master e08238cdd74: Speed up Eshell smart display module

[Jim Porter]

branch: master
commit e08238cdd74719d4cd99cf5a4f743eb8c6d1d251
Author: Morgan Smith <Morgan.J.Smith@outlook.com>
Commit: Jim Porter <jporterbugs@gmail.com>

    Speed up Eshell smart display module
    
    em-smart was forcibly re-displaying the screen upwards of 500 times
    per screen of output.  This caused the Eshell to feel quite slow when
    the module was in use.  By using fewer hooks and never explicitly
    calling 'redisplay' (which was unnecessary) the performance issues go
    away (bug#57367).
    
    lisp/eshell/em-smart.el:
    
    (em-smart-unload-hook, eshell-smart-unload-hook): Remove
    'eshell-smart-scroll' instead of the now deleted
    'eshell-refresh-windows'.
    
    (eshell-smart-displayed, eshell-currently-handling-window)
    (eshell-refresh-windows): Delete.
    
    (eshell-smart-scroll-window): Rename to 'eshell-smart-scroll-windows'
    and add a bunch of logic originally from 'eshell-refresh-windows'.
    
    (eshell-smart-initialize): Don't add a hook onto
    'window-scroll-functions'.  Replace 'eshell-refresh-windows' with
    'eshell-smart-scroll-windows'.
    
    (eshell-smart-display-setup): Don't refresh windows.
    
    (eshell-smart-redisplay): Rename to 'eshell-smart-scroll'.  Delete
    'eobp' case.
---
 lisp/eshell/em-smart.el | 81 ++++++++++++++++++-------------------------------
 1 file changed, 29 insertions(+), 52 deletions(-)

diff --git a/lisp/eshell/em-smart.el b/lisp/eshell/em-smart.el
index 4c39a991ec6..fc283547519 100644
--- a/lisp/eshell/em-smart.el
+++ b/lisp/eshell/em-smart.el
@@ -95,7 +95,7 @@ it to get a real sense of how it works."
   (list
    (lambda ()
      (remove-hook 'window-configuration-change-hook
-                  'eshell-refresh-windows)))
+                  'eshell-smart-scroll)))
   "A hook that gets run when `eshell-smart' is unloaded."
   :type 'hook
   :group 'eshell-smart)
@@ -159,9 +159,7 @@ The options are `begin', `after' or `end'."
 
 ;;; Internal Variables:
 
-(defvar eshell-smart-displayed nil)
 (defvar eshell-smart-command-done nil)
-(defvar eshell-currently-handling-window nil)
 
 ;;; Functions:
 
@@ -174,10 +172,9 @@ The options are `begin', `after' or `end'."
     (setq-local eshell-scroll-to-bottom-on-input nil)
     (setq-local eshell-scroll-show-maximum-output t)
 
-    (add-hook 'window-scroll-functions 'eshell-smart-scroll-window nil t)
-    (add-hook 'window-configuration-change-hook 'eshell-refresh-windows)
+    (add-hook 'window-configuration-change-hook 'eshell-smart-scroll nil t)
 
-    (add-hook 'eshell-output-filter-functions 'eshell-refresh-windows t t)
+    (add-hook 'eshell-output-filter-functions 'eshell-smart-scroll-windows 90 
t)
 
     (add-hook 'after-change-functions 'eshell-disable-after-change nil t)
 
@@ -193,28 +190,15 @@ The options are `begin', `after' or `end'."
       (add-hook 'eshell-post-command-hook
                'eshell-smart-maybe-jump-to-end nil t))))
 
-;; This is called by window-scroll-functions with two arguments.
-(defun eshell-smart-scroll-window (wind _start)
-  "Scroll the given Eshell window WIND accordingly."
-  (unless eshell-currently-handling-window
-    (let ((eshell-currently-handling-window t))
-      (with-selected-window wind
-       (eshell-smart-redisplay)))))
-
-(defun eshell-refresh-windows (&optional frame)
-  "Refresh all visible Eshell buffers."
-  (let (affected)
-    (walk-windows
-     (lambda (wind)
-       (with-current-buffer (window-buffer wind)
-         (if eshell-mode
-             (let (window-scroll-functions) ;;FIXME: Why?
-               (eshell-smart-scroll-window wind (window-start))
-               (setq affected t)))))
-     0 frame)
-    (if affected
-       (let (window-scroll-functions) ;;FIXME: Why?
-          (redisplay)))))
+(defun eshell-smart-scroll-windows ()
+  "Scroll all eshell windows to display as much output as possible, smartly."
+  (walk-windows
+   (lambda (wind)
+     (with-current-buffer (window-buffer wind)
+       (if eshell-mode
+           (with-selected-window wind
+             (eshell-smart-scroll)))))
+   0 t))
 
 (defun eshell-smart-display-setup ()
   "Set the point to somewhere in the beginning of the last command."
@@ -231,8 +215,7 @@ The options are `begin', `after' or `end'."
    (t
     (error "Invalid value for `eshell-where-to-jump'")))
   (setq eshell-smart-command-done nil)
-  (add-hook 'pre-command-hook 'eshell-smart-display-move nil t)
-  (eshell-refresh-windows))
+  (add-hook 'pre-command-hook 'eshell-smart-display-move nil t))
 
 ;; Called from after-change-functions with 3 arguments.
 (defun eshell-disable-after-change (_b _e _l)
@@ -254,28 +237,22 @@ and the end of the buffer are still visible."
     (goto-char (point-max))
     (remove-hook 'pre-command-hook 'eshell-smart-display-move t)))
 
-(defun eshell-smart-redisplay ()
-  "Display as much output as possible, smartly."
-  (if (eobp)
+(defun eshell-smart-scroll ()
+  "Scroll WINDOW to display as much output as possible, smartly."
+  (let ((top-point (point)))
+    (and (memq 'eshell-smart-display-move pre-command-hook)
+         (>= (point) eshell-last-input-start)
+         (< (point) eshell-last-input-end)
+         (set-window-start (selected-window)
+                           (pos-bol) t))
+    (when (pos-visible-in-window-p (point-max) (selected-window))
       (save-excursion
-       (recenter -1)
-       ;; trigger the redisplay now, so that we catch any attempted
-       ;; point motion; this is to cover for a redisplay bug
-        (redisplay))
-    (let ((top-point (point)))
-      (and (memq 'eshell-smart-display-move pre-command-hook)
-          (>= (point) eshell-last-input-start)
-          (< (point) eshell-last-input-end)
-          (set-window-start (selected-window)
-                            (line-beginning-position) t))
-      (if (pos-visible-in-window-p (point-max))
-         (save-excursion
-           (goto-char (point-max))
-           (recenter -1)
-           (unless (pos-visible-in-window-p top-point)
-             (goto-char top-point)
-             (set-window-start (selected-window)
-                               (line-beginning-position) t)))))))
+        (goto-char (point-max))
+        (recenter -1)
+        (unless (pos-visible-in-window-p top-point (selected-window))
+          (goto-char top-point)
+          (set-window-start (selected-window)
+                            (pos-bol) t))))))
 
 (defun eshell-smart-goto-end ()
   "Like `end-of-buffer', but do not push a mark."
@@ -323,7 +300,7 @@ and the end of the buffer are still visible."
        (remove-hook 'pre-command-hook 'eshell-smart-display-move t))))
 
 (defun em-smart-unload-hook ()
-  (remove-hook 'window-configuration-change-hook #'eshell-refresh-windows))
+  (remove-hook 'window-configuration-change-hook #'eshell-smart-scroll))
 
 (provide 'em-smart)