Fix bugs in selection data manipulation code

* eat.el (eat--t-term): Put a vector of length 8 (instead of
10) in 'cut-buffers' slot.
* eat.el (eat--t-manipulate-selection): Don't process the
targets '8' and '9', since they are not in the protocol.
Return correct list of queried targets to the client.  Make
sure base64 encoded data doesn't contain line breaks.
* eat.el (eat--t-handle-output): Tolerate invalid targets in
OSC 52 (manipulate selection data).
* eat.el (eat--manipulate-kill-ring): Handle 'nil' correctly.

README.org

@@ -13,7 +13,7 @@ It has many features that other Emacs terminal emulator still don't
 have, for example complete mouse support, shell integration, etc.
 
 It flickers less than other Emacs terminal emulator, so you get more
-performance and a smooth experience.
+performance and a smoother experience.
 
 To get the most out of Eat, you should also setup shell integration.
 

eat.el

@@ -976,7 +976,7 @@ Nil when not in alternative display mode.")
   (mouse-encoding nil :documentation "Current mouse event encoding.")
   (focus-event-mode nil :documentation "Whether to send focus event.")
   (cut-buffers
-   (1value (make-vector 10 nil))
+   (1value (make-vector 8 nil))
    :documentation "Cut buffers.")
   ;; NOTE: Change the default value of parameters when changing this.
   (bold-face 'eat-term-bold :documentation "Face for bold text.")
@@ -2604,8 +2604,8 @@ output."
   "Set and send current selection.
 
 TARGETS is a string containing zero or more characters from the set
-`c', `p', `q', `s', `0', `1', `2', `3', `4', `5', `6', `7', `8', `9'.
-DATA is the selection data encoded in base64."
+`c', `p', `q', `s', `0', `1', `2', `3', `4', `5', `6', and `7'.  DATA
+is the selection data encoded in base64."
   (when (string-empty-p targets)
     (setq targets "s0"))
   (if (string= data "?")
@@ -2614,8 +2614,16 @@ DATA is the selection data encoded in base64."
       (funcall
        (eat--t-term-input-fn eat--t-term) eat--t-term
        (let ((str nil)
-             (source nil)
              (n 0))
+         ;; Remove invalid and duplicate targets from TARGETS before
+         ;; processing it and sending it back.
+         (setq targets
+               (apply #'string
+                      (cl-delete-duplicates
+                       (cl-delete-if-not
+                        (lambda (c) (or (<= ?0 c ?7)
+                                        (memq c '(?c ?p ?q ?s))))
+                        (string-to-list targets)))))
          (while (and (not str) (< n (length targets)))
            (setq
             str
@@ -2640,22 +2648,17 @@ DATA is the selection data encoded in base64."
                 eat--t-term :select t))
               ;; 0 to 9 targets are handled by us, and always work.
               ((and (pred (<= ?0))
-                    (pred (>= ?9))
+                    (pred (>= ?7))
                     i)
                (aref (eat--t-term-cut-buffers eat--t-term)
                      (- i ?0)))))
-           ;; If we got a string to send, record the source to inform
-           ;; the client.
-           (when str
-             (setq source (string (aref targets n))))
            (cl-incf n))
-         ;; No string to send, so send an empty string and an empty
-         ;; target string meaning that we don't have any answer.
-         (unless str
-           (setq str "")
-           (setq source ""))
-         (format "\e]52;%s;%s\e\\" source
-                 (base64-encode-string str))))
+         ;; No string to send, so send an empty string.
+         (unless str (setq str ""))
+         (format "\e]52;%s;%s\e\\" targets
+                 (base64-encode-string (encode-coding-string
+                                        str locale-coding-system)
+                                       'no-line-break))))
     ;; The client is requesting to set clipboard content, let's try to
     ;; fulfill the request.
     (let ((str (ignore-errors
@@ -2677,9 +2680,9 @@ DATA is the selection data encoded in base64."
           (?s
            (funcall (eat--t-term-manipulate-selection-fn eat--t-term)
                     eat--t-term :select str))
-          ;; 0 to 9 targets are handled by us, and always work.
+          ;; 0 to 7 targets are handled by us, and always work.
           ((and (pred (<= ?0))
-                (pred (>= ?9))
+                (pred (>= ?7))
                 i)
            (aset (eat--t-term-cut-buffers eat--t-term) (- i ?0)
                  str)))))))
@@ -3206,8 +3209,7 @@ DATA is the selection data encoded in base64."
                       ;; OSC 5 2 ; <t> ; <s> ST.
                       ((rx string-start "52;"
                            (let targets
-                             (zero-or-more (any ?c ?p ?q ?s
-                                                (?0 . ?9))))
+                             (zero-or-more (not ?\;)))
                            ?\; (let data (zero-or-more anything))
                            string-end)
                        (eat--t-manipulate-selection
@@ -3578,7 +3580,7 @@ should not change point and buffer restriction.
 
 To set it, use (`setf' (`eat-term-ring-bell-function' TERMINAL)
 FUNCTION), where FUNCTION is the function to ring the bell."
-  (eat--t-term-manipulate-selection-fn terminal))
+  (eat--t-term-bell-fn terminal))
 
 (gv-define-setter eat-term-ring-bell-function (function terminal)
   `(setf (eat--t-term-bell-fn ,terminal) ,function))
@@ -4560,6 +4562,9 @@ selection, or nil if none."
        (when eat-enable-yank-to-terminal
          (ignore-error error
            (current-kill 0 'do-not-move))))
+      ('nil
+       (when eat-enable-kill-from-terminal
+         (kill-new "")))
       ((and (pred stringp) str)
        (when eat-enable-kill-from-terminal
          (kill-new str))))))