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Ubuntu 10.04.1 LTS - gnome, using metacity (no effects). Bug occurs on
two dell laptops, and several desktop machines, dell and others.
To reproduce:
1) Turn off visual effects (System -> preferences -> appearance ->
visual effects -> "None")
2) start gconf-editor; set apps -> metacity -> general -> num_workspaces
to 17
3) right click on title bar of any window.
Analysis:
workspace switcher preferences widget allows you to specify number of
workspaces (can also do this via gconf-editor -> apps -> metacity ->
general -> num_workspaces). However, it appears that there is *now*
software that depends on a hard-wired limit of 16 workspaces (limitation
inherited from compiz).
under the workspace switcher preferences widget, if you increase the
number of workspaces to 17, an additional workspace name is created
("Workspace 17"). (in the past, there was no limit on the number of
workspaces except what would fit in the panel.)
now, under gconf-editor -> apps -> metacity -> workspace_names there are
16 variable names, name_1 through name_16. if you change gconf-editor
-> apps -> metacity -> general -> num_workspaces to 17, no additional
workspace name variable is created.
After setting num_workspaces to 17, if you right click on the title bar
of any window, the window manager will crash.
Code somewhere in metacity (apparently) frequently scans down the list
of workspace names, and uses num_workspaces as a limit for how far to
scan. When it increments past the compiz limit of 16, it is referencing
uninitialized memory. Results after this are (of course) somewhat
unpredictable, but generally the window manager either dies or goes into
an infinite loop.
Since the window manager is dead, it is hard to collect data, but I have
seen an error message that said something like:
"window manager exception: workspace_name[i] != NULL", I'm really sorry
that I didn't write down the exact wording - I'm afraid my recollection
isn't good enough to support a pattern search.
I should point out that the compiz limit of 16 workspaces seems to be
based on the design of the visual effect added for the workspace
switcher -- it goes off the screen if you have a large number of
workspaces. However, a large number of workspaces is one of the killer
features of the gnome desktop for me (I regularly configure my systems
to use 20-30 workspaces, and use them to organize my work), and the
limitation in compiz has forced me to turn off visual effects on all my
systems. Please Please Please lose the workspace switcher effect, or at
least give an option to use the old behavior.
** Affects: gnome-panel (Ubuntu)
Importance: Undecided
Status: New
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workspace switcher applet crashes window manager
https://bugs.edge.launchpad.net/bugs/611373
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