Improve PropertyChanged performance scenarios

[pictos]

In .NET Maui apps something that's triggered a lot is the PropertyChanged so I decided to spend some time profiling it and looking for places where performance can be improved.

I did create a couple of Benchmark tests to measure it. It starts with a simple property changing on controls and after a more real world test, where a bunch of properties are set.

During my tests I found 3 main issues.

1. New instances of PropertyChangedEventArgs instantiated every time

2. High SolidColorBrush churn caused by implicit Color -> Brush conversions, which also amplified allocations in the bindable property storage (Dictionary<,>.Entry[]).

From my profiler session (running the benchmark as a console app) I could see:

• · High SolidColorBrush allocation volume attributed to implicit conversions.

• · Cost (observed run before fix):

• · Microsoft.Maui.Controls.SolidColorBrush: 2,000 allocations, ~608,000 bytes

• · This correlated with high bindable storage growth allocations:

• · Dictionary<,>.Entry[]: ~471,056 bytes

3. Boolean boxing in VisualElement.CoerceIsEnabledProperty (exceeded profiler threshold).

From my profiler session (running the benchmark as a console app) I could see:

• · (BindableObject, object)
• · Cost (observed run):
• · ~1,000 boxed booleans
• · ~24,000 bytes

I believe that any improvement on this area is a huge win, since it's a hot hot path on real world applications.