From 38a8b40df277d801fdca10a3c4451781c9f91b07 Mon Sep 17 00:00:00 2001
From: Pierre Neidhardt <mail@ambrevar.xyz>
Date: Fri, 22 Jan 2021 21:16:22 +0100
Subject: [PATCH] SLY: Add sly-narrow-to-prompt.

---
 .emacs.d/lisp/init-sly-narrow.el | 41 ++++++++++++++++++++++++++++++++
 .emacs.d/lisp/init-sly.el        |  2 ++
 2 files changed, 43 insertions(+)
 create mode 100644 .emacs.d/lisp/init-sly-narrow.el

diff --git a/.emacs.d/lisp/init-sly-narrow.el b/.emacs.d/lisp/init-sly-narrow.el
new file mode 100644
index 00000000..d9f9999a
--- /dev/null
+++ b/.emacs.d/lisp/init-sly-narrow.el
@@ -0,0 +1,41 @@
+;; Requires `ambrevar/sly-end-of-prompt-p'.
+
+(defun ambrevar/sly-prompt-begin-position ()
+  (cond
+   ((and (get-text-property (point) 'sly-mrepl--prompt)
+         (not (get-text-property (1- (point)) 'sly-mrepl--prompt)))
+    (point))
+   ((or (get-text-property (point) 'sly-mrepl--prompt)
+        (ambrevar/sly-end-of-prompt-p))
+    (previous-single-char-property-change
+     (point) 'sly-mrepl--prompt))
+   (t (previous-single-char-property-change
+       (previous-single-char-property-change
+        (point) 'sly-mrepl--prompt)
+       'sly-mrepl--prompt))))
+
+(defun ambrevar/sly-prompt-end-position ()
+  (save-excursion
+    (goto-char (ambrevar/sly-prompt-begin-position))
+    (call-interactively #'sly-mrepl-next-prompt)
+    (point)))
+
+(defun ambrevar/sly-output-end-position ()
+  (if (get-text-property (point) 'sly-mrepl--prompt)
+      (next-single-char-property-change
+       (next-single-char-property-change
+        (point) 'sly-mrepl--prompt)
+       'sly-mrepl--prompt)
+    (next-single-char-property-change
+     (point) 'sly-mrepl--prompt)))
+
+(defun ambrevar/sly-narrow-to-prompt ()
+  "Narrow buffer to prompt at point."
+  (interactive)
+  (narrow-to-region
+   (ambrevar/sly-prompt-begin-position)
+   (ambrevar/sly-output-end-position)))
+
+(define-key sly-mrepl-mode-map (kbd "C-x n d") 'ambrevar/sly-narrow-to-prompt)
+
+(provive 'init-sly-narrow)
diff --git a/.emacs.d/lisp/init-sly.el b/.emacs.d/lisp/init-sly.el
index 36d5b9b1..32d401ed 100644
--- a/.emacs.d/lisp/init-sly.el
+++ b/.emacs.d/lisp/init-sly.el
@@ -316,4 +316,6 @@ returns a string."
 (advice-add 'sly-mrepl-next-prompt :override #'ambrevar/sly-mrepl-next-prompt)
 (advice-add 'sly-mrepl-previous-prompt :override #'ambrevar/sly-mrepl-previous-prompt)
 
+(require 'init-sly-narrow)
+
 (provide 'init-sly)