Correct way for resizing the SkSurface when the GL viewport changes

[Matthew Leibowitz]

Hi Skia Experts,

I have been using Skia for some time now, and I really like it. But, I have been struggling to get started with GPU features.

Right now, I want to start drawing on a OpenGL surface. Using the GLFWTest example, I managed to create this tiny app with GLUT: https://gist.github.com/mattleibow/fb6bfa5146d776f26febfa3a6d4286f0

I can draw text and some cool things, but when the window is resized, the drawing is stretched. If I was to remove the Skia drawing, and use a glutWireCube, it is not stretched. Of course, I am resetting the viewport, but I am not sure how to do the equivalent with Skia. Is it correct to re-create the surface, or is there the correct way?

CODE:

Init once:

 skiaContext = GrContext::Create(kOpenGL_GrBackend, 0);

 GrBackendRenderTargetDesc desc;
 desc.fWidth = w;
 desc.fHeight = h;
 desc.fConfig = kSkia8888_GrPixelConfig;
 desc.fOrigin = kBottomLeft_GrSurfaceOrigin;
 desc.fSampleCnt = 1;
 desc.fStencilBits = 0;
 desc.fRenderTargetHandle = 0;  // assume default framebuffer

 skiaSurface = SkSurface::MakeFromBackendRenderTarget(skiaContext, desc, NULL)

On each frame:

 SkCanvas* skiaCanvas = skiaSurface->getCanvas();

 SkPaint paint;
 paint.setColor(SK_ColorWHITE);

 skiaCanvas->drawCircle(100, 100, 50, paint);

 skiaCanvas->flush();

[Brian Osman]

Yes, you should re-create the surface (at least when a resize event is detected, but you can simply do it every frame, if that's easier).

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[Matthew Leibowitz]

Thanks Brian,

This is what I was looking for: The SkSurface is not too expensive to keep re-creating.

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