1180307 - OS X autoscrolling doesn't work if window touches bottom edge of screen

Status: RESOLVED INVALID

(Core :: Widget: Cocoa, defect)

Description

[Ken Harris]

User Agent: 
Build ID: 20150630154324

Steps to reproduce:

1. On OS X (10.9, in my case), open a Firefox window that has a lot of text (so the window needs to scroll vertically to show it all).
2. Position the window so the bottom edge is exactly touching the bottom edge of the screen.  (You may need to move the Dock to the side.)  Just drag the bottom edge of the window to the bottom of the screen.
3. Press and hold the mouse button oven an empty area, and drag down to select text.


Actual results:

The text selection extends to the bottom of the window's viewport, but that's it.  It doesn't scroll to let me select any more text.

(In the Mac world, this feature is called "automatic scrolling" or "autoscroll", but the Firefox world seems to use that term for something completely different.)


Expected results:

It should scroll the window content to let me select more text, even though my mouse cursor is not literally outside the window.

For example, if you open TextEdit.app with a lot of text, position the window in the same place, and drag down, the window will scroll.  If you open Pages.app with a lot of text, it will also scroll, and Pages even provides some acceleration so that it starts out slow and goes faster the longer you hold it there.

Firefox does provide automatic scrolling, in some cases, but I assume it was designed back when Firefox windows had a status bar on the bottom.  Now that the web content extends all the way to the bottom of the window (and thus often to the bottom of the screen), there's no way to drag outside of it, so Firefox's automatic scrolling doesn't seem to triggered.

Comment 1

[Steven Michaud [:smichaud] (Retired)]

This also happens in Safari.  So it's an Apple bug, or maybe a design flaw.

Comment 2

[Ken Harris]

I don't understand why it's relevant that it also happens in Safari.

If something is broken in Firefox, and also happens to be broken in Safari at the same time, that would not be "an Apple bug, or maybe a design flaw", unless both applications used the same system-provided library for that feature.  In this case, they don't.  Automatic scrolling in custom views depends on the application implementing it properly [1].

Furthermore, automatic scrolling behavior is described in the Apple Human Interface Guidelines.  I've seen many bugs filed (and fixed) on the basis that it's what's called for in the HIG.  Firefox doesn't have a policy of "Follow what Safari does, over what the Apple HIG says", nor should we.  There's no reason not to have this feature: it's useful, users expect it, and it doesn't detract from any other useful functionality.

FWIW, I've reported the Safari bug to Apple, too.  But Firefox doesn't use Webkit so even after they fix it there, how would it help us here?


[1]: https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/NSScrollViewGuide/Articles/Scrolling.html#//apple_ref/doc/uid/TP40003463-SW3

Comment 3

[Steven Michaud [:smichaud] (Retired)]

> I don't understand why it's relevant that it also happens in Safari.

It shows that this is an Apple bug.

Furthermore, since this Apple bug also effects Safari, Apple is quite likely to fix it.

Mozilla has very limited resources.  We're not going to spend time working around an Apple bug that Apple's likely to fix.