From d0d04fc44572635d5b9302a90cf219f52b618841 Mon Sep 17 00:00:00 2001
From: Simon Lydell <simon.lydell@gmail.com>
Date: Sat, 3 Dec 2016 22:56:01 +0100
Subject: [PATCH] Improve holding keys for scrolling by page

Fixes #843.
---
 documentation/options.md      |  9 +++++++++
 extension/lib/commands.coffee | 25 +++++++++++++++++--------
 extension/lib/defaults.coffee |  1 +
 3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/documentation/options.md b/documentation/options.md
index abd65d6..0c7a89b 100644
--- a/documentation/options.md
+++ b/documentation/options.md
@@ -486,6 +486,15 @@ Firefox’s `layout.css.scroll-behavior.spring-constant` option. It is reset aga
 after one second (by default). If that doesn’t work out for you, you can
 customize that timeout using the `scroll.reset_timeout` option.
 
+Another quirk of Firefox’s smooth scrolling is that it doesn’t like if you ask
+for smooth scrolling too often: The scrolling can get stuttery, progressively
+slower and even grind to a halt. On a long page with lots of elements, simply
+holding `d`, `u`, `<space>` or `<s-space>` can be too much. By default, keyboard
+software typically repeats keypresses every 30ms when holding keys. Because of
+this, VimFx only asks for smooth scrolling if more than 65ms (two repeats) has
+passed since the last request. You can customize that timeout via the
+`scroll.repeat_timeout` option.
+
 The Firefox option `general.smoothScroll` lets you turn off smooth scrolling
 entirely, including all of VimFx’s scrolling commands.
 
diff --git a/extension/lib/commands.coffee b/extension/lib/commands.coffee
index 3a6e85c..1fcf56f 100644
--- a/extension/lib/commands.coffee
+++ b/extension/lib/commands.coffee
@@ -147,9 +147,10 @@ commands.stop_all = ({vim}) ->
 
 
 
-springConstant = {
+scrollData = {
   nonce: null
-  value: null
+  springConstant: null
+  lastRepeat: 0
 }
 
 helper_scroll = (vim, event, args...) ->
@@ -157,6 +158,14 @@ helper_scroll = (vim, event, args...) ->
     method, type, directions, amounts
     properties = null, adjustment = 0, name = 'scroll', extra = {}
   ] = args
+
+  elapsed = event.timeStamp - scrollData.lastRepeat
+
+  if event.repeat and elapsed < vim.options['scroll.repeat_timeout']
+    return
+
+  scrollData.lastRepeat = event.timeStamp
+
   options = {
     method, type, directions, amounts, properties, adjustment, extra
     smooth: (
@@ -168,18 +177,18 @@ helper_scroll = (vim, event, args...) ->
   # Temporarily set Firefox’s “spring constant” pref to get the desired smooth
   # scrolling speed. Reset it `reset_timeout` milliseconds after the last
   # scrolling command was invoked.
-  springConstant.nonce = nonce = {}
-  springConstant.value ?= prefs.root.get(SPRING_CONSTANT_PREF)
+  scrollData.nonce = nonce = {}
+  scrollData.springConstant ?= prefs.root.get(SPRING_CONSTANT_PREF)
   prefs.root.set(
     SPRING_CONSTANT_PREF,
     vim.options["smoothScroll.#{type}.spring-constant"]
   )
   reset = ->
     vim.window.setTimeout((->
-      return unless springConstant.nonce == nonce
-      prefs.root.set(SPRING_CONSTANT_PREF, springConstant.value)
-      springConstant.nonce = null
-      springConstant.value = null
+      return unless scrollData.nonce == nonce
+      prefs.root.set(SPRING_CONSTANT_PREF, scrollData.springConstant)
+      scrollData.nonce = null
+      scrollData.springConstant = null
     ), vim.options['scroll.reset_timeout'])
 
   helpScroll = help.getHelp(vim.window)?.querySelector('.wrapper')
diff --git a/extension/lib/defaults.coffee b/extension/lib/defaults.coffee
index 6dcf7dd..eb7581f 100644
--- a/extension/lib/defaults.coffee
+++ b/extension/lib/defaults.coffee
@@ -186,6 +186,7 @@ advanced_options =
   'smoothScroll.pages.spring-constant': '2500'
   'smoothScroll.other.spring-constant': '2500'
   'scroll.reset_timeout':               1000
+  'scroll.repeat_timeout':              65
   'scroll.horizontal_boost':            6
   'scroll.vertical_boost':              3
   'scroll.full_page_adjustment':        40
-- 
2.39.3