[PATCH] Improve `tab-line-tabs-fixed-window-buffers` sorting performance

[Eval Exec <execvy@gmail.com>]

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Hello,
After noticing severe lag when `buffer-list` exceeds 1000 buffers,
particularly
with `tab-line-switch-to-prev-tab` and `tab-line-switch-to-next-tab`,
a profiler
revealed that the sorting operation in
`tab-line-tabs-fixed-window-buffers` heavily
relies on the `seq-position` function. This reliance significantly
impacts performance.
To address this, I have proposed a patch to optimize the buffer
sorting mechanism within
`tab-line-tabs-fixed-window-buffers`. The solution involves replacing
the inefficient
`seq-position` calls with a hash table to cache buffer positions,
which markedly
enhances performance when handling large buffer lists.

This is my first attempt at hacking Emacs. Do you have any suggestions
on this idea?

Thank you

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From fa047a52c0d40aace236bd56f1d8ca70935f438a Mon Sep 17 00:00:00 2001
From: Eval EXEC <execvy@gmail.com>
Date: Fri, 5 Jul 2024 18:53:36 +0800
Subject: [PATCH] Improve `tab-line-tabs-fixed-window-buffers` sorting
 performance

* lsp/tab-line.el (tab-line-tabs-fixed-window-buffers): Enhanced
`tab-line-tabs-fixed-window-buffers` performance by optimizing buffer
sorting mechanism. Replaced inefficient `seq-position` calls with a hash
table to cache buffer positions, significantly improving speed when
handling large buffer lists.
---
 lisp/tab-line.el | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lisp/tab-line.el b/lisp/tab-line.el
index 1d14fda9825..e4908c61542 100644
--- a/lisp/tab-line.el
+++ b/lisp/tab-line.el
@@ -555,10 +555,14 @@ This means that switching to a buffer previously shown in the same
 window will keep the same order of tabs that was before switching.
 And newly displayed buffers are added to the end of the tab line."
   (let* ((old-buffers (window-parameter nil 'tab-line-buffers))
+         (buffer-positions (let ((index-table (make-hash-table :test 'eq)))
+                             (seq-do-indexed
+                              (lambda (buf idx) (puthash buf idx index-table))
+                              old-buffers)
+                             index-table))
          (new-buffers (sort (tab-line-tabs-window-buffers)
                             :key (lambda (buffer)
-                                   (or (seq-position old-buffers buffer)
-                                       most-positive-fixnum)))))
+                                   (gethash buffer buffer-positions most-positive-fixnum)))))
     (set-window-parameter nil 'tab-line-buffers new-buffers)
     new-buffers))
 
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2.44.1