Support charset meta tag.

[kennyj]

I know GH #3539 and #149.
But I want to propose it again, because I have another motivation.

I'm Japanese and resident in the multibyte world.
In my experience, if we don't write charset meta tag, we've got trouble in terms of the next.

If we save a page as html file.

When we open the html file, we'll miss a charset .

[josevalim]

This is a very good point but I would like a simpler implementation. Maybe we should just check response.charset given #3878 is merged.

[wycats]

Why do you need the charset tag when we are already sending the Content-Type header containing a charset?

[josevalim]

He just explained: "If we save a page as html file. When we open the html file, we'll miss a charset."

[kennyj]

@josevalim

I think that response.charset is empty in the charset_meta_tag rendering time
except we explicitly assign response.charset (a.k.a. normal case)

Thus, I used charset argument, Content-Type, response.charset and AD::Response.default_charset in above patch.

But, certainly, my implementation is a little complexity.
For example, do we stop arguement and Content-Type support ?

      def charset_meta_tag
        tag('meta', :charset => (response.charset || response.class.default_charset)).html_safe
      end

[josevalim]

IMHO:

  def charset_meta_tag(arg=nil)
    tag('meta', :charset => (arg || response.charset || response.class.default_charset)).html_safe
  end

[kennyj]

@josevalim OK!

I'll fix and squash it after work.

Just FYI:
In my past java experience, and in rare cases, I must have to be different for response header charset and meta tag's charset.

Java runtime know Windows-31J encoding, and this encoding is necessary for properly character conversion.
But, it seems that IE6 don't know Windows-31J. We must set Shift_JIS (that is like to Windows-31J) to meta tag's charset ;-)

[josevalim]

Yeah, if this is the case, you should set response.charset then, and you
will probably be fine. Confirm/deny?

[kennyj]

Confirm. It's work fine (I set response.charset in a controller... My interpretation of the English, right?)

I fixed and squished.

[kennyj]

This method is usefull for me, but not for majority (I guess)
I'm closing this PR :)