ox: Provide offset to [+-]n in SRC/EXAMPLE export

* lisp/org-element.el (org-element-example-block-parser): Use cons cell
  for :number-lines specifying offset in addition to type (new/continue).
  ('continue . offset) for :number-lines will add this offset count to
  the last line number. ('new . offset) for :number-lines will reset the
  line number counting starting at offset
(org-element-src-block-parser): same for SRC block as EXAMPLE block

* lisp/ox-html.el (org-html-format-code):
* lisp/ox-latex.el (org-latex-src-block):
* lisp/ox-odt.el (org-odt-format-code):
* lisp/ox.el (org-export-resolve-coderef):
(org-export-get-loc):
(org-export-format-code-default):
* contrib/lisp/ox-groff.el (org-groff-src-block): Use new cons cell
  for :number-lines.

* testing/lisp/test-ox.el  (ert-deftest test-org-export/get-loc): Tests for
changes
(test-org-gen-loc-list): Helper function for `test-org-export/get-loc'.

7 files changed, 153 insertions, 32 deletions

diff --git a/contrib/lisp/ox-groff.el b/contrib/lisp/ox-groff.el
index b49edce..25ed8b0 100644
--- a/contrib/lisp/ox-groff.el
+++ b/contrib/lisp/ox-groff.el
@@ -1488,9 +1488,7 @@ contextual information."
          (custom-env (and lang
                           (cadr (assq (intern lang)
                                       org-groff-custom-lang-environments))))
-         (num-start (case (org-element-property :number-lines src-block)
-                      (continued (org-export-get-loc src-block info))
-                      (new 0)))
+         (num-start (org-export-get-loc src-block info))
          (retain-labels (org-element-property :retain-labels src-block))
          (caption (and (not (org-export-read-attribute
 			     :attr_groff src-block :disable-caption))
diff --git a/lisp/org-element.el b/lisp/org-element.el
index 368da60..2b92617 100644
--- a/lisp/org-element.el
+++ b/lisp/org-element.el
@@ -1893,11 +1893,19 @@ containing `:begin', `:end', `:number-lines', `:preserve-indent',
 		  (progn
 		    (looking-at "^[ \t]*#\\+BEGIN_EXAMPLE\\(?: +\\(.*\\)\\)?")
 		    (org-match-string-no-properties 1)))
-		 ;; Switches analysis
+		 ;; Switches analysis.
 		 (number-lines
-		  (cond ((not switches) nil)
-			((string-match "-n\\>" switches) 'new)
-			((string-match "+n\\>" switches) 'continued)))
+		  (and switches
+		       (string-match "\\([-+]\\)n\\(?: *\\([0-9]+\\)\\)?\\>"
+				     switches)
+		       (cons
+			(if (equal (match-string 1 switches) "-")
+			    'new
+			  'continued)
+			(if (not (match-end 2)) 0
+			  ;; Subtract 1 to give number of lines before
+			  ;; first line.
+			  (1- (string-to-number (match-string 2 switches)))))))
 		 (preserve-indent
 		  (and switches (string-match "-i\\>" switches)))
 		 ;; Should labels be retained in (or stripped from) example
@@ -2391,20 +2399,28 @@ Assume point is at the beginning of the block."
 		 (language
 		  (progn
 		    (looking-at
-		     (concat "^[ \t]*#\\+BEGIN_SRC"
-			     "\\(?: +\\(\\S-+\\)\\)?"
-			     "\\(\\(?: +\\(?:-l \".*?\"\\|[-+][A-Za-z]\\)\\)+\\)?"
-			     "\\(.*\\)[ \t]*$"))
+		     "^[ \t]*#\\+BEGIN_SRC\
+\\(?: +\\(\\S-+\\)\\)?\
+\\(\\(?: +\\(?:-\\(?:l \".+\"\\|[ikr]\\)\\|[-+]n\\(?: *[0-9]+\\)?\\)\\)+\\)?\
+\\(.*\\)[ \t]*$")
 		    (org-match-string-no-properties 1)))
 		 ;; Get switches.
 		 (switches (org-match-string-no-properties 2))
 		 ;; Get parameters.
 		 (parameters (org-match-string-no-properties 3))
-		 ;; Switches analysis
+		 ;; Switches analysis.
 		 (number-lines
-		  (cond ((not switches) nil)
-			((string-match "-n\\>" switches) 'new)
-			((string-match "+n\\>" switches) 'continued)))
+		  (and switches
+		       (string-match "\\([-+]\\)n\\(?: *\\([0-9]+\\)\\)?\\>"
+				     switches)
+		       (cons
+			(if (equal (match-string 1 switches) "-")
+			    'new
+			  'continued)
+			(if (not (match-end 2)) 0
+			  ;; Subtract 1 to give number of lines before
+			  ;; first line.
+			  (1- (string-to-number (match-string 2 switches)))))))
 		 (preserve-indent (and switches
 				       (string-match "-i\\>" switches)))
 		 (label-fmt
diff --git a/lisp/ox-html.el b/lisp/ox-html.el
index e33d91e..3f5802a 100644
--- a/lisp/ox-html.el
+++ b/lisp/ox-html.el
@@ -2207,9 +2207,7 @@ a plist used as a communication channel."
 	 ;; Does the src block contain labels?
 	 (retain-labels (org-element-property :retain-labels element))
 	 ;; Does it have line numbers?
-	 (num-start (case (org-element-property :number-lines element)
-		      (continued (org-export-get-loc element info))
-		      (new 0))))
+	 (num-start (org-export-get-loc element info)))
     (org-html-do-format-code code lang refs retain-labels num-start)))
 
 
diff --git a/lisp/ox-latex.el b/lisp/ox-latex.el
index 21e0a8b..0946fe4 100644
--- a/lisp/ox-latex.el
+++ b/lisp/ox-latex.el
@@ -2763,9 +2763,7 @@ contextual information."
 	   (custom-env (and lang
 			    (cadr (assq (intern lang)
 					org-latex-custom-lang-environments))))
-	   (num-start (case (org-element-property :number-lines src-block)
-			(continued (org-export-get-loc src-block info))
-			(new 0)))
+	   (num-start (org-export-get-loc src-block info))
 	   (retain-labels (org-element-property :retain-labels src-block))
 	   (attributes (org-export-read-attribute :attr_latex src-block))
 	   (float (plist-get attributes :float))
diff --git a/lisp/ox-odt.el b/lisp/ox-odt.el
index d996689..548445c 100644
--- a/lisp/ox-odt.el
+++ b/lisp/ox-odt.el
@@ -3168,9 +3168,7 @@ and prefix with \"OrgSrc\".  For example,
 	 ;; Does the src block contain labels?
 	 (retain-labels (org-element-property :retain-labels element))
 	 ;; Does it have line numbers?
-	 (num-start (case (org-element-property :number-lines element)
-		      (continued (org-export-get-loc element info))
-		      (new 0))))
+	 (num-start (org-export-get-loc element info)))
     (org-odt-do-format-code code info lang refs retain-labels num-start)))
 
 (defun org-odt-src-block (src-block _contents info)
diff --git a/lisp/ox.el b/lisp/ox.el
index 5ad17ec..714000b 100644
--- a/lisp/ox.el
+++ b/lisp/ox.el
@@ -4148,9 +4148,7 @@ error if no block contains REF."
 	      (when (re-search-backward ref-re nil t)
 		(cond
 		 ((org-element-property :use-labels el) ref)
-		 ((eq (org-element-property :number-lines el) 'continued)
-		  (+ (org-export-get-loc el info) (line-number-at-pos)))
-		 (t (line-number-at-pos)))))))
+		 (t (+ (or (org-export-get-loc el info) 0) (line-number-at-pos))))))))
 	info 'first-match)
       (signal 'org-link-broken (list ref))))
 
@@ -4457,7 +4455,8 @@ objects of the same type."
 INFO is the plist used as a communication channel.
 
 ELEMENT is excluded from count."
-  (let ((loc 0))
+  (let ((loc 0)
+        (linum (org-element-property :number-lines element)))
     (org-element-map (plist-get info :parse-tree)
 	`(src-block example-block ,(org-element-type element))
       (lambda (el)
@@ -4472,10 +4471,17 @@ ELEMENT is excluded from count."
 	      ;; Accumulate locs or reset them.
 	      (let ((lines (org-count-lines
 			    (org-trim (org-element-property :value el)))))
-		(setq loc (if (eq linums 'new) lines (+ loc lines))))))
+		(if (eq (car linums) 'new)
+		    (setq loc 0))
+		(setq loc (+ loc lines (cdr linums))))))
 	  ;; Return nil to stay in the loop.
 	  nil)))
       info 'first-match)
+    ;; Add the offset from [+-]n to the loc for the final starting
+    ;; number of lines before the first starting line.
+    (setq loc (cl-case (car linum)
+		(continued (+ (cdr linum) loc))
+		(new (cdr linum))))
     ;; Return value.
     loc))
 
@@ -4573,9 +4579,7 @@ code."
       (let* ((refs (and (org-element-property :retain-labels element)
 			(cdr code-info)))
 	     ;; Handle line numbering.
-	     (num-start (cl-case (org-element-property :number-lines element)
-			  (continued (org-export-get-loc element info))
-			  (new 0)))
+	     (num-start (org-export-get-loc element info))
 	     (num-fmt
 	      (and num-start
 		   (format "%%%ds  "
diff --git a/testing/lisp/test-ox.el b/testing/lisp/test-ox.el
index e27954c..209dc64 100644
--- a/testing/lisp/test-ox.el
+++ b/testing/lisp/test-ox.el
@@ -2586,6 +2586,70 @@ Paragraph[fn:1][fn:2][fn:lbl3:C<<target>>][[test]][[target]]
        (lambda (link) (org-export-resolve-fuzzy-link link info))
        info t))))
 
+(defun test-org-gen-loc-list(text type)
+    (org-test-with-parsed-data text
+			       (org-element-map tree type
+				 (lambda(el) (or (org-export-get-loc el info) "nil")))))
+
+(ert-deftest test-org-export/get-loc ()
+  "Test `org-export-get-loc' specifications."
+  (should
+   ;; "-n" resets line number.
+   (equal '(0)
+	  (test-org-gen-loc-list  "#+BEGIN_EXAMPLE -n\n  Text\n#+END_EXAMPLE" 'example-block)))
+  ;; The first "+n" has 0 lines before it
+  (should
+   (equal '(0)
+	  (test-org-gen-loc-list "#+BEGIN_EXAMPLE +n\n  Text\n#+END_EXAMPLE" 'example-block)))
+  ;; "-n 10" resets line number but has "9 lines" before it.
+  (should
+   (equal '(9)
+	  (test-org-gen-loc-list "#+BEGIN_EXAMPLE -n 10\n  Text\n#+END_EXAMPLE" 'example-block)))
+  ;; -n10 with two lines then +n 15
+  (should
+   (equal '(9 25)
+	  (test-org-gen-loc-list "#+BEGIN_EXAMPLE -n 10\n  Text_10\n  Second line(11)\n#+END_EXAMPLE
+#+BEGIN_EXAMPLE +n 15\n  Text line (11 + 15)\n#+END_EXAMPLE"  'example-block)))
+  (should
+   (equal '(9 19 0)
+	  (test-org-gen-loc-list "#+BEGIN_EXAMPLE -n 10\n  Text\n#+END_EXAMPLE
+#+BEGIN_EXAMPLE +n 10\n  Text \n#+END_EXAMPLE\n
+#+BEGIN_EXAMPLE -n\n  Text \n#+END_EXAMPLE" 'example-block)))
+  (should
+   ;; an Example Block without -n does not add to the line count
+   (equal '(9 "nil" 19)
+	  (test-org-gen-loc-list "#+BEGIN_EXAMPLE -n 10\n  Text\n#+END_EXAMPLE
+#+BEGIN_EXAMPLE\n  Text\n#+END_EXAMPLE
+#+BEGIN_EXAMPLE +n 10\n  Text\n#+END_EXAMPLE" 'example-block)))
+  (should
+   ;; "-n" resets line number.
+   (equal '(0)
+	  (test-org-gen-loc-list "#+BEGIN_SRC emacs-lisp -n \n  (- 1 1) \n#+END_SRC" 'src-block)))
+  (should
+   ;; The first "+n" has 0 lines before it
+   (equal '(0)
+	  (test-org-gen-loc-list "#+BEGIN_SRC emacs-lisp +n \n  (+ 0 (- 1 1))\n#+END_SRC" 'src-block)))
+  (should
+   ;; "-n 10" resets line number but has "9 lines" before it.
+   (equal '(9)
+	  (test-org-gen-loc-list "#+BEGIN_SRC emacs-lisp -n 10\n  (- 10 1)\n#+END_SRC" 'src-block)))
+  (should
+   (equal '(9 25)
+	  (test-org-gen-loc-list "#+BEGIN_SRC emacs-lisp -n 10\n  (- 10 1)\n  (+ (- 10 1) 1)\n#+END_SRC
+#+BEGIN_SRC emacs-lisp +n 15\n  (+ (- 10 1) 2 (- 15 1))\n#+END_SRC" 'src-block)))
+  (should
+   (equal '(9 19 0)
+	  (test-org-gen-loc-list "#+BEGIN_SRC emacs-lisp -n 10\n  (- 10 1)\n#+END_SRC
+#+BEGIN_SRC emacs-lisp +n 10\n  (+ (- 10 1) 1 (- 10 1))\n#+END_SRC
+#+BEGIN_SRC emacs-lisp -n\n  (- 1 1)\n#+END_SRC" 'src-block)))
+  (should
+   ;; an SRC Block without -n does not add to the line count
+   (equal '(9 "nil" 19)
+	  (test-org-gen-loc-list
+	   "#+BEGIN_SRC emacs-lisp -n 10\n  (+ (-10 1) 1)\n#+END_SRC
+#+BEGIN_SRC emacs-lisp \n  (+ 2 2) \n#+END_SRC
+#+BEGIN_SRC emacs-lisp +n 10\n  (+ (- 10 1) 1 (- 10 1))\n#+END_SRC" 'src-block))))
+
 (ert-deftest test-org-export/resolve-coderef ()
   "Test `org-export-resolve-coderef' specifications."
   (let ((org-coderef-label-format "(ref:%s)"))
@@ -2596,10 +2660,32 @@ Paragraph[fn:1][fn:2][fn:lbl3:C<<target>>][[test]][[target]]
 	    "#+BEGIN_EXAMPLE -n -k -r\nText (ref:coderef)\n#+END_EXAMPLE"
 	  (org-export-resolve-coderef "coderef" info))))
     (should
+     (= 10
+	(org-test-with-parsed-data
+	 "#+BEGIN_EXAMPLE -n 10 -k -r\nText (ref:coderef)\n#+END_EXAMPLE"
+	 (org-export-resolve-coderef "coderef" info))))
+    (should
+     (= 135
+	(org-test-with-parsed-data
+	 "#+BEGIN_EXAMPLE -n 10 -k -r\nText \n#+END_EXAMPLE\n
+#+BEGIN_EXAMPLE +n 125 -k -r\nText (ref:coderef)\n#+END_EXAMPLE"
+	 (org-export-resolve-coderef "coderef" info))))
+    (should
      (= 1
 	(org-test-with-parsed-data
 	    "#+BEGIN_SRC emacs-lisp -n -k -r\n(+ 1 1) (ref:coderef)\n#+END_SRC"
 	  (org-export-resolve-coderef "coderef" info))))
+    (should
+     (= 10
+	(org-test-with-parsed-data
+	 "#+BEGIN_SRC emacs-lisp -n 10 -k -r\n(+ 1 1) (ref:coderef)\n#+END_SRC"
+	 (org-export-resolve-coderef "coderef" info))))
+    (should
+     (= 135
+	(org-test-with-parsed-data
+	 "#+BEGIN_SRC emacs-lisp -n 10 -k -r\n(+ 1 1) \n#+END_SRC\n
+#+BEGIN_SRC emacs-lisp +n 125 -k -r\n(+ 1 1) (ref:coderef)\n#+END_SRC"
+	 (org-export-resolve-coderef "coderef" info))))
     ;; A link to a "-n -r" block returns line number.
     (should
      (= 1
@@ -2607,10 +2693,33 @@ Paragraph[fn:1][fn:2][fn:lbl3:C<<target>>][[test]][[target]]
 	    "#+BEGIN_EXAMPLE -n -r\nText (ref:coderef)\n#+END_EXAMPLE"
 	  (org-export-resolve-coderef "coderef" info))))
     (should
+     (= 10
+	(org-test-with-parsed-data
+	 "#+BEGIN_EXAMPLE -n 10 -r\nText (ref:coderef)\n#+END_EXAMPLE"
+	 (org-export-resolve-coderef "coderef" info))))
+    (should
+     (= 135
+	(org-test-with-parsed-data
+	 "#+BEGIN_EXAMPLE +n 10 -r\nText \n#+END_EXAMPLE
+#+BEGIN_EXAMPLE +n 125 -r\nText (ref:coderef)\n#+END_EXAMPLE"
+	 (org-export-resolve-coderef "coderef" info))))
+
+    (should
      (= 1
 	(org-test-with-parsed-data
 	    "#+BEGIN_SRC emacs-lisp -n -r\n(+ 1 1) (ref:coderef)\n#+END_SRC"
 	  (org-export-resolve-coderef "coderef" info))))
+    (should
+     (= 10
+	(org-test-with-parsed-data
+	 "#+BEGIN_SRC emacs-lisp -n10 -r\n(+ 1 1) (ref:coderef)\n#+END_SRC"
+	 (org-export-resolve-coderef "coderef" info))))
+    (should
+     (= 135
+	(org-test-with-parsed-data
+	 "#+BEGIN_SRC emacs-lisp -n10 -r\n(+ 1 1) \n#+END_SRC
+#+BEGIN_SRC emacs-lisp +n125 -r\n(+ 1 1) (ref:coderef)\n#+END_SRC"
+	 (org-export-resolve-coderef "coderef" info))))
     ;; A link to a "-n" block returns coderef.
     (should
      (equal "coderef"