Blazor API Review: Renderer

[rynowak]

Summary

The Renderer is the host for components and the main entry point for systems that want to run components and update UI.

The Renderer is also a point of customization - primarily subclassing. Hosting environments like B-lectron or future Blazor-native implementations need to customize the behaviour of the renderer in a way that's appropriate for their environment.

As such, our main concerns here are:

• that we're not exposing bad APIs (things you shouldn't call)
• that we can maintain existing API surface if requirements change
• that we're exposing enough control for implementations to actually use this

APIs

namespace Microsoft.AspNetCore.Components.Rendering
{
    public abstract partial class Renderer : System.IDisposable
    {
        public Renderer(System.IServiceProvider serviceProvider, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory) { }
        public abstract Microsoft.AspNetCore.Components.Dispatcher Dispatcher { get; }
        public event System.UnhandledExceptionEventHandler UnhandledSynchronizationException { add { } remove { } }
        protected internal int AssignRootComponentId(Microsoft.AspNetCore.Components.IComponent component) { throw null; }
        public virtual System.Threading.Tasks.Task DispatchEventAsync(ulong eventHandlerId, Microsoft.AspNetCore.Components.Rendering.EventFieldInfo fieldInfo, System.EventArgs eventArgs) { throw null; }
        public void Dispose() { }
        protected virtual void Dispose(bool disposing) { }
        protected abstract void HandleException(System.Exception exception);
        protected Microsoft.AspNetCore.Components.IComponent InstantiateComponent(System.Type componentType) { throw null; }
        protected virtual void ProcessPendingRender() { }
        protected System.Threading.Tasks.Task RenderRootComponentAsync(int componentId) { throw null; }
        [System.Diagnostics.DebuggerStepThroughAttribute]
        protected System.Threading.Tasks.Task RenderRootComponentAsync(int componentId, Microsoft.AspNetCore.Components.ParameterView initialParameters) { throw null; }
        protected abstract System.Threading.Tasks.Task UpdateDisplayAsync(in Microsoft.AspNetCore.Components.Rendering.RenderBatch renderBatch);
    }

    public partial class EventFieldInfo
    {
        public EventFieldInfo() { }
        public int ComponentId { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute]set { } }
        public object FieldValue { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute]set { } }
    }

[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)]
    public readonly partial struct RenderBatch
    {
        private readonly object _dummy;
        public Microsoft.AspNetCore.Components.RenderTree.ArrayRange<int> DisposedComponentIDs { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } }
        public Microsoft.AspNetCore.Components.RenderTree.ArrayRange<ulong> DisposedEventHandlerIDs { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } }
        public Microsoft.AspNetCore.Components.RenderTree.ArrayRange<Microsoft.AspNetCore.Components.RenderTree.RenderTreeFrame> ReferenceFrames { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } }
        public Microsoft.AspNetCore.Components.RenderTree.ArrayRange<Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiff> UpdatedComponents { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } }
    }
}

Action Items

• Move Renderer, EventFieldInfo, RenderBatch to .RenderTree so it's pubternal

[SteveSandersonMS]

AssignRootComponentId is a weird name. Its real role is "attach root component", but the name was chosen to explain why it returns an int. Maybe it should be AttachRootComponent(Type componentType, out int componentId).

[SteveSandersonMS]

We need to make a final call about the question of component ID being int or not.

[SteveSandersonMS]

RenderRootComponentAsync really only exists for prerendering. If there was a way of moving that into HtmlRenderer that would be great. Update No wait, that's a protected method. I can't quite remember how this is organized.

Also let's consider whether HtmlRenderer could move into the .Web assembly.

[SteveSandersonMS]

No need for two separate overloads of RenderRootComponentAsync. We could just have the one that takes a ParameterView, and pass ParameterView.Empty if no params are needed.

[SteveSandersonMS]

ComponentRenderedText is pretty unusual (IEnumerable<string>). I know it was designed around perf considerations. If it was moved into .Web along with HtmlRenderer that would be ideal.