(July 2018) Example of using Skia with an SFML OpenGL window. Snippet extracted from a side project

skia_and_sfml.cpp

#include <iostream>

#include "GrGLInterface.h"
#include "GrBackendSurface.h"
#include "GrContext.h"
#include "SkCanvas.h"
#include "SkColorSpace.h"
#include "SkSurface.h"

#include <SFML/Graphics.hpp>
#include <SFML/Window/Window.hpp>

// Provides the OpenGL method context for Skia
#include <SFML/OpenGL.hpp>

int width = 800;
int height = 600;

GrContext* context;
SkSurface* surface;

void make_skia_surface () {
    GrContextOptions options;
    context = GrContext::MakeGL(nullptr, options).release();
    
    GrGLFramebufferInfo framebufferInfo;
    framebufferInfo.fFBOID = 0; // assume default framebuffer
    framebufferInfo.fFormat = GL_RGBA8;
    
    SkColorType colorType;
    if (kRGBA_8888_GrPixelConfig == kSkia8888_GrPixelConfig) {
        colorType = kRGBA_8888_SkColorType;
    } else {
        colorType = kBGRA_8888_SkColorType;
    }

    GrBackendRenderTarget backendRenderTarget(width, height,
        0, // sample count
        0, // stencil bits
        framebufferInfo);
    
    surface = SkSurface::MakeFromBackendRenderTarget(context, backendRenderTarget, kBottomLeft_GrSurfaceOrigin, colorType, nullptr, nullptr).release();
    
    if (surface == nullptr) {
        std::cerr << "SkSurface is null" << std::endl;
        exit(1);
    }
}

int main() {
    const char * title = "Skia and SFML example";
    
    sf::RenderWindow *window = new sf::RenderWindow(sf::VideoMode(width, height), title);
    
    make_skia_surface();
    
    const char* helpMessage = "Click and drag to create rects.  Press esc to quit.";
    SkPaint paint;
    
    while (window->isOpen()) {
        sf::Event event;
        while (window->pollEvent(event))  {
            // "close requested" event: we close the window
            if (event.type == sf::Event::Closed) {
                window->close();
            } else if (event.type == sf::Event::Resized) {
                // adjust the viewport when the window is resized
                glViewport(0, 0, event.size.width, event.size.height);
                // simply re-create the canvas on resize
                make_skia_surface();
            }
        }
        
        SkCanvas* canvas = surface->getCanvas();
        
        canvas->clear(SK_ColorWHITE);
        paint.setColor(SK_ColorGREEN);
        canvas->drawText(helpMessage, strlen(helpMessage), SkIntToScalar(100), SkIntToScalar(100), paint);
        canvas->flush();
        
        window->display();
    }
}