HWC Multimonitor work

Daniel van Vugt daniel.van.vugt at canonical.com
Thu Dec 11 02:50:48 UTC 2014

Even displays of the same refresh rate are a problem (see in X/Compiz 
where all but one of your displays will tear).

In Mir (the DRM platform) we've solved this with parallel rendering 
while waiting for the previous page flips. Because if you have multiple 
monitors at the same refresh rate, the upper limit on time to wait for 
vsync on all of them is (asymptotically) double that of a single monitor.

It's possible HWC could support such an approach, so long as we have the 
required triple-buffering in the compositor.

On 11/12/14 10:31, Christopher James Halse Rogers wrote:
> On Thu, Dec 11, 2014 at 7:59 AM, Kevin DuBois
> <kevin.dubois at canonical.com> wrote:
>> Details of why:
>> HWC's prepare() and set() functions post to all the displays in one call.
> Incidentally, how does this work with displays of different refresh
> rate? Does HWC drop pending flips when a new flip is scheduled?

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