In Firefox, scrolling and then pressing Ctrl causes zoom

[Jonas Olson]

When scrolling a heavy webpage in Firefox tend to lag on my computer so that the motion of the page continues after I have stopped giving scrolling commands. If I then, before the page has stopped, press Ctrl (to Ctrl-Tab switch between tabs, for example) Firefox starts to zoom the page (as when you scroll while holding Ctrl). This is unwanted behaviour every time for me. I'm using Ubuntu 11.04 with Firefox 5 (5.0+build1+nobinonly-0ubuntu0.11.04.2). In Ubuntu 10.10, the behaviour was the expected, i.e., zooming or scrolling was determined based on if you held Ctrl pressed while rolled your scroll wheel, not whether Ctrl was pressed during the motion of the page.

To reproduce:
1. Open a webpage in Firefox, preferably a large and heavy one.
2. Make sure your computer is slow enough that the scrolling motion of the page lags appreciably behind the scrolling commands of your mouse wheel.
3. Stop rolling the wheel and while the page is still scrolling, press Ctrl. This causes Firefox to zoom the page.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: firefox 5.0+build1+nobinonly-0ubuntu0.11.04.2
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
Architecture: i386
Date: Wed Jun 29 10:10:27 2011
FirefoxPackages:
 firefox 5.0+build1+nobinonly-0ubuntu0.11.04.2
 flashplugin-installer 10.3.181.26ubuntu0.11.04.1
 adobe-flashplugin N/A
 icedtea-plugin 1.1~20110420-0ubuntu1.1
ProcEnviron:
 LANGUAGE=sv_SE:en
 PATH=(custom, user)
 LANG=sv_SE.UTF-8
 SHELL=/bin/bash
SourcePackage: firefox
UpgradeStatus: Upgraded to natty on 2011-06-03 (25 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[dimovnike (dimovnike)]

this is so annoying! this is happening in chromium too..

[dimovnike (dimovnike)]

it doesnt matter how slow is computer as mentioned in the bug description. Its happening on simple pages (e.g. on this one) on i7 with 8gb ram and SSD so the PC slowness is not an issue. It looks like the touchpad is sending scroll events even after you lift the fingers up from touchpad.

[Jonas Olson (jolson)]

dimovnike wrote: "It looks like the touchpad is sending scroll events even after you lift the fingers up from touchpad."

Perhaps so. However, I don't remember having this problem on earlier versions of Firefox on the same computer.

(PS. What is the proper way to quote other comments?)

[bitinerant (bitinerant)]

As dimovnike wrote, this happens on simple pages too--as long as they are at least several screens long. Two-finger scrolling has momentum, or "coasts" a while after removing your fingers from the touchpad if they are in motion. I love this feature and think it works well. The problem is that the Ctrl key should not zoom the document while Firefox is coasting! This bug can unintentionally zoom in or out, depending on the scroll direction. I suspect most people who face this problem never realize why the document zoomed in or out.

[sillyxone (sillyxone)]

I got so annoyed by this behavior, too. The easiest solution for me is to disable zooming with Ctrl-Scroll in Firefox:
- go to about:config
- change the value of mousewheel.withcontrolkey.action (changed mine to 1 for normal scrolling)

https://support.mozilla.org/en-US/questions/821743

[sillyxone (sillyxone)]

correction: for my current version of Firefox (v31), the config key is "mousewheel.with_control.action"

[bitinerant (bitinerant)]

This issue is not limited to Firefox or even the control key. When scrolling and then coasting in one application and then using alt-tab to switch to another application, often the coasting continues.

For example, begin scrolling a long web page in Firefox and let it coast. While it is still coasting, press alt-tab but don't release the alt key. Every time I do this, the highlighted application in the application switcher 'coasts' right or left (depending on whether I am coasting up or down) and then slowly stops after a couple of seconds.

Here is another (less reproducible) example. I began scrolling and coasting in Terminator, then pressed alt-tab to switch to Image Viewer (eog) and the picture I had open zoomed out, which is the 'scroll down' action in Image Viewer.

Perhaps what I am describing is a different bug, but if so, I it seems closely connected. The way coasting is done seems fragile. It might be that the fix is simply to stop coasting when any key is pressed, or it might be a lot more complicated than this.

[Dominic Chambers (dominic-chambers)]

Yes, this is happening for me on any app that supports zooming using scrolling and a key modifier, like Nautilus, Chrome & Firefox. I'm using an XPS 13 (9343). Does anybody know the correct component (e.g. Gnome or Synaptics?) to raise this bug against?

[Dominic Chambers (dominic-chambers)]

Okay, looks like this is unfixable until the switch to libinput (Wayland):

  * https://bugs.freedesktop.org/show_bug.cgi?id=76094

The workaround until then is to disable coasting:

```
Option "CoastingSpeed" "0"
```

or to make it part of your muscle memory not to do it I guess :-).