You can set the scroll amount for the mouse wheel via mousewheel prefs on the about:config page

mousewheel.withnokey.numlines = 2
mousewheel.withnokey.sysnumlines = false

Look at this pref to set the scrolling behavior with the keyboard.

toolkit.scrollbox.verticalScrollDistance (3)

• http://kb.mozillazine.org/about:config
• http://kb.mozillazine.org/About:config_entries#Mousewheel.

There are extensions that work both for the mouse and the keyboard to set the scroll amount, but they can only be set to scroll an amount of pixels and not to scroll one line regardless of font-size (height) of the text.

• SmoothWheel: https://addons.mozilla.org/firefox/addon/smoothwheel/
• Yet Another Smooth Scrolling: https://addons.mozilla.org/firefox/addon/yet-another-smooth-scrolling/

Thank you for your reply. I apologize for my miscommunication on my original post, but I meant to say that that the "mousewheel.withnokey.numlines" & "mousewheel.withnokey.sysnumlines" no longer work for me under FF 17. If I r-click and choose "Reset", the lines completely disappear from about:config & the mouse wheel scrolling continues to jump too far, until I changed this line

mousewheel.system_scroll_override_on_root_content.enabled;false

It changes back to the slower FF 16 mouse scroll speed. The problem now is, if I want to change the scroll speed to something else, the Mozillazine instructions no longer work.

Scrolling behavior w/ the keyboard is fine. I am unable to use any type of smooth scrolling, as it makes me motion sick.

There seem to be different prefs, one for the scroll amount and other for the various axes (x, y, z)

mousewheel.min_line_scroll_amount
mousewheel.default.delta_multiplier_x
mousewheel.default.delta_multiplier_y

So you can modify the mousewheel.min_line_scroll_amount pref to specify how many lines to scroll.

I thought the same thing when I saw that min_line_scroll setting, and I changed the numbers around, but no such luck.

Playing around w/ the delta modifiers DOES change the mouse scroll speed, though it would be nice for a more user-friendly explanation. Changing the "y" value to something lower than 100 changes the scroll speed to 1 line, no matter what. Changing any values on "x" to anything other than 100 while "y" is not set at 100 still creates the 1 line scroll speed. Putting the "y" value back to 100 & playing around w/ the "x" value DOES change the scroll speed beyond 1 line scrolling, though guessing how many lines it scrolls is not readily apparent. However, thank you for the idea of playing w/ the delta settings.

Anything else would be the alt+scrolling feature that seems to be gone. The Gecko wiki on mouse scrolling no longer has the option to scroll line per line, as it did w/ previous FF versions.

See:

• https://wiki.mozilla.org/Gecko:Mouse_Wheel_Scrolling
• https://wiki.mozilla.org/Gecko:Mouse_Wheel_Scrolling#Mozilla_17_.28Firefox_17.29_or_later

Yes, I was reading that before posting and had some difficulty making sense of it. Now, after our conversation here & playing w/ the default delta multipliers earlier, I played w/ the "y" alt.delta_multiplier & *think* that I'm back at scrolling one line at a time w/ alt held down (36). I'm still not sure though, since I do not understand how the values work.

But, thank you for all the help! I take it I'll need to go another route for suggestions on future FF releases? Having a more user friendly way on changing mouse scroll speed would be helpful.

There are some test cases that Mozilla uses to make sure that Firefox is working properly.

• http://mxr.mozilla.org/mozilla-central/search?string=delta_multiplier&tree=mozilla-central

Note that you normally want to modify the vertical (y) axis and not the horizontal (x) axis delta_multiplier values.
The delta_multiplier are internally floats of type double and are converted to an integer for the prefs by multiplying them with 100.

• https://developer.mozilla.org/en/Mozilla_event_reference/wheel
• https://developer.mozilla.org/en/DOM/WheelEvent

~ = mousewheel.system_scroll_override_on_root_content

` = mousewheel

basically, the num of lines to scroll becomes relative to OS wheel setting. we used to be able to specify it explicitly through `.<modifier-key>.numlines, when `.<modifier-key>.sysnumlines = false

now, we always specify percentage of the OS wheel-line through the new `.<modifier-key>.delta_multiplier_<direction>. eg. if your OS wheel-line is 4, then to vertically scroll 2 lines per wheel event, set `.<modifier-key>.delta_multiplier_y to 50

while the above is per modifier key, ~.* apply a percentage of the OS wheel-line for no/any modifier key

• if ~.enabled = false, then `.<modifier-key>.delta_multiplier_<direction> is used
• if ~.enabled = true: if ~.vertical.factor >= `.<modifier-key>.delta_multiplier_y, then use ~.vertical.factor, otherwise use `.<modifier-key>.delta_multiplier_y (same goes for horizontal scroll)

in essence, if ~.enabled = true, choose the bigger percentage to apply, not both, for each direction, for each modifier key

btw, don't take my words for those behaviors, i got that accidentally while i was trying to figure out how to mouse-scroll by pages/by pixels (which i failed, any idea?)

i quote this from source: pref("mousewheel.min_line_scroll_amount", 5) // If line-height is lower than this value (in device pixels), 1 line-scroll scrolls this height.