Comment 6 for bug 927898

I see that there are different needs that require different implementations of snapping options:
 - ability to fine trim snapping with the possibility to select exactly snapping sources and targets which should be as much differentiated as possible (for example I'm thinking about also differentiating intersection between paths, guides, path and guide, etc... someone could ask for it);
 - ability to quickly change sources and targets so if you want to turn off node snapping you don't have to press plenty of buttons and then again to turn it back on; also, more flexibility = more buttons = more confusing GUI and less space on canvas.

One solution could be having one button for each snapping sources-targets "family" (what we have now, but maybe even less), then with a right click on each "family" button you open a dialog window fully-filled with checkboxes in which you can select, with regards to all other sources-targets (also in different families) what should snap to what. In this way you can have guides snapping to cusps but not to smooth nodes, but only if both the "nodes snap" and the "guides snap" buttons are pressed and the checkbox "snap to cusps" is selected under the "guides snapping table" dialog (no matter if the "snap to guides" checkbox under the "nodes snapping table" is selected or not).

Hence a single "on - off" button will control snapping super-fine tuned to the user needs for a whole category of snapping sources or targets.
If one user has very precise needs that seldom change, he could have all buttons always pressed and use their respective checkboxes only.
Otherwise, if someone else only needs "families", he could have all checkboxes always checked and quickly configure the snapping behavior using only buttons (and this could be the default option, very similar to what we have now).
Of course, between these two extreme cases there can be a wide variety of possible configurations.
The "snapping tables" should be accessible also from the document options: a combo box to select the "family" with the checkboxes table under it .