Enable GTK+ 3 builds

Registered by Alex Valavanis

Inkscape currently makes use of the GTK+ 2.24 library API. Ultimately, we will need to switch to the new GTK+ 3 API. This version of the library introduces a number of major changes that are incompatible with GTK, so we need to make some changes to Inkscape.

Whiteboard

To configure a test-build against GTK+ 3:

configure --enable-gtk3-experimental

[2015-02-23 ~suv] @Alex - do you consider the blueprint at its current state as 'Implemented' in 0.91 (0.91 does compile and launch with GTK3), or should we move the milestone to 0.92 for now (or even 1.0), with the blueprint aiming for the full switch to GTK3 (as default configure option)?

[2015-02-24 valavanisalex] @~suv - it's implemented, in that the builds are now enabled. It still needs thorough testing, but that's really an open-ended task. We should probably follow up with a new blueprint for an actual switchover, that specifies the testing protocol and prerequisites properly!

(?)

Work Items

Work items:
Build with G_DISABLE_SINGLE_INCLUDES: DONE
Build with GTK_DISABLE_SINGLE_INCLUDES: DONE
Build with G_DISABLE_DEPRECATED: DONE
Build with GLIBMM_DISABLE_DEPRECATED: DONE
Build with GTKMM_DISABLE_DEPRECATED (bug #943225): DONE
Build with GDKMM_DISABLE_DEPRECATED (bug #943222): DONE
Build with GTK_DISABLE_DEPRECATED (bug #367607): DONE
Build with GDK_DISABLE_DEPRECATED (bug #943207): DONE
Build with GSEAL_ENABLE (bug #979018): DONE

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