//////////////////////////////////////////////////////////////////////////////
//
//  Triangles.cpp
//
//////////////////////////////////////////////////////////////////////////////
#include "vgl.h"
#include "LoadShaders.h"
 
enum VAO_IDs { Triangles, NumVAOs };
enum Buffer_IDs { ArrayBuffer, NumBuffers };
enum Attrib_IDs { vPosition = 0 };
GLuint  VAOs[NumVAOs];
GLuint  Buffers[NumBuffers];
const GLuint  NumVertices = 6;
//----------------------------------------------------------------------------
//
// init
//
 
void
init( void )
{
    glGenVertexArrays( NumVAOs, VAOs );
    glBindVertexArray( VAOs[Triangles] );
    GLfloat  vertices[NumVertices][2] = {
        { -0.90f, -0.90f }, {  0.85f, -0.90f }, { -0.90f,  0.85f },  // Triangle 1
        {  0.90f, -0.85f }, {  0.90f,  0.90f }, { -0.85f,  0.90f }   // Triangle 2
    };
    glCreateBuffers( NumBuffers, Buffers );
    glBindBuffer( GL_ARRAY_BUFFER, Buffers[ArrayBuffer] );
    glBufferStorage( GL_ARRAY_BUFFER, sizeof(vertices), vertices, 0);
    ShaderInfo  shaders[] =
    {
        { GL_VERTEX_SHADER, "media/shaders/triangles/triangles.vert" },
        { GL_FRAGMENT_SHADER, "media/shaders/triangles/triangles.frag" },
        { GL_NONE, NULL }
    };
    GLuint program = LoadShaders( shaders );
    glUseProgram( program );
    glVertexAttribPointer( vPosition, 2, GL_FLOAT,
                           GL_FALSE, 0, BUFFER_OFFSET(0) );
    glEnableVertexAttribArray( vPosition );
}
//----------------------------------------------------------------------------
//
// display
//
 
void
display( void )
{
    static const float black[] = { 1.0f, 0.0f, 0.0f, 0.0f };
    glClearBufferfv(GL_COLOR, 0, black);
    glBindVertexArray( VAOs[Triangles] );
    glDrawArrays( GL_TRIANGLES, 0, NumVertices );
}
//----------------------------------------------------------------------------
//
// main
//
#ifdef _WIN32
int CALLBACK WinMain(
  _In_ HINSTANCE hInstance,
  _In_ HINSTANCE hPrevInstance,
  _In_ LPSTR     lpCmdLine,
  _In_ int       nCmdShow
)
#else
int
main( int argc, char** argv )
#endif
{
    glfwInit();
    GLFWwindow* window = glfwCreateWindow(800, 600, "Triangles", NULL, NULL);
    glfwMakeContextCurrent(window);
    gl3wInit();
    init();
    while (!glfwWindowShouldClose(window))
    {
        display();
        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glfwDestroyWindow(window);
    glfwTerminate();
}