ol-ext: Snap guides interaction
handles snapping of vector features using guides lines while modifying or drawing them.
The snap interaction modifies map browser event coordinate and pixel properties to force the snap to occur
to any interaction that them.
You can add guidelines to snap to.
You can set an ol.interaction.Draw (setDrawInteraction)to control orthogonal drawing (similar to OLE snapping with OL2).
You can also set an ol.interaction.Modify (setModifyInteraction) to control orthogonal drawing while modifying.
With ol6 use ol/layer/VectorImage class as vectorClass options to enhance drawing performances.