├── NEWS.org ├── README.org ├── ultra-scroll.el ├── README.md └── LICENSE /NEWS.org: -------------------------------------------------------------------------------- 1 | #+title: ultra-scroll - Changelog 2 | #+author: J.D. Smith 3 | #+language: en 4 | 5 | * v0.5.0 (2025-12-15) 6 | 7 | - Introduced ~ultra-scroll-preserve-column~. If this option is enabled, ~ultra-scroll~ will try to preserve column position of point across scrolls. 8 | 9 | * v0.4.2 (2025-07-14) 10 | 11 | - Released on MELPA. 12 | 13 | * 0.4.1 (2025-06-09) 14 | 15 | - Work around redisplay bugs when the cursor is partially visible, which can lead to ~redisplay~ slowdowns of 150-500x. 16 | - Guard against ~posn-x-y~ returning ~nil~ on discovered position. 17 | 18 | * v0.4 (2025-05-05) 19 | 20 | - Support ~scroll-conservatively~ < 100, altering the value temporarily during scroll. Note that ~scroll-margin~ = 0 is still required. 21 | - Do not rely on ~:phase~ information from the mouse events, since only certain hardware on mac provides it. 22 | 23 | * v0.3.5 (2025-04-17) 24 | 25 | - Fix freeze when scrolling down /very/ short windows like few-line child frame tooltips (#30). 26 | 27 | * v0.3.4 (2025-04-02) 28 | 29 | - Correctly handle very large scroll-down deltas, which may occur for ultra-fast mice wheels with short windows. 30 | 31 | * v0.3.3 (2025-03-11) 32 | 33 | - Do not move point to ~point-min/max~ when scroll reaches buffer beginning/end, unless the cursor has been hidden. 34 | 35 | * v0.3.2 (2025-01-26) 36 | 37 | - Re-enable ~make-cursor-line-fully-visible~, which recent versions of ~pixel-scroll-precision-mode~ disable. 38 | 39 | * v0.3.1 (2025-01-18) 40 | 41 | - Add ~ultra-scroll-hide-functions~ hook, to support disabling/re-enabling arbitrary modes or calling other functions when scrolling starts/stops. 42 | - Doc improvements. 43 | 44 | * v0.3 (2025-01-12) 45 | 46 | - Hide cursor (and ~hl-line~) during scrolls by default. See ~ultra-scroll-hide-cursor~. Thanks to @minad; see #15. 47 | - Put custom variables in group ~scrolling~. 48 | - Improve ~ultra-scroll-check~: 49 | + Correctly interrogate a group of wheel events to determine if they are "real" or fake. Some Linux systems report ~PIXEL-DELTA~'s with fixed values (a line height), which effectively reverts ~ultra-scroll~ to line-by-line scrolling. 50 | + Guard against up+down scrolling falsely indicating diverse scrolls pixel offsets. 51 | + Report event timing (how fast /is/ your mouse)? 52 | - Check for ~--with-xinput2~ on Linux and warning if not found (needed for pixel scrolling; see #14). 53 | - Enable ~pixel-scroll-precision-mode~ directly, rather than just re-using its keymap. This allows commands like ~vertico-mouse~ to turn off ~ultra-scroll~ indirectly by disabling ~pixel-scroll-precision-mode~. 54 | 55 | * v0.2.1 (2025-01-09) 56 | 57 | - Introduce ~ultra-scroll-check~, to provide a means for users to check their wheel event stream to determine the character of their pixel delta scroll data. 58 | 59 | * v0.2 (2025-01-08) 60 | 61 | - Support all (compatible) builds and hardware using the ~PIXEL-DELTA~ data in wheel events, continuing to support ~emacs-mac~ style wheel events too. 62 | - Rename to ~ultra-scroll~. 63 | - Update documentation. 64 | 65 | * v0.1 (2024-04-06) 66 | 67 | - Reduce garbage collection during scroll with new configuration options. 68 | - Many documentation improvements. 69 | 70 | * v0.0.1 (2023-11-28) 71 | 72 | - Introduced, supporting ~emacs-mac~ wheel events. 73 | -------------------------------------------------------------------------------- /README.org: -------------------------------------------------------------------------------- 1 | * ultra-scroll: scroll emacs like lightning ⚡🖱️⚡ 2 | #+html: MELPA 3 | 4 | ~ultra-scroll~[fn:1] is a smooth-scrolling package for emacs, with native support for standard builds as well as [[https://bitbucket.org/mituharu/emacs-mac][emacs-mac]]. It provides highly optimized, pixel-precise smooth scrolling which can readily keep up with the /very/ high event rates of modern track-pads and high-precision wheel mice. 5 | 6 | You move your fingers, the page responds, /instantly/: 7 | 8 | [[https://github-production-user-asset-6210df.s3.amazonaws.com/93749/290018933-ed5cf414-eab5-4ba8-b077-30cac0c5ace0.mov]] 9 | 10 | Importantly, ~ultra-scroll~ can cleanly /scroll right across/ tall images and other jumbo lines -- a perennial problem with scrolling packages to date. As a bonus, it enables relatively smooth scrolling even with dumb third party mice. 11 | 12 | Note, the ~previous-buffer~ animation above is from two-finger track-pad swiping, and is an [[https://github.com/jdtsmith/emacs-mac][emacs-mac]] exclusive. 13 | 14 | #+begin_note 15 | *Do you need this?* 16 | 17 | If you don't scroll with a high-speed device (modern mouse or track-pad), no. If you do, but aren't sure, here's a good test to try: 18 | 19 | Open a heavy emacs buffer full screen on your largest monitor. While scrolling smoothly such that lines would move across your window's full height in about 5 seconds, /can you easily read the text you see/, without stopping, in both directions? Now, try this exercise again with your browser -- I bet it's /very/ readable there. Shouldn't emacs be like this? 20 | 21 | In addition, if you scroll buffers with tall images visible, this is also a good reason to give ~ultra-scroll~ a try. 22 | #+end_note 23 | 24 | ** Release Information 25 | 26 | See the [[./NEWS.org][NEWS]]. 27 | 28 | ** Compatibility 29 | 30 | ~ultra-scroll~ should work across all systems that provide pixel-level scrolling information for your input hardware. If you don't think ~ultra-scroll~ is working for you, run ~M-x ultra-scroll-check~, and follow the directions. If it reports: 31 | 32 | - *Normal pixel scroll data*: you are good to go, everything is working. 33 | - *No real pixel scroll data*: your system and hardware are delivering pixel scrolling data, but they /never change/ (test again to be sure). This is equivalent to line-by-line scrolling. ~ultra-scroll~ will work fine for you, but /without/ any smooth scrolling. You can use it for the improved large image scrolling behavior, or see below for another option. 34 | - The /error/ *Malformed wheel event*: your system does not deliver /any/ pixel-level scroll data. Either upgrade your hardware/system to a known working config (see [[../../issues/18][this issue]] for user experiences), or see below. 35 | 36 | For systems which do /not/ provide normal pixel scroll data, you can try the built-in ~pixel-scroll-precision-mode~ with ~pixel-scroll-precision-interpolate-mice~ (which "creates" events by interpolation) instead. 37 | 38 | #+begin_important 39 | *Your Help Needed!* While ~ultra-scroll~ works out of the box for most people, it's impossible to test all combinations of systems and hardware, so please take a moment to [[../../discussions][report your smooth-scrolling experiences]] for the benefit of others. 40 | #+end_important 41 | 42 | ** Installation 43 | 44 | ~ultra-scroll~ is in MELPA. Starting from Emacs 30, you can also use the new ~:vc~ keyword to download directly from this repository. Configuration is then simple: 45 | 46 | #+begin_src emacs-lisp 47 | (use-package ultra-scroll 48 | ;:vc (:url "https://github.com/jdtsmith/ultra-scroll") ; if desired (emacs>=v30) 49 | :init 50 | (setq scroll-conservatively 3 ; or whatever value you prefer, since v0.4 51 | scroll-margin 0) ; important: scroll-margin>0 not yet supported 52 | :config 53 | (ultra-scroll-mode 1)) 54 | #+end_src 55 | 56 | ** Usage 57 | Just start scrolling :). 58 | 59 | #+begin_tip 60 | For best performance, use a build with native-compilation (see [[#Speed][Speed]]). 61 | #+end_tip 62 | 63 | ** Configuration 64 | 65 | There is little to no configuration. 66 | 67 | *** Altering dumb mice behavior on emacs-mac 68 | 69 | If desired for use with dumb mice on ~emacs-mac~, the variable ~ultra-scroll-mac-multiplier~ can be set to a number smaller or larger than ~1.0~ to decrease/increase mouse-wheel scrolling speed. Note that many fancier wheeled mice have drivers that /simulate/ track-pads, so this variable will have no effect on them. For these, and for track-pads generally, scrolling speed should be configured in system settings. 70 | 71 | #+begin_note 72 | Only certain systems provide real variable pixel scroll offset data (~PIXEL-DELTA~) for older/wheeled ("dumb") mice. Use ~M-x ultra-scroll-check~ to see if yours does. If not, it's recommended to upgrade hardware, or stick with ~pixel-scroll-precision-mode~. 73 | #+end_note 74 | 75 | *** Mitigating garbage collection pauses 76 | 77 | To reduce the likelihood of garbage collection during scroll, which can introduce slight pauses, the value of ~gc-cons-percentage~ is temporarily increased, and reset during idle time. The defaults should work well for most situations, but if necessary, can be configured using ~ultra-scroll-gc-percentage~ and ~ultra-scroll-gc-idle-time~. 78 | 79 | *** Hiding cursor, disabling other modes during scroll, and restoring column 80 | 81 | By default, ~ultra-scroll~ hides the cursor (and a ~hl-line~ if active) once it reaches the window edge, to prevent "bouncing cursor" behavior. This can be disabled, or the time delay to restore the cursor set, with ~ultra-scroll-hide-cursor~. 82 | 83 | In addition to the cursor, it is sometimes useful to temporarily disable other modes during the scroll. The special hook variable ~ultra-scroll-hide-functions~ can be used for this, e.g.: 84 | 85 | #+begin_src emacs-lisp 86 | (add-hook 'ultra-scroll-hide-functions 'hl-line-mode) 87 | #+end_src 88 | 89 | By default, the hook contains ~hl-line-mode~. 90 | 91 | You can optionally enable restoring the visual column position after the scroll completes; see ~ultra-scroll-preserve-column~. 92 | 93 | ** ~pixel-scroll-precision~ comparison and interoperability 94 | 95 | Emacs has a built-in smooth scrolling system called ~pixel-scroll-precision-mode~. In fact, by design, ~ultra-scroll~ /activates/ the builtin ~pixel-scroll-precision-mode~, remapping its scrolling function with its own. The latter also has the capability of /faking/ smooth scrolling using interpolation. It can do this for non-mouse movements, like ~scroll-up/down-command~ (usually on =PgUp= / =PgDown=). To use these additional capabilities, simply set the relevant variables, like ~pixel-scroll-precision-interpolate-page~, and they should "just work". 96 | 97 | Note that ~ultra-scroll~ disables ~pixel-scroll-precision-use-momentum~, since it may not handle tall image scrolling well. Some systems (MacOS) get momentum scrolling "for free" from the OS, independent of this setting. If you experiment with re-enabling ~pixel-scroll-precision-use-momentum~ on other systems like Linux, please open an issue to report your findings. 98 | 99 | #+begin_warning 100 | ~ultra-scroll~ activates ~pixel-scroll-precision-mode~ by side effect. If you are experimenting with both modes during a single session, always disable ~ultra-scroll-mode~ first and then re-enable ~pixel-scroll-precision-mode~. 101 | #+end_warning 102 | 103 | *** A comparison between ultra-scroll and pixel-scroll-precision 104 | 105 | See also [[#how-does-this-compare-to-the-built-in-smooth-scrolling][this question]]. 106 | 107 | ~pixel-scroll-precision-mode~: 108 | 109 | - Supports smooth scrolling even on systems which do /not/ provide pixel scroll data, using interpolation (see ~pixel-scroll-precision-interpolate-mice~). 110 | - Can simulate a "momentum" scrolling phase on systems which do not provide this capability (see ~pixel-scroll-precision-use-momentum~). 111 | - Has occasional issues scrolling tall images. 112 | 113 | ~ultra-scroll~: 114 | 115 | - Fully supports /only/ those system and hardware combos that deliver /real/ pixel scroll data (see [[#Compatibility][Compatibility]]). 116 | - Provides "momentum" scrolling only on systems which provide this themselves. 117 | - Is somewhat faster (see [[#Speed][Speed]]). 118 | - Handles tall image scrolling without issue. 119 | 120 | ** Related packages and functionality 121 | 122 | - emacs-mac's own builtin ~mac-mwheel-scroll~ :: This venerable code was introduced with [[https://bitbucket.org/mituharu/emacs-mac/][emacs-mac]] more than a decade ago, and was the first to provide smooth scrolling in any version of emacs. 123 | - ~pixel-scroll-precision-mode~ :: A fast pixel scrolling by Po Lu, built in to Emacs as of v29.1 (see =pixel-scroll.el=). Does not support ~emacs-mac~. ~ultra-scroll~ was initially based on its design, but many design elements have changed. 124 | - ~pixel-scroll-mode~ :: A simpler line-by-line pixel scrolling mode, also found in the file =pixel-scroll.el=. 125 | - [[https://github.com/io12/good-scroll.el][good-scroll]] :: An update to ~pixel-scroll-mode~ with variable speed. 126 | - [[https://github.com/zk-phi/sublimity][sublimity]] :: Includes smooth scrolling based on sublime editor. 127 | 128 | ** Questions 129 | 130 | *** What was the motivation behind this? 131 | 132 | Picture it: a fast new laptop and 5K monitor with a large heavy-duty, full-screen buffer in ~python-ts-mode~. Scrolling line-by-line with a decent mouse is mostly OK, but smooth pixel scrolling with the track-pad is just... /painful/. Repeated attempts to rationalize this fail, especially because it's notably worse in one direction than the other. Scrolling Emacs feels like moving through (light) molasses. /No bueno/. 133 | 134 | Checking into it, the smooth scroll event callback takes 15-20ms scrolling in one direction, and 3--5x longer in the other. This performance is perfectly fine for normal mice which deliver a few scrolling events a second. /But track-pad and fancy mouse scroll events are arriving every 10ms, or less/! The code just couldn't keep up. Hence: molasses. 135 | 136 | I also wanted to be able to scroll through image-rich documents without worrying about jumpy/loopy scrolling behavior. And my extra dumb mouse didn't work well either: small scrolls did nothing: you'd have scroll pretty aggressively to get any movement at all. 137 | 138 | How hard could it be to fix this? And the adventure began... 139 | 140 | *** Why was this initially for emacs-mac only? 141 | 142 | This packaged used to be called ~ultra-scroll-mac~. The ~emacs-mac~ port of emacs exposes pixel-level scrolling event stream of Mac track-pads (and other fancy mice) in a distinct way, which is not supported by ~pixel-scroll-precision-mode~. And unfortunately the default smooth-scrolling library included in ~emacs-mac~ is quite low performance (see above). 143 | 144 | *** How does this compare to the built-in smooth scrolling? 145 | 146 | On the ~emacs-mac~ build, there is no comparison, because ~pixel-scroll-precision-mode~ doesn't work there. On other builds, they are fairly comparable. Compared to ~pixel-scroll-precision-mode~, ~ultra-scroll~ obviously works with ~emacs-mac~, but is also even [[#Speed][faster]], and can cleanly scroll past images taller than the window. 147 | 148 | In addition to fast scrolling, the built-in ~pixel-scroll-precision-mode~ (new in Emacs v29.1) can simulate a /feature-complete track-pad driver/ in elisp for older mice or systems which do not supply pixel scroll information. This comes complete with elisp-based /scroll interpolation/, a timer-based /momentum/ phase, etc. 149 | 150 | *** Why are there so many smooth scrolling modes? Why is this so hard? It's just /scrolling/... 151 | 152 | Emacs was designed long before mice were common, not to mention modern high-resolution track-pads and mice which send rapid micro-updates ("move up one pixel!") 60-120 times per second. Unlike other programs, Emacs /insists/ on keeping the cursor (point) visible at all times. Deep in its re-display code, Emacs tracks where point is, and works diligently to ensure it never falls outside the visible window. It does this /not/ by moving point itself (that's the user's job), but by moving the /window/ (visible range of lines) surrounding point. 153 | 154 | Once you are used to this behavior, it's actually pretty nice for navigating with =C-n= / =C-p= and friends. But for smooth scrolling with a track-pad or mouse, it is /very problematic/ -- nothing screams "janky scrolling" like the window lurching back or forth half a page during a scroll. Or worse: getting caught in an endless loop of scroll-in-one-direction/jump-back-in-the-other. 155 | 156 | So what should be done? The elisp info manual (~Textual Scrolling~ / ~set-window-start~) helpfully mentions: 157 | 158 | #+begin_quote 159 | ...for reliable results Lisp programs that call this function should 160 | always move point to be inside the window whose display starts at 161 | POSITION. 162 | #+end_quote 163 | 164 | Which is all well and good, but /where/ do you find such a point, in advance, safely /inside the window/? Often this isn't terribly hard, but there is one common case where this admonition falls comically flat: scrolling past an image or other content which is /taller than the window/ -- what I call *jumbo lines*. Where can I place point /inside the window/ when a jumbo line occupies the entire window height? 165 | 166 | As a result of these types of difficulties, pixel scrolling codes and packages are often quite involved, with much of the logic boiling down to a stalwart and increasingly heroic pile of interwoven attempts to /keep the damn point on screen/ and prevent juddering and looping as you scroll. 167 | 168 | *** What should I know about developing scrolling modes for Emacs? 169 | 170 | For posterity, some things I discovered in my own mostly-victorious battle against unwanted re-centering during smooth scroll, including across jumbo lines: 171 | 172 | - ~scroll-conservatively=101~ is very helpful, since with this Emacs will "scroll just enough text to bring point into view, even if you move far away". It does not defeat re-centering, but makes it... more manageable. 173 | - You cannot let-bind ~scroll-conservatively~ for effect, as it comes into play only on re-display (after your event handler returns). But you /can/ set it temporarily and restore it in idle time without ill effect. 174 | - ~scroll-margin>0~ is a no-no. This setting always moves point at least that many lines from the window boundaries, which, unless you can reliably place point there during the scroll (even in the presence of jumbo lines; see below), will cause loop-back. See #3. 175 | - Virtual Scroll: 176 | + ~vscroll~ -- a virtual rendered scrolling window hiding /below/ the current window -- is key to smooth scrolling, and altering ~vscroll~ to move the view-port is incredibly fast. 177 | + There is plenty of ~vscroll~ room available, including the entirety of any tall lines (as for displayed images) in view. 178 | + ~vscroll~ can sometimes place the point off the visible window (I know, sacrilege), but more often triggers re-centering. 179 | - Scrolling asymmetry: 180 | + Sadly ~vscroll~ is purely /one-sided/: you can only access a ~vscroll~ area /beneath/ the current window view; /there is no negative ~vscroll~/. 181 | + Unlike ~window-start~, ~window-end~ does not get updated promptly between re-displays and cannot always be trusted. Computing it is expensive, so should be avoided during re-display. 182 | + For these two reasons, smooth scrolling up and scrolling down are /not symmetric/ with each other, and will likely never be. You need different approaches for each. 183 | + If the two approaches for scrolling up and down perform quite differently, the user will definitely feel this difference. 184 | - For avoiding re-centering, naive movement doesn't work well. You need to learn the basic layout of lines on the window /before re-display/ has occurred. 185 | - The "usable window height" deducts any header and the old-fashioned tab-bar, but /not/ the tab-bar-mode bar. 186 | - Jumbo lines (lines taller than the window's height): 187 | + Scrolling towards buffer end: 188 | * When scrolling past jumbo lines towards the buffer's end (with ~vscroll~), simply keep /point on the jumbo line/ until it /fully disappears/ from view. As a special case, Emacs will not re-center when this happens. 189 | * This is /not/ true for lines that are shorter than the usable window height (even if they are tall). In this case, you must /avoid/ placing point on any line which falls partially out of view. 190 | + Scrolling towards buffer start: 191 | * When scrolling up past jumbo lines towards the buffer's start using ~set-window-start~ (lines of content move down), you must keep point on the jumbo, but /only until it clears the top of the window area/ (even by one pixel). 192 | * After this, you must move the point to the line above it. 193 | * In some cases (depending on truncation/visual-line-mode/etc.), this movement must occur from a position beyond the first full height object (which may not be at the line's start). E.g. one before the visual line end. 194 | - ~pos-visible-in-window~ doesn't always give correct results near the window boundaries. Better to use the first line at the window's top or directly identify the final line (both via ~pos-at-x-y~) and adjust from there. 195 | 196 | So all in all, it's quite complicated to get something that works as you'd hope. The cutting room floor is littered with literally dozens of almost-but-not-quite-working versions of ~ultra-scroll~. I'm sure there are many more corner cases, but the current design gets most things right in my usage. 197 | 198 | ** Display bugs 199 | ~ultra-scroll~ exercises some rare corner cases of Emacs' redisplay logic, and as a result has revealed and helped fix a number of display bugs. These bugs lead to behaviors like slightly staccato scrolling in buffers with diverse line heights (e.g. inline images). If you think you have found a display bug, open an issue to discuss. 200 | 201 | - A [[https://debbugs.gnu.org/cgi/bugreport.cgi?bug=67533][display bug]] with inline images that cause them to sometimes misreport pixel measurements and positions has been fixed in master as of Dec, 2023, so scrolling with lots of inline images should be much smoother starting from Emacs v30. 202 | - As of June, 2025, another [[https://debbugs.gnu.org/cgi/bugreport.cgi?bug=67604][display bug]] related to line-skipping of visual (i.e. word) wrapped lines with inline images at line start has been fixed (for Emacs v31). This caused additional (but even rarer) "hitches" in smooth scrolling in buffers with numerous inline images. 203 | - Another display bug which leads to scrolling (and general UI) slowdown in some edge-case situations with ~make-cursor-line-fully-visible=t~ was also [[../../issues/32][found]] and [[https://debbugs.gnu.org/cgi/bugreport.cgi?bug=78766][fixed]] in June, 2025. This fix will be included with Emacs v31. 204 | 205 | ** Speed 206 | :PROPERTIES: 207 | :ID: E5E845A0-E4EE-4F73-9840-C98040007537 208 | :END: 209 | 210 | I often wonder how many people who claim "emacs is laggy" form that impression from scrolling. Scrolling at 60-120Hz or faster with modern mice and track-pads puts a lot of stress on systems, and is often the first place lag appears. So ~ultra-scroll~ is fast /by design/. I made some observations about its speed using ~ELP~ to measure the average call duration of individual scroll functions (~ultra-scroll-up/down~) with various buffer and window sizes[fn:2]. 211 | 212 | *** Take-aways 213 | 214 | 1. Very large window sizes and buffers with "extra" processing going on, like treesitter, LSP modes, elaborate font-locking, tons of overlays, etc. can slow down scrolling. 215 | 2. If the scroll command does its work in <10ms, you do not notice it. You can definitely start feeling it when scroll commands take more than 15ms. 216 | 3. The underlying scroll primitives need to leave some overhead in time, so that all the other emacs commands that occur when new content is brought into view (font-lock) can run without causing scroll lag, for all your different modes. *Faster is better*: 3ms or less[fn:2] in a light buffer would be /ideal/. 217 | 4. Building ~--with-native-comp~ is /essential/ for ultra-smooth scrolling. It increases the speed of each individual scroll command by *>3x*, which is important since these commands are called so frequently. 218 | 5. On the exact same build (NS, v29.4, with native-comp), ~ultra-scroll~ is about *40% faster* than ~pixel-scroll-precision-mode~. Except on slower machines, or in very heavy buffers and/or on large window sizes where your performance is right on the edge, this shouldn't be too noticeable. 219 | 6. On the same system (an M2 mac), ~ultra-scroll~ on ~emacs-mac~ is 10-15% faster than it is on NS builds like ~emacs-plus~. Very likely not noticeable. 220 | 7. The mode-line gets updated /very often/ during smooth scrolls (and in general), and poorly written fancy modeline add-ons are a common source of slow-down. Good modeline modes will /rate-limit/ their updates behind timers and/or cache results in local/global variables. If your scrolling (or any other aspect of Emacs) "lags", try ~(setq mode-line-format "NADA")~ and see if that solves it. If so, suspect your fancy modeline. 221 | 222 | * Footnotes 223 | [fn:1] Formerly ~ultra-scroll-mac~. 224 | 225 | [fn:2] To try this yourself, ~M-x elp-instrument-function~ on both ~ultra-scroll-up/down~, scroll around (both directions) in a big buffer with a large window, then ~M-x elp-results~. The last column gives average time in seconds. Less than 0.003s (i.e. 3ms) is ideal, 8ms is still perfectly usable, 15ms you'll feel a bit, 50ms will be very frustrating. ~scroll-down~ is always faster than ~scroll-up~ due to an asymmetry in Emacs' ~vscroll~ buffer. 226 | -------------------------------------------------------------------------------- /ultra-scroll.el: -------------------------------------------------------------------------------- 1 | ;;; ultra-scroll.el --- Fast and smooth scrolling -*- lexical-binding: t; -*- 2 | ;; Copyright (C) 2023-2025 J.D. Smith 3 | 4 | ;; Author: J.D. Smith 5 | ;; URL: https://github.com/jdtsmith/ultra-scroll 6 | ;; Package-Requires: ((emacs "29.1")) 7 | ;; Version: 0.5.0 8 | ;; Keywords: convenience 9 | ;; Prefix: ultra-scroll 10 | ;; Separator: - 11 | 12 | ;; ultra-scroll is free software: you can redistribute it and/or 13 | ;; modify it under the terms of the GNU General Public License as 14 | ;; published by the Free Software Foundation, either version 3 of the 15 | ;; License, or (at your option) any later version. 16 | 17 | ;; ultra-scroll is distributed in the hope that it will be useful, but 18 | ;; WITHOUT ANY WARRANTY; without even the implied warranty of 19 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 20 | ;; General Public License for more details. 21 | 22 | ;; You should have received a copy of the GNU General Public License 23 | ;; along with this program. If not, see . 24 | 25 | ;;; Commentary: 26 | ;; ultra-scroll enables fast, smooth, jump-free scrolling for Emacs on 27 | ;; all builds that support varying pixel scroll delta event data. On 28 | ;; emacs-mac it retains the swipe-to-scroll and pinch-out for tab 29 | ;; overview capabilities of that port. On all ports, it can scroll 30 | ;; past images or other content taller than the window without issue. 31 | ;; 32 | ;; The strongly recommended scroll settings are: 33 | ;; 34 | ;; scroll-margin=0 35 | ;; 36 | ;; See also `pixel-scroll-precision-mode' in pixel-scroll.el. 37 | 38 | ;;; Code: 39 | ;;;; Requires 40 | (require 'mac-win nil 'noerror) 41 | (require 'pixel-scroll) 42 | (require 'mwheel) 43 | (require 'timer) 44 | 45 | ;;;; Customize 46 | (defcustom ultra-scroll-mac-multiplier 1. 47 | "Multiplier for smooth scroll step for wheeled mice on emacs-mac. 48 | This multiplies the fractional delta-y values generated by 49 | regular mouse wheels by the value returned by 50 | `frame-char-height'. Increase it to increase scrolling speed on 51 | such mice. Note that some mice drivers emulate trackpads, and so 52 | will not be affected by this setting. Adjust scrolling speed 53 | directly with those drivers instead." 54 | :group 'scrolling 55 | :type 'float) 56 | 57 | (defcustom ultra-scroll-gc-percentage 0.67 58 | "Value to temporarily set `gc-cons-percentage'. 59 | This is set on initial scrolling, and restored during idle 60 | time (see `ultra-scroll-idle-time')." 61 | :type '(choice (const :value nil :tag "Disable") (float :tag "Fraction")) 62 | :group 'scrolling) 63 | 64 | (defcustom ultra-scroll-idle-time 0.5 65 | "Idle time in sec after which to restore GC and scroll parameters. 66 | GC percentage is restored only if `ultra-scroll-gc-percentage' is non-nil." 67 | :type 'float 68 | :group 'scrolling) 69 | (make-obsolete-variable 'ultra-scroll-gc-idle-time 'ultra-scroll-idle-time "0.4") 70 | 71 | (defcustom ultra-scroll-hide-cursor 0.25 72 | "Hide the cursor during scrolls after it reaches the window bounds. 73 | Time in sec after which to restore the cursor. Set to nil to 74 | disable cursor hiding. Note that, if this is active, any 75 | additional functions or modes specified in 76 | `ultra-scroll-hide-functions' are also called." 77 | :type '(choice (const :value nil :tag "Disable") (float :tag "Time (s)")) 78 | :group 'scrolling) 79 | 80 | (defcustom ultra-scroll-preserve-column nil 81 | "Restore the column position after scroll completes. 82 | Only takes effect if `ultra-scroll-hide-cursor' is non-nil." 83 | :type 'boolean 84 | :group 'scrolling) 85 | 86 | (defcustom ultra-scroll-hide-functions '(hl-line-mode) 87 | "Functions to call when scrolling begins and ends. 88 | This hook can also be used to specify modes to disable 89 | temporarily during scrolling, and is only active if 90 | `ultra-scroll-hide-cursor' is non-nil. Each function will be 91 | called with a single argument: -1 when scrolling starts, and 1 92 | when it ends (see `ultra-scroll-hide-cursor' for the timing of 93 | this). 94 | 95 | If a member of this hook is a symbol ending in \"-mode\", the 96 | associated mode function is only called if the symbol is bound 97 | and non-nil. This is to facilitate including mode functions 98 | directly, toggling them only if they are already active." 99 | :type 'hook 100 | :group 'scrolling) 101 | 102 | ;;;; Cursor Hiding 103 | (defvar-local ultra-scroll--hide-cursor-timer nil) 104 | (defvar-local ultra-scroll--hide-cursor-start nil) 105 | (defvar-local ultra-scroll--hide-cursor-undo-hook nil) 106 | (defun ultra-scroll--hide-cursor-undo (buf) 107 | "Undo cursor hiding in BUF." 108 | (when (buffer-live-p buf) 109 | (with-current-buffer buf 110 | ;; TODO It would be nice to recenter the point here, 111 | ;; but this leads to problems with tall images. 112 | ;; (when-let* ((win (get-buffer-window buf))) 113 | ;; (with-selected-window win 114 | ;; (goto-char (/ (+ (window-start) (window-end nil t)) 2)) 115 | ;; (beginning-of-line))) 116 | ;; re-enable 117 | (run-hook-with-args 'ultra-scroll--hide-cursor-undo-hook 1) 118 | (kill-local-variable 'ultra-scroll--hide-cursor-start) 119 | (kill-local-variable 'ultra-scroll--hide-cursor-timer) 120 | (kill-local-variable 'ultra-scroll--hide-cursor-undo-hook)))) 121 | 122 | (defun ultra-scroll--restore-column (_v) 123 | "Attempt to restore the starting column position." 124 | (when-let* ((uss (window-parameter nil 'ultra-scroll--start))) 125 | (vertical-motion (cons (/ uss (frame-char-width)) 0)))) 126 | 127 | (defun ultra-scroll--hide-cursor (window) 128 | "Hide cursor in WINDOW." 129 | (when ultra-scroll-hide-cursor 130 | (if ultra-scroll--hide-cursor-timer 131 | (timer-set-time ultra-scroll--hide-cursor-timer ; reschedule 132 | (timer-relative-time nil ultra-scroll-hide-cursor)) 133 | (setq ultra-scroll--hide-cursor-start (window-point window) 134 | ultra-scroll--hide-cursor-timer 135 | (run-at-time ultra-scroll-hide-cursor nil 136 | #'ultra-scroll--hide-cursor-undo 137 | (window-buffer window)))) 138 | (unless (or ultra-scroll--hide-cursor-undo-hook ; already hiding 139 | (eq (window-point window) ; not yet at window boundary 140 | ultra-scroll--hide-cursor-start)) 141 | (push (if (local-variable-p 'cursor-type) 142 | (let ((orig cursor-type)) 143 | (lambda (_v) (setq-local cursor-type orig))) 144 | (lambda (_v) (kill-local-variable 'cursor-type))) 145 | ultra-scroll--hide-cursor-undo-hook) 146 | (when ultra-scroll-preserve-column 147 | (push #'ultra-scroll--restore-column 148 | ultra-scroll--hide-cursor-undo-hook)) 149 | (setq-local cursor-type nil) 150 | (run-hook-wrapped 151 | 'ultra-scroll-hide-functions 152 | (lambda (fun) 153 | (when (or (not (symbolp fun)) 154 | (not (string-suffix-p "-mode" (symbol-name fun))) 155 | (and (boundp fun) (symbol-value fun))) 156 | (push fun ultra-scroll--hide-cursor-undo-hook) 157 | (funcall fun -1)) ; disable 158 | nil))))) 159 | 160 | ;;;; Other scroll begin/end actions 161 | (defvar ultra-scroll--gc-percentage-orig nil) 162 | (defvar ultra-scroll--scroll-conservatively-orig nil) 163 | (defvar ultra-scroll--timer nil) 164 | (defun ultra-scroll--end-scroll () 165 | "Reset GC variable and scroll settings during idle time." 166 | (when ultra-scroll--gc-percentage-orig 167 | (setq gc-cons-percentage ultra-scroll--gc-percentage-orig)) 168 | (when ultra-scroll--scroll-conservatively-orig 169 | (setq scroll-conservatively ultra-scroll--scroll-conservatively-orig)) 170 | (setq ultra-scroll--timer nil)) 171 | 172 | (defsubst ultra-scroll--prepare-to-scroll () 173 | "Prepare to scroll by lifting GC percentage and setting scroll parameters. 174 | See `ultra-scroll-gc-percentage' to configuring whether GC changes occur 175 | and the `gc-cons-percentage' level to set temporarily." 176 | (unless ultra-scroll--timer 177 | (unless (and (window-parameter nil 'ultra-scroll--start) 178 | ;; preserve target for multiple consecutive scroll commands 179 | (memq last-command '( ultra-scroll ultra-scroll-mac 180 | mac-mwheel-scroll pixel-scroll-precision))) 181 | (set-window-parameter nil 'ultra-scroll--start 182 | (car (posn-x-y (posn-at-point))))) 183 | ;; Work around lag when same buffer has vscroll in another window (#32) 184 | (dolist (w (cdr (get-buffer-window-list (current-buffer)))) 185 | (set-window-vscroll w 0)) 186 | (let (changed) 187 | (when ultra-scroll-gc-percentage 188 | (setq changed t 189 | gc-cons-percentage ; reduce GC's during scroll 190 | (max gc-cons-percentage ultra-scroll-gc-percentage))) 191 | (when (< scroll-conservatively 100) 192 | (setq changed t 193 | ultra-scroll--scroll-conservatively-orig scroll-conservatively 194 | scroll-conservatively 101)) 195 | (when changed 196 | (setq ultra-scroll--timer 197 | (run-with-idle-timer ultra-scroll-idle-time nil 198 | #'ultra-scroll--end-scroll)))))) 199 | 200 | ;;;; Scroll 201 | (defun ultra-scroll-down (delta) 202 | "Scroll the current window down by DELTA pixels. 203 | DELTA should not be larger than the height of the current window." 204 | (let* ((initial (point)) 205 | (edges (window-edges nil t nil t)) 206 | (win-height (- (nth 3 edges) (nth 1 edges))) 207 | (current-vs (window-vscroll nil t)) 208 | (off (+ (window-tab-line-height) (window-header-line-height))) 209 | (new-start (posn-point (posn-at-x-y 0 (+ delta off)))) 210 | (new-start-posn (and new-start (posn-at-point new-start)))) 211 | (unless new-start-posn ; scroll delta could be larger than win height! 212 | (let ((last-start (or new-start 0)) quit) 213 | (while (and (> delta (- win-height off)) (not quit)) 214 | (setq new-start (posn-point (posn-at-x-y 0 (1- win-height)))) 215 | (if (<= new-start last-start) 216 | (setq quit t) ; no progress being made 217 | (setq new-start-posn (posn-at-point new-start) 218 | last-start new-start 219 | delta (- delta (or (cdr (posn-x-y new-start-posn)) 0))) 220 | (set-window-start nil new-start))))) 221 | (when new-start 222 | (goto-char new-start) 223 | (unless (zerop (window-hscroll)) 224 | (setq new-start (beginning-of-visual-line))) 225 | (if (>= (line-pixel-height) win-height) 226 | ;; Jumbo line at top: just stay on it and increment vscroll 227 | (set-window-vscroll nil (+ current-vs delta) t t) 228 | (if (eq new-start (window-start)) ; same start: just vscroll a bit more 229 | (setq delta (+ current-vs delta)) 230 | (setq new-start-posn (posn-at-point new-start) 231 | delta (- delta (or (cdr (posn-x-y new-start-posn)) 0))) 232 | (set-window-start nil new-start (not (zerop delta)))) 233 | (set-window-vscroll nil delta t t) 234 | ;; Avoid recentering 235 | (goto-char (posn-point (posn-at-x-y 0 off))) ; window-start may be above 236 | (if (zerop (vertical-motion 1)) ; move down 1 line from top 237 | (signal 'end-of-buffer nil)) 238 | (if (> initial (point)) (goto-char initial)))))) 239 | 240 | (defun ultra-scroll-up (delta) 241 | "Scroll the current window up by DELTA pixels. 242 | DELTA should be less than the window's height." 243 | (let* ((initial (point)) 244 | (edges (window-edges nil t nil t)) 245 | (win-height (- (nth 3 edges) (nth 1 edges))) 246 | (win-start (window-start)) 247 | (current-vs (window-vscroll nil t)) 248 | (start win-start)) 249 | (if (<= delta current-vs) ; simple case: just reduce vscroll 250 | (setq delta (- current-vs delta)) 251 | ; Not enough vscroll: measure size above window-start 252 | (let* ((dims (window-text-pixel-size nil (cons start (- current-vs delta)) 253 | start nil nil nil t)) 254 | (pos (nth 2 dims)) 255 | (height (nth 1 dims))) 256 | (when (or (not pos) (eq pos (point-min))) 257 | (signal 'beginning-of-buffer nil)) 258 | (setq start (nth 2 dims) 259 | delta (- (+ height current-vs) delta))) ; should be >= 0 260 | (unless (eq start win-start) 261 | (set-window-start nil start (not (zerop delta))))) 262 | (when (>= delta 0) (set-window-vscroll nil delta t t)) 263 | 264 | ;; Position point to avoid recentering, moving up one line from 265 | ;; the bottom, if necessary. "Jumbo" lines (taller than the 266 | ;; window height, usually due to images) must be handled 267 | ;; carefully. Once they are within the window, point should stay 268 | ;; on the first tall object on the line until the top of the jumbo 269 | ;; line clears the top of the window, then immediately moved off 270 | ;; (above), via the full height character. This is the only way to 271 | ;; avoid unwanted re-centering/motion trapping. 272 | (if (> (line-pixel-height) win-height) ; a jumbo on the line! 273 | (let ((end (max (point) 274 | (save-excursion 275 | (end-of-visual-line) 276 | (1- (point)))))) ; don't fall off 277 | (when-let* ((pv (pos-visible-in-window-p end nil t)) 278 | ((and (> (length pv) 2) ; falls outside window 279 | (zerop (nth 2 pv))))) ; but not at the top 280 | (goto-char end) ; eol is usually full height 281 | (goto-char start))) ; now move up 282 | (when-let* ((p (posn-at-x-y 0 (1- win-height)))) 283 | (goto-char (posn-point p)) 284 | (vertical-motion -1) 285 | (if (< initial (point)) (goto-char initial)))))) 286 | 287 | (defsubst ultra-scroll--scroll (delta window) 288 | "Scroll WINDOW by DELTA pixels (positive or negative)." 289 | (let (ignore) 290 | (unless (or (zerop delta) 291 | (and (setq ignore (window-parameter window 'ultra-scroll--ignore)) 292 | (or ; ignoring this window moving this direction 293 | (and (eq (point) (car ignore)) 294 | (eq (cdr ignore) (< delta 0))) 295 | (set-window-parameter window 'ultra-scroll--ignore nil)))) 296 | (with-selected-window window 297 | (condition-case err 298 | (if (< delta 0) 299 | (ultra-scroll-down (- delta)) 300 | (ultra-scroll-up delta)) 301 | ;; Do not ding at buffer limits. Show a message instead (once!). 302 | ((beginning-of-buffer end-of-buffer) 303 | (let* ((end (eq (car err) 'end-of-buffer)) 304 | (p (if end (point-max) (point-min)))) 305 | (when ultra-scroll--hide-cursor-undo-hook (goto-char p)) 306 | (set-window-start window p) 307 | (set-window-vscroll window 0 t t) 308 | (set-window-parameter window 'ultra-scroll--ignore 309 | (cons (point) end)) 310 | (message (error-message-string 311 | (if end '(end-of-buffer) '(beginning-of-buffer))))))) 312 | (ultra-scroll--hide-cursor window))))) 313 | 314 | (defun ultra-scroll (event &optional arg) 315 | "Smooth scroll EVENT. 316 | EVENT and optional ARG are passed to `mwheel-scroll', unless 317 | EVENT is a scrolling event." 318 | (interactive "e") 319 | (let ((delta (nth 4 event))) 320 | (if (not delta) 321 | (mwheel-scroll event arg) 322 | (ultra-scroll--prepare-to-scroll) 323 | (ultra-scroll--scroll (round (cdr delta)) (mwheel-event-window event))))) 324 | 325 | (declare-function mac-forward-wheel-event "mac-win") 326 | (defun ultra-scroll-mac (event &optional arg) 327 | "Smooth scroll EVENT for emacs-mac. 328 | EVENT and optional ARG are passed on to `mwheel-scroll', for any 329 | events not handled here. If swipe-tracking is enabled for 330 | swipe-between-pages at the OS level, left-/right-swipe events 331 | will be replayed for left/right touch ends." 332 | (interactive "e") 333 | (let ((ev-type (event-basic-type event)) 334 | (plist (nth 3 event))) 335 | (if (not (memq ev-type '(wheel-up wheel-down))) 336 | (when (memq ev-type '(wheel-left wheel-right)) 337 | (if mouse-wheel-tilt-scroll 338 | (mac-forward-wheel-event t 'mwheel-scroll event arg) 339 | (when (and ;; "Swipe between pages" enabled. 340 | (plist-get plist :swipe-tracking-from-scroll-events-enabled-p) 341 | (eq (plist-get plist :momentum-phase) 'began)) 342 | ;; Post a swipe event when left/right momentum phase begins 343 | (push (cons (event-convert-list 344 | (nconc (delq 'click 345 | (delq 'double 346 | (delq 'triple 347 | (event-modifiers event)))) 348 | (if (eq (event-basic-type event) 'wheel-left) 349 | '(swipe-left) '(swipe-right)))) 350 | (cdr event)) 351 | unread-command-events)))) 352 | ;; Note: emacs-mac encodes all scrolling information in the PLIST, as follows: 353 | ;; trackpads: 354 | ;; - `:scrolling-delta-x' and `:scrolling-delta-y' are set 355 | ;; to pixel scroll amounts. 356 | ;; - `:phase' is set to `began' on first scroll, then `changed'. 357 | ;; - During momentum scroll, `:momentum-phase' is set to 358 | ;; `began' then `changed', while `:phase' is `none'. 359 | ;; some regular wheeled mice: 360 | ;; - `:delta-x' and `:delta-y' are set to floating 361 | ;; fractional line scroll amounts. 362 | ;; - `:phase' is set to `began' on first scroll, then `changed'. 363 | ;; - `:momentum-phase' is always `none'. 364 | (ultra-scroll--prepare-to-scroll) 365 | (let* ((scroll-delta (plist-get plist :scrolling-delta-y)) 366 | (delta (or scroll-delta 367 | ;; regular non-touch scroll: fraction of a line 368 | (* (plist-get plist :delta-y) (frame-char-height) 369 | ultra-scroll-mac-multiplier)))) 370 | (ultra-scroll--scroll (round delta) (mwheel-event-window event)))))) 371 | 372 | ; scroll-isearch support 373 | (put 'ultra-scroll 'scroll-command t) 374 | (put 'ultra-scroll-mac 'scroll-command t) 375 | 376 | ;;;; Testing scroll data 377 | (defun ultra-scroll-check (event-cnt) 378 | "Check and report on the scrolling event data your system provides. 379 | This reads EVENT-CNT independent scroll events (default: 30) and checks 380 | their PIXEL-DELTA values to see if they differ." 381 | (interactive "p") 382 | (let 383 | ((buf (get-buffer-create "*ultra-scroll-report*")) 384 | (nc (string-match "\\bNATIVE_COMP\\b" system-configuration-features)) 385 | (inhibit-read-only t) 386 | (max-cnt (max event-cnt 30)) (cnt 1) deltas mac-basic ev tm) 387 | (message (concat "ultra-scroll: checking scroll data\n" 388 | (format 389 | "Scroll your mouse wheel or track-pad slow then fast to generate %d events" 390 | max-cnt))) 391 | (while (and (setq ev (read-event)) (< cnt max-cnt)) 392 | (when (memq (event-basic-type ev) '(wheel-up wheel-down)) 393 | (unless tm (setq tm (current-time))) 394 | (message "Detected %2d/%2d wheel event%s" cnt max-cnt (if (> cnt 1) "s" "")) 395 | (cl-incf cnt) 396 | (if (featurep 'mac-win) 397 | (let ((plist (nth 3 ev))) 398 | (when (null plist) 399 | (error "Malformed wheel event detected! %s" ev)) 400 | (if-let* ((sdy (plist-get plist :scrolling-delta-y))) 401 | (push sdy deltas) 402 | (if-let* ((dy (plist-get plist :delta-y))) 403 | (progn 404 | (push dy deltas) 405 | (setq mac-basic t)) 406 | (error "Malformed wheel event detected! %s" ev)))) 407 | (if-let* ((pix-delta (nth 4 ev))) 408 | (push (cdr pix-delta) deltas) 409 | (error "Malformed wheel event detected! %s" ev))))) 410 | (setq tm (float-time (time-since tm))) 411 | (with-current-buffer buf 412 | (erase-buffer) 413 | (help-mode) 414 | (insert " == ultra-scroll Scroll Event Report ==\n\n") 415 | (insert "* " (emacs-version) "\n* " (if nc "" "No ") "Native Comp Detected" 416 | (if nc "\n" " (use native-comp for fastest scrolling performance)\n") 417 | "\n") 418 | (when (and (featurep 'x) (not (featurep 'xinput2))) 419 | (insert " *** WARNING: Emacs on Linux/X11 must be compiled --with-xinput2\n")) 420 | (insert (format " ** %s scroll events%s detected in %0.2fs (%0.1f events/s)\n" cnt 421 | (if mac-basic " [Mac basic mouse]" "") tm (/ (float cnt) tm))) 422 | (if (cl-every (lambda (x) (= (abs x) (abs (car deltas)))) deltas) 423 | (insert (format " *** WARNING, all pixel scroll values == %0.2f " (car deltas)) 424 | "No real pixel scroll data stream?\n" 425 | " ** (try again, or use pixel-scroll-precision instead)\n") 426 | (let* ((deltas (mapcar #'abs deltas)) 427 | (mean (/ (cl-reduce #'+ deltas ) max-cnt)) 428 | (min (apply #'min deltas)) 429 | (max (apply #'max deltas))) 430 | (insert (format " *** %s pixel scroll data: %0.1f to %0.1f (%0.2f mean)\n" 431 | (if mac-basic "Mac line-based" "Normal") min max mean))))) 432 | (display-buffer buf))) 433 | 434 | ;;;; Mode 435 | ;;;###autoload 436 | (define-minor-mode ultra-scroll-mode 437 | "Toggle pixel precision scrolling. 438 | When enabled, this minor mode scrolls the display precisely using 439 | full trackpad or modern mouse capabilities. It correctly scrolls 440 | past images taller than the window height. The mode enables 441 | `pixel-scroll-precision-mode-map', overriding that mode's scroll 442 | command, but other mode features, including interpolated page 443 | scrolling, still function (if enabled). 444 | 445 | Note that `ultra-scroll' does NOT do any interpolation of scroll 446 | wheel data, and is intended for use with mouse/trackpad hardware 447 | on systems providing pixel-level scroll data; see 448 | `ultra-scroll-check' to investigate what kind of scrolling data 449 | your system and hardware provide." 450 | :global t 451 | :group 'scrolling 452 | (pixel-scroll-precision-mode (if ultra-scroll-mode 1 -1)) ;; reuse 453 | (cond 454 | (ultra-scroll-mode 455 | (unless (= scroll-margin 0) 456 | (warn "ultra-scroll: scroll-margin = 0 is required for glitch-free smooth scrolling")) 457 | (when (and (featurep 'x) (not (featurep 'xinput2))) 458 | (warn "ultra-scroll: Emacs on Linux/X11 must be compiled --with-xinput2")) 459 | (define-key pixel-scroll-precision-mode-map [remap pixel-scroll-precision] 460 | (if (featurep 'mac-win) #'ultra-scroll-mac #'ultra-scroll)) 461 | (setf (get 'pixel-scroll-precision-use-momentum 'us-orig-value) 462 | pixel-scroll-precision-use-momentum) 463 | (setq pixel-scroll-precision-use-momentum nil) 464 | ;; pixel-scroll-precision after emacs v30 turns this off. We 465 | ;; don't need to do so for scrolling, but a bug in half-visible 466 | ;; cursors lead to 150-400x slowdown in redisplay; see #32. 467 | (setq-default make-cursor-line-fully-visible nil) 468 | (setq ultra-scroll--gc-percentage-orig gc-cons-percentage 469 | ultra-scroll--scroll-conservatively-orig scroll-conservatively)) 470 | (t 471 | (define-key pixel-scroll-precision-mode-map [remap pixel-scroll-precision] nil) 472 | (setq pixel-scroll-precision-use-momentum 473 | (get 'pixel-scroll-precision-use-momentum 'us-orig-value))))) 474 | 475 | (provide 'ultra-scroll) 476 | ;;; ultra-scroll.el ends here 477 | 478 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # ultra-scroll: scroll emacs like lightning ⚡🖱️⚡ 2 | 3 | MELPA 4 | 5 | `ultra-scroll`[^1] is a smooth-scrolling package for emacs, with native 6 | support for standard builds as well as 7 | [emacs-mac](https://bitbucket.org/mituharu/emacs-mac). It provides 8 | highly optimized, pixel-precise smooth scrolling which can readily keep 9 | up with the *very* high event rates of modern track-pads and 10 | high-precision wheel mice. 11 | 12 | You move your fingers, the page responds, *instantly*: 13 | 14 | 15 | 16 | Importantly, `ultra-scroll` can cleanly *scroll right across* tall 17 | images and other jumbo lines – a perennial problem with scrolling 18 | packages to date. As a bonus, it enables relatively smooth scrolling 19 | even with dumb third party mice. 20 | 21 | Note, the `previous-buffer` animation above is from two-finger track-pad 22 | swiping, and is an [emacs-mac](https://github.com/jdtsmith/emacs-mac) 23 | exclusive. 24 | 25 | > [!NOTE] 26 | > **Do you need this?** 27 | > 28 | > If you don't scroll with a high-speed device (modern mouse or 29 | > track-pad), no. If you do, but aren't sure, here's a good test to try: 30 | > 31 | > Open a heavy emacs buffer full screen on your largest monitor. While 32 | > scrolling smoothly such that lines would move across your window's 33 | > full height in about 5 seconds, *can you easily read the text you 34 | > see*, without stopping, in both directions? Now, try this exercise 35 | > again with your browser – I bet it's *very* readable there. Shouldn't 36 | > emacs be like this? 37 | > 38 | > In addition, if you scroll buffers with tall images visible, this is 39 | > also a good reason to give `ultra-scroll` a try. 40 | 41 | ## Release Information 42 | 43 | See the [NEWS](./NEWS.org). 44 | 45 | ## Compatibility 46 | 47 | `ultra-scroll` should work across all systems that provide pixel-level 48 | scrolling information for your input hardware. If you don't think 49 | `ultra-scroll` is working for you, run `M-x ultra-scroll-check`, and 50 | follow the directions. If it reports: 51 | 52 | - **Normal pixel scroll data**: you are good to go, everything is 53 | working. 54 | - **No real pixel scroll data**: your system and hardware are delivering 55 | pixel scrolling data, but they *never change* (test again to be sure). 56 | This is equivalent to line-by-line scrolling. `ultra-scroll` will work 57 | fine for you, but *without* any smooth scrolling. You can use it for 58 | the improved large image scrolling behavior, or see below for another 59 | option. 60 | - The *error* **Malformed wheel event**: your system does not deliver 61 | *any* pixel-level scroll data. Either upgrade your hardware/system to 62 | a known working config (see [this issue](../../issues/18) for user 63 | experiences), or see below. 64 | 65 | For systems which do *not* provide normal pixel scroll data, you can try 66 | the built-in `pixel-scroll-precision-mode` with 67 | `pixel-scroll-precision-interpolate-mice` (which "creates" events by 68 | interpolation) instead. 69 | 70 | > [!IMPORTANT] 71 | > **Your Help Needed!** While `ultra-scroll` works out of the box for 72 | > most people, it's impossible to test all combinations of systems and 73 | > hardware, so please take a moment to [report your smooth-scrolling 74 | > experiences](../../discussions) for the benefit of others. 75 | 76 | ## Installation 77 | 78 | `ultra-scroll` is in MELPA. Starting from Emacs 30, you can also use the 79 | new `:vc` keyword to download directly from this repository. 80 | Configuration is then simple: 81 | 82 | ``` commonlisp 83 | (use-package ultra-scroll 84 | ;:vc (:url "https://github.com/jdtsmith/ultra-scroll") ; if desired (emacs>=v30) 85 | :init 86 | (setq scroll-conservatively 3 ; or whatever value you prefer, since v0.4 87 | scroll-margin 0) ; important: scroll-margin>0 not yet supported 88 | :config 89 | (ultra-scroll-mode 1)) 90 | ``` 91 | 92 | ## Usage 93 | 94 | Just start scrolling :). 95 | 96 | > [!TIP] 97 | > For best performance, use a build with native-compilation (see 98 | > [Speed](#Speed)). 99 | 100 | ## Configuration 101 | 102 | There is little to no configuration. 103 | 104 | ### Altering dumb mice behavior on emacs-mac 105 | 106 | If desired for use with dumb mice on `emacs-mac`, the variable 107 | `ultra-scroll-mac-multiplier` can be set to a number smaller or larger 108 | than `1.0` to decrease/increase mouse-wheel scrolling speed. Note that 109 | many fancier wheeled mice have drivers that *simulate* track-pads, so 110 | this variable will have no effect on them. For these, and for track-pads 111 | generally, scrolling speed should be configured in system settings. 112 | 113 | > [!NOTE] 114 | > Only certain systems provide real variable pixel scroll offset data 115 | > (`PIXEL-DELTA`) for older/wheeled ("dumb") mice. Use 116 | > `M-x ultra-scroll-check` to see if yours does. If not, it's 117 | > recommended to upgrade hardware, or stick with 118 | > `pixel-scroll-precision-mode`. 119 | 120 | ### Mitigating garbage collection pauses 121 | 122 | To reduce the likelihood of garbage collection during scroll, which can 123 | introduce slight pauses, the value of `gc-cons-percentage` is 124 | temporarily increased, and reset during idle time. The defaults should 125 | work well for most situations, but if necessary, can be configured using 126 | `ultra-scroll-gc-percentage` and `ultra-scroll-gc-idle-time`. 127 | 128 | ### Hiding cursor, disabling other modes during scroll, and restoring column 129 | 130 | By default, `ultra-scroll` hides the cursor (and a `hl-line` if active) 131 | once it reaches the window edge, to prevent "bouncing cursor" behavior. 132 | This can be disabled, or the time delay to restore the cursor set, with 133 | `ultra-scroll-hide-cursor`. 134 | 135 | In addition to the cursor, it is sometimes useful to temporarily disable 136 | other modes during the scroll. The special hook variable 137 | `ultra-scroll-hide-functions` can be used for this, e.g.: 138 | 139 | ``` commonlisp 140 | (add-hook 'ultra-scroll-hide-functions 'hl-line-mode) 141 | ``` 142 | 143 | By default, the hook contains `hl-line-mode`. 144 | 145 | You can optionally enable restoring the visual column position after the 146 | scroll completes; see `ultra-scroll-preserve-column`. 147 | 148 | ## `pixel-scroll-precision` comparison and interoperability 149 | 150 | Emacs has a built-in smooth scrolling system called 151 | `pixel-scroll-precision-mode`. In fact, by design, `ultra-scroll` 152 | *activates* the builtin `pixel-scroll-precision-mode`, remapping its 153 | scrolling function with its own. The latter also has the capability of 154 | *faking* smooth scrolling using interpolation. It can do this for 155 | non-mouse movements, like `scroll-up/down-command` (usually on `PgUp` / 156 | `PgDown`). To use these additional capabilities, simply set the relevant 157 | variables, like `pixel-scroll-precision-interpolate-page`, and they 158 | should "just work". 159 | 160 | Note that `ultra-scroll` disables `pixel-scroll-precision-use-momentum`, 161 | since it may not handle tall image scrolling well. Some systems (MacOS) 162 | get momentum scrolling "for free" from the OS, independent of this 163 | setting. If you experiment with re-enabling 164 | `pixel-scroll-precision-use-momentum` on other systems like Linux, 165 | please open an issue to report your findings. 166 | 167 | > [!WARNING] 168 | > `ultra-scroll` activates `pixel-scroll-precision-mode` by side effect. 169 | > If you are experimenting with both modes during a single session, 170 | > always disable `ultra-scroll-mode` first and then re-enable 171 | > `pixel-scroll-precision-mode`. 172 | 173 | ### A comparison between ultra-scroll and pixel-scroll-precision 174 | 175 | See also [this 176 | question](#how-does-this-compare-to-the-built-in-smooth-scrolling). 177 | 178 | `pixel-scroll-precision-mode`: 179 | 180 | - Supports smooth scrolling even on systems which do *not* provide pixel 181 | scroll data, using interpolation (see 182 | `pixel-scroll-precision-interpolate-mice`). 183 | - Can simulate a "momentum" scrolling phase on systems which do not 184 | provide this capability (see `pixel-scroll-precision-use-momentum`). 185 | - Has occasional issues scrolling tall images. 186 | 187 | `ultra-scroll`: 188 | 189 | - Fully supports *only* those system and hardware combos that deliver 190 | *real* pixel scroll data (see [Compatibility](#Compatibility)). 191 | - Provides "momentum" scrolling only on systems which provide this 192 | themselves. 193 | - Is somewhat faster (see [Speed](#Speed)). 194 | - Handles tall image scrolling without issue. 195 | 196 | ## Related packages and functionality 197 | 198 | emacs-mac's own builtin `mac-mwheel-scroll` 199 | This venerable code was introduced with 200 | [emacs-mac](https://bitbucket.org/mituharu/emacs-mac/) more than a 201 | decade ago, and was the first to provide smooth scrolling in any version 202 | of emacs. 203 | 204 | `pixel-scroll-precision-mode` 205 | A fast pixel scrolling by Po Lu, built in to Emacs as of v29.1 (see 206 | `pixel-scroll.el`). Does not support `emacs-mac`. `ultra-scroll` was 207 | initially based on its design, but many design elements have changed. 208 | 209 | `pixel-scroll-mode` 210 | A simpler line-by-line pixel scrolling mode, also found in the file 211 | `pixel-scroll.el`. 212 | 213 | [good-scroll](https://github.com/io12/good-scroll.el) 214 | An update to `pixel-scroll-mode` with variable speed. 215 | 216 | [sublimity](https://github.com/zk-phi/sublimity) 217 | Includes smooth scrolling based on sublime editor. 218 | 219 | ## Questions 220 | 221 | ### What was the motivation behind this? 222 | 223 | Picture it: a fast new laptop and 5K monitor with a large heavy-duty, 224 | full-screen buffer in `python-ts-mode`. Scrolling line-by-line with a 225 | decent mouse is mostly OK, but smooth pixel scrolling with the track-pad 226 | is just… *painful*. Repeated attempts to rationalize this fail, 227 | especially because it's notably worse in one direction than the other. 228 | Scrolling Emacs feels like moving through (light) molasses. *No bueno*. 229 | 230 | Checking into it, the smooth scroll event callback takes 15-20ms 231 | scrolling in one direction, and 3–5x longer in the other. This 232 | performance is perfectly fine for normal mice which deliver a few 233 | scrolling events a second. *But track-pad and fancy mouse scroll events 234 | are arriving every 10ms, or less*! The code just couldn't keep up. 235 | Hence: molasses. 236 | 237 | I also wanted to be able to scroll through image-rich documents without 238 | worrying about jumpy/loopy scrolling behavior. And my extra dumb mouse 239 | didn't work well either: small scrolls did nothing: you'd have scroll 240 | pretty aggressively to get any movement at all. 241 | 242 | How hard could it be to fix this? And the adventure began… 243 | 244 | ### Why was this initially for emacs-mac only? 245 | 246 | This packaged used to be called `ultra-scroll-mac`. The `emacs-mac` port 247 | of emacs exposes pixel-level scrolling event stream of Mac track-pads 248 | (and other fancy mice) in a distinct way, which is not supported by 249 | `pixel-scroll-precision-mode`. And unfortunately the default 250 | smooth-scrolling library included in `emacs-mac` is quite low 251 | performance (see above). 252 | 253 | ### How does this compare to the built-in smooth scrolling? 254 | 255 | On the `emacs-mac` build, there is no comparison, because 256 | `pixel-scroll-precision-mode` doesn't work there. On other builds, they 257 | are fairly comparable. Compared to `pixel-scroll-precision-mode`, 258 | `ultra-scroll` obviously works with `emacs-mac`, but is also even 259 | [faster](#Speed), and can cleanly scroll past images taller than the 260 | window. 261 | 262 | In addition to fast scrolling, the built-in 263 | `pixel-scroll-precision-mode` (new in Emacs v29.1) can simulate a 264 | *feature-complete track-pad driver* in elisp for older mice or systems 265 | which do not supply pixel scroll information. This comes complete with 266 | elisp-based *scroll interpolation*, a timer-based *momentum* phase, etc. 267 | 268 | ### Why are there so many smooth scrolling modes? Why is this so hard? It's just *scrolling*… 269 | 270 | Emacs was designed long before mice were common, not to mention modern 271 | high-resolution track-pads and mice which send rapid micro-updates 272 | ("move up one pixel!") 60-120 times per second. Unlike other programs, 273 | Emacs *insists* on keeping the cursor (point) visible at all times. Deep 274 | in its re-display code, Emacs tracks where point is, and works 275 | diligently to ensure it never falls outside the visible window. It does 276 | this *not* by moving point itself (that's the user's job), but by moving 277 | the *window* (visible range of lines) surrounding point. 278 | 279 | Once you are used to this behavior, it's actually pretty nice for 280 | navigating with `C-n` / `C-p` and friends. But for smooth scrolling with 281 | a track-pad or mouse, it is *very problematic* – nothing screams "janky 282 | scrolling" like the window lurching back or forth half a page during a 283 | scroll. Or worse: getting caught in an endless loop of 284 | scroll-in-one-direction/jump-back-in-the-other. 285 | 286 | So what should be done? The elisp info manual (`Textual Scrolling` / 287 | `set-window-start`) helpfully mentions: 288 | 289 | > …for reliable results Lisp programs that call this function should 290 | > always move point to be inside the window whose display starts at 291 | > POSITION. 292 | 293 | Which is all well and good, but *where* do you find such a point, in 294 | advance, safely *inside the window*? Often this isn't terribly hard, but 295 | there is one common case where this admonition falls comically flat: 296 | scrolling past an image or other content which is *taller than the 297 | window* – what I call **jumbo lines**. Where can I place point *inside 298 | the window* when a jumbo line occupies the entire window height? 299 | 300 | As a result of these types of difficulties, pixel scrolling codes and 301 | packages are often quite involved, with much of the logic boiling down 302 | to a stalwart and increasingly heroic pile of interwoven attempts to 303 | *keep the damn point on screen* and prevent juddering and looping as you 304 | scroll. 305 | 306 | ### What should I know about developing scrolling modes for Emacs? 307 | 308 | For posterity, some things I discovered in my own mostly-victorious 309 | battle against unwanted re-centering during smooth scroll, including 310 | across jumbo lines: 311 | 312 | - `scroll-conservatively=101` is very helpful, since with this Emacs 313 | will "scroll just enough text to bring point into view, even if you 314 | move far away". It does not defeat re-centering, but makes it… more 315 | manageable. 316 | - You cannot let-bind `scroll-conservatively` for effect, as it comes 317 | into play only on re-display (after your event handler returns). But 318 | you *can* set it temporarily and restore it in idle time without ill 319 | effect. 320 | - `scroll-margin>0` is a no-no. This setting always moves point at least 321 | that many lines from the window boundaries, which, unless you can 322 | reliably place point there during the scroll (even in the presence of 323 | jumbo lines; see below), will cause loop-back. See \#3. 324 | - Virtual Scroll: 325 | - `vscroll` – a virtual rendered scrolling window hiding *below* the 326 | current window – is key to smooth scrolling, and altering `vscroll` 327 | to move the view-port is incredibly fast. 328 | - There is plenty of `vscroll` room available, including the entirety 329 | of any tall lines (as for displayed images) in view. 330 | - `vscroll` can sometimes place the point off the visible window (I 331 | know, sacrilege), but more often triggers re-centering. 332 | - Scrolling asymmetry: 333 | - Sadly `vscroll` is purely *one-sided*: you can only access a 334 | `vscroll` area *beneath* the current window view; *there is no 335 | negative `vscroll`*. 336 | - Unlike `window-start`, `window-end` does not get updated promptly 337 | between re-displays and cannot always be trusted. Computing it is 338 | expensive, so should be avoided during re-display. 339 | - For these two reasons, smooth scrolling up and scrolling down are 340 | *not symmetric* with each other, and will likely never be. You need 341 | different approaches for each. 342 | - If the two approaches for scrolling up and down perform quite 343 | differently, the user will definitely feel this difference. 344 | - For avoiding re-centering, naive movement doesn't work well. You need 345 | to learn the basic layout of lines on the window *before re-display* 346 | has occurred. 347 | - The "usable window height" deducts any header and the old-fashioned 348 | tab-bar, but *not* the tab-bar-mode bar. 349 | - Jumbo lines (lines taller than the window's height): 350 | - Scrolling towards buffer end: 351 | - When scrolling past jumbo lines towards the buffer's end (with 352 | `vscroll`), simply keep *point on the jumbo line* until it *fully 353 | disappears* from view. As a special case, Emacs will not re-center 354 | when this happens. 355 | - This is *not* true for lines that are shorter than the usable 356 | window height (even if they are tall). In this case, you must 357 | *avoid* placing point on any line which falls partially out of 358 | view. 359 | - Scrolling towards buffer start: 360 | - When scrolling up past jumbo lines towards the buffer's start 361 | using `set-window-start` (lines of content move down), you must 362 | keep point on the jumbo, but *only until it clears the top of the 363 | window area* (even by one pixel). 364 | - After this, you must move the point to the line above it. 365 | - In some cases (depending on truncation/visual-line-mode/etc.), 366 | this movement must occur from a position beyond the first full 367 | height object (which may not be at the line's start). E.g. one 368 | before the visual line end. 369 | - `pos-visible-in-window` doesn't always give correct results near the 370 | window boundaries. Better to use the first line at the window's top or 371 | directly identify the final line (both via `pos-at-x-y`) and adjust 372 | from there. 373 | 374 | So all in all, it's quite complicated to get something that works as 375 | you'd hope. The cutting room floor is littered with literally dozens of 376 | almost-but-not-quite-working versions of `ultra-scroll`. I'm sure there 377 | are many more corner cases, but the current design gets most things 378 | right in my usage. 379 | 380 | ## Display bugs 381 | 382 | `ultra-scroll` exercises some rare corner cases of Emacs' redisplay 383 | logic, and as a result has revealed and helped fix a number of display 384 | bugs. These bugs lead to behaviors like slightly staccato scrolling in 385 | buffers with diverse line heights (e.g. inline images). If you think you 386 | have found a display bug, open an issue to discuss. 387 | 388 | - A [display bug](https://debbugs.gnu.org/cgi/bugreport.cgi?bug=67533) 389 | with inline images that cause them to sometimes misreport pixel 390 | measurements and positions has been fixed in master as of Dec, 2023, 391 | so scrolling with lots of inline images should be much smoother 392 | starting from Emacs v30. 393 | - As of June, 2025, another [display 394 | bug](https://debbugs.gnu.org/cgi/bugreport.cgi?bug=67604) related to 395 | line-skipping of visual (i.e. word) wrapped lines with inline images 396 | at line start has been fixed (for Emacs v31). This caused additional 397 | (but even rarer) "hitches" in smooth scrolling in buffers with 398 | numerous inline images. 399 | - Another display bug which leads to scrolling (and general UI) slowdown 400 | in some edge-case situations with `make-cursor-line-fully-visible=t` 401 | was also [found](../../issues/32) and 402 | [fixed](https://debbugs.gnu.org/cgi/bugreport.cgi?bug=78766) in 403 | June, 2025. This fix will be included with Emacs v31. 404 | 405 | ## Speed 406 | 407 | I often wonder how many people who claim "emacs is laggy" form that 408 | impression from scrolling. Scrolling at 60-120Hz or faster with modern 409 | mice and track-pads puts a lot of stress on systems, and is often the 410 | first place lag appears. So `ultra-scroll` is fast *by design*. I made 411 | some observations about its speed using `ELP` to measure the average 412 | call duration of individual scroll functions (`ultra-scroll-up/down`) 413 | with various buffer and window sizes[^2]. 414 | 415 | ### Take-aways 416 | 417 | 1. Very large window sizes and buffers with "extra" processing going 418 | on, like treesitter, LSP modes, elaborate font-locking, tons of 419 | overlays, etc. can slow down scrolling. 420 | 2. If the scroll command does its work in \<10ms, you do not notice it. 421 | You can definitely start feeling it when scroll commands take more 422 | than 15ms. 423 | 3. The underlying scroll primitives need to leave some overhead in 424 | time, so that all the other emacs commands that occur when new 425 | content is brought into view (font-lock) can run without causing 426 | scroll lag, for all your different modes. **Faster is better**: 3ms 427 | or less[^3] in a light buffer would be *ideal*. 428 | 4. Building `--with-native-comp` is *essential* for ultra-smooth 429 | scrolling. It increases the speed of each individual scroll command 430 | by **\>3x**, which is important since these commands are called so 431 | frequently. 432 | 5. On the exact same build (NS, v29.4, with native-comp), 433 | `ultra-scroll` is about **40% faster** than 434 | `pixel-scroll-precision-mode`. Except on slower machines, or in very 435 | heavy buffers and/or on large window sizes where your performance is 436 | right on the edge, this shouldn't be too noticeable. 437 | 6. On the same system (an M2 mac), `ultra-scroll` on `emacs-mac` is 438 | 10-15% faster than it is on NS builds like `emacs-plus`. Very likely 439 | not noticeable. 440 | 7. The mode-line gets updated *very often* during smooth scrolls (and 441 | in general), and poorly written fancy modeline add-ons are a common 442 | source of slow-down. Good modeline modes will *rate-limit* their 443 | updates behind timers and/or cache results in local/global 444 | variables. If your scrolling (or any other aspect of Emacs) "lags", 445 | try `(setq mode-line-format "NADA")` and see if that solves it. If 446 | so, suspect your fancy modeline. 447 | 448 | [^1]: Formerly `ultra-scroll-mac`. 449 | 450 | [^2]: To try this yourself, `M-x elp-instrument-function` on both 451 | `ultra-scroll-up/down`, scroll around (both directions) in a big 452 | buffer with a large window, then `M-x elp-results`. The last column 453 | gives average time in seconds. Less than 0.003s (i.e. 3ms) is ideal, 454 | 8ms is still perfectly usable, 15ms you'll feel a bit, 50ms will be 455 | very frustrating. `scroll-down` is always faster than `scroll-up` 456 | due to an asymmetry in Emacs' `vscroll` buffer. 457 | 458 | [^3]: To try this yourself, `M-x elp-instrument-function` on both 459 | `ultra-scroll-up/down`, scroll around (both directions) in a big 460 | buffer with a large window, then `M-x elp-results`. The last column 461 | gives average time in seconds. Less than 0.003s (i.e. 3ms) is ideal, 462 | 8ms is still perfectly usable, 15ms you'll feel a bit, 50ms will be 463 | very frustrating. `scroll-down` is always faster than `scroll-up` 464 | due to an asymmetry in Emacs' `vscroll` buffer. 465 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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No Surrender of Others' Freedom. 541 | 542 | If conditions are imposed on you (whether by court order, agreement or 543 | otherwise) that contradict the conditions of this License, they do not 544 | excuse you from the conditions of this License. If you cannot convey a 545 | covered work so as to satisfy simultaneously your obligations under this 546 | License and any other pertinent obligations, then as a consequence you may 547 | not convey it at all. For example, if you agree to terms that obligate you 548 | to collect a royalty for further conveying from those to whom you convey 549 | the Program, the only way you could satisfy both those terms and this 550 | License would be to refrain entirely from conveying the Program. 551 | 552 | 13. Use with the GNU Affero General Public License. 553 | 554 | Notwithstanding any other provision of this License, you have 555 | permission to link or combine any covered work with a work licensed 556 | under version 3 of the GNU Affero General Public License into a single 557 | combined work, and to convey the resulting work. The terms of this 558 | License will continue to apply to the part which is the covered work, 559 | but the special requirements of the GNU Affero General Public License, 560 | section 13, concerning interaction through a network will apply to the 561 | combination as such. 562 | 563 | 14. Revised Versions of this License. 564 | 565 | The Free Software Foundation may publish revised and/or new versions of 566 | the GNU General Public License from time to time. Such new versions will 567 | be similar in spirit to the present version, but may differ in detail to 568 | address new problems or concerns. 569 | 570 | Each version is given a distinguishing version number. If the 571 | Program specifies that a certain numbered version of the GNU General 572 | Public License "or any later version" applies to it, you have the 573 | option of following the terms and conditions either of that numbered 574 | version or of any later version published by the Free Software 575 | Foundation. If the Program does not specify a version number of the 576 | GNU General Public License, you may choose any version ever published 577 | by the Free Software Foundation. 578 | 579 | If the Program specifies that a proxy can decide which future 580 | versions of the GNU General Public License can be used, that proxy's 581 | public statement of acceptance of a version permanently authorizes you 582 | to choose that version for the Program. 583 | 584 | Later license versions may give you additional or different 585 | permissions. However, no additional obligations are imposed on any 586 | author or copyright holder as a result of your choosing to follow a 587 | later version. 588 | 589 | 15. Disclaimer of Warranty. 590 | 591 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 592 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 593 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY 594 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 595 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 596 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 597 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 598 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 599 | 600 | 16. Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | --------------------------------------------------------------------------------