Restore lost pager support.

Executing '<object>?' works correctly again with python kernels. Boggles the
mind why this feature was removed in the first place.

lisp/ein-pager.el

@@ -0,0 +1,98 @@
+;;; ein-pager.el --- Pager module
+
+;; Copyright (C) 2012- Takafumi Arakaki
+
+;; Author: Takafumi Arakaki <aka.tkf at gmail.com>
+
+;; This file is NOT part of GNU Emacs.
+
+;; ein-pager.el is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; ein-pager.el is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with ein-pager.el.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+
+(require 'ansi-color)
+
+(require 'ein-core)
+(require 'ein-events)
+(require 'view)
+
+;; FIXME: Make a class with `:get-notebook-name' slot like `ein:worksheet'
+
+(declare-function ess-help-underline "ess-help")
+
+(defun ein:pager-new (name events)
+  ;; currently pager = name.
+  (ein:pager-bind-events name events)
+  name)
+
+(defun ein:pager-bind-events (pager events)
+  "Bind events related to PAGER to the event handler EVENTS."
+  (ein:events-on events
+                 'open_with_text.Pager
+                 #'ein:pager--open-with-text
+                 pager))
+
+(defun ein:pager--open-with-text (pager data)
+  (let ((text (plist-get data :text)))
+    (unless (equal (ein:trim text) "")
+      (ein:pager-clear pager)
+      (ein:pager-expand pager)
+      (ein:pager-append-text pager text))))
+
+(defun ein:pager-clear (pager)
+  (ein:with-read-only-buffer (get-buffer-create pager)
+    (erase-buffer)))
+
+(defun ein:pager-expand (pager)
+  (pop-to-buffer (get-buffer-create pager))
+  (goto-char (point-min)))
+
+(defun ein:pager-append-text (pager text)
+  (ein:with-read-only-buffer (get-buffer-create pager)
+    (insert (ansi-color-apply text))
+    (if (featurep 'ess-help)
+        (ess-help-underline))
+    (unless (eql 'ein:pager-mode major-mode)
+      (ein:pager-mode))))
+
+;; FIXME: this should be automatically called when opening pager.
+(defun ein:pager-goto-docstring-bset-loc ()
+  "Goto the best location of the documentation."
+  (interactive)
+  (goto-char (point-min))
+  (search-forward-regexp "^Docstring:")
+  (beginning-of-line 0)
+  (recenter 0))
+
+(defvar ein:pager-mode-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map "\C-c\C-b" 'ein:pager-goto-docstring-bset-loc)
+    map)
+  "Keymap for ein:pager-mode.")
+
+(define-derived-mode ein:pager-mode view-mode "ein:pager"
+  "IPython notebook pager mode.
+Commands:
+\\{ein:pager-mode-map}"
+  (setq-local view-no-disable-on-exit t)
+  (font-lock-mode))
+
+
+(provide 'ein-pager)
+
+;;; ein-pager.el ends here