Added VPDF feature.

* lisp/pdf-virtual.el: New file handling virtual PDF documents.

* test/pdf-test.el: Tests for that feature.

* lisp/pdf-misc.el: Extend the menu appropriately.

* lisp/pdf-view.el: Make pdf-view-mode play nicer with it's derived
  mode pdf-virtual-view-mode.

* lisp/pdf-tools.el: Integrate pdf-virtual.

* NEWS: Added item.

* README.org: Mention it.

NEWS

@@ -12,7 +12,11 @@
     The return value of many pdf-info-* functions was changed in order
     to prefer alists over other data-structures (indexed lists,
     trees).
-
+** Virtual PDF
+   A virtual PDF is a collection of pages (or parts thereof) of
+   arbitrary documents, which appear to the rest of pdf-tools as one
+   big PDF, though they are always read-only.
+
 * Version 0.60
 ** Regexp support
    You may now search for perl-compatible regular expressions (PCRE)

README.org

@@ -47,12 +47,15 @@
 *** SyncTeX
     Jump from a position on a page directly to the TeX source and
     vice-versa.
+*** Virtual PDF
+    Use a collection of documents as if it where one, big single PDF.
 
 *** Misc
    + Display PDF's metadata.
    + Mark a region and kill the text from the PDF.
    + Keep track of visited pages via a history.
    + Apply a color filter for reading in low light conditions.
+
 ** Installation
    The package may be installed via melpa and it will try to build the
    server part when it is actiated the first time, though next section

lisp/pdf-misc.el

@@ -88,6 +88,15 @@
     ["Go Forward" pdf-history-forward
      :visible (bound-and-true-p pdf-history-minor-mode)
      :active (not (pdf-history-end-of-history-p))]
+    ["--" nil
+     :visible (derived-mode-p 'pdf-virtual-view-mode)]
+    ["Next file" pdf-virtual-buffer-forward-file
+     :visible  (derived-mode-p 'pdf-virtual-view-mode)
+     :active (pdf-virtual-document-next-file
+              (pdf-view-current-page))]
+    ["Previous file" pdf-virtual-buffer-backward-file
+     :visible (derived-mode-p 'pdf-virtual-view-mode)
+     :active (not (eq 1 (pdf-view-current-page)))]
     ["--" nil
      :visible (bound-and-true-p pdf-history-minor-mode)]
     ["Add text annotation" pdf-annot-mouse-add-text-annotation
@@ -145,9 +154,14 @@
     ["--" nil :visible (and (featurep 'pdf-sync)
                             (equal last-command-event
                                    last-nonmenu-event))]
-    ["Print" pdf-misc-print-document]
+    ["Print" pdf-misc-print-document
+     :active (and (pdf-view-buffer-file-name)
+                  (file-readable-p (pdf-view-buffer-file-name)))]
     ["Create image" pdf-view-extract-region-image
      :help "Create an image of the page or the selected region(s)."]
+    ["Create virtual PDF" pdf-virtual-buffer-create
+     :help "Create a PDF containing all documents in this directory."
+     :visible (bound-and-true-p pdf-virtual-global-minor-mode)]
     "--"
     ["Revert buffer" pdf-view-revert-buffer
      :visible (pdf-info-writable-annotations-p)]
@@ -246,9 +260,7 @@ It is called with one argument, the PDF file."
 (defun pdf-misc-print-document (filename &optional interactive-p)
   (interactive
    (list (pdf-view-buffer-file-name) t))
-  (unless (file-readable-p filename)
-    (signal 'wrong-type-argument
-            (list 'file-readable-p filename)))
+  (cl-check-type filename (and string file-readable))
   (let ((programm (pdf-misc-print-programm interactive-p)))
     (unless programm
       (error "No print programm available"))

lisp/pdf-tools.el

@@ -123,7 +123,8 @@ In order to customize dark and light colors use
     pdf-misc-context-menu-minor-mode
     pdf-cache-prefetch-minor-mode
     pdf-view-auto-slice-minor-mode
-    pdf-occur-global-minor-mode))
+    pdf-occur-global-minor-mode
+    pdf-virtual-global-minor-mode))
 
 (defcustom pdf-tools-enabled-modes
   '(pdf-history-minor-mode
@@ -137,7 +138,9 @@ In order to customize dark and light colors use
     pdf-sync-minor-mode
     pdf-misc-context-menu-minor-mode
     pdf-cache-prefetch-minor-mode
-    pdf-occur-global-minor-mode) 
+    pdf-occur-global-minor-mode
+    ;; pdf-virtual-global-minor-mode
+    )
   "A list of automatically enabled minor-modes.
 
 PDF Tools is build as a series of minor-modes.  This variable and
@@ -332,6 +335,7 @@ MODES defaults to `pdf-tools-enabled-modes'."
   (pdf-tools-set-modes-enabled nil modes))
 
 (declare-function pdf-occur-global-minor-mode "pdf-occur.el")
+(declare-function pdf-virtual-global-minor-mode "pdf-virtual.el")
 
 ;;;###autoload
 (defun pdf-tools-install (&optional force-compile-p skip-dependencies-p no-error)
@@ -360,6 +364,9 @@ See `pdf-view-mode' and `pdf-tools-enabled-modes'."
     (when (memq 'pdf-occur-global-minor-mode
                 pdf-tools-enabled-modes)
       (pdf-occur-global-minor-mode 1))
+    (when (memq 'pdf-virtual-global-minor-mode
+                pdf-tools-enabled-modes)
+      (pdf-virtual-global-minor-mode 1))
     (add-hook 'pdf-view-mode-hook 'pdf-tools-enable-minor-modes)
     (dolist (buf (buffer-list))
       (with-current-buffer buf
@@ -375,6 +382,7 @@ See `pdf-view-mode' and `pdf-tools-enabled-modes'."
   (setq-default auto-mode-alist
     (remove pdf-tools-auto-mode-alist-entry auto-mode-alist))
   (pdf-occur-global-minor-mode -1)
+  (pdf-virtual-global-minor-mode -1)
   (remove-hook 'pdf-view-mode-hook 'pdf-tools-enable-minor-modes)
   (dolist (buf (buffer-list))
     (with-current-buffer buf

lisp/pdf-view.el

@@ -271,10 +271,11 @@ PNG images in Emacs buffers."
   :abbrev-table nil
   :syntax-table nil
   ;; Setup a local copy for remote files.
-  (when (or jka-compr-really-do-compress
-            (let ((file-name-handler-alist nil))
-              (not (and buffer-file-name
-                        (file-readable-p buffer-file-name)))))
+  (when (and (or jka-compr-really-do-compress
+                 (let ((file-name-handler-alist nil))
+                   (not (and buffer-file-name
+                             (file-readable-p buffer-file-name)))))
+             (pdf-tools-pdf-buffer-p))             
     (let ((tempfile (pdf-util-make-temp-file
                      (concat (if buffer-file-name
                                  (file-name-nondirectory
@@ -317,7 +318,8 @@ PNG images in Emacs buffers."
   ;; No auto-save at the moment.
   (setq-local buffer-auto-save-file-name nil)
   ;; No undo at the moment.
-  (buffer-disable-undo)
+  (unless buffer-undo-list
+    (buffer-disable-undo))
   ;; Enable transient-mark-mode, so region deactivation when quitting
   ;; will work.
   (setq-local transient-mark-mode t)