indexing
	description: "[
	
		3D counterpart to EM_FONT that can be used to render strings
		when working with Em3d.

	]"
	author: ""
	date: "$Date$"
	revision: "$Revision$"

deferred class
	EM3D_FONT

feature -- Basic operations

	cache_string (a_string: STRING) is
			-- Chache implementation specific data needed to render `a_string
			-- Use this before compiling OpenGL display lists.
		deferred
		end

	render_string (a_string: STRING; a_pos: EM_VECTOR3D; a_point_size: DOUBLE; a_color: EM_COLOR) is
			-- Render `a_string' at `a_pos', using current font with `a_point_size' and `a_color'
			-- subject to all OpenGL transformations.
			-- `a_pos' is start of the baseline.
			-- This implies that the OpenGL modelview and projection matrices
			-- are set to an appropriate transformation.
			-- Something like gluOrtho (0, w, h, 0) should give the expected
			-- results with regard to the 2D equivalent of this function:
			-- {EM_TTF_FONT}.draw_string
			-- The modelview transformation can also easily be set using
			-- {EM_COORDINATE_FRAME}.set_opengl
		deferred
		end

	render_string_point_snapped (a_string: STRING; a_pos: EM_VECTOR3D; a_point_size: DOUBLE; a_color: EM_COLOR) is
			-- Same as `render_string', but tries to render `a_string' at integral coordinates to
			-- achieve greater visual quality.
		deferred
		end

feature -- Measurements

	optimal_point_size: DOUBLE is
			-- Rendering strings using optimal_point_size and orthographic
			-- projection representing viewport dimensions should give the
			-- nicest results.
		deferred
		end

	line_skip (a_point_size: DOUBLE): DOUBLE is
			-- Line spacing for given `point_size'
		deferred
		end

	ascent (a_point_size: DOUBLE): DOUBLE is
			--Max ascent for given `point_size'
		deferred
		end

	descent (a_point_size: DOUBLE): DOUBLE is
			-- Max descent for given `point_size'
		deferred
		end

	baseline_offset (a_point_size: DOUBLE): DOUBLE is
			-- Offset of baseline from top boundary
		deferred
		end

	char_width (a_chr: CHARACTER; a_point_size: DOUBLE): DOUBLE is
			-- Width of `a_chr' in points
		deferred
		end

	string_width (a_string: STRING; a_point_size: DOUBLE): DOUBLE is
			-- Width of `string' in points
		deferred
		end

	string_height (a_string: STRING; a_point_size: DOUBLE): DOUBLE is
			-- Height of `string' in points
		deferred
		end

end