257011 - advanced.system.supportDDEExec pref ineffective

Status: RESOLVED WONTFIX

(Firefox :: General, defect)

Description

[Dan M]

Mozilla is supposed to reuse an extant window to open an URL handed it from an
external application if the pref

user_pref("advanced.system.supportDDEExec", true)

has been set (this is the default value). Recent trunk builds of Firefox seem to
always open URLs in a new window, as if the pref were set to false, regardless
of its setting. Restoring this functionality would arguably fix the largest part
of bug 172962.

NB: Surprisingly I couldn't find this bug among the bunches of already opened
DDE bugs. The DDE/Single-Window universe is a complicated place, with extensions
and OS settings and I don't know what else all vying for attention. I suspect
this behaviour was lost while fixing something else but it's kind of sorely missed.

Comment 1

[Dan M]

Note Firefox 0.9.3 is also affected.

Comment 2

[Benjamin Smedberg]

I don't understand why a pref named "SupportDDEExec" would affect whether we
open in a current window or a new window. Maybe it's just historical accident. I
specifically removed this code from Firefox during semi-single-profile work
because in Seamonkey the behavior is non-deteministic, depending on whether you
have already selected a profile or not (which affects the pref, though there is
no pref observer).
http://lxr.mozilla.org/aviarybranch/source/xpfe/bootstrap/nsNativeAppSupportWin.cpp#2055

How does this change the codepaths that are being used? I told Blake that this
might be affecting the bug where firefox opens two windows, and he had dome some
hacking in this code... we should ask him what he found.

Comment 3

[Dan M]

Since you removed the code, this one's yours, Benjamin. BTW I agree it's the
most unlikely name for a preference controlling whether the browser opens a new
window. As far as I know that was the only effect of this code.

Comment 4

[Dan M]

On the other hand the new-window-or-not functionality is being taken over by bug
172962. Closing WONTFIX and dependent on that bug.