Hello
r12782 introduces a third-level namespace called "Tools", i.e. Inkscape::UI::Tools. There are some problems with this:
1. While this does follow current practice, I don't think the current practice is any good. The only result of having such deeply nested namespace hierarchies is the need to tediously type this all out, since if there actually is a naming conflict they prevent, it's a symptom of bad design / naming.
2. "Tools" is pluralized, while "Dialog" and "Widget" are not. This is inconsistent.
It is sufficient to put all UI code in Inkscape::UI. This would also remove any doubt over whether to use e.g. "Inkscape::UI::Dialog::Print" (which makes the name as used within the namespace ambigous - "Print" what?) or "Inkscape::UI::Dialog::PrintDialog" (which is redundant) - one would simply use "Inkscape::UI::PrintDialog".
In general, 2 levels of namespaces are entirely sufficient. XML tree goes into Inkscape::XML, UI code goes into Inkscape::UI, object (SP) tree goes into Inkscape::SVG (in the future), and so on.
Regards, Krzysztof