Subdivide loop at custom position without stretching the texture How can one subdivide at an arbitrary position, say the cylinder side faces, using CTRL+R (subdivide loop tool), so that the texture is not stretched like this:

Before



After



If this is not possible with this tool, is there another way, like for instance recalculating a group of UV coordinates by means of their vertex position and their surrounding vertices.
The loop cut operator has an option to correct UVs. Enable it in the redo panel, below the tool shelf or with F6:



You could also use the knife tool (K), with angle constrain (C) and cut through (Z):