It seems like a thread is constantly repainting the image (profiling shows GdipCreateSolidFill calls in a thread taking up a significant amount of time).

Confirmed in master build.

This seems to have begun at the below commit.
Michael, could you possibly take a look at this one?
Thanks

author    Michael Meeks <michael.meeks@collabora.com>    2015-11-24 16:59:29 (GMT)
committer    Michael Meeks <michael.meeks@collabora.com>    2015-11-24 19:46:02 (GMT)
commit    87199d3829257420429057336283c55be6ae7481 (patch)
tree    40f63144f9b20cebbaa6cb6fd64184e27c7b192f
parent    9b52b8999be86e5c6e5f5901b2640b16f08a2323 (diff)
vcl: re-introduce idle handling.
 564a31a6903a2ae896058e5509236ccdc91062a3 is the first bad commit
commit 564a31a6903a2ae896058e5509236ccdc91062a3
Author: Norbert Thiebaud <nthiebaud@gmail.com>
Date:   Tue Nov 24 21:51:11 2015 -0800

    source 87199d3829257420429057336283c55be6ae7481

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Hokay - so this is a pre-existing bug in:

svx/source/dialog/graphctl.cxx:

IMPL_LINK_TYPED( GraphCtrl, UpdateHdl, Idle*, pTimer, void )
{
    aUpdateLink.Call( this );

    pTimer->Start();
}

We switched from some frequent timeout calling this 'Update' link on the graphics control all the time - to an idle handler doing it - which even at low priority consumes a great chunk of CPU time - we do nothing else ;-)

Quite why we need such a nonsense is not entirely clear to me (yet) - but this is the cause.

Adding Cc: to Michael Meeks

Working on this - to try to avoid restoring the busy/timeout which was hardly better ...

Not really a huge problem burning the CPU there I think, but fixed up in master - lets see how that shakes down there before back-porting to 5.2 or somesuch.

Michael Meeks committed a patch related to this issue.
It has been pushed to "master":

http://cgit.freedesktop.org/libreoffice/core/commit/?id=1498c4f631e9c90b11dbdb18e8b094b90e143466

tdf#101827 - mend busy contour dialog.

It will be available in 5.3.0.

The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
http://wiki.documentfoundation.org/Testing_Daily_Builds

Affected users are encouraged to test the fix and report feedback.

Seems to work fine from my testing, so please backport. Thanks.

Michael Meeks committed a patch related to this issue.
It has been pushed to "libreoffice-5-1":

http://cgit.freedesktop.org/libreoffice/core/commit/?id=47ba511bf4fcad8502d3501bc16b07621e2ae6d8&h=libreoffice-5-1

tdf#101827 - mend busy contour dialog.

It will be available in 5.1.7.

The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
http://wiki.documentfoundation.org/Testing_Daily_Builds

Affected users are encouraged to test the fix and report feedback.

Thanks for backporting.

Michael Meeks committed a patch related to this issue.
It has been pushed to "libreoffice-5-2":

http://cgit.freedesktop.org/libreoffice/core/commit/?id=0ba034f26883c0fd417d99ad410448bce44e33a6&h=libreoffice-5-2

tdf#101827 - mend busy contour dialog.

It will be available in 5.2.4.

The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
http://wiki.documentfoundation.org/Testing_Daily_Builds

Affected users are encouraged to test the fix and report feedback.