I think based on what I read here there is some confusion between
can support up to 4 bytes, versus
exclusively uses all 4 bytes? IDK for certain but I do see references in various google results to mb 3/4 so perhaps UTF-8 on its own negates the rest? This is what I think Phaelax is eluding to? ie when talking about it to account for software that does not fully implement all 4 bytes versus a fully supported software that auto decodes it all. Essentially, in a case where UTF-8 is not implemented beyond 1 byte, it does not force a name change from UTF-8 therefore the term is not directly tied to exclusivity. If any of this is true you are both right, but what Phaelax states is more accurate where AppGameKit is concerned, which is not the exact reason as such but implies there has been no need so far to flesh out implementation to support mb 2, 3 & 4?
As for Japanese, I am more comfortable with DBPro, in which case we would load a font with an additional value for charset, example "Arial",128. But then you would have to go and find the special characters for the IDE text. "ƒ_[ƒNƒx[ƒVƒbƒN" is similar to what would be needed(translates to Dark Basic as something like Da - ku be - si ? ku as there are no direct words for translation but this is nearest), the output in the executable/player for DBP would indeed be katakana characters.
This method does not appear to be an option for AGK. Then again I am not 100% familiar with AppGameKit, only partially.
Also the "special characters" I just detailed are not 100% correct, there has been some change with font support in the forum so they no longer show as they should...the following link shows this difference and is being covered in DBP while discussing GG and DBP making it a difficult task to find with specific searches such as Japanese/katakana. In the DBP case there was a point in time as per the link where katakana was implemented but was far from obvious and required the font demo in order for a long winded process to be worked out(which no doubt could be simplified - however I only spent a few hours on it and never touched it again). Perhaps implementation beyond 1 byte is there and just not obvious how to achieve desired results, certainly not the same way as DBP but perhaps another way? For example I have simply just gone through the text command list but in AppGameKit and there is an option with AppGameKit for values above 128 in ascii. It involves providing a font image(settextdefualtextendedimage). I think you should look into that for Japanese at least. Put it this way, you know what options you have, you will have to live with them or force TGC into full implementation, in which case the forums might not be the best place for that. But here is the thing, if no decent response is ascertained from forum or discord requests then the smartest thing to do would be to contact TGC and ask them directly. You may even get an exact reason for lack of full implementation which if DBP is anything to go by it might be the IDE itself forcing the limitation - note in the link the expected coding did not work, special characters had to be sought instead. By using a font image as suggested you should be able to achieve desired results for text.
All that said I do feel at this point that UTF-8 can support up to 4 bytes but is not exclusive to it. If it was, then this thread would have no need to exist right? ie it would already have been implemented but in the expected way, I doubt it will ever be as simple as one might think! If additional ascii characters can only be dealt with by a font image provided by the user as the help file states, then it only seems logical that there is a different way to deal with any other UTF-8 characters within AGK...a point eluded to earlier.
It may be noted the use of ? throughout my post - this is because I am asking not telling.
Edit: I have put strike through on an earlier statement, it would appear that only in the input box the text does not show correctly prior to posting! In fact it is only the hidden spacing that is an issue.
Edit 2: the link I forgot!
https://forum.thegamecreators.com/thread/213618?page=4#msg2558084Win 10 Home 64, Intel(R) Core(TM) i5-10300H, 8GB DDR4, NVidia GeForce GTX 1650 4GB GDDR6
