How to profile GPU signed distance field text generation (GrDistanceFieldGenFromVector.cpp) in Skia?

[Syuhai Chen]

I’m using Skia M130 with an OpenGL backend.
My goal is to profile the GPU SDF (signed distance field) text generation process.

In my code, I draw text using Skia’s SkCanvas:

void HelloWorld::onPaint(SkSurface* surface) {
    auto canvas = surface->getCanvas();
    canvas->clear(SK_ColorWHITE);
    SkFont font = ToolUtils::DefaultFont();
    font.setSize(300);
    SkPaint paint;
    paint.setColor(SK_ColorBLACK);
    canvas->drawString("BAD", 60, 620, font, paint);
    GrRecordingContext* recContext = surface->recordingContext();
    if (GrDirectContext* direct = recContext->asDirectContext()) {
        direct->flush();  // safe GPU flush
    }
} 

By RenderDoc, I can see the generated SDF texture and its being sampled in the fragment shader.    

However, I noticed that most SDF generation still goes through SkDistanceFieldGen.cpp (the improved CPU implementation of 8SSEDT by Gustavson and Danielsson).   

I would like to trigger and measure the GPU-based distance field generation method in the paper Practical Analytic 2D Signed Distance Field Generation which is implemented in
src/gpu/ganesh/GrDistanceFieldGenFromVector.cpp.  

How can I force or enable Skia to use the GPU distance field generator for text rendering?  Any insights on how Skia chooses between CPU and GPU distance field generation, or how to instrument this part for profiling, would be greatly appreciated.