On Tue, 16 Apr 2019 13:14:58 +0200
Erwin Burema <[email protected]> wrote:

> On Tue, 16 Apr 2019 at 12:51, Pekka Paalanen <[email protected]> wrote:
> >
> > On Sun, 14 Apr 2019 12:57:48 +0200
> > Erwin Burema <[email protected]> wrote:
> >  
> > > ---
> > >  .../cm_wayland_calibration.xml                | 106 ++++++++++++++++++
> > >  1 file changed, 106 insertions(+)
> > >  create mode 100644 
> > > unstable/color-manager-calibration/cm_wayland_calibration.xml
> > >
> > > diff --git 
> > > a/unstable/color-manager-calibration/cm_wayland_calibration.xml 
> > > b/unstable/color-manager-calibration/cm_wayland_calibration.xml
> > > new file mode 100644
> > > index 0000000..be9bb4b
> > > --- /dev/null
> > > +++ b/unstable/color-manager-calibration/cm_wayland_calibration.xml  
> >  
> > > +  <interface name="zcm_output_cal_v1" version="1">
> > > +    <description summary="Main calibration profiling interface">
> > > +      With this interface an calibration/profiling application can send 
> > > needed colors to the display, the compositors is responsible for placing 
> > > the colors (with the help of the user since we can't know the physical 
> > > location of the measurement device)
> > > +    </description>
> > > +
> > > +    <enum name="bitdepth">
> > > +      <entry name="8bit" value="0" summary="8 Bit display" />
> > > +      <entry name="10bit" value="1" summary="10 Bit display" />
> > > +      <entry name="12bit" value="2" summary="12 Bit display" />
> > > +      <entry name="14bit" value="3" summary="14 Bit display" />
> > > +    </enum>
> > > +
> > > +    <event name="display_depth">
> > > +      <description summary="Event send to inform application of display 
> > > depth"/>
> > > +      <arg name="depth" type="uint" enum="bitdepth" />
> > > +    </event>
> > > +
> > > +    <request name="set_color">
> > > +      <description summary="Request a color to be set to an area within 
> > > output">
> > > +        This request is semd to set a specific color to an output, this 
> > > color needs to be pushed to the screen as directly as possible (unless 
> > > the bool use_profile is true and with the exception of the HW LUT of the 
> > > graphics card or display itself) and preferably on top of everything 
> > > else. The compositor is responsible to place the output area inside the 
> > > output.
> > > +      </description>
> > > +      <arg name="red" type="uint" summary="Red component of color, only 
> > > least significant n bit are used where n depends on bitdepth of display" 
> > > />
> > > +      <arg name="green" type="uint" summary="Green component of color, 
> > > only least significant n bit are used where n depends on bitdepth of 
> > > display" />
> > > +      <arg name="blue" type="uint" summary="Blue component of color, 
> > > only least significant n bit are used where n depends on bitdepth of 
> > > display" />
> > > +      <arg name="use_profile" type="bool" allow-null="true" summary="If 
> > > profile should be applied, used to verify profile. If not set assume 
> > > false"/>
> > > +    </request>  
> >
> > Hi,
> >
> > would you not need a corresponding event to know the compositor has
> > shown the requested color?
> >
> > It could be as simple as a new_id argument with wl_callback interface.
> >  
> 
> Good point, will add that in the next version. Might also be an
> interesting way to measure GPU/display latency (time from callback
> received to actual change observed on screen although not sure how
> accurate that will be)

Hi,

the Wayland presentation-time extension is much better for latency
measurements as it delivers a flip timestamp hopefully from the
hardware. You can trivially compute the delay from client update to
hardware flip, and with a measurement device you can measure from flip
to light if you can synchronise the clocks.

But to use that you need a wl_surface.


Thanks,
pq

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