orca/sketches/triangleGLES/main.c

/*************************************************************************
*
*  Orca
*  Copyright 2023 Martin Fouilleul and the Orca project contributors
*  See LICENSE.txt for licensing information
*
**************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define _USE_MATH_DEFINES //NOTE: necessary for MSVC
#include <math.h>

#define OC_INCLUDE_GL_API 1
#include "orca.h"

unsigned int program;

const char* vshaderSource =
    //"#version 320 es\n"
    "attribute vec4 vPosition;\n"
    "uniform mat4 transform;\n"
    "void main()\n"
    "{\n"
    "   gl_Position = transform*vPosition;\n"
    "}\n";

const char* fshaderSource =
    //"#version 320 es\n"
    "precision mediump float;\n"
    "void main()\n"
    "{\n"
    "    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);\n"
    "}\n";

void compile_shader(GLuint shader, const char* source)
{
    glShaderSource(shader, 1, &source, 0);
    glCompileShader(shader);

    int err = glGetError();
    if(err)
    {
        oc_log_error("gl error: %i\n", err);
    }

    int status = 0;
    glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
    if(!status)
    {
        char buffer[256];
        int size = 0;
        glGetShaderInfoLog(shader, 256, &size, buffer);
        oc_log_error("shader error: %.*s\n", size, buffer);
    }
}

int main()
{
    oc_init();

    oc_rect rect = { .x = 100, .y = 100, .w = 800, .h = 600 };
    oc_window window = oc_window_create(rect, OC_STR8("test"), 0);

    //NOTE: create surface
    oc_surface surface = oc_surface_create_for_window(window, OC_GLES);
    oc_surface_select(surface);

    //NOTE: init shader and gl state
    GLuint vao;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);

    GLuint vertexBuffer;
    glGenBuffers(1, &vertexBuffer);

    GLfloat vertices[] = {
        -0.866 / 2, -0.5 / 2, 0, 0.866 / 2, -0.5 / 2, 0, 0, 0.5, 0
    };

    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    unsigned int vshader = glCreateShader(GL_VERTEX_SHADER);
    unsigned int fshader = glCreateShader(GL_FRAGMENT_SHADER);
    program = glCreateProgram();

    compile_shader(vshader, vshaderSource);
    compile_shader(fshader, fshaderSource);

    glAttachShader(program, vshader);
    glAttachShader(program, fshader);
    glLinkProgram(program);

    int status = 0;
    glGetProgramiv(program, GL_LINK_STATUS, &status);
    if(!status)
    {
        char buffer[256];
        int size = 0;
        glGetProgramInfoLog(program, 256, &size, buffer);
        oc_log_error("link error: %.*s\n", size, buffer);
    }

    glUseProgram(program);

    oc_window_bring_to_front(window);

    while(!oc_should_quit())
    {
        oc_arena_scope scratch = oc_scratch_begin();
        oc_pump_events(0);
        oc_event* event = 0;
        while((event = oc_next_event(scratch.arena)) != 0)
        {
            switch(event->type)
            {
                case OC_EVENT_WINDOW_CLOSE:
                {
                    oc_request_quit();
                }
                break;

                default:
                    break;
            }
        }

        glClearColor(0.3, 0.3, 1, 1);
        glClear(GL_COLOR_BUFFER_BIT);

        static float alpha = 0;
        //f32 aspect = frameSize.x/frameSize.y;
        f32 aspect = 800 / (f32)600;

        GLfloat matrix[] = { cosf(alpha) / aspect, sinf(alpha), 0, 0,
                             -sinf(alpha) / aspect, cosf(alpha), 0, 0,
                             0, 0, 1, 0,
                             0, 0, 0, 1 };

        alpha += 2 * M_PI / 120;

        glUniformMatrix4fv(0, 1, false, matrix);

        glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
        glEnableVertexAttribArray(0);

        glDrawArrays(GL_TRIANGLES, 0, 3);

        oc_surface_present(surface);

        oc_scratch_end(scratch);
    }

    oc_surface_destroy(surface);
    oc_window_destroy(window);
    oc_terminate();

    return (0);
}