net9.0-desktop : making platform specific calls?

[baskren]

My apologies for asking what I'm guessing is a very basic question. When targeting net9.0-desktop, how do we make platform specific (MacOS, Linux, or WPF) calls?

Conditional compilation via compiler directives does not work in VisualStudio or Rider:

namespace UnoApp9;

#if DESKTOP

using Uno;

#if MACOS
using Fondation;
#elif WINDOWS
using Pizza;
#elif LINUX
using Cheese;
#endif

#endif

public sealed partial class MainPage : Page

... which I guess is expected? But if they don't work, I'm not sure how other historical approaches (Runtime Platform Detection, Using [DllImport] attribute, abstraction, bait-and-switch) would work either.

I'm really interesting in porting to MacOS desktop and Windows Desktop but there's a handful of platform specific things I'd like to be sure are working.

[MartinZikmund]

Indeed, compiler constants do not work here as there is only one target framework -desktop == a single set of binaries. You can do runtime platform-specific checks though, using OperatingSystem.IsLinux() etc.

[baskren]

Thanks, @MartinZikmund

[baskren]

@MartinZikmund : Re-opening this dialog because I'm pretty sure I'm stuck.

I'm trying to implement a work around for the missing WebView2.CoreWebView2.PrintAsync() functionality. I have it working for everything but Desktop+MacOs (haven't tried testing in Linux yet). To get it working in Android and iOS, I had to:

• use reflection to get _nativeWebView from CoreWebView2
• cast _nativeWebView to an Android.WebView.WebView or WebView.WKWebView
• call native PrintAsync()

I highly suspect that WebView2 for MacOS Desktop uses Safari under the covers as there's a very specific bug I only see when using html2pdf.js with base64 encoded SVG images in a WebView2 for MacOS Desktop, iOS, and BrowserWasm on Safari. If I could get access to CoreWebView2._nativeWebView AND cast it to WKWebView, I'm pretty sure I'd have printing working in MacOS Desktop.

However, as far as I know, net9.0-desktop doesn't expose the corresponding native framework (wpf for Windows, AppKit for Mac, ??? for Linux). Or am I missing something? And yet, if my suspicions about WebView2 using Safari is correct, someone somewhere had to make this connection.

Would you have any guidance here to point me in the right direction?

[baskren]

OK, in MacOS Desktop, the CoreWebView2._nativeWebView field still exists and returns an instance of MacOSNativeWebView from Uno.UI.Runtime.Skia.MacOS.MacOSNativeWebView where it has a _webView field that is provided by NativeUno.uno_webview_create. But that's just a pointer, provided by:

	[LibraryImport("libUnoNativeMac.dylib", StringMarshalling = StringMarshalling.Utf8)]
	internal static partial nint uno_webview_create(nint window, string ok, string cancel);

and used to work with a WKWebView instantiated inside of libUnoNativeMac.dylib. Bummer.

[baskren]

OK, once I get this and the next project done,I might be working on my first pull requests (to implement CoreWebView2's PrintAsync() and PrintToPdfAsync()). Hopefully I'll have time starting in late September. I'll ping you then as so much has changed with the Skia Renderers and Desktop target and I might have some questions about setting up the repo.

In the meantime, if anyone cares, this repo is a proof of concept of the work-arounds. Feel free to make use of it as you wish.

[baskren]

Quick note about the above proof-of-concept app: The content for the WebView2 on the MainPage is provided via WebView2.CoreWebView2.SetVirtualHostNameToFolderMapping. However Folder Mapping doesn't work for BrowswerWasm or the Windows Desktop targets. I've worked around the BrowserWasm BUT that requires using something other than serving the app via an IDE. Using dotnet serve -d bin/Debug/net9.0-browserwasm/wwwroot works.