standalone/001_triangle_screenshot.cpp

Shows the basic usage of OGLplus with EGLplus

Copyright 2008-2014 Matus Chochlik. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#include <cassert>
#include <iostream>
#include <fstream>

#include <oglplus/gl.hpp>
#include <oglplus/all.hpp>

#include <eglplus/egl.hpp>
#define EGL_CONTEXT_MAJOR_VERSION 0x3098
#define EGL_CONTEXT_MINOR_VERSION 0x30FB
#define EGL_CONTEXT_FLAGS                   0x30FC
#define EGL_CONTEXT_OPENGL_PROFILE_MASK     0x30FD
#define EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY  0x31BD
#define EGL_OPENGL_ES3_BIT                  0x0040
#define EGL_NO_RESET_NOTIFICATION           0x31BE
#define EGL_LOSE_CONTEXT_ON_RESET           0x31BF
#define EGL_CONTEXT_OPENGL_DEBUG_BIT               0x00000001
#define EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT  0x00000002
#define EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT       0x00000004
#define EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT          0x00000001
#define EGL_CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT 0x00000002

#include <eglplus/all.hpp>

void render_frame(void)
{
    using namespace oglplus;

    Context gl;

    VertexShader vs;
    vs.Source(" \
        #version 120\n \
        attribute vec3 Position; \
        void main(void) \
        { \
            gl_Position = vec4(Position, 1.0); \
        } \
    ");
    vs.Compile();

    FragmentShader fs;
    fs.Source(" \
        #version 120\n \
        void main(void) \
        { \
            gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0); \
        } \
    ");
    fs.Compile();

    Program prog;
    prog.AttachShader(vs);
    prog.AttachShader(fs);
    prog.Link();
    prog.Use();

    VertexArray triangle;
    triangle.Bind();

    GLfloat triangle_verts[9] = {
         0.0f, 0.0f, 0.0f,
        -1.0f, 0.0f, 0.0f,
         0.0f, 1.0f, 0.0f
    };

    oglplus::Buffer verts;
    verts.Bind(Buffer::Target::Array);
    Buffer::Data(
        Buffer::Target::Array,
        9,
        triangle_verts
    );

    VertexArrayAttrib vert_attr(prog, "Position");
    vert_attr.Setup<Vec3f>();
    vert_attr.Enable();

    gl.ClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    gl.Clear().ColorBuffer();

    gl.DrawArrays(PrimitiveType::Triangles, 0, 3);
}

void save_frame(unsigned width, unsigned height, const char* screenshot_path)
{
    std::vector<char> pixels(width * height * 3);
    glReadPixels(
        0, 0,
        width,
        height,
        GL_RGB,
        GL_UNSIGNED_BYTE,
        pixels.data()
    );
    std::ofstream output(screenshot_path);
    output.write(pixels.data(), pixels.size());
    std::cout << screenshot_path << std::endl;
}

void make_screenshot(unsigned width, unsigned height, const char* screenshot_path)
{
    using namespace eglplus;

    eglplus::Display display;
    LibEGL egl(display);

    Configs configs(
        display,
        ConfigAttribs()
            .Add(ConfigAttrib::RedSize, 8)
            .Add(ConfigAttrib::GreenSize, 8)
            .Add(ConfigAttrib::BlueSize, 8)
            .Add(ConfigAttrib::DepthSize, 24)
            .Add(ConfigAttrib::StencilSize, 8)
            .Add(ColorBufferType::RGBBuffer)
            .Add(RenderableTypeBit::OpenGL)
            .Add(SurfaceTypeBit::Pbuffer)
            .Get()
    );

    Config config = configs.First();

    Surface surface = Surface::Pbuffer(
        display,
        config,
        SurfaceAttribs()
            .Add(SurfaceAttrib::Width, int(width))
            .Add(SurfaceAttrib::Height, int(height))
            .Get()
    );

    BindAPI(RenderingAPI::OpenGL);
    Context context(
        display,
        config,
        ContextAttribs()
            .Add(ContextAttrib::MajorVersion, 3)
            .Add(ContextAttrib::MinorVersion, 0)
            .Add(ContextFlag::OpenGLRobustAccess|ContextFlag::OpenGLDebug)
            .Add(OpenGLProfileBit::Core|OpenGLProfileBit::Compatibility)
            .Add(OpenGLResetNotificationStrategy::NoResetNotification)
            .Get()
    );

    context.MakeCurrent(surface);

    oglplus::GLAPIInitializer api_init;

    render_frame();

    context.WaitClient();

    save_frame(width, height, screenshot_path);
}

int main(int argc, char* argv[])
{
    try
    {
        glGetError();
        make_screenshot(
            800,
            600,
            (argc>1)?argv[1]:"screenshot.rgb"
        );
        return 0;
    }
    catch(oglplus::Error& oe)
    {
        std::cerr
            << "OGLplus error (in "
            << oe.GLFunc()
            << "'): "
            << oe.what()
            << " ["
            << oe.SourceFile()
            << ":"
            << oe.SourceLine()
            << "] "
            << std::endl;
    }
    catch(eglplus::Error& ee)
    {
        std::cerr
            << "EGLplus error (in "
            << ee.EGLFunc()
            << ") "
            << ee.what()
            << " ["
            << ee.SourceFile()
            << ":"
            << ee.SourceLine()
            << "] "
            << std::endl;
    }
    catch(std::exception& se)
    {
        std::cerr << "Error: " << se.what();
        std::cerr << std::endl;
    }
    return 1;
}