Does SkiaSharp work on Linux? How?

[bmitc]

What are the steps required to use SkiaSharp on Linux on major distributions like Ubuntu or Linux Mint?

See also:

• [BUG] Exit code 139 (segmentation fault) when calling GRGlInterface.Create on Ubuntu and Linux Mint #2350
• https://stackoverflow.com/questions/74882243/how-do-i-properly-build-a-net-7-application-using-skiasharp-on-linux-getting-a

I know about the existence of:

• https://www.nuget.org/packages/SkiaSharp.NativeAssets.Linux
• https://www.nuget.org/packages/SkiaSharp.NativeAssets.Linux.NoDependencies

but I don't know how to use them, and they're undocumented as far as I can tell.

Specifically, I have tried using SkiaSharp on Ubuntu and Linux Mint with these, and I cannot get GRGlInterface.Create to not throw an exception. So I am either doing something with regards to SkiaSharp on Linux or there is a bug. This discussion is trying to address the former.

[mattleibow]

Using SkiaSharp with the GPU requires that you first set up the GPU context. In the case of OpenGL, you need a GL context that is current, and then the GLInterface will be constructed using that. If you have mutilple GL contexts then you will also need multiple GRContexts.

[bmitc]

Hi @mattleibow, thank you for the response! However, I'm not sure you're explaining any new information not already covered in the linked issue and StackOverflow post. Did you happen to take a look at them?

To be specific, what is wrong with the following code? You only need the Silk.NET.GLFW and SkiaSharp NuGet packages to run it. On Linux Mint or Ubuntu, the window opens, and then the application immediately crashes, apparently while creating the GRGlInterface given that only a few proc names are printed out. Exit code 139 is a segmentation fault. This code works perfectly fine on Windows. I don't currently have a macOS machine to test on.

open FSharp.NativeInterop

open Silk.NET.GLFW
open SkiaSharp

#nowarn "9"

let width, height = 800, 600

let glfw = Glfw.GetApi()
glfw.Init() |> printfn "Initialized?: %A"

let window = glfw.CreateWindow(width, height, "Test Window", NativePtr.ofNativeInt 0n, NativePtr.ofNativeInt 0n)
printfn "Window: %A" window
glfw.MakeContextCurrent(window)
let mutable error = nativeint<byte> 1uy |> NativePtr.ofNativeInt
glfw.GetError(&error) |> printfn "Error: %A"

let grGlInterface = GRGlInterface.Create(fun name ->
    printfn "Process/procedure name: %A" name
    glfw.GetProcAddress name)

if not(grGlInterface.Validate()) then
    raise (System.Exception("Invalid GRGlInterface"))

let grContext = GRContext.CreateGl(grGlInterface)
let grGlFramebufferInfo = new GRGlFramebufferInfo(0u, SKColorType.Rgba8888.ToGlSizedFormat()) // 0x8058
let grBackendRenderTarget = new GRBackendRenderTarget(width, height, 1, 0, grGlFramebufferInfo)
let surface = SKSurface.Create(grContext, grBackendRenderTarget, GRSurfaceOrigin.BottomLeft, SKColorType.Rgba8888)
let canvas = surface.Canvas
grContext.ResetContext()

while not (glfw.WindowShouldClose(window)) do
    glfw.PollEvents()
    canvas.Clear(SKColors.WhiteSmoke)
    canvas.Flush()
    glfw.SwapBuffers(window)
        
glfw.DestroyWindow(window)
glfw.Terminate()

As already mentioned in the links, this returns:

$ dotnet run --project SilkNETPerformanceTest
Initialized?: true
Window: 93998088633456n
Error: NoError
Process/procedure name: "glGetString"
Process/procedure name: "glGetString"
Process/procedure name: "glGetStringi"
Process/procedure name: "glGetIntegerv"
Process/procedure name: "eglQueryString"
Process/procedure name: "eglGetCurrentDisplay"

$ echo $?
139

$ glxinfo | grep "OpenGL version"
OpenGL version string: 4.6 (Compatibility Profile) Mesa 22.0.5