Commit 1bda71ec authored by Tak Kunihiro's avatar Tak Kunihiro Committed by Eli Zaretskii

Improve pixel-scroll-mode

Scroll vertically by number of pixels returned by
'frame-char-height' with or without horizontally scrolled.
(Bug#28922)

* lisp/pixel-scroll.el (pixel-resolution-fine-flag): When t, scroll
by number of pixels returned by 'frame-char-height'.
(pixel-scroll-up): Scroll by 'frame-char-height'. Fix algorithm to
move cursor to avoid unexpected jump.
(pixel-scroll-down): Scroll by 'frame-char-height'.
(pixel-bob-at-top-p): Consider number of pixels that is about to
scroll.
(pixel-posn-y-at-point): Consider existence of an overlay string.
Return nil when horizontally scrolled.
(pixel-point-at-top-p): Consider number of pixels that is about to
scroll. Use different algorithm when horizontally scrolled.
(pixel-point-at-bottom-p): Consider number of pixels that is about
to scroll. Return nil when horizontally scrolled.
(pixel-scroll-pixel-down): Move cursor when horizontally scrolled.
(pixel--whistlestop-line-up): Change cosmetics and move cursor when
horizontally scrolled.
(pixel-line-height): Call 'pixel-visual-line-height' instead of
'line-pixel-height'.
(pixel-visual-line-height): New function to return height in pixels
of text line where cursor is with or without horizontally scrolled,
considering response of display engine.
(pixel-visible-pos-in-window): New function to return position of
a char shown on text line where cursor is on screen with or without
horizontally scrolled.
parent 196106d3
......@@ -74,10 +74,13 @@
More wait will result in slow and gentle scroll.")
(defvar pixel-resolution-fine-flag nil
"Set scrolling resolution to a pixel instead of a line.
After a pixel scroll, typing C-n or C-p scrolls the window to
make it fully visible, and undoes the effect of the pixel-level
scroll.")
"Set scrolling resolution to pixels instead of a line.
When it is t, scrolling resolution is number of pixels obtained
by `frame-char-height' instead of a line. When it is number,
scrolling resolution is set to number of pixels specified. In
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.")
;;;###autoload
(define-minor-mode pixel-scroll-mode
......@@ -102,13 +105,16 @@ This is an alternative of `scroll-up'. Scope moves downward."
(interactive)
(or arg (setq arg 1))
(dotimes (ii arg) ; move scope downward
(if (pixel-eob-at-top-p) ; when end-of-the-buffer is close
(scroll-up 1) ; relay on robust method
(when (pixel-point-at-top-p) ; prevent too late
(vertical-motion 1)) ; move point downward
(pixel-scroll-pixel-up (if pixel-resolution-fine-flag
1
(pixel-line-height)))))) ; 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.
......@@ -116,48 +122,63 @@ This is and alternative of `scroll-down'. Scope moves upward."
(interactive)
(or arg (setq arg 1))
(dotimes (ii arg)
(if (or (pixel-bob-at-top-p) ; 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
(while (pixel-point-at-bottom-p) ; prevent too late (multi tries)
(vertical-motion -1))
(pixel-scroll-pixel-down (if pixel-resolution-fine-flag
1
(pixel-line-height -1))))))
(defun pixel-bob-at-top-p ()
"Return non-nil if beginning of buffer is at top of window."
(equal (window-start) (point-min)))
(let ((amt (if pixel-resolution-fine-flag
(if (integerp pixel-resolution-fine-flag)
pixel-resolution-fine-flag
(frame-char-height))
(pixel-line-height -1))))
(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
(while (pixel-point-at-bottom-p amt) ; prevent too late (multi tries)
(vertical-motion -1))
(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.
Window must be vertically scrolled by not more than AMT pixels."
(and (equal (window-start) (point-min))
(< (window-vscroll nil t) amt)))
(defun pixel-eob-at-top-p ()
"Return non-nil if end of buffer is at top of window."
(<= (count-lines (window-start) (window-end)) 2)) ; count-screen-lines
(defun pixel-posn-y-at-point ()
"Return y coordinates of point in pixels of current window."
(let ((hscroll0 (window-hscroll))
(y (cdr (posn-x-y (posn-at-point)))))
;; when point is out of scope by hscroll
(unless y
(save-excursion
(set-window-hscroll nil (current-column))
(setq y (cdr (posn-x-y (posn-at-point))))
(set-window-hscroll nil hscroll0)))
y))
(defun pixel-point-at-top-p ()
"Return if point is located at top of a window."
(let* ((y (pixel-posn-y-at-point))
(top-margin y))
(< top-margin (pixel-line-height))))
(defun pixel-point-at-bottom-p ()
"Return if point is located at bottom of a window."
(let* ((y (pixel-posn-y-at-point))
(edges (window-inside-pixel-edges))
"Return y coordinates of point in pixels of current window.
This returns nil when horizontally scrolled."
(when (equal (window-hscroll) 0)
(save-excursion
;; When there's an overlay string on a line, move
;; point by (beginning-of-visual-line).
(beginning-of-visual-line)
;; (- (cadr (pos-visible-in-window-p (point) nil t))
;; (line-pixel-height))
(cdr (posn-x-y (posn-at-point))))))
(defun pixel-point-at-top-p (amt)
"Return if point is located at top of a window on coming scroll of AMT pixels.
When location of point was not obtained, this returns if point is at top
of window."
(let ((y (pixel-posn-y-at-point))
top-margin)
(cond
(y
(setq top-margin y)
(< top-margin amt))
(t
(<= (count-lines (window-start) (point)) 1)))))
(defun pixel-point-at-bottom-p (amt)
"Return if point is located at bottom of window on coming scroll of AMT pixels.
When location of point was not obtained, this returns nil."
(let* ((edges (window-inside-pixel-edges))
(height (- (nth 3 edges) (nth 1 edges))) ; (- bottom top)
(bottom-margin (- height (+ y (line-pixel-height))))) ; bottom margin
(< bottom-margin (pixel-line-height -1)))) ; coming unseen line
(y (pixel-posn-y-at-point))
bottom-margin)
(when y
(setq bottom-margin (- height (+ y (pixel-visual-line-height))))
(< bottom-margin amt)))) ; coming unseen line
(defun pixel-scroll-pixel-up (amt)
"Scroll text of selected windows up AMT pixels.
......@@ -173,8 +194,12 @@ Scope moves upward."
(while (> amt 0)
(let ((vs (window-vscroll nil t)))
(if (equal vs 0)
(pixel-scroll-down-and-set-window-vscroll
(1- (pixel-line-height -1)))
(progn
;; On horizontal scrolling, move cursor.
(when (> (window-hscroll) 0)
(vertical-motion -1))
(pixel-scroll-down-and-set-window-vscroll
(1- (pixel-line-height -1))))
(set-window-vscroll nil (1- vs) t))
(setq amt (1- amt))
(sit-for pixel-wait))))
......@@ -189,11 +214,16 @@ Scope moves downward. This function returns number of pixels
that was scrolled."
(let* ((src (window-vscroll nil t)) ; EXAMPLE (initial) @0 @8 @88
(height (pixel-line-height)) ; 25 25 23
(line (1+ (/ src height))) ; catch up + one line Ä1 Ä1 Ä4
(line (1+ (/ src height))) ; catch up + one line 1 1 4
(dst (* line height)) ; goal @25 @25 @92
(delta (- dst src))) ; pixels to be scrolled 25 17 4
(pixel--whistlestop-pixel-up (1- delta)) ; until one less @24 @24 @91
(scroll-up line) (sit-for pixel-wait) ; scroll 1 pixel @0 @0 @0
(dotimes (ii line)
;; On horizontal scrolling, move cursor.
(when (> (window-hscroll) 0)
(vertical-motion 1))
(scroll-up 1))
(sit-for pixel-wait) ; scroll 1 pixel @0 @0 @0
delta))
(defun pixel--whistlestop-pixel-up (n)
......@@ -211,9 +241,61 @@ unseen line above the first line, respectively, is provided."
(or pos (setq pos (window-start)))
(when (< pos 0)
(setq pos (pixel-point-at-unseen-line)))
(save-excursion
(goto-char pos)
(line-pixel-height))) ; frame-char-height
(let ((vs1 (window-vscroll nil t))
height)
(set-window-vscroll nil 0 t)
(save-excursion
(goto-char pos)
(setq height (pixel-visual-line-height))) ; line-pixel-height, frame-char-height
(set-window-vscroll nil vs1 t)
height))
(defun pixel-visual-line-height ()
"Return height in pixels of text line where cursor is in the selected window."
(let ((pos (pixel-visible-pos-in-window)))
(cond
;; When a char of line is shown, obtain height by
;; (line-pixel-height).
(pos (save-excursion (goto-char pos) (line-pixel-height)))
;; When no char of line is shown but the line is at the top,
;; obtain height by (line-pixel-height). This is based on
;; expected response from display engine. See following
;; discussion.
;; https://lists.gnu.org/archive/html/emacs-devel/2017-10/msg00621.html
((equal (count-lines (window-start) (point)) 1)
(line-pixel-height))
;; No char of line is shown and the line is not at the top,
;; obtain height by (frame-char-height).
(t (frame-char-height)))))
(defun pixel-visible-pos-in-window ()
"Return position shown on text line where cursor is in the selected window.
This will look for positions of point and end-of-visual-line,
then positions from beginning-of-visual-line to
end-of-visual-line. When no char in a line is shown, this
returns nil."
(let* ((beginning-of-visual-line-pos (save-excursion (beginning-of-visual-line) (point)))
(end-of-visual-line-pos (save-excursion (end-of-visual-line) (point)))
(pos-list (number-sequence beginning-of-visual-line-pos end-of-visual-line-pos))
(edges (window-inside-pixel-edges))
(width (- (nth 2 edges) (nth 0 edges)))
posn-x
visible-pos)
;; Optimize list of position to be surveyed.
(push end-of-visual-line-pos pos-list)
(push (point) pos-list)
(delete-dups pos-list)
;; Find out a char with position X that is more than zero and less
;; than width of screen.
(while (and (not visible-pos)
pos-list)
(setq posn-x (car (pos-visible-in-window-p (car pos-list) nil t)))
(if (and posn-x
(<= 0 posn-x)
(< posn-x width))
(setq visible-pos (car pos-list))
(setq pos-list (cdr pos-list))))
visible-pos))
(defun pixel-point-at-unseen-line ()
"Return the character position of line above the selected window.
......
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