use GLUtil functions

example.rb

@@ -2,6 +2,9 @@
 
 require 'sfml/all'
 require 'opengl'
+require 'glutil'
+
+include GLUtil
 
 class Example
   include SFML
@@ -15,8 +18,7 @@ class Example
   end
 
   def load_shaders
-    v_id = glCreateShader(GL_VERTEX_SHADER)
-    glShaderSource(v_id, <<-EOS)
+    v_shader = GLShader.new(GL_VERTEX_SHADER, <<-EOS)
       uniform vec2 offset;
       uniform vec2 screen_size;
       attribute vec2 pos;
@@ -31,13 +33,8 @@ class Example
         gl_Position = pos_i;
       }
     EOS
-    glCompileShader(v_id)
-    unless glGetShaderiv(v_id, GL_COMPILE_STATUS)
-      raise glGetShaderInfoLog(v_id)
-    end
 
-    f_id = glCreateShader(GL_FRAGMENT_SHADER)
-    glShaderSource(f_id, <<-EOS)
+    f_shader = GLShader.new(GL_FRAGMENT_SHADER, <<-EOS)
       varying vec4 pos_i;
 
       void main()
@@ -47,22 +44,11 @@ class Example
                             0, 1);
       }
     EOS
-    glCompileShader(f_id)
-    unless glGetShaderiv(f_id, GL_COMPILE_STATUS)
-      raise glGetShaderInfoLog(f_id)
-    end
 
-    p_id = glCreateProgram()
-    glAttachShader(p_id, v_id)
-    glAttachShader(p_id, f_id)
-    glLinkProgram(p_id)
-    unless glGetProgramiv(p_id, GL_LINK_STATUS)
-      raise glGetProgramInfoLog(p_id)
-    end
-    $offset_loc = glGetUniformLocation(p_id, "offset")
-    $screen_size_loc = glGetUniformLocation(p_id, "screen_size")
-
-    glUseProgram(p_id)
+    program = GLProgram.new([v_shader, f_shader])
+    $offset_loc = program.get_uniform_location("offset")
+    $screen_size_loc = program.get_uniform_location("screen_size")
+    program.use
   end
 
   def create_window
@@ -81,9 +67,7 @@ class Example
                   -0.02, 0.02,
                   -0.02, -0.02,
                   0.02, -0.02].pack("f*")
-    b_id = glGenBuffers(1).first
-    glBindBuffer(GL_ARRAY_BUFFER, b_id);
-    glBufferData(GL_ARRAY_BUFFER, 2 * 4 * 4, quad_attrs, GL_STATIC_DRAW);
+    buffer = GLBuffer.new(GL_ARRAY_BUFFER, GL_STATIC_DRAW, quad_attrs, 2 * 4 * 4)
 
     x, y = 0, 0
     while @window.open?