[android] use a custom Resource.designer.cs

[jonathanpeppers]

Description of Change

Context: https://github.com/jonathanpeppers/CustomResourceDesigner
Context: dotnet/android#6310

We found a systemic problem with Xamarin.Android class libraries:

• Include AndroidX & Google Material
• Include at least one @(AndroidResource) and use the ID from C#
• Resource.designer.cs has 2,700+ fields. That's a lot!

This problem compounds itself as you include more class libraries that
depend on each other. The main app will end up repeatedly setting
these fields at startup for each library that contains fields in
Resource.designer.cs...

Reviewing the .NET MAUI fields, I found:

src\Core\src\obj\Debug\net6.0-android\Resource.designer.cs
5310
src\Controls\src\Core\obj\Debug\net6.0-android\Resource.designer.cs
5167 fields
src\Controls\src\Xaml\obj\Release\net6.0-android\Resource.designer.cs
5167 fields
src\Compatibility\Core\src\obj\Debug\net6.0-android\Resource.designer.cs
5333 fields
src\Essentials\src\obj\Debug\net6.0-android\Resource.designer.cs
204 fields

In fact, I found 21,497 fields were set at startup for a dotnet new maui app in Resource.designer.cs!

This shows up as a "hot path" if you profile Android startup:

In many projects you can simply set $(AndroidGenerateResourceDesigner)
to false, but the issue is .NET MAUI actually uses some of the C#
Resource.designer.cs values at runtime.

So to solve the problem here, I came up with a new pattern:

https://github.com/jonathanpeppers/CustomResourceDesigner

We can copy the contents of Resource.designer.cs and manually delete
all the fields we don't need. This allows
$(AndroidGenerateResourceDesigner) to be turned off.

We are working on a long-term solution for this issue in
Xamarin.Android, but we can do this workaround in .NET MAUI now.

Results

Building a dotnet new maui then dotnet build -c Release and
running on a Pixel 5.

Before:

• 21,497 fields set at startup in UpdateIdValues()
• Activity Displayed: 1s454ms
• .apk size: 17300275 bytes

After:

• 65 fields set at startup in UpdateIdValues()
• Activity Displayed: 1s079ms
• .apk size: 16677683 bytes

> apkdiff -f before.apk after.apk
Size difference in bytes ([*1] apk1 only, [*2] apk2 only):
-         233 assemblies/Microsoft.Maui.Controls.Compatibility.Android.FormsViewGroup.dll
-       5,264 assemblies/Microsoft.Maui.Essentials.dll
-     103,010 assemblies/Microsoft.Maui.dll
-     103,260 assemblies/Microsoft.Maui.Controls.Compatibility.dll
-     103,811 assemblies/Microsoft.Maui.Controls.Xaml.dll
-     106,127 assemblies/Microsoft.Maui.Controls.dll
-     201,031 assemblies/foo.dll
Summary:
+           0 Other entries 0.00% (of 2,139,558)
-     622,736 Assemblies -6.93% (of 8,987,664)
+           0 Dalvik executables 0.00% (of 6,440,988)
+           0 Shared libraries 0.00% (of 9,860,264)
-   1,340,928 Uncompressed assemblies -6.55% (of 20,465,016)
-     622,592 Package size difference -3.60% (of 17,300,275)

Additions made

None

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)
• Targets a single property for a single control (or intertwined few properties)
• Adds the property to the appropriate interface
• Avoids any changes not essential to the handler property
• Adds the mapping to the PropertyMapper in the handler
• Adds the mapping method to the Android, iOS, and Standard aspects of the handler
• Implements the actual property updates (usually in extension methods in the Platform section of Core)
• Tags ported renderer methods with [PortHandler]
• Adds an example of the property to the sample project (MainPage)
• Adds the property to the stub class
• Implements basic property tests in DeviceTests

Does this PR touch anything that might affect accessibility?

No

[jonathanpeppers]

I need to enable $(AndroidGenerateResourceDesigner) in various test projects:

/Users/builder/azdo/_work/1/s/src/Compatibility/ControlGallery/src/Android/CustomRenderers.cs(429,46): error CS0117: 'Resource.Id' does not contain a definition for 'Image'

[jonathanpeppers]

Manually checked Microsoft.Maui.Core.Runtime.android.6.0.101-preview.9.7280.nupkg from the PR build, and ILSpy shows it has a small Resource class:

// Microsoft.Maui.Resource
using System.CodeDom.Compiler;
using Android.Runtime;

[GeneratedCode("Xamarin.Android.Build.Tasks", "12.0.99.31")]
public class Resource
{
	public class Attribute
	{
		public static int colorSwitchThumbNormal;

		public static int maui_splash;

		public static int scrollViewStyle;

		static Attribute()
		{
			colorSwitchThumbNormal = 2130903268;
			maui_splash = 2130903657;
			scrollViewStyle = 2130903809;
			ResourceIdManager.UpdateIdValues();
		}
	}

	public class Animation
	{
		public static int nav_default_enter_anim;

		public static int nav_default_exit_anim;

		public static int nav_default_pop_enter_anim;

		public static int nav_default_pop_exit_anim;

		static Animation()
		{
			nav_default_enter_anim = 2130772000;
			nav_default_exit_anim = 2130772001;
			nav_default_pop_enter_anim = 2130772002;
			nav_default_pop_exit_anim = 2130772003;
			ResourceIdManager.UpdateIdValues();
		}
	}

	public class Drawable
	{
		public static int abc_ic_clear_material;

		static Drawable()
		{
			abc_ic_clear_material = 2131165213;
			ResourceIdManager.UpdateIdValues();
		}
	}

	public class Id
	{
		public static int automation_tag_id;

		public static int maui_toolbar;

		public static int nav_host;

		public static int search_button;

		public static int search_close_btn;

		static Id()
		{
			automation_tag_id = 2131230809;
			maui_toolbar = 2131230983;
			nav_host = 2131231021;
			search_button = 2131231082;
			search_close_btn = 2131231083;
			ResourceIdManager.UpdateIdValues();
		}
	}

	public class Layout
	{
		public static int navigationlayout;

		static Layout()
		{
			navigationlayout = 2131427417;
			ResourceIdManager.UpdateIdValues();
		}
	}

	public class Style
	{
		public static int Maui_MainTheme_NoActionBar;

		public static int scrollViewTheme;

		static Style()
		{
			Maui_MainTheme_NoActionBar = 2131624184;
			scrollViewTheme = 2131624673;
			ResourceIdManager.UpdateIdValues();
		}
	}

	static Resource()
	{
		ResourceIdManager.UpdateIdValues();
	}
}

[jonathanpeppers]

@PureWeen are you the one that would know: How often do you add new @(AndroidResource) files?

Are the steps below reasonable?

[PureWeen]

Rarely, especially once we're GA

I'd say these steps are fine

[PureWeen]

As luck would have it, I have a PR currently open that this will break :-)

So, I'll be able to give the steps a test right after merging.