O.K here goes
I've got a simple plane , which is subdivided in 64 equal parts (8*8) I select the inner 16 faces and unwrap them , in the object data tab I give it a name , lets's say "this one"
Now , in the (cycles) material editor I create a mix shader ,which consists of a simple diffuse shader and a texture map that will have the image for the selected inner faces ) The texture map get's its coordinates from the UV map node( set to 'this one '') . Now , when going into the image editor /view mode we can see our selected /unwrapped inner faces and start drawing . I make sure that the unwrapped uv,s are centered in the image editor , surrounded by enough empty space As expected , only the inner faces are affected and thus coloured
Here's the thing , as soon as I draw in one of the corners of the image editor (just a tiny 1 pixel dot is enough) ,all the other faces are also affected which are not unwrapped at all . How come ? So my question is ,are the corners of the image editor some kind of boundary ?