mu4e: update html/URL handling

Make mu4e-view-toggle-html _not_ toggle the global value of of
mu4e-view-prefer-html, but only the current one.

Make the link map 'permanent', so it survives the buffer changes when
refreshing. This fixes issue #904.

mu4e/mu4e-message.el

@@ -158,12 +158,16 @@ This is equivalent to:
   (mu4e-message-field (mu4e-message-at-point) FIELD)."
   (mu4e-message-field (mu4e-message-at-point) field))
 
-(defun mu4e-message-body-text (msg)
+(defvar mu4e~message-body-html nil
+  "Whether the body text uses HTML.")
+
+(defun mu4e-message-body-text (msg &optional prefer-html)
   "Get the body in text form for this message.
-This is either :body-txt, or if not available, :body-html converted
+This is either :body-txt, or if not available, :body-html
-to text, using `mu4e-html2text-command' is non-nil, it will use
+converted to text, using `mu4e-html2text-command' is non-nil, it
-that. Normally, thiss function prefers the text part, but this can
+will use that. Normally, this function prefers the text part,
-be changed by setting `mu4e-view-prefer-html'."
+unless PREFER-HTML is non-nil."
+  (setq mu4e~message-body-html nil) ;; default
   (let* ((txt (mu4e-message-field msg :body-txt))
 	  (html (mu4e-message-field msg :body-html))
 	  (body
@@ -176,7 +180,7 @@ be changed by setting `mu4e-view-prefer-html'."
 	      ((and (> (* mu4e-view-html-plaintext-ratio-heuristic
                       (length txt)) (length html))
 		 ;; use html if it's prefered, unless there is no html
-		 (or (not mu4e-view-prefer-html) (not html)))
+		 (or (not prefer-html) (not html)))
 		txt)
 	      ;; otherwise, it there some html?
 	      (html
@@ -192,6 +196,7 @@ be changed by setting `mu4e-view-prefer-html'."
 		    ((functionp mu4e-html2text-command)
 		      (funcall mu4e-html2text-command))
 		    (t (mu4e-error "Invalid `mu4e-html2text-command'")))
+		  (setq mu4e~message-body-html t)
 		  (buffer-string))
                 )
 	      (t ;; otherwise, an empty body

mu4e/mu4e-view.el

@@ -247,7 +247,7 @@ found."
 		 (mu4e~view-custom-field msg field))))))
       mu4e-view-fields "")
     "\n"
-    (let ((body (mu4e-message-body-text msg)))
+    (let ((body (mu4e-message-body-text msg mu4e-view-prefer-html)))
       (when (fboundp 'add-face-text-property)
         (add-face-text-property 0 (length body) 'mu4e-view-body-face t body))
       body)))
@@ -747,6 +747,10 @@ FUNC should be a function taking two arguments:
   (make-local-variable 'mu4e~view-attach-map)
   (make-local-variable 'mu4e~view-cited-hidden)
 
+  ;; make permanent too, so they'll survive changing the mode
+  (put 'mu4e~view-link-map 'permanent-local t)
+  (put 'mu4e~view-attach-map 'permanent-local t)
+
   ;; show context in mode-string
   (set (make-local-variable 'global-mode-string) '(:eval (mu4e-context-label))) 
  
@@ -932,8 +936,8 @@ the new docid. Otherwise, return nil."
 (defun mu4e-view-toggle-html ()
   "Toggle html-display of the message body (if any)."
   (interactive)
-  (setq mu4e-view-prefer-html (not mu4e-view-prefer-html)) 
+  (let ((mu4e-view-prefer-html (not mu4e~message-body-html))) 
-  (mu4e-view-refresh)) 
+    (mu4e-view-refresh))) 
 
 (defun mu4e-view-refresh ()
   "Redisplay the current message."