[WinUI] Cache gesture event subscriptions

[MartyIX]

Description of Change

Interops operations on Windows are costly. This PR avoids unsubscribing events that were not subscribed in the first place and thus improving performance.

Speedscope

• Maui.Controls.Sample.Sandbox.exe_20240420_185714.speedscope.json - main
• Maui.Controls.Sample.Sandbox.exe_20240420_185847.speedscope.json - PR

-> 70% improvement for that particular method.

I test with my complex grid sample basically.

Issues Fixed

Contributes to #21787

[dotnet-policy-service]

Hey there @MartyIX! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[MartyIX]

Note that this event WAS NOT unsubscribed at all.

[MartyIX]

Note that this event WAS NOT unsubscribed at all.

[MartyIX]

@jonathanpeppers would you mind taking a look please?

[jonathanpeppers]

One concern here is adding 6 bool fields is actually adding 6 bytes of memory usage for every View.

So, some ideas:

• Could we make this one bool field instead? If a default view doesn't subscribe, maybe we could just store the state of all the events in one bool _subscribed;? If one event subscribes it would attempt to unsubscribe all?

• If we need all 6 distinct values, we could consider:

[Flags]
enum SubscriptionFlags : byte
{
    None = 0,
    ContainerDragEventsSubscribed = 1 << 0,
    ContainerDropEventsSubscribed = 1 << 1,
    ContainerPgrPointerEventsSubscribed = 1 << 2,
    ContainerManipulationAndPointerEventsSubscribed= 1 << 3,
// etc.
}

And store a single SubscriptionFlags enum in a field, that would take 1 byte instead of 6.

If there were a BenchmarkDotNet benchmark, we might know exactly how much extra memory is used. But I don't think we have a Windows equivalent of this project:

• https://github.com/dotnet/maui/tree/main/src/Core/tests/Benchmarks.Droid

[MartyIX]

Unsubscriptions are costly because of interops and there are always some events subscribed AFAIK so I don't think that we can go with bool _subscribed. I went with the other suggestion instead.

[MartyIX]

Measurements with commit a5f8d56 addressing #21959 (comment) by adding SubscriptionFlags

• Maui.Controls.Sample.Sandbox.exe_20240423_100728.speedscope.json - master
• Maui.Controls.Sample.Sandbox.exe_20240423_100904.speedscope.json - PR

[jonathanpeppers]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[jonathanpeppers]

This looks good to me from a performance perspective. Someone familiar with these gestures on Windows should review as well. 👍

[MartyIX]

@rmarinho Could you take a look please?

[MartyIX]

@jfversluis Could you take a look please?

[jfversluis]

@Foda might be the right person here

[MartyIX]

@Foda Could you take a look please?

[Foda]

LGTM

[MartyIX]

@rmarinho Is it good to be merged or does it need to wait until SR6?

[MartyIX]

@rmarinho Anything else to do here?