persp-get-scratch-buffer: get or create a scratch buffer

Delegate 'persp-get-scratch-buffer' to get/create a perspective's
scratch buffer named "*scratch* (NAME)".  Modify 'persp-new' into
using this new function.

When a scratch buffer is created by 'persp-get-scratch-buffer' it
is properly set.  An existing buffer is returned as is.

2 files changed, 20 insertions, 7 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2d61c0b..e5f6b19 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -42,6 +42,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Added
 
+- `persp-get-scratch-buffer`: utility function to properly get/create a scratch buffer.
 - `persp-forget-buffer`: disassociate buffer with perspective without the risk of killing it.  This balances `persp-add-buffer`.  Newly created buffers via `get-buffer-create` are rogue buffers not found in any perspective, this function allows to get back to that state.
 - `persp-maybe-kill-buffer`: designed as `kill-buffer-query-functions` hook to keep a perspective's last left buffer from being killed.
 - `persp-get-buffer-names`: get any perspective's list of live buffers.
@@ -50,6 +51,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 
+- `persp-new`: call `persp-get-scratch-buffer` to get/create a scratch buffer.
 - `persp-switch`: remove duplicated code.  It's now possible to call `persp-new` either to get an existing perspective or to create a new one.
 - `persp-mode`: add/remove `persp-maybe-kill-buffer` hook.
 - `persp-kill`: switch `persp-maybe-kill-buffer` on/off to allow killing a perspective's last left buffer.
diff --git a/perspective.el b/perspective.el
index bffda68..f178edf 100644
--- a/perspective.el
+++ b/perspective.el
@@ -216,6 +216,23 @@ filtering in buffer display modes like ibuffer."
             (unless initial-persp
               (format " (%s)" name)))))
 
+(defun persp-get-scratch-buffer (&optional name)
+  "Return the \"*scratch* (NAME)\" buffer.
+Create it if the current perspective doesn't have one yet."
+  (let* ((scratch-buffer-name (persp-scratch-buffer name))
+         (scratch-buffer (get-buffer scratch-buffer-name)))
+    ;; Do not interfere with an existing scratch buffer's status.
+    (unless scratch-buffer
+      (setq scratch-buffer (get-buffer-create scratch-buffer-name))
+      (with-current-buffer scratch-buffer
+        (when (eq major-mode 'fundamental-mode)
+          (funcall initial-major-mode))
+        (when (and (zerop (buffer-size))
+                   initial-scratch-message)
+          (insert (substitute-command-keys initial-scratch-message))
+          (set-buffer-modified-p nil))))
+    scratch-buffer))
+
 (defalias 'persp-killed-p 'persp-killed
   "Return whether the perspective CL-X has been killed.")
 
@@ -556,13 +573,7 @@ The new perspective will start with only an `initial-major-mode'
 buffer called \"*scratch* (NAME)\"."
   (or (gethash name (perspectives-hash))
       (make-persp :name name
-        (switch-to-buffer (persp-scratch-buffer name))
-        (when (eq major-mode 'fundamental-mode)
-          (funcall initial-major-mode))
-        (when (and (zerop (buffer-size))
-                   initial-scratch-message)
-          (insert (substitute-command-keys initial-scratch-message))
-          (set-buffer-modified-p nil))
+        (switch-to-buffer (persp-get-scratch-buffer name))
         (persp-reset-windows))))
 
 (defun persp-reactivate-buffers (buffers)