/**
* \brief Enables a given shader.
* \param p The shader to enable.
*/
void bear::visual::gl_screen::use_program( const shader_program& p ) const
{
const gl_shader_program* const s
( static_cast<const gl_shader_program*>(p.get_impl()) );
glUseProgram( s->program_id() );
VISUAL_GL_ERROR_THROW();
shader_program::variable_visitor_type visitor;
shader_program::input_variable_map vars( p.get_variables() );
visitor.run( vars, uniform_setter( s->program_id() ) );
} // gl_screen::use_program()
void bear::visual::detail::apply_shader( const shader_program& shader )
{
assert ( shader.is_valid() );
const gl_shader_program* const s
( static_cast<const gl_shader_program*>( shader.get_impl() ) );
assert( s->program_id() != 0 );
glUseProgram( s->program_id() );
VISUAL_GL_ERROR_THROW();
shader_program::variable_visitor_type visitor;
shader_program::input_variable_map vars( shader.get_variables() );
visitor.run( vars, uniform_setter( s->program_id() ) );
}