main.cpp

#include "include/gpu/GrBackendSurface.h"
#include <SDL2/SDL.h>
#include "include/core/SkCanvas.h"
#include "include/core/SkFont.h"
#include "include/core/SkSurface.h"
#include "include/utils/SkRandom.h"

#include "include/gpu/gl/GrGLInterface.h"
#include "src/gpu/gl/GrGLUtil.h"

#define SK_GL
#include "include/gpu/GrDirectContext.h"

#if defined(SK_BUILD_FOR_ANDROID)
#include <GLES/gl.h>
#elif defined(SK_BUILD_FOR_UNIX)
#include <GL/gl.h>
#elif defined(SK_BUILD_FOR_MAC)
#include <OpenGL/gl.h>
#elif defined(SK_BUILD_FOR_IOS)
#include <OpenGLES/ES2/gl.h>
#endif


struct Circle {
	SkPoint center;
	SkScalar radius;
};

struct ApplicationState {
    ApplicationState() : fQuit(false) {}
    SkTArray<Circle> circles;
	SkPoint pressedPosition;
	SkPoint lineEndPosition;
    bool fQuit;
};

static void handle_error() {
    const char* error = SDL_GetError();
    SkDebugf("SDL Error: %s\n", error);
    SDL_ClearError();
}

static void handle_events(ApplicationState* state, SkCanvas* canvas) {
    SDL_Event event;
    while(SDL_PollEvent(&event)) {
        switch (event.type) {
            case SDL_MOUSEMOTION:
                if (event.motion.state == SDL_PRESSED) {
                    Circle& circle = state->circles.back();
					auto linePosition = SkPoint::Make(SkIntToScalar(event.button.x),
						SkIntToScalar(event.button.y));
					state->lineEndPosition = linePosition;
					auto distance = SkPoint::Distance(state->pressedPosition, 
						SkPoint::Make(SkIntToScalar(event.button.x), SkIntToScalar(event.button.y)));
                    circle.radius = distance;
                }
                break;
            case SDL_MOUSEBUTTONDOWN:
                if (event.button.state == SDL_PRESSED) {
					state->pressedPosition = SkPoint::Make(SkIntToScalar(event.button.x), SkIntToScalar(event.button.y));
					Circle circle;
					circle.center = SkPoint::Make(SkIntToScalar(event.button.x), SkIntToScalar(event.button.y));
					state->circles.push_back() = circle;
                }
                break;
            case SDL_KEYDOWN: {
                SDL_Keycode key = event.key.keysym.sym;
                if (key == SDLK_ESCAPE) {
                    state->fQuit = true;
                }
                break;
            }
            case SDL_QUIT:
                state->fQuit = true;
                break;
            default:
                break;
        }
    }
}


#if defined(SK_BUILD_FOR_ANDROID)
int SDL_main(int argc, char** argv) {
#else
int main(int argc, char** argv) {
#endif
    uint32_t windowFlags = 0;

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);

    SDL_GLContext glContext = nullptr;
#if defined(SK_BUILD_FOR_ANDROID) || defined(SK_BUILD_FOR_IOS)
    // For Android/iOS we need to set up for OpenGL ES and we make the window hi res & full screen
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
    windowFlags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE |
                  SDL_WINDOW_BORDERLESS | SDL_WINDOW_FULLSCREEN_DESKTOP |
                  SDL_WINDOW_ALLOW_HIGHDPI;
#else
    // For all other clients we use the core profile and operate in a window
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);

    windowFlags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE;
#endif
    static const int kStencilBits = 8;  // Skia needs 8 stencil bits
    SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 0);
    SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, kStencilBits);

    SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);

    // If you want multisampling, uncomment the below lines and set a sample count
    static const int kMsaaSampleCount = 0; //4;
    // SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
    // SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, kMsaaSampleCount);

    /*
     * In a real application you might want to initialize more subsystems
     */
    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS) != 0) {
        handle_error();
        return 1;
    }

    // Setup window
    // This code will create a window with the same resolution as the user's desktop.
    SDL_DisplayMode dm;
    if (SDL_GetDesktopDisplayMode(0, &dm) != 0) {
        handle_error();
        return 1;
    }

    SDL_Window* window = SDL_CreateWindow("Path", SDL_WINDOWPOS_CENTERED,
                                          SDL_WINDOWPOS_CENTERED, dm.w, dm.h, windowFlags);

    if (!window) {
        handle_error();
        return 1;
    }

    // To go fullscreen
    // SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN);

    // try and setup a GL context
    glContext = SDL_GL_CreateContext(window);
    if (!glContext) {
        handle_error();
        return 1;
    }

    int success =  SDL_GL_MakeCurrent(window, glContext);
    if (success != 0) {
        handle_error();
        return success;
    }

    uint32_t windowFormat = SDL_GetWindowPixelFormat(window);
    int contextType;
    SDL_GL_GetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, &contextType);


    int dw, dh;
    SDL_GL_GetDrawableSize(window, &dw, &dh);

    glViewport(0, 0, dw, dh);
    glClearColor(1, 1, 1, 1);
    glClearStencil(0);
    glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

    // setup GrContext
    auto interface = GrGLMakeNativeInterface();

    // setup contexts
    sk_sp<GrDirectContext> grContext(GrDirectContext::MakeGL(interface));
    SkASSERT(grContext);

    // Wrap the frame buffer object attached to the screen in a Skia render target so Skia can
    // render to it
    GrGLint buffer;
    GR_GL_GetIntegerv(interface.get(), GR_GL_FRAMEBUFFER_BINDING, &buffer);
    GrGLFramebufferInfo info;
    info.fFBOID = (GrGLuint) buffer;
    SkColorType colorType;

    //SkDebugf("%s", SDL_GetPixelFormatName(windowFormat));
    // TODO: the windowFormat is never any of these?
    if (SDL_PIXELFORMAT_RGBA8888 == windowFormat) {
        info.fFormat = GR_GL_RGBA8;
        colorType = kRGBA_8888_SkColorType;
    } else {
        colorType = kBGRA_8888_SkColorType;
        if (SDL_GL_CONTEXT_PROFILE_ES == contextType) {
            info.fFormat = GR_GL_BGRA8;
        } else {
            // We assume the internal format is RGBA8 on desktop GL
            info.fFormat = GR_GL_RGBA8;
        }
    }

    GrBackendRenderTarget target(dw, dh, kMsaaSampleCount, kStencilBits, info);

    // setup SkSurface
    // To use distance field text, use commented out SkSurfaceProps instead
    // SkSurfaceProps props(SkSurfaceProps::kUseDeviceIndependentFonts_Flag,
    //                      SkSurfaceProps::kUnknown_SkPixelGeometry);
    SkSurfaceProps props;

    sk_sp<SkSurface> surface(SkSurface::MakeFromBackendRenderTarget(grContext.get(), target,
                                                                    kBottomLeft_GrSurfaceOrigin,
                                                                    colorType, nullptr, &props));

    SkCanvas* canvas = surface->getCanvas();
    canvas->scale((float)dw/dm.w, (float)dh/dm.h);

    ApplicationState state;

    SkPaint paint;

    // create a surface for CPU rasterization
    sk_sp<SkSurface> cpuSurface(SkSurface::MakeRaster(canvas->imageInfo()));

    SkCanvas* offscreen = cpuSurface->getCanvas();
    offscreen->save();
    offscreen->translate(50.0f, 50.0f);
    offscreen->restore();

    sk_sp<SkImage> image = cpuSurface->makeImageSnapshot();

    int rotation = 0;
    SkFont font;
    while (!state.fQuit) { // Our application loop
        SkRandom rand;
        canvas->clear(SK_ColorWHITE);
        handle_events(&state, canvas);

        paint.setColor(SK_ColorWHITE);
		paint.setAntiAlias(true);
        for (int i = 0; i < state.circles.count(); i++) {
            paint.setColor(rand.nextU() | 0x99202080);
			auto [center, radius] = state.circles[i];
            canvas->drawCircle(center, radius, paint);
			paint.reset();
			SkPath path;
			path.moveTo(state.pressedPosition);
			path.lineTo(state.lineEndPosition);
			paint.setStrokeWidth(3);
			paint.setStyle(SkPaint::kStrokeAndFill_Style);
			canvas->drawPath(path, paint);
        }
        // draw offscreen canvas
        canvas->save();
        canvas->translate(dm.w / 2.0, dm.h / 2.0);
        canvas->rotate(rotation++);
        canvas->drawImage(image, -50.0f, -50.0f);
        canvas->restore();

        canvas->flush();
        SDL_GL_SwapWindow(window);
    }

    if (glContext) {
        SDL_GL_DeleteContext(glContext);
    }

    //Destroy window
    SDL_DestroyWindow(window);

    //Quit SDL subsystems
    SDL_Quit();
    return 0;
}