SKPathEffect.Create2DLine Crashes on Android Emulators

[ollira]

My Android emulators appear to have some problem with SKPathEffect.Create2DLine method on version 1.53.1.1. Is this a known issue?

Regards,
Olli Raisa

Sample code:

    // OR: v1.53.1.1 crashes on Android emulators, OK on Windows
    public static void PathEffect2DLine(SKCanvas canvas, int width, int height)
    {
        float margin = Math.Min(width, height) / 5f;
        float scale = 10.0f;

        canvas.Clear(SKColors.White);

        using (var paint = new SKPaint())
        using (var effect = SKPathEffect.Create2DLine(1f, SKMatrix.MakeScale(scale, scale)))
        {
            paint.PathEffect = effect;
            canvas.DrawRect(new SKRect(margin, margin, width - margin, height - margin), paint);
        }
    }

Output from Visual Studio 2015 (Update 3):

08-22 02:35:33.270 E/mono-rt ( 2454): Stacktrace:
08-22 02:35:33.270 E/mono-rt ( 2454):
08-22 02:35:33.270 E/mono-rt ( 2454): at <0xffffffff>
08-22 02:35:33.270 E/mono-rt ( 2454): at (wrapper managed-to-native) SkiaSharp.SkiaApi.sk_path_effect_create_2d_line (single,SkiaSharp.SKMatrix) <0x00015>
08-22 02:35:33.270 E/mono-rt ( 2454): at SkiaSharp.SKPathEffect.Create2DLine (single,SkiaSharp.SKMatrix) <IL 0x00002, 0x000a7>
08-22 02:35:33.270 E/mono-rt ( 2454): at SkiaSharp.Demos.PathEffect2DLine (SkiaSharp.SKCanvas,int,int) [0x00028] in D:\src\SkiaSharp\samples\SharedDemo\SkiaSharp.Demos.cs:1038
08-22 02:35:33.270 E/mono-rt ( 2454): at Skia.Forms.Demo.SkiaView.Draw (SkiaSharp.SKCanvas) [0x00001] in D:\src\SkiaSharp\samples\Skia.Forms.Demo\SkiaView.cs:28
08-22 02:35:33.270 E/mono-rt ( 2454): at Skia.Forms.Demo.SkiaView.Skia.Forms.Demo.ISkiaViewController.SendDraw (SkiaSharp.SKCanvas) [0x00001] in D:\src\SkiaSharp\samples\Skia.Forms.Demo\SkiaView.cs:18
08-22 02:35:33.270 E/mono-rt ( 2454): at Skia.Forms.Demo.Droid.NativeSkiaView.OnDraw (Android.Graphics.Canvas) [0x000dc] in D:\src\SkiaSharp\samples\Skia.Forms.Demo\Droid\NativeSkiaView.cs:37
08-22 02:35:33.270 E/mono-rt ( 2454): at Android.Views.View.n_OnDraw_Landroid_graphics_Canvas_ (intptr,intptr,intptr) [0x00011] in /Users/builder/data/lanes/3540/1cf254db/source/monodroid/src/Mono.Android/platforms/android-23/src/generated/Android.Views.View.cs:14205
08-22 02:35:33.270 E/mono-rt ( 2454): at (wrapper dynamic-method) object.b284673e-3f63-410e-9c6d-14aa958db100 (intptr,intptr,intptr) <IL 0x00017, 0x00027>
08-22 02:35:33.270 E/mono-rt ( 2454): at (wrapper native-to-managed) object.b284673e-3f63-410e-9c6d-14aa958db100 (intptr,intptr,intptr) <IL 0x0001f, 0x0007b>
08-22 02:35:33.270 E/mono-rt ( 2454):
08-22 02:35:33.270 E/mono-rt ( 2454): Attempting native Android stacktrace:
08-22 02:35:33.270 E/mono-rt ( 2454):
08-22 02:35:33.280 E/mono-rt ( 2454): at sk_path_effect_create_2d_line+25 [0x9646cf79]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+61095 [0x962f9ea7]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+59295 [0x962f979f]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+39681 [0x9718fb01]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+39352 [0x9718f9b8]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+18237 [0x9718a73d]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+10934 [0x97188ab6]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+9103 [0x97d1e38f]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+23819 [0x9765dd0b]
08-22 02:35:33.280 E/mono-rt ( 2454): at dvmPlatformInvoke+79 [0xb4cc80eb]
08-22 02:35:33.280 E/mono-rt ( 2454): at dvmCallJNIMethod(unsigned int const_, JValue_, Method const_, Thread_)+285 [0xb4d2489d]
08-22 02:35:33.280 E/mono-rt ( 2454): at ???+257 [0x101]
08-22 02:35:33.280 E/mono-rt ( 2454):
08-22 02:35:33.280 E/mono-rt ( 2454): =================================================================
08-22 02:35:33.280 E/mono-rt ( 2454): Got a SIGSEGV while executing native code. This usually indicates
08-22 02:35:33.280 E/mono-rt ( 2454): a fatal error in the mono runtime or one of the native libraries
08-22 02:35:33.280 E/mono-rt ( 2454): used by your application.
08-22 02:35:33.280 E/mono-rt ( 2454): =================================================================
08-22 02:35:33.280 E/mono-rt ( 2454):
08-22 02:35:33.280 F/libc ( 2454): Fatal signal 11 (SIGSEGV) at 0x41200000 (code=1), thread 2454 (skia_forms_demo)

[ollira]

The same thing happens also in SKPathEffect.Create2DPath

Code sample

    public static void PathEffect2DPath(SKCanvas canvas, int width, int height)
    {
        float margin = Math.Min(width, height) / 5f;
        float scale = 30f;

        canvas.Clear(SKColors.White);

        SKPath path = new SKPath();
        path.AddCircle(0, 0, scale/3f, SKPathDirection.Clockwise);

        using (var paint = new SKPaint())
        using (var effect = SKPathEffect.Create2DPath(SKMatrix.MakeScale(scale, scale), path))
        {
            paint.PathEffect = effect;
            canvas.DrawRect(new SKRect(margin, margin, width - margin, height - margin), paint);
        }
    }

The respective C functions expect pointers to matrix data:

SK_API sk_path_effect_t* sk_path_effect_create_2d_line(float width, const sk_matrix_t* matrix);
SK_API sk_path_effect_t* sk_path_effect_create_2d_path(const sk_matrix_t* matrix, const sk_path_t* path);

SkiaSharp uses SKMatrix as the parameter type:

    [DllImport(SKIA, CallingConvention = CallingConvention.Cdecl)]
    public extern static sk_path_effect_t sk_path_effect_create_2d_line(float width, SKMatrix matrix);
    [DllImport(SKIA, CallingConvention = CallingConvention.Cdecl)]
    public extern static sk_path_effect_t sk_path_effect_create_2d_path(SKMatrix matrix, sk_path_t path);

Perhaps a matrix reference is needed here.

Regards,
Olli Raisa

[mattleibow]

Hi @ollira Thanks for reporting and taking the time to have a poke around in the code.
Your suggestion was correct, we were not marshalling the struct properly.