SkiaGL.cpp

#include <stdio.h>

#include <GL/glut.h>

#include <GrContext.h>
#include <SkSurface.h>
#include <SkCanvas.h>
#include <SkPaint.h>
#include <SkShader.h>
#include <../effects/SkGradientShader.h>

GrContext* skiaContext = nullptr;
SkSurface* skiaSurface = nullptr;

static void init_skia(int w, int h)
{
	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).release();
}

static void cleanup_skia()
{
	delete skiaSurface;
	delete skiaContext;
}

static void draw_skia(SkCanvas* skiaCanvas)
{
	skiaCanvas->clear(SK_ColorBLACK);

	SkPaint paint;
	paint.setFilterQuality(kLow_SkFilterQuality);
	paint.setColor(SK_ColorWHITE);
	paint.setTextSize(24.0f);

	char outString[64];
	sprintf_s(outString, "C++ Rocks! (maybe)");

	skiaCanvas->drawText(outString, strlen(outString), 50.f, 200.f, paint);

	SkPoint points[] = { SkPoint::Make(0, 50), SkPoint::Make(0, 150) };
	SkColor colors[] = { SK_ColorRED, SK_ColorGREEN };
	paint.setShader(SkGradientShader::MakeLinear(points, colors, NULL, 2, SkShader::TileMode::kClamp_TileMode));

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

void reshape(int w, int h)
{
	glViewport(0, 0, (GLsizei)w, (GLsizei)h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(65.0, (GLfloat)w / (GLfloat)h, 1.0, 20.0);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glTranslatef(0.0, 0.0, -5.0);
}

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT);

	SkCanvas* skiaCanvas = skiaSurface->getCanvas();

	draw_skia(skiaCanvas);

	skiaCanvas->flush();

	glutSwapBuffers();
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutInitWindowSize(500, 500);
	glutInitWindowPosition(100, 100);
	glutCreateWindow(argv[0]);
	glutDisplayFunc(display);
	glutReshapeFunc(reshape);
	glClearColor(0.0, 0.0, 0.0, 0.0);
	glShadeModel(GL_FLAT);

	init_skia(500, 500);

	glutMainLoop();

	cleanup_skia();

	return 0;
}