[development] $custom_theme when does it take effect... when does it not

[Jon Saints]

I notice a bug in D6.4 and CVS in the block module. This post,
however, is not to report the bug (i will use bug tracker for that).
This post is to ask a development question that will help me create a
patch for the issue.

On our website we use different themes for different sections of the
site.  As the user browses to different sections of the site, the
theme is changed automatically by changing $custom_theme global in
hook_init().

Bug background: The bug occurs when administering blocks.  For
example, if my current active theme is foo_theme and I click
admin/build/block/list/bar_theme a list of blocks for bar_theme is not
displayed.  Instead, a list of blocks for the active theme foo_theme
is displayed.  When the user clicks the link "Bar theme" they could
reasonably expect that a list of the blocks for bar_theme should
display.

The development question: I think the bug has something to do with the
code in the block module function block_admin_display(). In this
function the author of the code tries to display a list of blocks for
the theme the user selected by changing  the global variable
$custom_theme. The problem with this approach is that outside of
hook_init() I have found that changing $custom_theme variable has no
effect on changing the active theme.

Have others found this to be the case that changes to $custom_theme
variable have no effect on changing the active theme outside of
hook_init()?

If this is the case then we need to rethink how we are pulling the
list of blocks in the block module admin.

Thanks
Jon