# LibTmux.FSharp.Mirror.startRefreshing

- **Module:** LibTmux.FSharp
- **Package:** LibTmux.FSharp
- **Language:** F#
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/src/LibTmux.FSharp/Control.fsi#L133
- **Page:** https://libtmux.org/en/fsharp/latest/reference/libtmux-fsharp-mirror-startrefreshing/

```
val startRefreshing:
        cancellationToken: CancellationToken -> every: TimeSpan -> anchor: LibTmux.Session -> Task<ServerMirror>
```

Mirrors a server, also capturing whenever it has been quiet for an interval.

The caller owns and asynchronously disposes the returned mirror.

## Examples

Keep a current copy of a server's sessions, windows and panes as tmux announces changes, and wait until it shows a state instead of polling. Use Linux or macOS with Git, tmux 3.2a or newer, .NET SDK 10.0.303, and the .NET 8 and 10 runtimes. In an empty directory, fetch the documented library revision:

```console
$ git clone https://github.com/libtmux/libtmux-dotnet.git libtmux-source && \
  git -C libtmux-source checkout --detach cf34b255c896d19a97e7d7fabea58609c916012d
```

Save this complete consumer setup as global.json:

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/global.json).

```json
{
  "sdk": {
    "version": "10.0.303",
    "rollForward": "disable",
    "allowPrerelease": false
  },
  "test": {
    "runner": "Microsoft.Testing.Platform"
  }
}
```

Save this complete consumer setup as NuGet.config:

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/examples/api/NuGet.config).

```xml
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <clear />
    <add key="libtmux-source" value="libtmux-source/artifacts/api-example-packages" />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
  <packageSourceMapping>
    <clear />
    <packageSource key="libtmux-source">
      <package pattern="LibTmux" />
      <package pattern="LibTmux.*" />
    </packageSource>
    <packageSource key="nuget.org">
      <package pattern="*" />
    </packageSource>
  </packageSourceMapping>
</configuration>
```

Save this complete consumer setup as Example.fsproj:

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/examples/api/fsharp/Example.fsproj).

```xml
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFrameworks>net8.0;net10.0</TargetFrameworks>
    <LangVersion>10.0</LangVersion>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
    <DisableImplicitFSharpCoreReference>true</DisableImplicitFSharpCoreReference>
    <DisableImplicitLibraryPacksFolder>true</DisableImplicitLibraryPacksFolder>
  </PropertyGroup>
  <ItemGroup>
    <Compile Include="Program.fs" />
    <PackageReference Include="FSharp.Core" Version="[10.1.303]" />
    <PackageReference Include="LibTmux.FSharp" Version="[0.0.0-alpha.20]" />
  </ItemGroup>
</Project>
```

Save this complete program as Program.fs. It creates a private server with LibTmux.Server.CreateOwnedAsync; use! disposes owned scopes after success, cancellation or failure. The F# facade has no separate server constructor.

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/examples/LibTmux.FSharp.Examples/Programs/LiveState.fs).

```fsharp
// fsharp-snippet: LiveState
open System
open System.Threading
open LibTmux
open LibTmux.FSharp

let runAsync () =
    task {
        use deadline = new CancellationTokenSource(TimeSpan.FromSeconds 20.)
        let token = deadline.Token

        let options =
            ServerConnectionOptions(
                SocketName = "fsharp-live-" + Guid.NewGuid().ToString("N"),
                ConfigurationFile = "/dev/null"
            )

        use! owned = options |> Server.createOwned token

        let! session =
            owned.Value.CreateSessionAsync(
                NewSessionRequest(Name = "work", WindowName = "shell", Command = "/bin/sh"),
                token
            )

        // Captures again on each change tmux announces, and every 200 ms for
        // changes it does not, such as the command a pane runs.
        use! mirror =
            session |> Mirror.startRefreshing token (TimeSpan.FromMilliseconds 200.)

        let! _ =
            session.CreateWindowAsync(NewWindowRequest(Name = "logs", Command = "/bin/sh"), token)

        let! withLogs =
            mirror
            |> Mirror.waitUntil token (TimeSpan.FromSeconds 5.) (fun view ->
                view.Server.Windows |> Seq.exists (fun window -> window.Name = "logs"))

        let! panes = session |> Session.panes |> Query.list token

        do! panes[0] |> Pane.sendLine token "exec sleep 30"

        // tryWaitUntil answers None when no view matched in time.
        let! sleeping =
            mirror
            |> Mirror.tryWaitUntil token (TimeSpan.FromSeconds 5.) (fun view ->
                view.Server.Panes |> Seq.exists (fun pane -> pane.CurrentCommand = "sleep"))

        printfn "windows: %s" (String.Join(", ", [ for window in withLogs.Server.Windows -> window.Name ]))

        match sleeping with
        | Some sleeping ->
            printfn
                "sleeping panes: %d"
                (sleeping.Server.Panes
                 |> Seq.filter (fun pane -> pane.CurrentCommand = "sleep")
                 |> Seq.length)

            printfn "newer view: %b" (sleeping.Epoch > withLogs.Epoch)
        | None -> printfn "no pane ran sleep within five seconds"
    }

runAsync().GetAwaiter().GetResult()
// endfsharp-snippet
```

Build the exact source packages and the saved consumer, then run both supported frameworks. The local package feed prevents an unrelated published package from satisfying the restore. Each program checks its result and exits unsuccessfully after an unhandled error:

```console
$ export NUGET_PACKAGES="$PWD/packages" && \
  dotnet restore libtmux-source/src/LibTmux.FSharp/LibTmux.FSharp.fsproj --locked-mode && \
  dotnet pack libtmux-source/src/LibTmux/LibTmux.csproj \
    --configuration Release --no-restore -p:ContinuousIntegrationBuild=true \
    --output "$PWD/libtmux-source/artifacts/api-example-packages" && \
  dotnet pack libtmux-source/src/LibTmux.FSharp/LibTmux.FSharp.fsproj \
    --configuration Release --no-restore -p:ContinuousIntegrationBuild=true \
    --output "$PWD/libtmux-source/artifacts/api-example-packages" && \
  dotnet restore Example.fsproj --configfile NuGet.config && \
  dotnet build Example.fsproj --configuration Release --no-restore --warnaserror && \
  export LIBTMUX_TMUX="$(command -v tmux)" && \
  export TMUX_TMPDIR=/tmp/libtmux-dotnet-dev && \
  mkdir -p "$TMUX_TMPDIR" && \
  unset TMUX TMUX_PANE && \
  dotnet bin/Release/net8.0/Example.dll && \
  dotnet bin/Release/net10.0/Example.dll
```

Expected program output from each framework:

```text
windows: shell, logs
sleeping panes: 1
newer view: true
```

## Parameters

- `cancellationToken` (`CancellationToken`)
- `every` (`TimeSpan`)
- `anchor` (`LibTmux.Session`)

## Raises

- [`System.ArgumentOutOfRangeException`](https://learn.microsoft.com/dotnet/api/system.argumentoutofrangeexception): The interval is negative.