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Make pixel-wise scrolling less laggy

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* lisp/pixel-scroll.el (pixel-dead-time, pixel-last-scroll-time):
New variables.
(pixel-scroll-up, pixel-scroll-down): Invoke 'scroll-up' or
'scroll-down' when called within 'pixel-dead-time'.  (Bug#29737)
This commit is contained in:
Tak Kunihiro 2018-01-07 09:17:09 +02:00 committed by Eli Zaretskii
parent f92264fc2a
commit 1dfc27576a
1 changed files with 48 additions and 23 deletions
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71
lisp/pixel-scroll.el
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@ -82,6 +82,27 @@ case you need scrolling resolution of a pixel, set to 1. After a
pixel scroll, typing \\[next-line] or \\[previous-line] scrolls the window to make it
fully visible, and undoes the effect of the pixel-level scroll.")
(defvar pixel-dead-time 0.1
"Minimal interval in seconds before next smooth scrolling.
If another scrolling request arrives within this period, scrolling
will be carried out without pixel resolution. If zero, scrolling
is always with pixel resolution.")
(defvar pixel-last-scroll-time 0
"Time when the last scrolling was made, in second since the epoch.")
(defun pixel-scroll-in-rush-p ()
"Return non-nil if next scroll should be non-smooth.
When scrolling request is delivered soon after the previous one,
user is in hurry. When the time since last scroll is larger than
`pixel-dead-time', we are ready for another smooth scroll, and this
function returns nil."
(let* ((current-time (float-time))
(scroll-in-rush-p (< (- current-time pixel-last-scroll-time)
pixel-dead-time)))
(setq pixel-last-scroll-time current-time)
scroll-in-rush-p))
;;;###autoload
(define-minor-mode pixel-scroll-mode
"A minor mode to scroll text pixel-by-pixel.
@ -104,35 +125,39 @@ if ARG is omitted or nil."
This is an alternative of `scroll-up'. Scope moves downward."
(interactive)
(or arg (setq arg 1))
(dotimes (ii arg) ; move scope downward
(let ((amt (if pixel-resolution-fine-flag
(if (integerp pixel-resolution-fine-flag)
pixel-resolution-fine-flag
(frame-char-height))
(pixel-line-height))))
(if (pixel-eob-at-top-p) ; when end-of-the-buffer is close
(scroll-up 1) ; relay on robust method
(while (pixel-point-at-top-p amt) ; prevent too late (multi tries)
(vertical-motion 1)) ; move point downward
(pixel-scroll-pixel-up amt))))) ; move scope downward
(if (pixel-scroll-in-rush-p)
(scroll-up arg)
(dotimes (ii arg) ; move scope downward
(let ((amt (if pixel-resolution-fine-flag
(if (integerp pixel-resolution-fine-flag)
pixel-resolution-fine-flag
(frame-char-height))
(pixel-line-height))))
(if (pixel-eob-at-top-p) ; when end-of-the-buffer is close
(scroll-up 1) ; relay on robust method
(while (pixel-point-at-top-p amt) ; prevent too late (multi tries)
(vertical-motion 1)) ; move point downward
(pixel-scroll-pixel-up amt)))))) ; move scope downward
(defun pixel-scroll-down (&optional arg)
"Scroll text of selected window down ARG lines.
This is and alternative of `scroll-down'. Scope moves upward."
(interactive)
(or arg (setq arg 1))
(dotimes (ii arg)
(let ((amt (if pixel-resolution-fine-flag
(if (integerp pixel-resolution-fine-flag)
pixel-resolution-fine-flag
(frame-char-height))
(pixel-line-height -1))))
(while (pixel-point-at-bottom-p amt) ; prevent too late (multi tries)
(vertical-motion -1)) ; move point upward
(if (or (pixel-bob-at-top-p amt) ; when beginning-of-the-buffer is seen
(pixel-eob-at-top-p)) ; for file with a long line
(scroll-down 1) ; relay on robust method
(pixel-scroll-pixel-down amt)))))
(if (pixel-scroll-in-rush-p)
(scroll-down arg)
(dotimes (ii arg)
(let ((amt (if pixel-resolution-fine-flag
(if (integerp pixel-resolution-fine-flag)
pixel-resolution-fine-flag
(frame-char-height))
(pixel-line-height -1))))
(while (pixel-point-at-bottom-p amt) ; prevent too late (multi tries)
(vertical-motion -1)) ; move point upward
(if (or (pixel-bob-at-top-p amt) ; when beginning-of-the-buffer is seen
(pixel-eob-at-top-p)) ; for file with a long line
(scroll-down 1) ; relay on robust method
(pixel-scroll-pixel-down amt))))))
(defun pixel-bob-at-top-p (amt)
"Return non-nil if window-start is at beginning of the current buffer.