '1') do_simple();
>    if (x == '2') do_adv();
> #elif BUILD == BUILD_LIGHT
>    do_simple();
> #endif
> 

The really simple answer is, don't do that.


> If I'm building the project as BUILD_FULL, there's at least one 
> additional string to translate.

The slightly more complex answer is that you end up with an extra string 
in one build or the other.  Almost certainly, this is not worth 
bothering about.  And if it is - say you have a large number of extra 
strings in a debug test build - then I'm sure you can find convenient 
ways to handle that.  At a minimum, you'd probably not bother having 
translated versions but fall back to English.

> 
> Another big problem is the Python preprocessor should understand C 
> syntax; it shouldn't simply search for DisplayPrintf occurrences.

Why not?

> For example:
> 
> /* DisplayPrintf(old_string, "This is an old message"); */
> DisplayPrintf(new_string, "This is a new message");
> 
> Of course, only one string is present in the source file, but it's not 
> simple to extract it.
> 

It's extremely simple to extract it.  Remember - /you/ make the rules. 
If you don't want to bother skipping such commented-out lines, /you/ 
pick a convenient way to do so.  For example, you would decide that the 
opening comment token must be at the start of the white-space stripped 
line :

	if line.strip().startswith("/*") :
		return False

	if line.strip().startswith("//") :
		return False

(I've been talking about Python here, because that's the language I use 
for such tools, and it's a very common choice.  If you are not familiar 
with Python then you can obviously use any other language you like.)


Or alternatively, have :

	#define XDisplayPrintf(...)

And now your commenting system becomes :

	XDisplayPrintf(old_string, "This is an old message");
	DisplayPrintf(new_string, "This is a new message");

The "XDisplayPrintf" can be inside comments or conditionally uncompiled 
code if you like.  (You do have to filter out XDisplayPrintf bits from 
the earlier check for DisplayPrintf.)

> 
> Thanks for the suggestion, the idea is great. However I'm not able to 
> write a Python preprocessor that works well.
> 

Sure you can.  You just have to redefine what you mean by "works well" 
to suit what you can write :-)


For my own use, I probably wouldn't even bother handling commented-out 
strings.  I have used this kind of technique for message translation and 
a variety of other situations.


For more fun, you could switch to modern C++ and use user-defined 
literals combined with constexpr template variables to put together a 
system that is all within the one source language and is fully checked 
at compile-time.  I'm not sure it would be clearer, however!

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Thread

How to add the second (or other) languages pozz <pozzugno@gmail.com> - 2025-02-12 17:26 +0100
  Re: How to add the second (or other) languages Stefan Reuther <stefan.news@arcor.de> - 2025-02-12 18:14 +0100
    Re: How to add the second (or other) languages David Brown <david.brown@hesbynett.no> - 2025-02-12 20:50 +0100
      Re: How to add the second (or other) languages pozz <pozzugno@gmail.com> - 2025-02-16 19:59 +0100
        Re: How to add the second (or other) languages David Brown <david.brown@hesbynett.no> - 2025-02-17 09:51 +0100
          Re: How to add the second (or other) languages pozz <pozzugno@gmail.com> - 2025-02-17 16:05 +0100
            Re: How to add the second (or other) languages David Brown <david.brown@hesbynett.no> - 2025-02-17 19:09 +0100
      Re: How to add the second (or other) languages pozz <pozzugno@gmail.com> - 2025-02-16 22:56 +0100
        Re: How to add the second (or other) languages David Brown <david.brown@hesbynett.no> - 2025-02-17 09:57 +0100
    Re: How to add the second (or other) languages pozz <pozzugno@gmail.com> - 2025-02-16 23:15 +0100
      Re: How to add the second (or other) languages David Brown <david.brown@hesbynett.no> - 2025-02-17 09:59 +0100
      Re: How to add the second (or other) languages Stefan Reuther <stefan.news@arcor.de> - 2025-02-17 19:00 +0100
  Re: How to add the second (or other) languages "Niocláiſín Cóilín de Ġloſtéir" <Master_Fontaine_is_dishonest@Strand_in_London.Gov.UK> - 2025-02-13 22:51 +0100

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