### Querying for Running Subsystems

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/docs/mrtk3-overview/architecture/subsystems.md

Use `XRSubsystemHelpers` to retrieve running subsystem implementations. The `GetFirstRunningSubsystem` method returns the first started and running instance, while `GetFirstSubsystem` retrieves the first instance regardless of its start state. `GetAllRunningSubsystemsNonAlloc` can be used to collect all running instances into a provided list.

```csharp
T mySubsystem = XRSubsystemHelpers.GetFirstRunningSubsystem<T>();

// Gets the first valid implementation of T, even if it hasn't been started.
T mySubsystem = XRSubsystemHelpers.GetFirstSubsystem<T>();

// If multiple implementations of T are loaded, get all of them.
List<T> allOfThem = new List<T>();
GetAllRunningSubsystemsNonAlloc<T>(allOfThem);
```

--------------------------------

### Clone Repository with Specific Branch

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/contributions/code-contributions.md

Use this command to clone the repository and immediately switch to the 'main' branch, ensuring you start on the correct branch.

```bash
git clone --branch main YOUR_GIT_URL
```

--------------------------------

### Get Subsystem Configuration

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/org.mixedrealitytoolkit.tools/SubsystemWizard/Templates/ApplyConfigTemplate.txt

Retrieves the configuration object for a specific subsystem using XRSubsystemHelpers.GetConfiguration. This is typically done in the subsystem provider's constructor.

```csharp
protected %CONFIGNAME% Config { get; }

            public %SUBSYSTEMNAME%Provider() : base()
            {
                Config = XRSubsystemHelpers.GetConfiguration<%CONFIGNAME%, %SUBSYSTEMNAME%>();
                
                // TODO: Apply the configuration to the provider.
            }
```

--------------------------------

### Accessing Subsystem Descriptor Capabilities

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/docs/mrtk3-overview/architecture/subsystems.md

Retrieve the descriptor for a running subsystem to access its capability information. This example shows how to check if a `HandsSubsystem` implementation reports physical data.

```csharp
// Get the first running hands subsystem.
var handsSubsystem = XRSubsystemHelpers.GetFirstRunningSubsystem<HandsSubsystem>();

// If we found one...
if (handsSubsystem != null)
{
    // Read the capability information off the implementation's descriptor.
    bool isPhysicalData = handsSubsystem.subsystemDescriptor.IsPhysicalData;
}
```

--------------------------------

### Get Subsystem Configuration

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/docs/mrtk3-overview/architecture/subsystems.md

Retrieve the configuration object for a specific subsystem type. Ensure the generic type parameters TConfig and TSubsystem are correctly specified.

```csharp
XRSubsystemHelpers.GetConfiguration<TConfig, TSubsystem>()
```

--------------------------------

### Run Play Mode Tests with Custom Arguments

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/contributions/code-contributions.md

Run play mode tests locally in batch mode with specified Unity version and project path. This allows for testing against different Unity versions or project configurations.

```powershell
./Tooling/Tests/run_playmode_tests.ps1 -unityVersion 2021.3.5f1 -projectPath ../my/project/path
```

--------------------------------

### Subsystem Configuration Class Template

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/org.mixedrealitytoolkit.tools/SubsystemWizard/Templates/SubsystemConfigTemplate.txt

Defines a configuration asset for a subsystem. Use this as a base for custom subsystem configurations.

```csharp
// TODO: [Optional] Add copyright and license statement(s).

using MixedReality.Toolkit;
using UnityEngine;

namespace %NAMESPACE%
{
    /// <summary>
    /// The configuration object for all %SUBSYSTEMBASECLASSNAME% implementations.
    /// </summary>
    [CreateAssetMenu(
        fileName = "%SUBSYSTEMBASECLASSNAME%Config.asset",
        menuName = "Custom/Subsystems/%SUBSYSTEMBASECLASSNAME% Config")]
    public class %SUBSYSTEMBASECLASSNAME%Config : BaseSubsystemConfig
    {
        // TODO: Add subsystem specific configuration properties.
    }
}
```

--------------------------------

### Subsystem Configuration Info Class

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/org.mixedrealitytoolkit.tools/SubsystemWizard/Templates/SubsystemDescriptorTemplate.txt

Defines the configuration parameters for a subsystem. Inherits from MRTKSubsystemCinfo and can include subsystem-specific properties. Override Equals for custom comparison.

```csharp
using MixedReality.Toolkit;
using MixedReality.Toolkit.Subsystems;
using System;

namespace %NAMESPACE%
{
    /// <summary>
    /// Encapsulates the parameters for creating a new <see cref="%SUBSYSTEMBASECLASSNAME%Descriptor"/>.
    /// </summary>
    public class %SUBSYSTEMBASECLASSNAME%Cinfo : MRTKSubsystemCinfo
    {
        // TODO: Add subsystem specific properties.

        /// <summary>
        /// Tests for equality.
        /// </summary>
        /// <param name="other">The other <see cref="%SUBSYSTEMNAME%"/> to compare against.</param>
        /// <returns>`True` if every field in <paramref name="other"/> is equal to this <see cref="%SUBSYSTEMBASECLASSNAME%"/>, otherwise false.</returns>
        public override bool Equals(MRTKSubsystemCinfo other)
        {
            // TODO: Add comparison of subsystem specific property values.
            return base.Equals(other);
        }
    }

```

--------------------------------

### Subsystem Base Class Template

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/org.mixedrealitytoolkit.tools/SubsystemWizard/Templates/SubsystemBaseClassTemplate.txt

This C# code defines the base class for a custom MRTK subsystem. It inherits from MRTKSubsystem and includes a constructor and a nested abstract Provider class. Use this as a starting point for your own subsystem implementations.

```csharp
// TODO: [Optional] Add copyright and license statement(s).

using MixedReality.Toolkit.Subsystems;
using UnityEngine.Scripting;
using UnityEngine.SubsystemsImplementation;

namespace %NAMESPACE%
{
    [Preserve]
    public class %SUBSYSTEMBASECLASSNAME% :
        MRTKSubsystem<%SUBSYSTEMBASECLASSNAME%, %SUBSYSTEMBASECLASSNAME%Descriptor, %SUBSYSTEMBASECLASSNAME%.Provider>,
        I%SUBSYSTEMBASECLASSNAME%
    {
        /// <summary>
        /// Construct the <c>%SUBSYSTEMBASECLASSNAME%</c>.
        /// </summary>
        public %SUBSYSTEMBASECLASSNAME%()
        { }

        [Preserve]
        public abstract class Provider : MRTKSubsystemProvider<%SUBSYSTEMBASECLASSNAME%>, I%SUBSYSTEMBASECLASSNAME%
        {
            #region I%SUBSYSTEMBASECLASSNAME% implementation

            // TODO: Implement abstract Provider class.

            #endregion I%SUBSYSTEMBASECLASSNAME% implementation
        }

        #region I%SUBSYSTEMBASECLASSNAME% implementation

        // TODO: Calls into abstract Provider (ex: public int MaxValue => provider.MaxValue;

        #endregion I%SUBSYSTEMBASECLASSNAME% implementation

        /// <summary>
        /// Registers a %SUBSYSTEMBASECLASSNAME% implementation based on the given subsystem parameters.
        /// </summary>
        /// <param name="subsystemParams">The parameters defining the %SUBSYSTEMBASECLASSNAME%
        /// functionality implemented by the subsystem provider.</param>
        /// <returns>
        /// <c>true</c> if the subsystem implementation is registered. Otherwise, <c>false</c>.
        /// </returns>
        public static bool Register(%SUBSYSTEMBASECLASSNAME%Cinfo subsystemParams)
        {
            %SUBSYSTEMBASECLASSNAME%Descriptor Descriptor = %SUBSYSTEMBASECLASSNAME%Descriptor.Create(subsystemParams);
            SubsystemDescriptorStore.RegisterDescriptor(Descriptor);
            return true;
        }
    }
}
```

--------------------------------

### Run Play Mode Tests Locally

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/contributions/code-contributions.md

Execute play mode tests locally in batch mode using the provided PowerShell script. This helps identify issues that may only occur in non-graphics batch mode.

```powershell
./Tooling/Tests/run_playmode_tests.ps1
```

--------------------------------

### Create a New Feature Branch

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/contributions/code-contributions.md

Create a new branch for your changes or fixes to keep your work organized and separate from the main development line.

```bash
git checkout -b foobar_fix
```

--------------------------------

### Subsystem Descriptor Class

Source: https://github.com/mixedrealitytoolkit/mixedrealitytoolkit-unity/blob/main/org.mixedrealitytoolkit.tools/SubsystemWizard/Templates/SubsystemDescriptorTemplate.txt

Defines the descriptor for a subsystem, specifying its interface and provider type. Includes a factory method for creation and validation.

```csharp
    /// <summary>
    /// Specifies a functionality description that may be registered for each implementation that provides the
    /// <see cref="%SUBSYSTEMBASECLASSNAME%"/> interface.
    /// </summary>
    public class %SUBSYSTEMBASECLASSNAME%Descriptor :
        MRTKSubsystemDescriptor<%SUBSYSTEMBASECLASSNAME%, %SUBSYSTEMBASECLASSNAME%.Provider>
    {
        /// <summary>
        /// Constructs a <c>%SUBSYSTEMBASECLASSNAME%Descriptor</c> based on the given parameters.
        /// </summary>
        /// <param name="cinfo">The parameters required to initialize the descriptor.</param>
        %SUBSYSTEMBASECLASSNAME%Descriptor(%SUBSYSTEMBASECLASSNAME%Cinfo cinfo) : base(cinfo)
        {
            // TODO: Initialize subsystem specific properties.
        }

        // TODO: Add subsystem specific properties.

        /// <summary>
        /// Creates a <c>%SUBSYSTEMBASECLASSNAME%Descriptor</c> based on the given parameters validating that the
        /// <c>id</c> and <c>implentationType</c> properties are specified.
        /// </summary>
        /// <param name="cinfo">The parameters required to initialize the descriptor.</param>
        /// <returns>
        /// The created <c>%SUBSYSTEMBASECLASSNAME%Descriptor</c>.
        /// </returns>
        internal static %SUBSYSTEMBASECLASSNAME%Descriptor Create(%SUBSYSTEMBASECLASSNAME%Cinfo cinfo)
        {
            // Validates cinfo.
            if (!XRSubsystemHelpers.CheckTypes<%SUBSYSTEMBASECLASSNAME%, %SUBSYSTEMBASECLASSNAME%.Provider>(
                    cinfo.Name,
                    cinfo.SubsystemTypeOverride,
                    cinfo.ProviderType))
            {
                throw new ArgumentException("Could not create %SUBSYSTEMBASECLASSNAME%Descriptor.");
            }

            return new %SUBSYSTEMBASECLASSNAME%Descriptor(cinfo);
        }
    }
}
```