Read a matrix uniform back from shader.

Might require additions to kwinglutils_func in desktop profile

lib/kwinglutils.cpp

@@ -1096,6 +1096,23 @@ void GLShader::bindAttributeLocation(int index, const char* name)
     // TODO: relink the shader
     }
 
+QMatrix4x4 GLShader::getUniformMatrix4x4(const char* name)
+{
+    int location = uniformLocation(name);
+    if (location >= 0) {
+        GLfloat m[16];
+        glGetUniformfv(mProgram, location, m);
+        QMatrix4x4 matrix(m[0], m[1],  m[2], m[3],
+                          m[4], m[5],  m[6], m[7],
+                          m[8], m[9], m[10], m[11],
+                          m[12], m[13], m[14], m[15]);
+        matrix.optimize();
+        return matrix;
+    } else {
+        return QMatrix4x4();
+    }
+}
+
 //****************************************
 // ShaderManager
 //****************************************

lib/kwinglutils.h

@@ -269,6 +269,11 @@ class KWIN_EXPORT GLShader
          * @since 4.7
          */
         void bindAttributeLocation(int index, const char* name);
+        /**
+         * @return The value of the uniform as a matrix
+         * @since 4.7
+         **/
+        QMatrix4x4 getUniformMatrix4x4(const char* name);
 
         void setTextureWidth( float width );
         void setTextureHeight( float height );