LGTM, with minor nits.
https://codereview.appspot.com/561810045/diff/551840043/scm/backend-library.scm File scm/backend-library.scm (right): https://codereview.appspot.com/561810045/diff/551840043/scm/backend-library.scm#newcode143 scm/backend-library.scm:143: ;; When the directory already exists, it raises system-error. s/When/If/ https://codereview.appspot.com/561810045/diff/551840043/scm/backend-library.scm#newcode161 scm/backend-library.scm:161: ;; When the file already exists, it raises system-error. s/When/If/ https://codereview.appspot.com/561810045/diff/551840043/scm/backend-library.scm#newcode188 scm/backend-library.scm:188: ;; When the file already exists, it raises system-error. s/When/If/ https://codereview.appspot.com/561810045/diff/551840043/scm/framework-ps.scm File scm/framework-ps.scm (right): https://codereview.appspot.com/561810045/diff/551840043/scm/framework-ps.scm#newcode284 scm/framework-ps.scm:284: from file `~a' index ~a...") Maybe for subfont ~a of file ~a") ? https://codereview.appspot.com/561810045/diff/551840043/scm/framework-ps.scm#newcode544 scm/framework-ps.scm:544: (_ "Font file `~a' already exists, skipping.") s/\./.../ to be in sync with other, similar error messages. Alternatively, you might do s/\.\.\././ in the other error messages :-) https://codereview.appspot.com/561810045/
