I wish to round the corners of some SVG documents in a such a way that it hides whatever gets in that corner. Like a clipping Mask of any other objects.
Is this possible in SVG, or in Inkscape?
Mask or clipping an SVG layer (an object or even a group) can be done using clipPath. This page provides excellent instructions on how to create and apply a clipPath: http://sawyerhollenshead.com/writing/using-svg-clippath/
These are the two pieces that are essential:
Notice how you first define a clipPath with an ID. This defines the area of the clip or mask. Then you apply that to the element you want to mask using this syntax:
Whenever I've used this functionality, I've edited the svg file manually, so I'm not familiar with how or even whether it's possible to do in Inkscape. But it's fairly easy to edit the svg files with a text editor.
Hope that helps!