I do not quite understand. You want other keys to switch to level3, right? A number of options is available for that (for various keys).

Is it what you're asking about? Or something else?

Probably we think the same.
In KDE bugzilla (https://bugs.kde.org/show_bug.cgi?id=251480) I created the mock-up for it:
http://bugsfiles.kde.org/attachment.cgi?id=51866

But Andriy Rysin said:

"Well, here's the thing Wojciech — I am trying to close bugs that don't belong
to KDE keyboard module so that I can concentrate on the ones I can help with or
fix. We can keep this one open though something tells me that during those two
months since this issue was reported it could have been solved by now at
xkeyboard-config bug system. :)
Maintainer of xkeyboard-config is quite a nice guy so there's no reason to
avoid him :)"

so now I'm confused. :(

I am still confused as to what you mean with 'typographic characters'.
I believe it is a non-standard terminology. In addition, 'diacritic characters', as you use them is non-standard. Do you mean 'characters with diacritics' rather than the diacritics themselves, instead?

I follow this report because I experience a layout bug in KDE/QT. And now that I think about it, it could be the very same problem that you are trying to describe.

Typically, you can type characters when you press them as is (for example, for 'a' I press the 'a' key'). Similarly, for æ on my keyboard I press AltGr + 'a'. Both these are of the same type of  functionality.

The other type of functionality is when I need to press the so-called dead keys. To get á on my keyboard layout, I press AltGr + ; (nothing appears on the screen), and then I hit 'a'. At this point I see á on my screen. This type of functionality is known as 'using dead keys' or 'using compose sequences'.

Therefore, if the bug you experience is the second type of functionality, then the bug goes back to KDE/QT, and I would be interested to follow it as well.

(In reply to comment #3)
> I am still confused as to what you mean with 'typographic characters'.
> I believe it is a non-standard terminology. 

You can find it in KDE under: System settings > Input devices > Advanced > Miscellaneous compatibility options > Enable extra typographic characters

I think it's compatible with Mac OS where it's present.

> In addition, 'diacritic
> characters', as you use them is non-standard. Do you mean 'characters with
> diacritics' rather than the diacritics themselves, instead?

OK, you're right. I missed them up. Polish ą is a basic latin a + diacritic tail.

> Typically, you can type characters when you press them as is (for example, for
> 'a' I press the 'a' key'). Similarly, for æ on my keyboard I press AltGr + 'a'.

Yeah, for mentioned above ą I press Right ALT + a.

> The other type of functionality is when I need to press the so-called dead
> keys. To get á on my keyboard layout, I press AltGr + ; (nothing appears on 
> the screen), and then I hit 'a'. At this point I see á on my screen. This
> type of functionality is known as 'using dead keys' or 'using compose 
> sequences'.

I know compose sequences and it can be also enabled in KDE System settings. I use it (or used to use it) to produce some typographic characters. But what are typographic characters to begin with? They are some characters used in typography or desktop publishing. For example:

… - ellipsis - the sequence for it is Compose key + .. (2 x dot)
– - en dash - Compose key + --
– - em dash - Compose key + --.
« and » - German (?) inside quotes - Compose key + Shift + .. and Compose key + Shift + ,,

So they are typographic characters.
But KDE allows you to produce these characters using special option: 
Enable extra typographic characters as I mentioned at the top of the post.

Using this option to create ellipsis (…) just press Right ALT + /

But problem is it uses ALT key as the trigger. Hence I can't type ą character any longer cause Right ALT + a produces ́  character.
The same is with ALT + e, ALT + s, ALT + x and ALT + l
That's why I said they clashes with each other.

I thought it isn't a problem in KDE because we could use other 'trigger' key like META one. But I was told it is and it's xkeyboard-config issue.

Hope my description is clear now. :)

(In reply to comment #4)
> (In reply to comment #3)
> > I am still confused as to what you mean with 'typographic characters'.
> > I believe it is a non-standard terminology. 
> 
> You can find it in KDE under: System settings > Input devices > Advanced >
> Miscellaneous compatibility options > Enable extra typographic characters
> 
> I think it's compatible with Mac OS where it's present.
> 

I just realised that 'Enable extra typographic characters' is actually a  feature in xkeyboard-config.
It is found at 
http://cgit.freedesktop.org/xkeyboard-config/tree/symbols/typo
It is also available in GNOME.

> > In addition, 'diacritic
> > characters', as you use them is non-standard. Do you mean 'characters with
> > diacritics' rather than the diacritics themselves, instead?
> 
> OK, you're right. I missed them up. Polish ą is a basic latin a + diacritic
> tail.
> 
> > Typically, you can type characters when you press them as is (for example, for
> > 'a' I press the 'a' key'). Similarly, for æ on my keyboard I press AltGr + 'a'.
> 
> Yeah, for mentioned above ą I press Right ALT + a.
> 

So what you get here is special 'trickery' that allows to type additional characters. I have not used this, so Sergey might be able to help.

> > The other type of functionality is when I need to press the so-called dead
> > keys. To get á on my keyboard layout, I press AltGr + ; (nothing appears on 
> > the screen), and then I hit 'a'. At this point I see á on my screen. This
> > type of functionality is known as 'using dead keys' or 'using compose 
> > sequences'.
> 
> I know compose sequences and it can be also enabled in KDE System settings. I
> use it (or used to use it) to produce some typographic characters. But what are
> typographic characters to begin with? They are some characters used in
> typography or desktop publishing. For example:
> 
> … - ellipsis - the sequence for it is Compose key + .. (2 x dot)
> – - en dash - Compose key + --
> – - em dash - Compose key + --.
> « and » - German (?) inside quotes - Compose key + Shift + .. and Compose key +
> Shift + ,,
> 
> So they are typographic characters.

The other terminology is that these are 'Unicode characters', as found at http://www.unicode.org/charts/
Unicode is extending the character sets that has managed to go well ahead of standard typographic characters.

> But KDE allows you to produce these characters using special option: 
> Enable extra typographic characters as I mentioned at the top of the post.
> 
> Using this option to create ellipsis (…) just press Right ALT + /
> 
> But problem is it uses ALT key as the trigger. Hence I can't type ą character
> any longer cause Right ALT + a produces ́  character.
> The same is with ALT + e, ALT + s, ALT + x and ALT + l
> That's why I said they clashes with each other.
> 
> I thought it isn't a problem in KDE because we could use other 'trigger' key
> like META one. But I was told it is and it's xkeyboard-config issue.
> 
> Hope my description is clear now. :)

Yep, it's clear now.
I think there are several bugs in X.Org that relate to the interaction of the keys, especially Alt and AltGr. Most probably your case has to do with the internal input subsystem in X.Org and not xkeyboard-config. You can search for bug reports on this bugzilla, reports that mention AltGr.

I think I understand now. I do not know what would be the proper solution for your problem.

The thing is that both Polish diacritics chars and typographic XKB option are using the same 3rd level. So if some keycode on 3rd level produces some typographic character - it cannot produce, at the same time, diacritic character. 

For example, in Polish default layout
key <AB03>	{ [         c,          C,       cacute,       Cacute ]	};

If you add typographic option, it adds
key <AB03> { [NoSymbol, NoSymbol, copyright, cent] };

As the result, you are losing cacute/Cacute:
key <AB03>	{ [ c, C, copyright, cent] };

I hope now you understand _why_ that happens.

Now, the question is what can we do about that? I sincerely do not know... Any ideas are welcome.

(In reply to comment #6)
> I think I understand now. I do not know what would be the proper solution for
> your problem.

Is it true that all languages with accents (German, French, Spain to name a few) will have problem with it? :)

Yes.

Hello again. The solution was simpler than I thought. I just did my own keyboard layout incorporating Latin + Polish + typographic characters. In the same time I got rid of unnecessary characters. Now my layout totally fit my needs.

cheers!

happy days:)