docs/development/components/v1/verbose_logging.md

# Enable verbose logging for input events (Components v1)

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Adding extra logging for input event dispatch allows you to see what (and how)
components are handling event dispatch.

To enable vebose logging for components that use
<code>[fxl](/docs/development/languages/c-cpp/logging.md)</code> to parse their
args, add the `--verbose` flag to its invocation. For example, `Root Presenter`
and `Scenic` components can issue verbose logging.

The following sample code shows the
[component manifest](/docs/concepts/components/v1/component_manifests.md) (`.cmx`) of a
test that starts a `Scenic` component in its `injected-services` clause:

```json
{
  "facets": {
    "fuchsia.test": {
      "injected-services": {
        "fuchsia.ui.scenic.Scenic": "fuchsia-pkg://fuchsia.com/scenic#meta/scenic.cmx",
```

To add extra logging for input event dispatch, modify the
`fuchsia.ui.scenic.Scenic` line in the following way:

```json
"fuchsia.ui.scenic.Scenic": [ "fuchsia-pkg://fuchsia.com/scenic#meta/scenic.cmx", "--verbose=2" ],
```

Each service instance of `Scenic` (or `Root Presenter`) must be
modified, unless you know which service is invoked first.

In most ways, this is identical to modifying a
<code>[sysmgr](/src/sys/sysmgr/sysmgr-configuration.md)</code> services
configuration file.