GTK+/Quartz: GTK+ >= 2.24.19 breaks text entering on-canvas (text tool)

[su_v]

Upgrading GTK+/Quartz from 2.24.18 to 2.24.19 breaks entering text on-canvas with the text tool in current stable and trunk builds of Inkscape. The regression persists with latest release GTK+ 2.24.20.

Steps to reproduce:
1) launch Inkscape (with default preferences)
2) in the new document, create a text object (doesn't matter whether regular or flowed) and type an arbitrary text as content.

Expected result:
Any keys typed while the text tool cursor is visible (blinking) on-canvas go directly to the content of the text object

Actual result:
Any keys typed in the text tool context with an active text object on-canvas act as keyboard shortcuts instead. It is not possible to create new text objects, nor to edit the content of existing text objects beyond modifying the style.

System:
Tested and verified on OS X 10.7.5 by reverting GTK+/Quartz (installed via MacPorts) from 2.24.19 to 2.24.18, and repeating the STR with the same inkscape builds.

Not reproduced with
- GTK+/X11 2.24.19 (-> issue limited to the Quartz backend of GTK+)
- GTK+/Quartz 3.8.2 (-> issue limited to GTK2)
- GTK+/Quartz <= 2.24.18 (-> issue limited to the Quartz backend of GTK+ >= 2.24.19)

Regression seems to have been triggered initially by this upstream commit:
<https://git.gnome.org/browse/gtk+/commit/?h=gtk-2-24&id=21c775a2c811662881ae0b2f7606ab6c0875011b>
and persists in recently released GTK+ 2.24.20 as well.

Related upstream issue:
694273 - Support for NSTextInputClient in text widgets
<https://bugzilla.gnome.org/show_bug.cgi?id=694273>

Any help to figure out whether this upstream change in the Quartz backend of GTK2 requires fixes in Inkscape (stable as well as trunk), or needs to be adjusted upstream to not break inkscape, would be highly appreciated.

[su_v (suv-lp)]

What still works:
- adding content to new flowed text objects via 'Text' tab of the 'Text and Font' dialog
  (does not work to create new regular text objects)
- using arrow keys to navigate the cursor position on-canvas within the text content of a selected existing text object
- deleting text content of a selected existing text object with <Backspace>
- pasting text from the clipboard into a new or existing text object (on-canvas)

[su_v (suv-lp)]

A workaround has been committed upstream to master, gtk-3-8 as well as gtk-2-24.

According to GTK+ devs, the underlying issue needs to be addressed in Inkscape itself: please see the discussion in bugzilla for additional details (comment #30 and later):
<https://bugzilla.gnome.org/show_bug.cgi?id=694273#c30>

[Krzysztof Kosinski (tweenk)]

The problem described on the Gnome Bugzilla should be fixed in r13072.

[Krzysztof Kosinski (tweenk)]

Backported to 0.48.x stable branch in r10012.