input_pipeline

Reviewed on: 2021-05-07

input_pipeline is a library for creating an input pipeline. For more information, see Input client library.

Building

To add input to your build, append --with //src/ui/lib/input_pipeline to the fx set invocation.

Using

input_pipeline can be used by depending on the //src/ui/lib/input_pipeline GN target.

input_pipeline is not available in the SDK.

Testing

Unit tests for input_pipeline are available in the input_pipeline_lib_tests package.

$ fx test input_pipeline_lib_tests

Source layout

The main implementation is linked in src/lib.rs.

Implementation notes

Keymap handler

Change the keymap using the following commands, for example:

fx shell run fuchsia-pkg://fuchsia.com/setui_client#meta/setui_client.cmx keyboard --keymap UsQwerty

Use:

fx shell run fuchsia-pkg://fuchsia.com/setui_client#meta/setui_client.cmx keyboard --help

for more information.

Autorepeater

Change the autorepeat settings using the following commands, for example:

fx shell run fuchsia-pkg://fuchsia.com/setui_client#meta/setui_client.cmx keyboard \
    --autorepeat-delay 500{s,second,seconds,ms,millisecond,milliseconds}
    --autorepeat-period 200{s,second,seconds,ms,millisecond,milliseconds}

Use:

fx shell run fuchsia-pkg://fuchsia.com/setui_client#meta/setui_client.cmx keyboard --help

for more information.

Inspect handler

The inspect handler records useful metrics gleaned from processing the input events. The metrics are exposed using Fuchsia's standard Inspect interfaces.

To see the recorded metrics use a command line such as this one:

fx ffx inspect show \
    "core/session-manager/session:\:session/scene_manager"

The output will be like this:

core/session-manager/session\:session/scene_manager:
  metadata:
    filename = fuchsia.inspect.Tree
    component_url = fuchsia-pkg://fuchsia.com/scene_manager#meta/scene_manager.cm
    timestamp = 62182195088
  payload:
    root:
      input_pipeline:
        input_pipeline_entry:
          events_count = 4
          last_generated_timestamp_ns = 36293071683
          last_seen_timestamp_ns = 36293838930
        input_pipeline_exit:
          events_count = 0
          last_generated_timestamp_ns = 0
          last_seen_timestamp_ns = 0

The interpretation of the metrics is as follows:

• events_count: The total number of InputEvents that the stage has seen.
• last_generated_timestamp_ns: The timestamp of the last seen InputEvent, as propagated with the event. Note that setting this timestamp is not yet very consistent so you may find that sometimes this is zero.
• last_seen_timestamp_ns: The timestamp at which the stage last saw an input event. This can be compared to the metadata.timestamp to see how recently events have been processed.

You can insert however many inspect handlers you want, if your goal is to expose metrics at multiple places in the input pipeline. In the example above, the input pipeline has been configured with two inspect handlers: one at the entry, and one at the pipeline exit. Normally the latter should see no events.