GTK3: warning: enumeration value 'GDK_SCROLL_SMOOTH' not handled in switch [-Wswitch]

[su_v]

The compiler warning "enumeration value 'GDK_SCROLL_SMOOTH' not handled in switch [-Wswitch]" prevents building with '-Werror=switch'.

Build log r13211 on Ubuntu 14.04:

  CXX ui/tools/spray-tool.o
../../src/ui/tools/spray-tool.cpp: In member function 'virtual bool Inkscape::UI::Tools::SprayTool::root_handler(GdkEvent*)':
../../src/ui/tools/spray-tool.cpp:681:24: warning: enumeration value 'GDK_SCROLL_SMOOTH' not handled in switch [-Wswitch]
                 switch (event->scroll.direction) {
                        ^

<https://launchpadlibrarian.net/170720270/buildlog_ubuntu-trusty-amd64.inkscape-trunk_1%3A0.48%2Bdevel%2B13210%2B47~ubuntu14.04.1_UPLOADING.txt.gz>

Warning from clang (LLVM 3.1svn):

../../src/ui/tools/spray-tool.cpp:681:25: warning: enumeration value 'GDK_SCROLL_SMOOTH' not handled in switch [-Wswitch-enum]
                switch (event->scroll.direction) {
                        ^

[Alex Valavanis (valavanisalex)]

Here's some documentation from upstream:

https://developer.gnome.org/gdk3/stable/gdk3-Event-Structures.html#GdkEventScroll

Basically, this kind of scroll event can be in any direction and any magnitude rather than just the fixed UP/DOWN/LEFT/RIGHT scrolling that was handled in Gtk+ 2. We need to use gdk_event_get_scroll_deltas() to obtain the x and y displacements rather than using fixed increments... hopefully it shouldn't be too painful to implement.