indexing
	description: " A fragment shader that can be passed to EM_SHADER_PROGRAM "
	date: "$Date$"
	revision: "$Revision$"

class
	GL_FRAGMENT_SHADER

inherit

	MEMORY
		export {NONE} all
		redefine dispose end
	
	EM_CONSTANTS
		export {NONE} all end
	
	GL_FUNCTIONS
		export {NONE} all end
	
	GLEXT_FUNCTIONS
		export {NONE} all end
	
create
	make_from_file,
	make_and_compile_from_file,
	make_from_source
	
feature {NONE} -- Initialization
	get_file_string( a_filename: STRING ):STRING is
			-- get the text strig out of a file
		local
			text_file: PLAIN_TEXT_FILE
		do
			create text_file.make( a_filename )
			text_file.open_read				
			text_file.read_stream ( text_file.count )
			result := text_file.last_string
		end
		

	make_from_file( a_filename: STRING ) is
			-- make a new fragment shader from a file
		require
			shader_is_supported: is_extension_supported ( "GL_ARB_fragment_shader" )
		do
			make_from_source( get_file_string( a_filename ) )
		ensure
			id >= 0
		end
	
	make_and_compile_from_file( a_filename: STRING ) is
			-- make a new fragment shader from a file
		require
			shader_is_supported: is_extension_supported ( "GL_ARB_fragment_shader" )
		do
			make_from_source( get_file_string( a_filename ) )
			compile
		ensure
			id >= 0
		end
	
	make_from_source( a_source: STRING ) is
			-- make a new fragment shader from a given source string
		require
			shader_is_supported: is_extension_supported ( "GL_ARB_fragment_shader" )
		local
			source: ARRAY[ POINTER ]
			tmp: ANY
		do
			create source.make(0,0)
			tmp := a_source.to_c
			source.put( $tmp, 0 )


			id := gl_create_shader_object_arb ( em_gl_fragment_shader_arb )

			tmp := source.to_c
			gl_shader_source_arb ( id, 1, $tmp, default_pointer)
		ensure
			id >= 0
		end
		
feature -- Access

	id: INTEGER
	
feature -- Commands
	compile is
			-- compile the shader
		require
			id >= 0
		local
			compiled: INTEGER
		do
			gl_compile_shader_arb( id )
			gl_get_object_parameteriv_arb (id, em_gl_object_compile_status_arb, $compiled)
			is_compiled := compiled/=0
			if not is_compiled then
				print(log)
			end
		ensure
			shader_compiled: is_compiled
		end
		
feature{NONE} -- Clean up
	dispose is
			-- clean up the opengl memory
		do
			gl_delete_object_arb (id)
			Precursor
		end

feature -- Status
	is_compiled: BOOLEAN
	
	log:STRING is
			-- Return the error log
		local
			tmp_str: STRING
			tmp: ANY
			length: INTEGER
		do
			gl_get_object_parameteriv_arb ( id, em_gl_info_log_length, $length)
			create tmp_str.make ( length )
			tmp := tmp_str.to_c
			gl_get_info_log_arb_external ( id, length, $length , $tmp )
			create result.make_from_c ( $tmp )
		end
		
end