From 8b64d6d5a803aeb5850aa4a989162032ccdeab20 Mon Sep 17 00:00:00 2001
From: Brandon Wright <bearoso@gmail.com>
Date: Thu, 21 Oct 2010 21:32:47 -0500
Subject: [PATCH] Allow use of only vertex or fragment programs.

---
 gtk/src/gtk_display_driver_opengl.cpp | 30 +++++++++++++++++----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/gtk/src/gtk_display_driver_opengl.cpp b/gtk/src/gtk_display_driver_opengl.cpp
index f479676b..77d1847e 100644
--- a/gtk/src/gtk_display_driver_opengl.cpp
+++ b/gtk/src/gtk_display_driver_opengl.cpp
@@ -547,24 +547,32 @@ S9xOpenGLDisplayDriver::load_shaders (const char *shader_file)
         }
     }
 
-    if (!vertex || !fragment)
+    if (!vertex && !fragment)
     {
-        fprintf (stderr, _("Shader is missing either a vertex or fragment program.\n"));
+        fprintf (stderr, _("Shader lacks any programs.\n"));
         xmlFreeDoc (xml_doc);
         return 0;
     }
 
     program = glCreateProgram ();
-    vertex_shader = glCreateShader (GL_VERTEX_SHADER);
-    fragment_shader = glCreateShader (GL_FRAGMENT_SHADER);
-    glShaderSource (vertex_shader, 1, (const GLchar **) &vertex, NULL);
-    glShaderSource (fragment_shader, 1, (const GLchar **) &fragment, NULL);
-    glCompileShader (vertex_shader);
-    glCompileShader (fragment_shader);
-    glAttachShader (program, vertex_shader);
-    glAttachShader (program, fragment_shader);
-    glLinkProgram (program);
 
+    if (vertex)
+    {
+        vertex_shader = glCreateShader (GL_VERTEX_SHADER);
+        glShaderSource (vertex_shader, 1, (const GLchar **) &vertex, NULL);
+        glCompileShader (vertex_shader);
+        glAttachShader (program, vertex_shader);
+    }
+
+    if (fragment)
+    {
+        fragment_shader = glCreateShader (GL_FRAGMENT_SHADER);
+        glShaderSource (fragment_shader, 1, (const GLchar **) &fragment, NULL);
+        glCompileShader (fragment_shader);
+        glAttachShader (program, fragment_shader);
+    }
+
+    glLinkProgram (program);
     glUseProgram (program);
 
     xmlFreeDoc (xml_doc);