From 1d89df9e2a03c72a1b5789b066128555fc086d82 Mon Sep 17 00:00:00 2001
From: Christoph Helma <helma@in-silico.ch>
Date: Wed, 12 Jul 2017 21:19:22 +0200
Subject: initial stdin parsing

---
 shader.frag |  34 +++++++++++++++
 shader.vert |   4 ++
 sv.c        | 136 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 174 insertions(+)
 create mode 100644 shader.frag
 create mode 100644 shader.vert
 create mode 100644 sv.c

diff --git a/shader.frag b/shader.frag
new file mode 100644
index 0000000..cf44e70
--- /dev/null
+++ b/shader.frag
@@ -0,0 +1,34 @@
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform vec2 resolution;
+uniform float time;
+uniform float color;
+
+float box(in vec2 _st, in vec2 _size){
+    _size = vec2(0.5) - _size*0.5;
+    vec2 uv = smoothstep(_size,
+                        _size+vec2(0.001),
+                        _st);
+    uv *= smoothstep(_size,
+                    _size+vec2(0.001),
+                    vec2(1.0)-_st);
+    return uv.x*uv.y;
+}
+
+float cross(in vec2 _st, float _size){
+    return  box(_st, vec2(_size,_size/4.)) + 
+            box(_st, vec2(_size/4.,_size));
+}
+
+void main(){
+    vec2 st = gl_FragCoord.xy/resolution.xy;
+    vec3 c = vec3(0.);
+
+    c += vec3(cross(st,0.5*abs(cos(time))));
+    c.r -= color;
+    //c *= u_color;
+
+    gl_FragColor = vec4(c,1.0);
+}
diff --git a/shader.vert b/shader.vert
new file mode 100644
index 0000000..24eb59c
--- /dev/null
+++ b/shader.vert
@@ -0,0 +1,4 @@
+#version 420 core
+#extension GL_ARB_shading_language_420pack : require
+const vec2 quadVertices[4] = { vec2(-1.0, -1.0), vec2(1.0, -1.0), vec2(-1.0, 1.0), vec2(1.0, 1.0) };
+void main() { gl_Position = vec4(quadVertices[gl_VertexID], 0.0, 1.0); }
diff --git a/sv.c b/sv.c
new file mode 100644
index 0000000..669babb
--- /dev/null
+++ b/sv.c
@@ -0,0 +1,136 @@
+#include <GL/glew.h>
+#include <GLFW/glfw3.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <pthread.h>
+
+static void error_callback(int error, const char* description) { fputs(description, stderr); }
+
+static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods) {
+    if (key == GLFW_KEY_Q && action == GLFW_PRESS) glfwSetWindowShouldClose(window, GL_TRUE);
+}
+
+const char * readShader(char * path) {
+  fputs(path,stderr);
+  fputs("\n",stderr);
+  FILE *file = fopen(path, "r");
+  if (!file) {
+    fputs("Cannot read ",stderr);
+    fputs(path,stderr);
+    exit(EXIT_FAILURE);
+  }
+  char source[2000];
+  int res = fread(source,1,2000-1,file);
+  source[res] = 0;
+  fclose(file);
+  const char *c_str = source;
+  return c_str;
+}
+
+GLuint compileShader(const char * source, GLenum type) {
+  GLuint shader = glCreateShader(type);
+  glShaderSource(shader, 1, &source, NULL);
+  glCompileShader(shader);
+  int success;
+  glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
+  if (!success) {
+    char infoLog[512];
+    glGetShaderInfoLog(shader, 512, NULL, infoLog);
+    fputs("Shader compilation failed:\n",stderr);
+    fputs(infoLog,stderr);
+    exit(EXIT_FAILURE);
+  }
+  else { return shader; }
+}
+
+GLuint linkShader(GLuint vertex, GLuint fragment) {
+  GLuint shaderProgram = glCreateProgram();
+  glAttachShader(shaderProgram, vertex);
+  glAttachShader(shaderProgram, fragment);
+  glLinkProgram(shaderProgram);
+  int success;
+  char infoLog[512];
+  glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
+  if (!success) {
+      glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
+      fputs("Shader linking failed:\n",stderr);
+      fputs(infoLog,stderr);
+  }
+  glDetachShader(shaderProgram, vertex); 
+  glDetachShader(shaderProgram, fragment); 
+  glDeleteShader(vertex);
+  glDeleteShader(fragment);
+  glUseProgram(shaderProgram);
+  return shaderProgram;
+}
+
+GLFWwindow* createWindow() {
+  glfwInit();
+  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
+  GLFWwindow* window = glfwCreateWindow(1920,1080, "", NULL, NULL);
+  glfwMakeContextCurrent(window);
+  //glfwSetKeyCallback(window, key_callback);
+  glfwSetErrorCallback(error_callback);
+  glewInit();
+  return window;
+}
+
+GLuint createShader() {
+  GLuint vertexShader = compileShader(readShader("shader.vert"), GL_VERTEX_SHADER);
+  GLuint fragmentShader = compileShader(readShader("shader.frag"),GL_FRAGMENT_SHADER);
+  GLuint shaderProgram = linkShader(vertexShader,fragmentShader);
+  unsigned int VAO;
+  glGenVertexArrays(1, &VAO);
+  glBindVertexArray(VAO);
+  return shaderProgram;
+};
+
+void uniform1f(GLuint * shader, char * var, float f) {
+  int v = glGetUniformLocation(*shader, var);
+  glUniform1f(v, f);
+}
+
+void uniform2f(GLuint shader, char * var, float f0, float f1) {
+  int v = glGetUniformLocation(shader, var);
+  glUniform2f(v,f0,f1);
+}
+
+float color = 0.9;
+
+void *readStdin(void * s) {
+  GLuint *shader = s;
+  while (1) {
+    char * str;
+    size_t l = 80;
+    getline(&str,&l,stdin);
+    char * variable = strtok (str," ");
+    float value = atof(strtok (NULL,"\n"));
+    printf("%.1f\n",value);
+    color = value;
+  }
+}
+
+int main(void) {
+
+  GLFWwindow* window = createWindow();
+  GLuint shader = createShader();
+  uniform2f(shader, "resolution", 1920,1080);
+  pthread_t tid;
+  pthread_create(&tid, NULL, readStdin, &shader);
+
+  while (!glfwWindowShouldClose(window)) {
+    uniform1f(&shader, "time",glfwGetTime());
+    uniform1f(&shader, "color",color);
+    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+    glfwSwapBuffers(window);
+    //glfwPollEvents();
+  }
+
+  //pthread_join(tid, NULL);
+  //printf("After Thread\n");
+  glfwDestroyWindow(window);
+  glfwTerminate();
+ 
+  exit(EXIT_SUCCESS);
+}
-- 
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