Clients can't get high frequency input in Unity8

[Daniel van Vugt]

Clients can't get high frequency input in Unity8.

Using native (non-nested) Mir servers, clients can get the full speed input stream if they so choose (MIR_CLIENT_INPUT_RATE=0). And it's planned that this will become a formal API feature: bug 1439590

However in Unity8, because it is a nested server, the client no longer has the option of getting this high frequency input.

Examples of clients that utilize high frequency input for improved visual quality:
   mir_demo_client_fingerpaint -w--desktop_file_hint=unity8
   mir_demo_client_target -n--desktop_file_hint=unity8
You may also want to experiment with those using ultra-high frequency input by adding a kernel parameter: usbhid.mousepoll=1

This is a tricky problem because for touch at least we do want the input stream to be throttled to the display rate from the top level down. Perhaps the answer is to enhance Unity8 to be a full-speed (non-resampled) client and then the clients of Unity8 can then still have a choice of whether they get resampling or not.

[Daniel van Vugt (vanvugt)]

See also: bug 1486341

[Daniel van Vugt (vanvugt)]

Test case for mako (using Mir 0.16 syntax):

   env MIR_CLIENT_PERF_REPORT=log mir_demo_client_target -n -- --desktop_file_hint=dialer-app

Expect: The reported FPS is higher than the display refresh rate (above 90 on mako).

[Gerry Boland (gerboland)]

In that case, shell should not resample events, and leave that up the client, no?

[Gerry Boland (gerboland)]

QtMir not deciding to resample, that's unity8.

[Daniel van Vugt (vanvugt)]

Yes, I think in the long run we want raw input being passed to clients and then to rely on the toolkits to do the right thing.

However I won't flick that switch until Qt's input resampling is usable for us. That might be possible after we do frame notification, and have more accurate and steady frame timing independent of nesting.

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity8 - 8.15+17.04.20170110.4-0ubuntu1

---------------
unity8 (8.15+17.04.20170110.4-0ubuntu1) zesty; urgency=medium

  [ Albert Astals Cid ]
  * Give focus to one of the buttons of the dialog
  * tst_WindowResizeArea: Use default values for mouseFlick speed and
    iterations (LP: #1651580)
  * Require Qt 5.6 & misc fixes

  [ Daniel van Vugt ]
  * Deprecate usage of Mir's input resampling, instead opting for: (LP:
    #1497105, #1591328)

  [ Josh Arenson ]
  * Allow the scopes list to automatically scroll when a scope is being
    dragged past the bounds of the screen. (LP: #1575319)

  [ Lukáš Tinkl ]
  * Fix touch window controls being unreachable when the overlay is
    being displayed (LP: #1648167)
  * Fixup paths for window state storage in snappy environment
  * Add Unity.Platform mock for our tests (LP: #1655336)

  [ Michael Zanetti ]
  * PreviewRatingInput: Use displayText instead of text to
    enable/disable the Send button (LP: #1595910)
  * Add a D-Bus interface to control some debug facilities on the fly
  * some launcher workarounds for the snapping

  [ Michał Sawicz ]
  * Nuke leftover Platform in IndicatorsManager

  [ Nick Dedekind ]
  * Added registry for application menus

  [ Michael Terry, Nick Dedekind ]
  * Run the qmluitests.sh autopkg test against the installed package.

  [ Michał Sawicz, Nick Dedekind ]
  * Application menus

  [ Rodney Dawes ]
  * Remove the payments widget and dependency on libpay as no longer
    needed.

 -- Michał Sawicz <email address hidden> Tue, 10 Jan 2017 14:48:42 +0000