How do you interpolate UV mapping coords in a quad tessellation evaluation shader?
The problem was else-where, the same interpolation works for UV coords.

vec2 uv1 = mix(teUv[0], teUv[1], gl_TessCoord.x);
vec2 uv2 = mix(teUv[2], teUv[3], gl_TessCoord.x);
fUv = mix(uv2, uv1, gl_TessCoord.y);