cpu usage high with windows change dir / winDialogString (PR#11045)

Good afternoon Duncan,

Thanks for that.  See below for my reply.

Best Regards,
Sean

On 28/03/2008 12:05 PM, seanpor at acm.org wrote:

 > Good afternoon,
 >
 > This is possibly a windows only bug, definitely of comparatively low
 > importance - but for the sake of completeness here we go.  I've
 > searched http://bugs.R-project.org/ etc., but can find no mention.
 >
 > For RGui.exe, the CPU usage goes to 100% for certain dialog boxes for
 > the duration that the dialog box is visible, e.g.
 >
 > * check CPU usage is low
 > * On the RGui.exe menu chose File / Change dir...
 > * the CPU usage goes to 100%
 > * hit OK
 > * the CPU usage goes back down again

 What is the bug here?  I'd guess it's not R using the cpu, rather some
 other process hooked to the dialog, but even if it really is R, why is
 this a bug?

Using Taskmanager it shows that RGui.exe is using 92-95% CPU while the
winDialogString() is open and 0% when the dialog is closed or a
different R dialog is used e.g. winDialog("yesnocancel", "Do you
agree?").  The bug is that the cpu usage is unusually high - by
comparison for other dialogs e.g. File / Open script... the cpu usage
stays low - for other windows applications it is not "normal" for cpu
usage to be at 100% while waiting for user input - on slower machines
(e.g. my ancient laptop) this can bring the machine to its' knees
(almost) for the short duration that the dialog is open!  If I select
the "Browse" button, the cpu usage for RGui.exe falls away to 0% so it
is only during the period that R is waiting for the user to fill in
the dialog.  Not an important bug by any means!

Best regards,
Sean