Display PDF pages with Telephone Line

EDIT: updated 2018.06.01 to be done properly

Upon switching over to the excellent Telephone Line modeline theme from my previous Smart Mode Line, I was generally pleased by the exceptional look and feel of it. That is, until I fired up a PDF a while later and found I’d lost my page-numbers that had always been there. Eventually I was able to solve this problem by adding two items to my use-package statements, one for pdf-tools and a subsequent one for telephone-line. I just had to reload my emacs and it worked.

(use-package pdf-tools
  :ensure t
  :demand t
  :bind (:map pdf-view-mode-map
          ("G" . pdf-view-goto-page))
  :config
  (pdf-tools-install)
  (setq pdf-view-continuous t ; don't automatically jump to next page
    pdf-misc-print-programm "/usr/bin/lp"
    pdf-misc-print-programm-args '( ;"-d ODH_Workroom"
                                   "-o media=letter"
                                   "-o sides=two-sided-long-edge"))

  (add-hook 'pdf-view-mode-hook 'auto-revert-mode)
  (define-pdf-cache-function pagelabels)
  (defun pdf-view-page-number ()
    (interactive)
    (if (called-interactively-p)
    (message "[pg %s/%s/%s]"
             (nth (1- (pdf-view-current-page))
                  (pdf-cache-pagelabels))
             (number-to-string (pdf-view-current-page))
             (number-to-string (pdf-cache-number-of-pages)))
      (format  "[pg %s/%s/%s]"
             (nth (1- (pdf-view-current-page))
                  (pdf-cache-pagelabels))
             (number-to-string (pdf-view-current-page))
             (number-to-string (pdf-cache-number-of-pages))))))

and then:

(use-package telephone-line
  :ensure t
  :after (pdf-view)
  :config
  ;;;;;;;;; THE CORRECT WAY
  (telephone-line-defsegment telephone-line-pdf-segment ()
    (if (eq major-mode 'pdf-view-mode)
    (propertize (pdf-view-page-number)
                'face '(:inherit)
                'display '(raise 0.0)
                'mouse-face '(:box 1)
                'local-map (make-mode-line-mouse-map
                            'mouse-1 (lambda ()
                                       (interactive)
                                       (pdf-view-goto-page))))))
  ;;;;;;
  (setq telephone-line-primary-left-separator 'telephone-line-cubed-left
    telephone-line-secondary-left-separator 'telephone-line-cubed-hollow-left
    telephone-line-primary-right-separator 'telephone-line-cubed-right
    telephone-line-secondary-right-separator 'telephone-line-cubed-hollow-right
    telephone-line-height 24
    telephone-line-evil-use-short-tag t)
 ;;; And this, including it as the first item in the mode-line
  (setq telephone-line-lhs '((accent telephone-line-vc-segment telephone-line-erc-modified-channels-segment telephone-line-process-segment telephone-line-pdf-segment)
                         (nil telephone-line-projectile-segment telephone-line-buffer-segment)))
  (telephone-line-mode t))