[android] reduce interop calls in MauiDrawable

[jonathanpeppers]

Context: #12130
Context: https://github.com/angelru/CvSlowJittering

Profiling a .NET MAUI customer sample while scrolling on a Pixel 5, I see some interesting time being spent in:

(0.76%) microsoft.maui!Microsoft.Maui.Graphics.MauiDrawable.OnDraw(Android.Graphics.Drawables.Shapes.Shape,Android.Graphics.Canv
(0.54%) microsoft.maui!Microsoft.Maui.Graphics.MauiDrawable.SetDefaultBackgroundColor()

This sample has a <Border/> inside a <CollectionView/> and so you can see this work happening while scrolling.

Specifically, I found a couple places we had code like:

_borderPaint.StrokeWidth = _strokeThickness;
_borderPaint.StrokeJoin = _strokeLineJoin;
_borderPaint.StrokeCap = _strokeLineCap;
_borderPaint.StrokeMiter = _strokeMiterLimit * 2;
if (_borderPathEffect != null)
    _borderPaint.SetPathEffect(_borderPathEffect);

This calls from C# to Java 5 times. Creating a new method in PlatformInterop.java allowed me to reduce it to 1.

I also found:

void SetDefaultBackgroundColor()
{
    using (var background = new TypedValue())
    {
        if (_context == null || _context.Theme == null || _context.Resources == null)
            return;

        if (_context.Theme.ResolveAttribute(global::Android.Resource.Attribute.WindowBackground, background, true))
        {
            var resource = _context.Resources.GetResourceTypeName(background.ResourceId);
            var type = resource?.ToLowerInvariant();

            if (type == "color")
            {
                var color = new AColor(ContextCompat.GetColor(_context, background.ResourceId));
                _backgroundColor = color;
            }
        }
    }
}

This is doing a lot of unnecessary stuff: looking up a resource by name, etc. I found a very simple Java example we could put in PlatformInterop.java:

https://stackoverflow.com/a/14468034

After these changes, I now see:

(0.28%) microsoft.maui!Microsoft.Maui.Graphics.MauiDrawable.OnDraw(Android.Graphics.Drawables.Shapes.Shape,Android.Graphics.Canv
(0.04%) microsoft.maui!Microsoft.Maui.Graphics.MauiDrawable.SetDefaultBackgroundColor()

This improves the performance of any <Border/> (and other shapes) on Android, and drops about ~1% of the CPU time while scrolling in this example.

[jonathanpeppers]

If _clipPath is null we can return early here, no need to call canvas.SaveLayer/RestoreToCount.

[jonathanpeppers]

@jsuarezruiz @PureWeen is there a sample I can test that it looks exactly the same?

Something with a Border & interesting clipping/shapes, etc.?

[jsuarezruiz]

@jsuarezruiz @PureWeen is there a sample I can test that it looks exactly the same?

Something with a Border & interesting clipping/shapes, etc.?

Launching the .NET MAUI Gallery can use the Control > border samples. Or, for example https://github.com/jsuarezruiz/netmaui-surfing-app-challenge

[jonathanpeppers]

Ok, I think it looks the same as before, this PR on the left, main on the right: