From 3ad598cad5f26b4d833af11931352de19db10fe9 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Thu, 11 May 2017 20:07:43 -0400
Subject: refactor link_program

---
 main.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 60 insertions(+), 7 deletions(-)

(limited to 'main.c')

diff --git a/main.c b/main.c
index fa61427..e02ab55 100644
--- a/main.c
+++ b/main.c
@@ -13,6 +13,11 @@
 // custom SDL_USEREVENT code for timer
 #define EVENT_CODE_TIMER 0
 
+typedef struct {
+  const GLuint type;
+  const char *src;
+} shader_t;
+
 static const float
 verts[] = {
   -0.5,  0.5, 0,
@@ -20,8 +25,8 @@ verts[] = {
    0.0, -0.5, 0,
 };
 
-static const char *
-vs_src = 
+static const char
+vs_src[] =
   "#version 320 es\n"
   "\n"
   "layout (location = 0) in mediump vec3 pos;\n"
@@ -30,8 +35,8 @@ vs_src =
   "  gl_Position = vec4(pos.x, pos.y, pos.z, 1);\n"
   "}\n";
 
-static const char *
-fs_src = 
+static const char
+fs_src[] =
   "#version 320 es\n"
   "\n"
   "out mediump vec4 color;\n"
@@ -42,6 +47,12 @@ fs_src =
   "  color = vec4(0.5f + 0.5 * sin(time * 3.141), 0, 0, 1);\n"
   "}\n";
 
+static const shader_t
+RENDER_SHADERS[] = {
+  { GL_VERTEX_SHADER,   vs_src },
+  { GL_FRAGMENT_SHADER, fs_src },
+};
+
 static GLuint
 compile_shader(
   const GLenum type,
@@ -68,6 +79,47 @@ compile_shader(
   return r;
 }
 
+static GLuint
+link_program(
+  const size_t num_shaders,
+  const shader_t *shaders
+) {
+  // create program
+  GLuint r = glCreateProgram();
+
+  // compile shaders
+  GLuint ids[128];
+  for (size_t i = 0; i < num_shaders; i++) {
+    // compile shader
+    ids[i] = compile_shader(shaders[i].type, shaders[i].src);
+
+    // attach shader
+    glAttachShader(r, ids[i]);
+  }
+
+  // link program
+  glLinkProgram(r);
+
+  // check link status
+  GLint ok;
+  glGetProgramiv(r, GL_LINK_STATUS, &ok);
+  if (!ok) {
+    GLchar log[1024];
+    glGetProgramInfoLog(r, sizeof(log), NULL, log);
+    fprintf(stderr, "Program Link Error: %s\n", log);
+    exit(EXIT_FAILURE);
+  }
+
+  // delete shaders
+  for (size_t i = 0; i < num_shaders; i++) {
+    glDeleteShader(ids[i]);
+  }
+
+  // return result
+  return r;
+}
+
+#if 0
 static GLuint
 link_render_program(
   const char * const vs_src,
@@ -97,13 +149,14 @@ link_render_program(
     exit(EXIT_FAILURE);
   }
 
-  // delete shaders 
+  // delete shaders
   glDeleteShader(vs);
   glDeleteShader(fs);
 
   // return result
   return r;
 }
+#endif /* 0 */
 
 #if 0
 static GLuint
@@ -114,7 +167,7 @@ link_compute_program(
   GLuint r = glCreateProgram();
 
 }
-#endif
+#endif /* 0 */
 
 static void
 update_viewport(
@@ -262,7 +315,7 @@ int main(int argc, char *argv[]) {
   glBindVertexArray(0);
 
   // link program
-  GLuint prog = link_render_program(vs_src, fs_src);
+  GLuint prog = link_program(2, RENDER_SHADERS);
   GLint u_time = glGetUniformLocation(prog, "time");
 
   // init flags
-- 
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