read shader sources from filesystem

src/fragment.glsl

@@ -0,0 +1,14 @@
+#version 120
+
+uniform sampler2D textures[2];
+
+varying float fade_factor;
+varying vec2 texcoord;
+
+void main()
+{
+  gl_FragColor = mix(texture2D(textures[0], texcoord),
+                     texture2D(textures[1], texcoord),
+                     fade_factor
+                     );
+}

src/main.c

@@ -10,54 +10,49 @@
 #include <glad/glad.h>
 #include <GLFW/glfw3.h>
 
+static void * read_file(const char * filename)
+{
+  int fd = open(filename, O_RDONLY);
+  if (fd == -1) {
+    fprintf(stderr, "open(%s): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+
+  off_t size = lseek(fd, 0, SEEK_END);
+  if (size == (off_t)-1) {
+    fprintf(stderr, "lseek(%s, SEEK_END): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+
+  off_t start = lseek(fd, 0, SEEK_SET);
+  if (start == (off_t)-1) {
+    fprintf(stderr, "lseek(%s, SEEK_SET): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+
+  void * buf = malloc(size+1);
+
+  ssize_t read_size = read(fd, buf, size);
+  if (read_size == -1) {
+    fprintf(stderr, "read(%s): %s\n", filename, strerror(errno));
+    return NULL;
+  }
+  ((char*)buf)[read_size] = 0;
+
+  return buf;
+}
+
 void framebuffer_size_callback(GLFWwindow* window, int width, int height)
 {
   glViewport(0, 0, width, height);
 }
 
-const char *vertexShaderSource = R"(
-#version 120
-
-attribute vec2 position;
-
-varying vec2 texcoord;
-
-void main()
-{
-  gl_Position = vec4(position, 0.0, 1.0);
-
-  vec2 tex = position * vec2(0.5) + vec2(0.5);
-
-  texcoord = vec2(tex.x * 400 / 512,
-                  (1.0 - tex.y) * 300 / 512);
-}
-  )"
-  ;
-
-const char *fragmentShaderSource = R"(
-#version 120
-
-uniform float fade_factor;
-uniform sampler2D textures[2];
-
-varying vec2 texcoord;
-
-void main()
-{
-  gl_FragColor = mix(texture2D(textures[0], texcoord),
-                     texture2D(textures[1], texcoord),
-                     fade_factor
-                     );
-}
-
-)"
-;
-
 unsigned int compile_shaders()
 {
+  void * vertexShaderSource = read_file("src/vertex.glsl");
   unsigned int vertexShader;
   vertexShader = glCreateShader(GL_VERTEX_SHADER);
-  glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
+  glShaderSource(vertexShader, 1, (const char **)&vertexShaderSource, NULL);
   glCompileShader(vertexShader);
   {
     int  success;
@@ -68,10 +63,12 @@ unsigned int compile_shaders()
       printf("vertex shader compile failed:\n%s\n", infoLog);
     }
   }
+  free(vertexShaderSource);
 
+  void * fragmentShaderSource = read_file("src/fragment.glsl");
   unsigned int fragmentShader;
   fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
-  glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
+  glShaderSource(fragmentShader, 1, (const char **)&fragmentShaderSource, NULL);
   glCompileShader(fragmentShader);
   {
     int  success;
@@ -82,6 +79,7 @@ unsigned int compile_shaders()
       printf("fragment shader compile failed:\n%s\n", infoLog);
     }
   }
+  free(fragmentShaderSource);
 
   unsigned int shaderProgram;
   shaderProgram = glCreateProgram();
@@ -118,47 +116,16 @@ static int make_buffer(unsigned int target,
 }
 
 static const float vertex_buffer_data[] = {
-  -1.0f, -1.0f,
+  -1.0f, -1.0f, 0.0f, 1.0f,
-   1.0f, -1.0f,
+   1.0f, -1.0f, 0.0f, 1.0f,
-  -1.0f,  1.0f,
+  -1.0f,  1.0f, 0.0f, 1.0f,
-   1.0f,  1.0f
+   1.0f,  1.0f, 0.0f, 1.0f,
 };
 
 static const unsigned short element_buffer_data[] = {
   0, 1, 2, 3
 };
 
-static void * read_file(const char * filename)
-{
-  int fd = open(filename, O_RDONLY);
-  if (fd == -1) {
-    fprintf(stderr, "open(%s): %s\n", filename, strerror(errno));
-    return NULL;
-  }
-
-  off_t size = lseek(fd, 0, SEEK_END);
-  if (size == (off_t)-1) {
-    fprintf(stderr, "lseek(%s, SEEK_END): %s\n", filename, strerror(errno));
-    return NULL;
-  }
-
-  off_t start = lseek(fd, 0, SEEK_SET);
-  if (start == (off_t)-1) {
-    fprintf(stderr, "lseek(%s, SEEK_SET): %s\n", filename, strerror(errno));
-    return NULL;
-  }
-
-  void * buf = malloc(size);
-
-  ssize_t read_size = read(fd, buf, size);
-  if (read_size == -1) {
-    fprintf(stderr, "read(%s): %s\n", filename, strerror(errno));
-    return NULL;
-  }
-
-  return buf;
-}
-
 static unsigned int make_texture(const char * filename)
 {
   unsigned int texture;
@@ -188,7 +155,7 @@ static unsigned int make_texture(const char * filename)
 
 struct location {
   struct {
-    unsigned int fade_factor;
+    unsigned int time;
     unsigned int textures[2];
   } uniform;
   struct {
@@ -236,12 +203,12 @@ int main()
 
   struct location location;
 
-  location.uniform.fade_factor = glGetUniformLocation(shaderProgram, "fade_factor");
+  location.uniform.time = glGetUniformLocation(shaderProgram, "time");
   location.uniform.textures[0] = glGetUniformLocation(shaderProgram, "textures[0]");
   location.uniform.textures[1] = glGetUniformLocation(shaderProgram, "textures[1]");
 
-  printf("uniforms:\n  fade_factor: %u\n  textures_0: %u\n  textures_1: %u\n",
+  printf("uniforms:\n  time: %u\n  textures_0: %u\n  textures_1: %u\n",
-         location.uniform.fade_factor,
+         location.uniform.time,
          location.uniform.textures[0],
          location.uniform.textures[1]);
 
@@ -249,7 +216,7 @@ int main()
   printf("attributes:\n  position %u\n",
          location.attrib.position);
 
-  float fade_factor = 0;
+  float time = 0;
 
   struct timespec last;
   struct timespec cur;
@@ -257,17 +224,23 @@ int main()
   clock_gettime(CLOCK_MONOTONIC, &last);
 
   while(!glfwWindowShouldClose(window)) {
+    clock_gettime(CLOCK_MONOTONIC, &cur);
+    uint64_t last_msec = (last.tv_sec * 1000) + (last.tv_nsec * 1e-06);
+    uint64_t cur_msec = (cur.tv_sec * 1000) + (cur.tv_nsec * 1e-06);
+    uint64_t dt = cur_msec - last_msec;
+    time = (float)((double)dt * 0.001);
+
     if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
       glfwSetWindowShouldClose(window, true);
 
-    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
+    glClearColor(0.1f, 0.1f, 0.1f, 0.1f);
     glClear(GL_COLOR_BUFFER_BIT);
 
     //
     // render
     //
     glUseProgram(shaderProgram);
-    glUniform1f(location.uniform.fade_factor, fade_factor);
+    glUniform1f(location.uniform.time, time);
 
     glActiveTexture(GL_TEXTURE0);
     glBindTexture(GL_TEXTURE_2D, texture_0);
@@ -279,10 +252,10 @@ int main()
 
     glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
     glVertexAttribPointer(location.attrib.position,
-                          2,
+                          4,
                           GL_FLOAT,
                           GL_FALSE,
-                          (sizeof (float)) * 2,
+                          (sizeof (float)) * 4,
                           (void*)0
                           );
     glEnableVertexAttribArray(location.attrib.position);
@@ -298,14 +271,6 @@ int main()
 
     glfwSwapBuffers(window);
     glfwPollEvents();
-
-    clock_gettime(CLOCK_MONOTONIC, &cur);
-    uint64_t last_msec = (last.tv_sec * 1000) + (last.tv_nsec * 1e-06);
-    uint64_t cur_msec = (cur.tv_sec * 1000) + (cur.tv_nsec * 1e-06);
-    uint64_t dt = cur_msec - last_msec;
-    fade_factor = sin(dt * 0.001f) * 0.5 + 0.5;
-
-    //last = cur;
   }
 
   glfwTerminate();

src/vertex.glsl

@@ -0,0 +1,20 @@
+#version 120
+
+uniform float time;
+
+attribute vec4 position;
+
+varying float fade_factor;
+varying vec2 texcoord;
+
+void main()
+{
+  gl_Position = position;
+
+  vec2 tex = position.xy * vec2(0.5) + vec2(0.5);
+
+  texcoord = vec2(tex.x * 400 / 512,
+                  (1.0 - tex.y) * 300 / 512);
+
+  fade_factor = sin(time) * 0.5 + 0.5;
+}