In border cases, Aquamacs jumps by a whole page when scrolling via Trackpad.

[treese]

Reported to Aquamacs-bugs. [WT: I have reproduced it with 3.5 on both Catalina with a mouse and Big Sur with a trackpad.]

In border cases, Aquamacs jumps by a whole page when scrolling via Trackpad.

To reproduce:

1. Use the Help menu to run without customizations.
2. Open a file with more lines than the height of the frame. [WT note: shows up in text mode, not in org mode]
3. Use set-variable to set line-spacing to, say, 0.55. Adjust the window size so that the last line visible in the frame fits nicely above the mode line (i.e. no "half lines").
4. Move the cursor to the last visible line of the frame.
5. Scroll up with the Trackpad. Instead of gently scrolling up, the last visible line will immediately become the top line of the frame.

I do not know whether changing line-spacing is relevant for the bug. It makes it easier to adjust the window size. With the default settings it was not possible for me to move the cursor to the last line.

That bug is relevant for me. I have (only slightly) adjusted line-spacing, and with my default face it quite naturally happens that the situation created in 3 above occurs.

In Aquamacs 3.5 GNU Emacs 25.3.50.1 (x86_64-apple-darwin18.7.0, NS appkit-1671.60 Version 10.14.6 (Build 18G6020))
dated 2020-09-04 rev. 9794896 built on cirocco.treese.org
Repository revision: 9794896
Operating System: OS X Version 10.15.7 (Build 19H15)
Configured using:
'configure --with-ns --without-x --without-jpeg --without-rsvg
'CFLAGS=-arch x86_64 -O3 -g -mtune=corei7 -mmacosx-version-min=10.11
-DMAC_OS_X_VERSION_MAX_ALLOWED=101100 -Werror=partial-availability'
'LDFLAGS=-arch x86_64 -O3 -g -mtune=corei7 -mmacosx-version-min=10.11
-DMAC_OS_X_VERSION_MAX_ALLOWED=101100 ''

Configured features:
NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
value of $LANG: en_US.UTF-8
locale-coding-system: utf-8-unix

Major mode: Emacs-Lisp

Minor modes in effect:
savehist-mode: t
smart-frame-positioning-mode: t
save-place-mode: t
aquamacs-autoface-mode: t
recentf-mode: t
osx-key-mode: t
tabbar-mwheel-mode: t
tabbar-mode: t
show-paren-mode: t
delete-selection-mode: t
cua-mode: t
tooltip-mode: t
global-eldoc-mode: t
electric-indent-mode: t
mouse-wheel-mode: t
tool-bar-mode: t
menu-bar-mode: t
file-name-shadow-mode: t
global-font-lock-mode: t
font-lock-mode: t
blink-cursor-mode: t
auto-composition-mode: t
auto-encryption-mode: t
auto-compression-mode: t
column-number-mode: t
line-number-mode: t
transient-mark-mode: t

Recent messages:
one-buffer-one-frame-mode disabled.
Mark set [31 times]
Aquamacs is based on GNU Emacs, a part of the GNU/Linux system. It is Free Software: you can improve and redistribute it under the GNU General Public License, version 3 or later. (C) 2019
Free Software Foundation, and D. Reitter. No Warranty.
You can run the command ‘set-variable’ with M-x se-va RET
Making completion list... [2 times]
is undefined
is undefined
is undefined
is undefined [3 times]

Load-path shadows:
/Applications/Aquamacs.app/Contents/Resources/lisp/aquamacs/edit-modes/auctex hides /Applications/Aquamacs.app/Contents/Resources/lisp/aquamacs/edit-modes/auctex/auctex

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec password-cache epg epg-config gnus-util mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
cursor-sensor parse-time aquamacs-mode-defaults auctex-config server
preview-latex auto-loads tex-site aquamacs-aux savehist
one-buffer-one-frame byte-opt bytecomp byte-compile cl-extra cconv
smart-frame-positioning drews_init color-theme-autoloads view saveplace
visual-line disp-table aquamacs-bug aquamacs-autoface-mode aquamacs-cl
aquamacs-editing recentf tree-widget cus-edit wid-edit osxkeys
emulate-mac-keyboard-mode frame-cmds strings misc-fns thingatpt+
thingatpt frame-fns avoid aquamacs-mac-fontsets fit-frame
aquamacs-frame-setup sendmail rfc2047 rfc2045 ietf-drums mm-util
help-fns help-mode mail-prsvr mail-utils aquamacs-tabbar tabbar-window
cl-macs cl cl-loaddefs cl-lib cus-start cus-load tabbar easy-mmode
aquamacs-site-start cocoa-compatibility mule-util matlab-load smart-dnd
revive aquamacs-redo check-for-updates aquamacs-menu aquamacs
osx_defaults aquamacs-tool-bar gv mac-extra-functions aquamacs-tools
aquamacs-macros time-date advice timezone paren delsel cua-base easymenu
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel ns-win subr-x pcase ucs-normalize term/common-win tool-bar dnd
fontset image regexp-opt fringe tabulated-list newcomment elisp-mode
lisp-mode prog-mode register page menu-bar rfn-eshadow timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core frame
cl-generic cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian
slovak czech european ethiopic indian cyrillic chinese charscript
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote kqueue cocoa ns
multi-tty make-network-process emacs)

Memory information:
((conses 16 288651 8037)
(symbols 48 25827 0)
(miscs 40 109 227)
(strings 32 28280 7618)
(string-bytes 1 960752)
(vectors 16 35974)
(vector-slots 8 687912 10590)
(floats 8 215 203)
(intervals 56 582 0)
(buffers 976 41))

Command line: (/Applications/Aquamacs.app/Contents/MacOS/Aquamacs)

PATH: /opt/local/bin:/opt/local/sbin:/anaconda3/bin:/Users/sturm/bin:/Users/sturm/homebrew/sbin:/Users/sturm/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/TeX/texbin:/usr/local/MacGPG2/bin:/opt/X11/bin:/Library/Apple/usr/bin:/opt/local/bin:/opt/local/sbin:/anaconda3/bin:/Users/sturm/bin:/Users/sturm/homebrew/sbin:/Users/sturm/homebrew/bin:/Users/sturm/reduce-algebra/trunk/bin:/Users/sturm/reduce-algebra/trunk/scripts:/Users/sturm/reduce-algebra/trunk/generic/redlogtest:/Users/sturm/reduce-algebra/trunk/generic/qreduce:/Users/sturm/reduce-algebra/trunk/generic/breduce:/Users/sturm/reduce-algebra/trunk/generic/rlsmt:/Users/sturm/reduce-algebra/trunk/generic/redfront/x86_64-mac_10.15_catalina-darwin19.6.0/redfront:/Users/sturm/Dynamic/Maple/src/Biomodels/Tools:/Users/sturm/Dynamic/sage:/Library/Frameworks/Maple.framework/Versions/2020/bin:/Users/sturm/Dynamic/src/qepcad/qesource/bin:/Users/sturm/Dynamic/src/qepcad/qesource/../simplify:/Users/sturm/Dynamic/src/z3/bin:/Users/sturm/homebrew/opt/go/libexec/bin:/Users/sturm/Documents/go/bin:/usr/texbin:/usr/local/texlive/2020/bin:/usr/local/texlive/2019/bin:/usr/local/texlive/2018/bin:/Users/sturm/reduce-algebra/trunk/bin:/Users/sturm/reduce-algebra/trunk/scripts:/Users/sturm/reduce-algebra/trunk/generic/redlogtest:/Users/sturm/reduce-algebra/trunk/generic/qreduce:/Users/sturm/reduce-algebra/trunk/generic/breduce:/Users/sturm/reduce-algebra/trunk/generic/rlsmt:/Users/sturm/reduce-algebra/trunk/generic/redfront/x86_64-mac_10.15_catalina-darwin19.6.0/redfront:/Users/sturm/Dynamic/Maple/src/Biomodels/Tools:/Users/sturm/Dynamic/sage:/Library/Frameworks/Maple.framework/Versions/2020/bin:/Users/sturm/Dynamic/src/qepcad/qesource/bin:/Users/sturm/Dynamic/src/qepcad/qesource/../simplify:/Users/sturm/Dynamic/src/z3/bin:/Users/sturm/homebrew/opt/go/libexec/bin:/Users/sturm/Documents/go/bin:/opt/local/bin:/opt/local/sbin:/anaconda3/bin:/Users/sturm/bin:/Users/sturm/homebrew/sbin:/Users/sturm/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/TeX/texbin:/usr/local/MacGPG2/bin:/opt/X11/bin:/Library/Apple/usr/bin:/Users/sturm/reduce-algebra/trunk/bin:/Users/sturm/reduce-algebra/trunk/scripts:/Users/sturm/reduce-algebra/trunk/generic/redlogtest:/Users/sturm/reduce-algebra/trunk/generic/qreduce:/Users/sturm/reduce-algebra/trunk/generic/breduce:/Users/sturm/reduce-algebra/trunk/generic/rlsmt:/Users/sturm/reduce-algebra/trunk/generic/redfront/x86_64-mac_10.15_catalina-darwin19.6.0/redfront:/Users/sturm/Dynamic/Maple/src/Biomodels/Tools:/Users/sturm/Dynamic/sage:/Library/Frameworks/Maple.framework/Versions/2020/bin:/Users/sturm/Dynamic/src/qepcad/qesource/bin:/Users/sturm/Dynamic/src/qepcad/qesource/../simplify:/Users/sturm/Dynamic/src/z3/bin:/Users/sturm/homebrew/opt/go/libexec/bin:/Users/sturm/Documents/go/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/texbin:/Library/TeX/texbin:/usr/local/texlive/2020/bin:/usr/local/texlive/2019/bin:/usr/local/texlive/2018/bin:/usr/texbin:/Library/TeX/texbin:/usr/local/texlive/2020/bin:/usr/local/texlive/2019/bin:/usr/local/texlive/2018/bin

exec-path: (/opt/local/bin /opt/local/sbin /anaconda3/bin /Users/sturm/bin /Users/sturm/homebrew/sbin /Users/sturm/homebrew/bin /usr/local/bin /usr/bin /bin /usr/sbin /sbin /Library/TeX/texbin /usr/local/MacGPG2/bin /opt/X11/bin /Library/Apple/usr/bin /opt/local/bin /opt/local/sbin /anaconda3/bin /Users/sturm/bin /Users/sturm/homebrew/sbin /Users/sturm/homebrew/bin /Users/sturm/reduce-algebra/trunk/bin /Users/sturm/reduce-algebra/trunk/scripts /Users/sturm/reduce-algebra/trunk/generic/redlogtest /Users/sturm/reduce-algebra/trunk/generic/qreduce /Users/sturm/reduce-algebra/trunk/generic/breduce /Users/sturm/reduce-algebra/trunk/generic/rlsmt /Users/sturm/reduce-algebra/trunk/generic/redfront/x86_64-mac_10.15_catalina-darwin19.6.0/redfront /Users/sturm/Dynamic/Maple/src/Biomodels/Tools /Users/sturm/Dynamic/sage /Library/Frameworks/Maple.framework/Versions/2020/bin /Users/sturm/Dynamic/src/qepcad/qesource/bin /Users/sturm/Dynamic/src/qepcad/qesource/../simplify /Users/sturm/Dynamic/src/z3/bin /Users/sturm/homebrew/opt/go/libexec/bin /Users/sturm/Documents/go/bin /usr/texbin /usr/local/texlive/2020/bin /usr/local/texlive/2019/bin /usr/local/texlive/2018/bin /Users/sturm/reduce-algebra/trunk/bin /Users/sturm/reduce-algebra/trunk/scripts /Users/sturm/reduce-algebra/trunk/generic/redlogtest /Users/sturm/reduce-algebra/trunk/generic/qreduce /Users/sturm/reduce-algebra/trunk/generic/breduce /Users/sturm/reduce-algebra/trunk/generic/rlsmt /Users/sturm/reduce-algebra/trunk/generic/redfront/x86_64-mac_10.15_catalina-darwin19.6.0/redfront /Users/sturm/Dynamic/Maple/src/Biomodels/Tools /Users/sturm/Dynamic/sage /Library/Frameworks/Maple.framework/Versions/2020/bin /Users/sturm/Dynamic/src/qepcad/qesource/bin /Users/sturm/Dynamic/src/qepcad/qesource/../simplify /Users/sturm/Dynamic/src/z3/bin /Users/sturm/homebrew/opt/go/libexec/bin /Users/sturm/Documents/go/bin /opt/local/bin /opt/local/sbin /anaconda3/bin /Users/sturm/bin /Users/sturm/homebrew/sbin /Users/sturm/homebrew/bin /usr/local/bin /usr/bin /bin /usr/sbin /sbin /Library/TeX/texbin /usr/local/MacGPG2/bin /opt/X11/bin /Library/Apple/usr/bin /Users/sturm/reduce-algebra/trunk/bin /Users/sturm/reduce-algebra/trunk/scripts /Users/sturm/reduce-algebra/trunk/generic/redlogtest /Users/sturm/reduce-algebra/trunk/generic/qreduce /Users/sturm/reduce-algebra/trunk/generic/breduce /Users/sturm/reduce-algebra/trunk/generic/rlsmt /Users/sturm/reduce-algebra/trunk/generic/redfront/x86_64-mac_10.15_catalina-darwin19.6.0/redfront /Users/sturm/Dynamic/Maple/src/Biomodels/Tools /Users/sturm/Dynamic/sage /Library/Frameworks/Maple.framework/Versions/2020/bin /Users/sturm/Dynamic/src/qepcad/qesource/bin /Users/sturm/Dynamic/src/qepcad/qesource/../simplify /Users/sturm/Dynamic/src/z3/bin /Users/sturm/homebrew/opt/go/libexec/bin /Users/sturm/Documents/go/bin /usr/bin /bin /usr/sbin /sbin /usr/texbin /Library/TeX/texbin /usr/local/texlive/2020/bin /usr/local/texlive/2019/bin /usr/local/texlive/2018/bin /Applications/Aquamacs.app/Contents/MacOS/libexec /Applications/Aquamacs.app/Contents/MacOS/bin)

[treese]

At this point I can't reproduce it on Big Sur with Aquamacs 3.5 or with the development version.