hint for vertical writing mode to input method

[Makoto Kato <m_kato ga2 so-net ne jp>]

Hi, GTK team.

Mozilla is implementing vertical-writing spec [*1] to Gecko rendering
engine.  But GTK has no API to add hint of vertical writing mode to
input method.

Other OS already has the following method / attribute for this case.

OSX / Cocoa
drawsVerticallyForCharacterAtIndex method
https://developer.apple.com/library/mac/documentation/Cocoa/Reference/NSTextInputClient_Protocol/index.html#//apple_ref/occ/intfm/NSTextInputClient/drawsVerticallyForCharacterAtIndex:

Windows / TSF
TSATTRID_Text_VerticalWriting attirubte
https://msdn.microsoft.com/en-us/library/windows/desktop/ms629018%28v=vs.85%29.aspx


Do you have a plan to add an attribute or API of vertical writing hint
to GTK?   If nothing, could you add this to any property such as adding
GTK_INPUT_HINT_VERTICAL_WRITING to GtkInputHints?


-- Makoto Kato

[*1] http://www.w3.org/TR/css3-writing-modes/