1//========================================================================
2// OpenGL ES 2.0 triangle example
3// Copyright (c) Camilla Löwy <elmindreda@glfw.org>
4//
5// This software is provided 'as-is', without any express or implied
6// warranty. In no event will the authors be held liable for any damages
7// arising from the use of this software.
8//
9// Permission is granted to anyone to use this software for any purpose,
10// including commercial applications, and to alter it and redistribute it
11// freely, subject to the following restrictions:
12//
13// 1. The origin of this software must not be misrepresented; you must not
14//    claim that you wrote the original software. If you use this software
15//    in a product, an acknowledgment in the product documentation would
16//    be appreciated but is not required.
17//
18// 2. Altered source versions must be plainly marked as such, and must not
19//    be misrepresented as being the original software.
20//
21// 3. This notice may not be removed or altered from any source
22//    distribution.
23//
24//========================================================================
25
26#define GLAD_GLES2_IMPLEMENTATION
27#include <glad/gles2.h>
28#define GLFW_INCLUDE_NONE
29#include <GLFW/glfw3.h>
30
31#include "linmath.h"
32
33#include <stdlib.h>
34#include <stddef.h>
35#include <stdio.h>
36
37typedef struct Vertex
38{
39    vec2 pos;
40    vec3 col;
41} Vertex;
42
43static const Vertex vertices[3] =
44{
45    { { -0.6f, -0.4f }, { 1.f, 0.f, 0.f } },
46    { {  0.6f, -0.4f }, { 0.f, 1.f, 0.f } },
47    { {   0.f,  0.6f }, { 0.f, 0.f, 1.f } }
48};
49
50static const char* vertex_shader_text =
51"#version 100\n"
52"precision mediump float;\n"
53"uniform mat4 MVP;\n"
54"attribute vec3 vCol;\n"
55"attribute vec2 vPos;\n"
56"varying vec3 color;\n"
57"void main()\n"
58"{\n"
59"    gl_Position = MVP * vec4(vPos, 0.0, 1.0);\n"
60"    color = vCol;\n"
61"}\n";
62
63static const char* fragment_shader_text =
64"#version 100\n"
65"precision mediump float;\n"
66"varying vec3 color;\n"
67"void main()\n"
68"{\n"
69"    gl_FragColor = vec4(color, 1.0);\n"
70"}\n";
71
72static void error_callback(int error, const char* description)
73{
74    fprintf(stderr, "GLFW Error: %s\n", description);
75}
76
77static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
78{
79    if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
80        glfwSetWindowShouldClose(window, GLFW_TRUE);
81}
82
83int main(void)
84{
85    glfwSetErrorCallback(error_callback);
86
87    if (!glfwInit())
88        exit(EXIT_FAILURE);
89
90    glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_ES_API);
91    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
92    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
93    glfwWindowHint(GLFW_CONTEXT_CREATION_API, GLFW_EGL_CONTEXT_API);
94
95    GLFWwindow* window = glfwCreateWindow(640, 480, "OpenGL ES 2.0 Triangle (EGL)", NULL, NULL);
96    if (!window)
97    {
98        glfwWindowHint(GLFW_CONTEXT_CREATION_API, GLFW_NATIVE_CONTEXT_API);
99        window = glfwCreateWindow(640, 480, "OpenGL ES 2.0 Triangle", NULL, NULL);
100        if (!window)
101        {
102            glfwTerminate();
103            exit(EXIT_FAILURE);
104        }
105    }
106
107    glfwSetKeyCallback(window, key_callback);
108
109    glfwMakeContextCurrent(window);
110    gladLoadGLES2(glfwGetProcAddress);
111    glfwSwapInterval(1);
112
113    GLuint vertex_buffer;
114    glGenBuffers(1, &vertex_buffer);
115    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
116    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
117
118    const GLuint vertex_shader = glCreateShader(GL_VERTEX_SHADER);
119    glShaderSource(vertex_shader, 1, &vertex_shader_text, NULL);
120    glCompileShader(vertex_shader);
121
122    const GLuint fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
123    glShaderSource(fragment_shader, 1, &fragment_shader_text, NULL);
124    glCompileShader(fragment_shader);
125
126    const GLuint program = glCreateProgram();
127    glAttachShader(program, vertex_shader);
128    glAttachShader(program, fragment_shader);
129    glLinkProgram(program);
130
131    const GLint mvp_location = glGetUniformLocation(program, "MVP");
132    const GLint vpos_location = glGetAttribLocation(program, "vPos");
133    const GLint vcol_location = glGetAttribLocation(program, "vCol");
134
135    glEnableVertexAttribArray(vpos_location);
136    glEnableVertexAttribArray(vcol_location);
137    glVertexAttribPointer(vpos_location, 2, GL_FLOAT, GL_FALSE,
138                          sizeof(Vertex), (void*) offsetof(Vertex, pos));
139    glVertexAttribPointer(vcol_location, 3, GL_FLOAT, GL_FALSE,
140                          sizeof(Vertex), (void*) offsetof(Vertex, col));
141
142    while (!glfwWindowShouldClose(window))
143    {
144        int width, height;
145        glfwGetFramebufferSize(window, &width, &height);
146        const float ratio = width / (float) height;
147
148        glViewport(0, 0, width, height);
149        glClear(GL_COLOR_BUFFER_BIT);
150
151        mat4x4 m, p, mvp;
152        mat4x4_identity(m);
153        mat4x4_rotate_Z(m, m, (float) glfwGetTime());
154        mat4x4_ortho(p, -ratio, ratio, -1.f, 1.f, 1.f, -1.f);
155        mat4x4_mul(mvp, p, m);
156
157        glUseProgram(program);
158        glUniformMatrix4fv(mvp_location, 1, GL_FALSE, (const GLfloat*) &mvp);
159        glDrawArrays(GL_TRIANGLES, 0, 3);
160
161        glfwSwapBuffers(window);
162        glfwPollEvents();
163    }
164
165    glfwDestroyWindow(window);
166
167    glfwTerminate();
168    exit(EXIT_SUCCESS);
169}
170
171