Merge pull request #19313 from unoplatform/mergify/bp/release/stable/…

…5.6/pr-19306

fix(linux): check for libXi before assuming XI2 support (backport #19306)

doc/articles/includes/additional-linux-setup-inline.md

@@ -1,19 +1,10 @@
-## [**Ubuntu 18.04**](#tab/ubuntu1804)
-
-- Install the required dependencies:
-
-    ```bash
-    sudo apt update
-    sudo apt-get install mesa-utils libgl1-mesa-glx ttf-mscorefonts-installer dbus libfontconfig1 libxrandr2
-    ```
-
 ## [**Ubuntu 20.04/22.04**](#tab/ubuntu2004)
 
 - Install the required dependencies:
 
     ```bash
     sudo apt update
-    sudo apt install mesa-utils libgl1-mesa-glx ttf-mscorefonts-installer dbus libfontconfig1 libxrandr2
+    sudo apt install mesa-utils libgl1-mesa-glx ttf-mscorefonts-installer dbus libfontconfig1 libxrandr2 libxi-dev
     ```
 
 ## [**ArchLinux 5.8.14 or later / Manjaro**](#tab/archlinux2004)
@@ -27,7 +18,7 @@
 - Install the necessary dependencies
 
     ```bash
-    sudo pacman -S dotnet-targeting-pack dotnet-sdk dotnet-host dotnet-runtime python ninja gn aspnet-runtime dbus libxrandr
+    sudo pacman -S dotnet-targeting-pack dotnet-sdk dotnet-host dotnet-runtime python ninja gn aspnet-runtime dbus libxrandr libxi
     ```
 
 ---

src/Uno.UI.Runtime.Skia.X11/X11XamlRootHost.XInput.cs

@@ -68,6 +68,8 @@
 // https://github.com/AvaloniaUI/Avalonia/blob/e0127c610c38701c3af34f580273f6efd78285b5/src/Avalonia.X11/XI2Manager.cs
 
 using System;
+using System.Runtime.InteropServices;
+using Uno.Foundation.Logging;
 namespace Uno.WinUI.Runtime.Skia.X11;
 
 // Excerpt from the spec :
@@ -117,13 +119,32 @@ private unsafe (XIVersion version, int opcode) GetXI2Details(IntPtr display)
 
 		if (!XLib.XQueryExtension(display, "XInputExtension", out var _xi2Opcode, out _, out _))
 		{
-			_xi2Details = (XIVersion.Unsupported, _xi2Opcode);
+			return (_xi2Details = (XIVersion.Unsupported, _xi2Opcode)).Value;
 		}
 
 		var version = X11Helper.XGetExtensionVersion(display, "XInputExtension");
 		if (version->major_version != 2)
 		{
-			_xi2Details = (XIVersion.Unsupported, _xi2Opcode);
+			if (this.Log().IsEnabled(LogLevel.Error))
+			{
+				this.Log().LogError($"X server does not support X Input Extension 2. Falling back to the core protocol implementation for pointer inputs. (For more information see: https://aka.platform.uno/skia-desktop");
+			}
+			return (_xi2Details = (XIVersion.Unsupported, _xi2Opcode)).Value;
+		}
+
+		// Just because XI2 is supported, doesn't mean that libXi is present, so we check explicitly for it.
+		// https://github.com/unoplatform/private/issues/600
+		if (NativeLibrary.TryLoad(XLib.libXInput, out var xiHandle))
+		{
+			NativeLibrary.Free(xiHandle);
+		}
+		else
+		{
+			if (this.Log().IsEnabled(LogLevel.Error))
+			{
+				this.Log().LogError($"X server supports X Input Extension 2, but libXi.so.6 was not found. Falling back to the core protocol implementation for pointer inputs. For more information see: https://aka.platform.uno/skia-desktop");
+			}
+			return (_xi2Details = (XIVersion.Unsupported, _xi2Opcode)).Value;
 		}
 
 		_xi2Details = version->minor_version switch
@@ -136,6 +157,11 @@ private unsafe (XIVersion version, int opcode) GetXI2Details(IntPtr display)
 			_ => throw new ArgumentException("XI2 version is not between 2.0 and 2.4. There should be no 2.5 or above.")
 		};
 
+		if (this.Log().IsEnabled(LogLevel.Debug))
+		{
+			this.Log().Debug($"Using X Input Extension 2.{version->minor_version}.");
+		}
+
 		return _xi2Details.Value;
 	}
 

src/Uno.UI.Runtime.Skia.X11/X11_Bindings/x11bindings_XLib.cs

@@ -45,7 +45,7 @@ public unsafe static partial class XLib
 	{
 		private const string libX11 = "libX11.so.6";
 		private const string libX11Randr = "libXrandr.so.2";
-		private const string libXInput = "libXi.so.6";
+		internal const string libXInput = "libXi.so.6";
 
 		[LibraryImport(libX11)]
 		public static partial IntPtr XOpenDisplay(IntPtr display);