[nongnu] elpa/popup 717c81eb3d 1/3: Make popup-replace-displayable much faster

[ELPA Syncer]

branch: elpa/popup
commit 717c81eb3d32e2e33ee75c813399909351d463b0
Author: gcv <gepardcv@gmail.com>
Commit: GitHub <noreply@github.com>

    Make popup-replace-displayable much faster
    
    One of my users reported a performance bug, which I tracked down to 
`popup-replace-displayable` (https://github.com/gcv/julia-snail/issues/110).
    
    Calling `popup-replace-displayable` takes ~3 seconds on a string of about 
8000 characters on my system, and becomes much slower on larger inputs.
    
    The attached PR eliminates the large number of string concatenations and 
significantly improves the function's performance.
---
 popup.el | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/popup.el b/popup.el
index c65118da6a..31ed9e92b5 100644
--- a/popup.el
+++ b/popup.el
@@ -244,15 +244,15 @@ ITEM is not string."
 
 Optional argument REP is the replacement string of
 non-displayable character."
-  (unless rep (setq rep ""))
-  (let ((result ""))
+  (let ((rep (or rep ""))
+        (results (list)))
     (dolist (string (split-string str ""))
       (let* ((char (string-to-char string))
              (string (if (char-displayable-p char)
                          string
                        rep)))
-        (setq result (concat result string))))
-    result))
+        (push string results)))
+    (string-join (reverse results))))
 
 (cl-defun popup-make-item (name
                            &key