indexing
	description:
		"Constants for use by and with EV_DRAWABLE."
	note:
		"With every drawing mode constant, a truth table is given.%N%
		%S means the source. This is the color of the pixel that is about%N%
		%to be applied. T means target. This is the color of the pixel that%N%
		%is currently on the place where the new pixel is about to be set."
	status: "See notice at end of class"
	keywords: "figures, primitives, drawing, line, point, ellipse" 
	date: "$Date$"
	revision: "$Revision$"

class
	EV_DRAWABLE_CONSTANTS

feature -- Constants

	Drawing_mode_copy: INTEGER is 0
			-- Normal drawing mode.
			--
			-- T\S | 0 | 1 |
			-- -------------
			--   0 | 0 | 1 |
			-- -------------
			--   1 | 0 | 1 |

	Drawing_mode_xor: INTEGER is 1
			-- Drawing mode where bitwise XOR is performed when a
			-- pixel is drawn.
			--
			-- T\S | 0 | 1 |
			-- -------------
			--   0 | 0 | 1 |
			-- -------------
			--   1 | 1 | 0 |

	Drawing_mode_invert: INTEGER is 2
			-- Drawing mode where bits are inverted before drawn.
			--
			-- T\S | 0 | 1 |
			-- -------------
			--   0 | 1 | 0 |
			-- -------------
			--   1 | 1 | 0 |

	Drawing_mode_and: INTEGER is 3
			-- Drawing mode where bitwise AND is performed when a
			-- pixel is drawn.
			--
			-- T\S | 0 | 1 |
			-- -------------
			--   0 | 0 | 0 |
			-- -------------
			--   1 | 0 | 1 |

	Drawing_mode_or: INTEGER is 4
			-- Drawing mode where bitwise OR is performed when a
			-- pixel is drawn.
			--
			-- T\S | 0 | 1 |
			-- -------------
			--   0 | 0 | 1 |
			-- -------------
			--   1 | 1 | 1 |

feature -- Contract support

	valid_drawing_mode (a_mode: INTEGER): BOOLEAN is
			-- Is `a_mode' a valid drawing mode?
		do
			Result := a_mode = Drawing_mode_copy or else
				a_mode = Drawing_mode_xor or else
				a_mode = Drawing_mode_invert or else
				a_mode = Drawing_mode_and or else
				a_mode = Drawing_mode_or
		end

end -- class EV_DRAWABLE_CONSTANTS

--|----------------------------------------------------------------
--| EiffelVision2: library of reusable components for ISE Eiffel.
--| Copyright (C) 1986-2001 Interactive Software Engineering Inc.
--| All rights reserved. Duplication and distribution prohibited.
--| May be used only with ISE Eiffel, under terms of user license. 
--| Contact ISE for any other use.
--|
--| Interactive Software Engineering Inc.
--| ISE Building
--| 360 Storke Road, Goleta, CA 93117 USA
--| Telephone 805-685-1006, Fax 805-685-6869
--| Electronic mail <info@eiffel.com>
--| Customer support: http://support.eiffel.com>
--| For latest info see award-winning pages: http://www.eiffel.com
--|----------------------------------------------------------------