Created attachment 6401 bug See screenshot, right click menu font is inpropriate
If you mean that menu items font is monospaced rather than proportional, I think I have seen that before. I kind of remember observing that and then checking Gedit and it also had the same. I cannot reproduce now, neither with gtk2 or gtk3 build and Gedit doesn't do it either, so I'm not sure. It could be a bug in GtkSourceView, making the font set with gtk_widget_modify|override_font() to be inherited by the menu or something. What is your GtkSourceView library version?
Mousepad from Mint 17.2. My second bug (grey background) may have the same root. I can't test build from ubuntu 15.04 cause it depends on libglib2.41 Package: libgtksourceview-3.0-1 Version: 3.10.2-0ubuntu1 Package: libgtksourceview2.0-0 Version: 2.10.5-1ubuntu2.14.04.1 Package: libgtksourceview2.0-0 Version: 2.10.5-1ubuntu2 Package: libgtksourceview2.0-dev Version: 2.10.5-1ubuntu2.14.04.1 Package: libgtksourceview2.0-dev Version: 2.10.5-1ubuntu2 Package: libgtksourceview-3.0-dev Version: 3.10.2-0ubuntu1 Package: libgtksourceview-3.0-common Version: 3.10.2-0ubuntu1 Package: libgtksourceview-3.0-doc Version: 3.10.2-0ubuntu1 Package: libgtksourceviewmm-3.0-0 Version: 3.2.0-1ubuntu1 Package: libgtksourceview2-cil-dev Version: 2.26.0-8 Package: libgtksourceview2-2.0-cil Version: 2.26.0-8 Package: libgtksourceview2.0-common Version: 2.10.5-1ubuntu2.14.04.1 Package: libgtksourceview2.0-common Version: 2.10.5-1ubuntu2 Package: libgtksourceview2.0-doc Version: 2.10.5-1ubuntu2.14.04.1 Package: libgtksourceview2.0-doc Version: 2.10.5-1ubuntu2 Package: libgtksourceviewmm-3.0-dbg Version: 3.2.0-1ubuntu1 Package: libgtksourceviewmm-3.0-dev Version: 3.2.0-1ubuntu1 Package: libgtksourceviewmm-3.0-doc Version: 3.2.0-1ubuntu1
Can't reproduce with newer gtk