[Enhancement] ProgressBar should implement System.IProgress<float>

Summary

ProgressBar reason of existence is for its progress to be updated as a task progresses. This is done by updating the double Progress property.

This means we have to pass the ProgressBar to the running task so the task can update the property, which means making the task by aware of the ProgressBar type.

API Changes

Simply let ProgressBar implement System.IProgress<double>

Optionally, it could also implement other types like System.IProgress<single> and System.IProgress<int>

e.g.

class ProgressBar : IProgress<double>, IProgress<float>, IProgress<int>
{
    void IProgress<double>.Progress(double progress) => SetProgressInternal(progress);
    void IProgress<float>.Progress(double progress) => SetProgressInternal(progress);
    void IProgress<int>.Progress(double progress) => SetProgressInternal(progress);

    void SetProgressInternal(double progress)
    {
       // not sure how UI threads work in MAUI, but it would be great this one would be
       // thread friendly, because it is expected to be called from running tasks...
       if ( !this.CheckAccess()) {  Dispatcher.Invoke( ()=> SetProgressInternal(progress) ); return; }

       this.Progress = progress;
    }
}

Intended Use Case

let's say we have an async method that reports the progress:

async Task SomeLongTask(IProgress<int> progressNotifier)
{
    for(int i=0; i < 100; ++i)
   {
       progressNotifier.Progress( i );
       await Task.Delay(100);
   }
}

// This async method could be called by passing a ProgressBar instance straight away.

var progressControl = new ProgressBar();

await SomeLongTask( progressControl );

Best of all, this could be done with async methods located in libraries that don't need to have knowledge of Maui types.

PD. Actually, it could have been great if Forms/WPF/Xamarin would also implement this in their respective controls...

dotnet / maui