See conal/vector-space@f5ef4fd . Note that we could make use of the new left-associativity to omit some parentheses here, which looks nice, but then we would have to jack up the lower bound on vector-space (which, for consistency, we'd want to do also on a bunch of other diagrams packages). For now, the current code should still compile with older versions of vector-space.
The motivation is to reduce the dependencies of diagrams-cairo. There were reports of people able to install the 'cairo' package but not 'gtk'. * Diagrams.Backend.Cairo.Gtk is now Diagrams.Backend.Gtk in the diagrams-gtk package. * Remove dependency on gtk package. * Remove the GTK output type. * Add a 'RenderOnly' output type, for when you don't care about the IO action but only want the cairo Render action * Add a Bool 'cairoBypassAdjust' option to bypass calling adjustDia2D, which is used by the GTK backend but is a sensible option to make available for general use.