[Windows] Cache full app package file path

[MartyIX]

Description of Change

I have noticed that one can cache Package.Current.InstalledLocation.Path to save about 4 ms (measured in Debug mode) for each call of FileSystemUtils.PlatformGetFullAppPackageFilePath¹ because there is no interop call to WinRT².

Testing

/~https://github.com/MartyIX/maui/tree/feature/2024-03-16-app-path-optimization-testing (MartyIX@ab01bf4)

Issues Fixed

Contributes to #8594

Footnotes

1. Called for each registered font (see Font loading impacts Windows desktop startup #8594). ↩

2. Please correct me if I got it wrong. ↩

[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]

cc @jonathanpeppers

[jonathanpeppers]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 3 pipeline(s).

[jonathanpeppers]

I think this change makes sense.

In the attached issue, there was:

@MartyIX do you have a more recent .speedscope from your app? We should get a second data point on how much time this can save in a real application.

[jonathanpeppers]

Oh, I found the .speedscope @MartyIX sent me last week:

Seems like an easy-win. 👍

[MartyIX]

I don't really know how to profile my real application with modified MAUI source code. So I'm testing with the sandbox project in MAUI source code.

However, I tested with MartyIX@ab01bf4 and it saved about 20 ms AFAIK. But it depends on the number of files. So if there is an app with 50 font files, then I would expect to save about 50 * <each call cost> and that can be certainly >100ms which is significant.

[jonathanpeppers]

If you ever need to test a local MAUI build, I do:

• dotnet cake --configuration=Release
• wipe NuGet cache: rm -r ~\.nuget\packages\*\*-dev\ (if you ever do this more than once)
• then build run an app with MAUI's .\bin\dotnet\dotnet.exe instead of the system-installed dotnet.exe

This might be trickier with a Windows app that is a "packaged" appx, though. Might have to launch VS with %PATH% set to .\bin\dotnet\.

[MartyIX]

@rmarinho Is this OK to merge? Or are there any concerns?

[rmarinho]

pinging @mattleibow as he knows more about this that me :)