From ad5d10a8ba891c0c79c2ecffdb33851aaaf93357 Mon Sep 17 00:00:00 2001
From: Maciej Suminski <maciej.suminski@cern.ch>
Date: Mon, 3 Jun 2013 10:54:24 +0200
Subject: [PATCH] Display linking errors in debug mode for shaders. Added
 SHADER::GetAttribute() function for getting shaders attribute location.

---
 common/gal/opengl/shader.cpp | 27 ++++++++++++++++++++-------
 include/gal/opengl/shader.h  | 11 ++++++++++-
 2 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/common/gal/opengl/shader.cpp b/common/gal/opengl/shader.cpp
index e38fbe1995..6cbd84850d 100644
--- a/common/gal/opengl/shader.cpp
+++ b/common/gal/opengl/shader.cpp
@@ -168,23 +168,30 @@ void SHADER::ConfigureGeometryShader( GLuint maxVertices, GLuint geometryInputTy
 }
 
 
-void SHADER::Link()
+bool SHADER::Link()
 {
     // Shader linking
     glLinkProgram( programNumber );
     ProgramInfo( programNumber );
 
     // Check the Link state
-    GLint linkStatus = 0;
-    glGetObjectParameterivARB( programNumber, GL_OBJECT_LINK_STATUS_ARB, &linkStatus );
+    glGetObjectParameterivARB( programNumber, GL_OBJECT_LINK_STATUS_ARB, (GLint*) &isShaderLinked );
 
-    if( !linkStatus )
+#ifdef __WXDEBUG__
+    if( !isShaderLinked )
     {
-        wxLogError( wxString::FromUTF8( "Can't link the shaders!" ) );
-        exit( 1 );
+        int maxLength;
+        glGetProgramiv( programNumber, GL_INFO_LOG_LENGTH, &maxLength );
+        maxLength = maxLength + 1;
+        char *linkInfoLog = new char[maxLength];
+        glGetProgramInfoLog( programNumber, maxLength, &maxLength, linkInfoLog );
+        std::cerr << "Shader linking error:" << std::endl;
+        std::cerr << linkInfoLog;
+        delete[] linkInfoLog;
     }
+#endif /* __WXDEBUG__ */
 
-    isShaderLinked = true;
+    return isShaderLinked;
 }
 
 
@@ -215,3 +222,9 @@ void SHADER::SetParameter( int parameterNumber, float value )
 {
     glUniform1f( parameterLocation[parameterNumber], value );
 }
+
+
+int SHADER::GetAttribute( std::string aAttributeName )
+{
+    return glGetAttribLocation( programNumber, aAttributeName.c_str() );
+}
diff --git a/include/gal/opengl/shader.h b/include/gal/opengl/shader.h
index 97852c27d4..71fa03109f 100644
--- a/include/gal/opengl/shader.h
+++ b/include/gal/opengl/shader.h
@@ -80,8 +80,9 @@ public:
 
     /**
      * Link the shaders.
+     * @return true in case of success, false otherwise.
      */
-    void Link();
+    bool Link();
 
     /**
      * Use the shader.
@@ -122,6 +123,14 @@ public:
      */
     void SetParameter( int aParameterNumber, float aValue );
 
+    /**
+     * @brief Gets an attribute location.
+     *
+     * @param aAttributeName is the name of the attribute.
+     * @return the location.
+     */
+    int GetAttribute( std::string aAttributeName );
+
 private:
 
     /**