Lua Cairo

-- taken from http://luaforge.net/projects/luacairo/

local cairo = require"lcairo"
local CAIRO = cairo

local w = 320
local h = 240
local outfile = "cairo_test2.png"

local cs = cairo.image_surface_create (CAIRO.FORMAT_RGB24, w, h)
local cr = cairo.create (cs)

cairo.set_source_rgb (cr, 1, 1, 1)
cairo.paint (cr)

cairo.set_source_rgb (cr, 0, 0, 0)
cairo.select_font_face (cr, "Sans", CAIRO.FONT_SLANT_NORMAL, CAIRO.FONT_WEIGHT_BOLD)
cairo.set_font_size (cr, w/6)
cairo.move_to (cr, 0, h/4)
cairo.show_text (cr, "Hello cairo!")

cairo.select_font_face (cr, "Sans", CAIRO.FONT_SLANT_NORMAL, CAIRO.FONT_WEIGHT_NORMAL)
cairo.set_font_size (cr, w/8)
cairo.move_to (cr, 0, 3*h/4)
cairo.text_path (cr, "Lua calling...")
cairo.set_source_rgb (cr, 0.5, 0.5, 1)
cairo.fill_preserve (cr)
cairo.set_source_rgb (cr, 0, 0, 0)
cairo.set_line_width (cr, w/200)
cairo.stroke (cr)

cairo.surface_write_to_png (cs, outfile)

-- Adapted from Sample

local cairo = require"lcairo"
local CAIRO = cairo

local w = 320
local h = 240
local outfile = "cairo_test2.png"

local cs = cairo.ImageSurface (CAIRO.FORMAT_RGB24, w, h)
local cr = cairo.Context (cs)

cr:set_source_rgb (1, 1, 1)
cr:paint ()

cr:set_source_rgb (0, 0, 0)
cr:select_font_face ("Sans", CAIRO.FONT_SLANT_NORMAL, CAIRO.FONT_WEIGHT_BOLD)
cr:set_font_size (w/6)
cr:move_to (0, h/4)
cr:show_text ("Hello cairo!")

cr:select_font_face ("Sans", CAIRO.FONT_SLANT_NORMAL, CAIRO.FONT_WEIGHT_NORMAL)
cr:set_font_size (w/8)
cr:move_to (0, 3*h/4)
cr:text_path ("Lua calling...")
cr:set_source_rgb (0.5, 0.5, 1)
cr:fill_preserve ()
cr:set_source_rgb (0, 0, 0)
cr:set_line_width (w/200)
cr:stroke ()

cs:write_to_png (outfile)

 *
 * #cairo_bool_t is used for boolean values. Returns of type
 * #cairo_bool_t will always be either 0 or 1, but testing against
 * these values explicitly is not encouraged; just use the
 * value as a boolean condition.
 *
 * 
 *  if (cairo_in_stroke (cr, x, y)) {
 *      /* do something */
 *  }
 * 

 *
 * A #cairo_t contains the current state of the rendering device,
 * including coordinates of yet to be drawn shapes.
 *
 * Cairo contexts, as #cairo_t objects are named, are central to
 * cairo and all drawing with cairo is always done to a #cairo_t
 * object.
 *
 * Memory management of #cairo_t is done with
 * cairo_reference() and cairo_destroy().

 *
 * A #cairo_surface_t represents an image, either as the destination
 * of a drawing operation or as source when drawing onto another
 * surface.  To draw to a #cairo_surface_t, create a cairo context
 * with the surface as the target, using cairo_create().
 *
 * There are different subtypes of #cairo_surface_t for
 * different drawing backends; for example, cairo_image_surface_create()
 * creates a bitmap image in memory.
 * The type of a surface can be queried with cairo_surface_get_type().
 *
 * Memory management of #cairo_surface_t is done with
 * cairo_surface_reference() and cairo_surface_destroy().

 * 
 * A #cairo_device_t represents the driver interface for drawing
 * operations to a #cairo_surface_t.  There are different subtypes of
 * #cairo_device_t for different drawing backends; for example,
 * cairo_xcb_device_create() creates a device that wraps the connection
 * to an X Windows System using the XCB library.
 *
 * The type of a device can be queried with cairo_device_get_type().
 *
 * Memory management of #cairo_device_t is done with
 * cairo_device_reference() and cairo_device_destroy().
 *
 * Since: 1.10

 [Lua] Implemented as user data
       local matrix = cairo.Matrix()
       local matrix = cairo.Matrix{xx=num, yx=num, xy=num, yy=num, x0=num, y0=num}

 *
 * @xx: xx component of the affine transformation
 * @yx: yx component of the affine transformation
 * @xy: xy component of the affine transformation
 * @yy: yy component of the affine transformation
 * @x0: X translation component of the affine transformation
 * @y0: Y translation component of the affine transformation
 *
 * A #cairo_matrix_t holds an affine transformation, such as a scale,
 * rotation, shear, or a combination of those. The transformation of
 * a point (x, y) is given by:
 * 
 *     x_new = xx * x + xy * y + x0;
 *     y_new = yx * x + yy * y + y0;
 * 

 *
 * A #cairo_pattern_t represents a source when drawing onto a
 * surface. There are different subtypes of #cairo_pattern_t,
 * for different types of sources; for example,
 * cairo_pattern_create_rgb() creates a pattern for a solid
 * opaque color.
 *
 * Other than various cairo_pattern_create_type
 * functions, some of the pattern types can be implicitly created
 * using vairous cairo_set_source_type functions;
 * for example cairo_set_source_rgb().
 *
 * The type of a pattern can be queried with cairo_pattern_get_type().
 *
 * Memory management of #cairo_pattern_t is done with
 * cairo_pattern_reference() and cairo_pattern_destroy().

 * 
 * @data: The data element being destroyed.
 *
 * #cairo_destroy_func_t the type of function which is called when a
 * data element is destroyed. It is passed the pointer to the data
 * element and should free any memory and resources allocated for it.

 * 
 * @unused: not used; ignore.
 *
 * #cairo_user_data_key_t is used for attaching user data to cairo
 * data structures.  The actual contents of the struct is never used,
 * and there is no need to initialize the object; only the unique
 * address of a #cairo_data_key_t object is used.  Typically, you
 * would just use the address of a static #cairo_data_key_t object.

 * 
 * @CAIRO_STATUS_SUCCESS: no error has occurred
 * @CAIRO_STATUS_NO_MEMORY: out of memory
 * @CAIRO_STATUS_INVALID_RESTORE: cairo_restore() called without matching cairo_save()
 * @CAIRO_STATUS_INVALID_POP_GROUP: no saved group to pop, i.e. cairo_pop_group() without matching cairo_push_group()
 * @CAIRO_STATUS_NO_CURRENT_POINT: no current point defined
 * @CAIRO_STATUS_INVALID_MATRIX: invalid matrix (not invertible)
 * @CAIRO_STATUS_INVALID_STATUS: invalid value for an input #cairo_status_t
 * @CAIRO_STATUS_NULL_POINTER: %NULL pointer
 * @CAIRO_STATUS_INVALID_STRING: input string not valid UTF-8
 * @CAIRO_STATUS_INVALID_PATH_DATA: input path data not valid
 * @CAIRO_STATUS_READ_ERROR: error while reading from input stream
 * @CAIRO_STATUS_WRITE_ERROR: error while writing to output stream
 * @CAIRO_STATUS_SURFACE_FINISHED: target surface has been finished
 * @CAIRO_STATUS_SURFACE_TYPE_MISMATCH: the surface type is not appropriate for the operation
 * @CAIRO_STATUS_PATTERN_TYPE_MISMATCH: the pattern type is not appropriate for the operation
 * @CAIRO_STATUS_INVALID_CONTENT: invalid value for an input #cairo_content_t
 * @CAIRO_STATUS_INVALID_FORMAT: invalid value for an input #cairo_format_t
 * @CAIRO_STATUS_INVALID_VISUAL: invalid value for an input Visual*
 * @CAIRO_STATUS_FILE_NOT_FOUND: file not found
 * @CAIRO_STATUS_INVALID_DASH: invalid value for a dash setting
 * @CAIRO_STATUS_INVALID_DSC_COMMENT: invalid value for a DSC comment (Since 1.2)
 * @CAIRO_STATUS_INVALID_INDEX: invalid index passed to getter (Since 1.4)
 * @CAIRO_STATUS_CLIP_NOT_REPRESENTABLE: clip region not representable in desired format (Since 1.4)
 * @CAIRO_STATUS_TEMP_FILE_ERROR: error creating or writing to a temporary file (Since 1.6)
 * @CAIRO_STATUS_INVALID_STRIDE: invalid value for stride (Since 1.6)
 * @CAIRO_STATUS_FONT_TYPE_MISMATCH: the font type is not appropriate for the operation (Since 1.8)
 * @CAIRO_STATUS_USER_FONT_IMMUTABLE: the user-font is immutable (Since 1.8)
 * @CAIRO_STATUS_USER_FONT_ERROR: error occurred in a user-font callback function (Since 1.8)
 * @CAIRO_STATUS_NEGATIVE_COUNT: negative number used where it is not allowed (Since 1.8)
 * @CAIRO_STATUS_INVALID_CLUSTERS: input clusters do not represent the accompanying text and glyph array (Since 1.8)
 * @CAIRO_STATUS_INVALID_SLANT: invalid value for an input #cairo_font_slant_t (Since 1.8)
 * @CAIRO_STATUS_INVALID_WEIGHT: invalid value for an input #cairo_font_weight_t (Since 1.8)
 * @CAIRO_STATUS_INVALID_SIZE: invalid value (typically too big) for the size of the input (surface, pattern, etc.) (Since 1.10)
 * @CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED: user-font method not implemented (Since 1.10)
 * @CAIRO_STATUS_DEVICE_TYPE_MISMATCH: the device type is not appropriate for the operation (Since 1.10)
 * @CAIRO_STATUS_DEVICE_ERROR: an operation to the device caused an unspecified error (Since 1.10)
 * @CAIRO_STATUS_LAST_STATUS: this is a special value indicating the number of
 *   status values defined in this enumeration.  When using this value, note
 *   that the version of cairo at run-time may have additional status values
 *   defined than the value of this symbol at compile-time. (Since 1.10)
 *
 * #cairo_status_t is used to indicate errors that can occur when
 * using Cairo. In some cases it is returned directly by functions.
 * but when using #cairo_t, the last error, if any, is stored in
 * the context and can be retrieved with cairo_status().
 *
 * New entries may be added in future versions.  Use cairo_status_to_string()
 * to get a human-readable representation of an error message.

 * 
 * @CAIRO_CONTENT_COLOR: The surface will hold color content only.
 * @CAIRO_CONTENT_ALPHA: The surface will hold alpha content only.
 * @CAIRO_CONTENT_COLOR_ALPHA: The surface will hold color and alpha content.
 *
 * #cairo_content_t is used to describe the content that a surface will
 * contain, whether color information, alpha information (translucence
 * vs. opacity), or both.
 *
 * Note: The large values here are designed to keep #cairo_content_t
 * values distinct from #cairo_format_t values so that the
 * implementation can detect the error if users confuse the two types.

 * 
 * @closure: the output closure
 * @data: the buffer containing the data to write
 * @length: the amount of data to write
 *
 * #cairo_write_func_t is the type of function which is called when a
 * backend needs to write data to an output stream.  It is passed the
 * closure which was specified by the user at the time the write
 * function was registered, the data to write and the length of the
 * data in bytes.  The write function should return
 * %CAIRO_STATUS_SUCCESS if all the data was successfully written,
 * %CAIRO_STATUS_WRITE_ERROR otherwise.
 *
 * Returns: the status code of the write operation

 * 
 * @closure: the input closure
 * @data: the buffer into which to read the data
 * @length: the amount of data to read
 *
 * #cairo_read_func_t is the type of function which is called when a
 * backend needs to read data from an input stream.  It is passed the
 * closure which was specified by the user at the time the read
 * function was registered, the buffer to read the data into and the
 * length of the data in bytes.  The read function should return
 * %CAIRO_STATUS_SUCCESS if all the data was successfully read,
 * %CAIRO_STATUS_READ_ERROR otherwise.
 *
 * Returns: the status code of the read operation

 * 
 * @CAIRO_OPERATOR_CLEAR: clear destination layer (bounded)
 * @CAIRO_OPERATOR_SOURCE: replace destination layer (bounded)
 * @CAIRO_OPERATOR_OVER: draw source layer on top of destination layer
 * (bounded)
 * @CAIRO_OPERATOR_IN: draw source where there was destination content
 * (unbounded)
 * @CAIRO_OPERATOR_OUT: draw source where there was no destination
 * content (unbounded)
 * @CAIRO_OPERATOR_ATOP: draw source on top of destination content and
 * only there
 * @CAIRO_OPERATOR_DEST: ignore the source
 * @CAIRO_OPERATOR_DEST_OVER: draw destination on top of source
 * @CAIRO_OPERATOR_DEST_IN: leave destination only where there was
 * source content (unbounded)
 * @CAIRO_OPERATOR_DEST_OUT: leave destination only where there was no
 * source content
 * @CAIRO_OPERATOR_DEST_ATOP: leave destination on top of source content
 * and only there (unbounded)
 * @CAIRO_OPERATOR_XOR: source and destination are shown where there is only
 * one of them
 * @CAIRO_OPERATOR_ADD: source and destination layers are accumulated
 * @CAIRO_OPERATOR_SATURATE: like over, but assuming source and dest are
 * disjoint geometries
 * @CAIRO_OPERATOR_MULTIPLY: source and destination layers are multiplied.
 * This causes the result to be at least as dark as the darker inputs.
 * @CAIRO_OPERATOR_SCREEN: source and destination are complemented and
 * multiplied. This causes the result to be at least as light as the lighter
 * inputs.
 * @CAIRO_OPERATOR_OVERLAY: multiplies or screens, depending on the
 * lightness of the destination color.
 * @CAIRO_OPERATOR_DARKEN: replaces the destination with the source if it
 * is darker, otherwise keeps the source.
 * @CAIRO_OPERATOR_LIGHTEN: replaces the destination with the source if it
 * is lighter, otherwise keeps the source.
 * @CAIRO_OPERATOR_COLOR_DODGE: brightens the destination color to reflect
 * the source color.
 * @CAIRO_OPERATOR_COLOR_BURN: darkens the destination color to reflect
 * the source color.
 * @CAIRO_OPERATOR_HARD_LIGHT: Multiplies or screens, dependant on source
 * color.
 * @CAIRO_OPERATOR_SOFT_LIGHT: Darkens or lightens, dependant on source
 * color.
 * @CAIRO_OPERATOR_DIFFERENCE: Takes the difference of the source and
 * destination color.
 * @CAIRO_OPERATOR_EXCLUSION: Produces an effect similar to difference, but
 * with lower contrast.
 * @CAIRO_OPERATOR_HSL_HUE: Creates a color with the hue of the source
 * and the saturation and luminosity of the target.
 * @CAIRO_OPERATOR_HSL_SATURATION: Creates a color with the saturation
 * of the source and the hue and luminosity of the target. Painting with
 * this mode onto a gray area prduces no change.
 * @CAIRO_OPERATOR_HSL_COLOR: Creates a color with the hue and saturation
 * of the source and the luminosity of the target. This preserves the gray
 * levels of the target and is useful for coloring monochrome images or
 * tinting color images.
 * @CAIRO_OPERATOR_HSL_LUMINOSITY: Creates a color with the luminosity of
 * the source and the hue and saturation of the target. This produces an
 * inverse effect to @CAIRO_OPERATOR_HSL_COLOR.
 *
 * #cairo_operator_t is used to set the compositing operator for all cairo
 * drawing operations.
 *
 * The default operator is %CAIRO_OPERATOR_OVER.
 *
 * The operators marked as unbounded modify their
 * destination even outside of the mask layer (that is, their effect is not
 * bound by the mask layer).  However, their effect can still be limited by
 * way of clipping.
 *
 * To keep things simple, the operator descriptions here
 * document the behavior for when both source and destination are either fully
 * transparent or fully opaque.  The actual implementation works for
 * translucent layers too.
 * For a more detailed explanation of the effects of each operator, including
 * the mathematical definitions, see
 * http://cairographics.org/operators/.

 * 
 * @CAIRO_ANTIALIAS_DEFAULT: Use the default antialiasing for
 *   the subsystem and target device
 * @CAIRO_ANTIALIAS_NONE: Use a bilevel alpha mask
 * @CAIRO_ANTIALIAS_GRAY: Perform single-color antialiasing (using
 *  shades of gray for black text on a white background, for example).
 * @CAIRO_ANTIALIAS_SUBPIXEL: Perform antialiasing by taking
 *  advantage of the order of subpixel elements on devices
 *  such as LCD panels
 *
 * Specifies the type of antialiasing to do when rendering text or shapes.

 * 
 * @CAIRO_FILL_RULE_WINDING: If the path crosses the ray from
 * left-to-right, counts +1. If the path crosses the ray
 * from right to left, counts -1. (Left and right are determined
 * from the perspective of looking along the ray from the starting
 * point.) If the total count is non-zero, the point will be filled.
 * @CAIRO_FILL_RULE_EVEN_ODD: Counts the total number of
 * intersections, without regard to the orientation of the contour. If
 * the total number of intersections is odd, the point will be
 * filled.
 *
 * #cairo_fill_rule_t is used to select how paths are filled. For both
 * fill rules, whether or not a point is included in the fill is
 * determined by taking a ray from that point to infinity and looking
 * at intersections with the path. The ray can be in any direction,
 * as long as it doesn't pass through the end point of a segment
 * or have a tricky intersection such as intersecting tangent to the path.
 * (Note that filling is not actually implemented in this way. This
 * is just a description of the rule that is applied.)
 *
 * The default fill rule is %CAIRO_FILL_RULE_WINDING.
 *
 * New entries may be added in future versions.

 * 
 * @CAIRO_LINE_CAP_BUTT: start(stop) the line exactly at the start(end) point
 * @CAIRO_LINE_CAP_ROUND: use a round ending, the center of the circle is the end point
 * @CAIRO_LINE_CAP_SQUARE: use squared ending, the center of the square is the end point
 *
 * Specifies how to render the endpoints of the path when stroking.
 *
 * The default line cap style is %CAIRO_LINE_CAP_BUTT.

 * 
 * @CAIRO_LINE_JOIN_MITER: use a sharp (angled) corner, see
 * cairo_set_miter_limit()
 * @CAIRO_LINE_JOIN_ROUND: use a rounded join, the center of the circle is the
 * joint point
 * @CAIRO_LINE_JOIN_BEVEL: use a cut-off join, the join is cut off at half
 * the line width from the joint point
 *
 * Specifies how to render the junction of two lines when stroking.
 *
 * The default line join style is %CAIRO_LINE_JOIN_MITER.

 * 
 * @x: X coordinate of the left side of the rectangle
 * @y: Y coordinate of the the top side of the rectangle
 * @width: width of the rectangle
 * @height: height of the rectangle
 *
 * A data structure for holding a rectangle.
 *
 * Since: 1.4

 * 
 * @status: Error status of the rectangle list
 * @rectangles: Array containing the rectangles
 * @num_rectangles: Number of rectangles in this list
 * 
 * A data structure for holding a dynamically allocated
 * array of rectangles.
 *
 * Since: 1.4

 *
 * A #cairo_scaled_font_t is a font scaled to a particular size and device
 * resolution. A #cairo_scaled_font_t is most useful for low-level font
 * usage where a library or application wants to cache a reference
 * to a scaled font to speed up the computation of metrics.
 *
 * There are various types of scaled fonts, depending on the
 * font backend they use. The type of a
 * scaled font can be queried using cairo_scaled_font_get_type().
 *
 * Memory management of #cairo_scaled_font_t is done with
 * cairo_scaled_font_reference() and cairo_scaled_font_destroy().

 *
 * A #cairo_font_face_t specifies all aspects of a font other
 * than the size or font matrix (a font matrix is used to distort
 * a font by sheering it or scaling it unequally in the two
 * directions) . A font face can be set on a #cairo_t by using
 * cairo_set_font_face(); the size and font matrix are set with
 * cairo_set_font_size() and cairo_set_font_matrix().
 *
 * There are various types of font faces, depending on the
 * font backend they use. The type of a
 * font face can be queried using cairo_font_face_get_type().
 *
 * Memory management of #cairo_font_face_t is done with
 * cairo_font_face_reference() and cairo_font_face_destroy().

 * 
 * @index: glyph index in the font. The exact interpretation of the
 *      glyph index depends on the font technology being used.
 * @x: the offset in the X direction between the origin used for
 *     drawing or measuring the string and the origin of this glyph.
 * @y: the offset in the Y direction between the origin used for
 *     drawing or measuring the string and the origin of this glyph.
 *
 * The #cairo_glyph_t structure holds information about a single glyph
 * when drawing or measuring text. A font is (in simple terms) a
 * collection of shapes used to draw text. A glyph is one of these
 * shapes. There can be multiple glyphs for a single character
 * (alternates to be used in different contexts, for example), or a
 * glyph can be a ligature of multiple
 * characters. Cairo doesn't expose any way of converting input text
 * into glyphs, so in order to use the Cairo interfaces that take
 * arrays of glyphs, you must directly access the appropriate
 * underlying font system.
 *
 * Note that the offsets given by @x and @y are not cumulative. When
 * drawing or measuring text, each glyph is individually positioned
 * with respect to the overall origin

 [Lua] Implemented as user data
       local te = cairo.TextExtents()
       local te = cairo.TextExtents{x_bearing=num, y_bearing=num, width=num, height=num, x_advance=num, y_advance=num}

 *
 * @x_bearing: the horizontal distance from the origin to the
 *   leftmost part of the glyphs as drawn. Positive if the
 *   glyphs lie entirely to the right of the origin.
 * @y_bearing: the vertical distance from the origin to the
 *   topmost part of the glyphs as drawn. Positive only if the
 *   glyphs lie completely below the origin; will usually be
 *   negative.
 * @width: width of the glyphs as drawn
 * @height: height of the glyphs as drawn
 * @x_advance:distance to advance in the X direction
 *    after drawing these glyphs
 * @y_advance: distance to advance in the Y direction
 *   after drawing these glyphs. Will typically be zero except
 *   for vertical text layout as found in East-Asian languages.
 *
 * The #cairo_text_extents_t structure stores the extents of a single
 * glyph or a string of glyphs in user-space coordinates. Because text
 * extents are in user-space coordinates, they are mostly, but not
 * entirely, independent of the current transformation matrix. If you call
 * cairo_scale(cr, 2.0, 2.0), text will
 * be drawn twice as big, but the reported text extents will not be
 * doubled. They will change slightly due to hinting (so you can't
 * assume that metrics are independent of the transformation matrix),
 * but otherwise will remain unchanged.

 [Lua] Implemented as user data
       local fe = cairo.FontExtents()
       local fe = cairo.FontExtents{ascent=num, descent=num, height=num, max_x_advance=num, max_y_advance=num}

 *
 * @ascent: the distance that the font extends above the baseline.
 *          Note that this is not always exactly equal to the maximum
 *          of the extents of all the glyphs in the font, but rather
 *          is picked to express the font designer's intent as to
 *          how the font should align with elements above it.
 * @descent: the distance that the font extends below the baseline.
 *           This value is positive for typical fonts that include
 *           portions below the baseline. Note that this is not always
 *           exactly equal to the maximum of the extents of all the
 *           glyphs in the font, but rather is picked to express the
 *           font designer's intent as to how the the font should
 *           align with elements below it.
 * @height: the recommended vertical distance between baselines when
 *          setting consecutive lines of text with the font. This
 *          is greater than @ascent+@descent by a
 *          quantity known as the line spacing
 *          or external leading. When space
 *          is at a premium, most fonts can be set with only
 *          a distance of @ascent+@descent between lines.
 * @max_x_advance: the maximum distance in the X direction that
 *         the the origin is advanced for any glyph in the font.
 * @max_y_advance: the maximum distance in the Y direction that
 *         the the origin is advanced for any glyph in the font.
 *         this will be zero for normal fonts used for horizontal
 *         writing. (The scripts of East Asia are sometimes written
 *         vertically.)
 *
 * The #cairo_font_extents_t structure stores metric information for
 * a font. Values are given in the current user-space coordinate
 * system.
 *
 * Because font metrics are in user-space coordinates, they are
 * mostly, but not entirely, independent of the current transformation
 * matrix. If you call cairo_scale(cr, 2.0, 2.0),
 * text will be drawn twice as big, but the reported text extents will
 * not be doubled. They will change slightly due to hinting (so you
 * can't assume that metrics are independent of the transformation
 * matrix), but otherwise will remain unchanged.

 * 
 * @CAIRO_FONT_SLANT_NORMAL: Upright font style
 * @CAIRO_FONT_SLANT_ITALIC: Italic font style
 * @CAIRO_FONT_SLANT_OBLIQUE: Oblique font style
 *
 * Specifies variants of a font face based on their slant.

 * 
 * @CAIRO_FONT_WEIGHT_NORMAL: Normal font weight
 * @CAIRO_FONT_WEIGHT_BOLD: Bold font weight
 *
 * Specifies variants of a font face based on their weight.

 * 
 * @CAIRO_SUBPIXEL_ORDER_DEFAULT: Use the default subpixel order for
 *   for the target device
 * @CAIRO_SUBPIXEL_ORDER_RGB: Subpixel elements are arranged horizontally
 *   with red at the left
 * @CAIRO_SUBPIXEL_ORDER_BGR:  Subpixel elements are arranged horizontally
 *   with blue at the left
 * @CAIRO_SUBPIXEL_ORDER_VRGB: Subpixel elements are arranged vertically
 *   with red at the top
 * @CAIRO_SUBPIXEL_ORDER_VBGR: Subpixel elements are arranged vertically
 *   with blue at the top
 *
 * The subpixel order specifies the order of color elements within
 * each pixel on the display device when rendering with an
 * antialiasing mode of %CAIRO_ANTIALIAS_SUBPIXEL.

 * 
 * @CAIRO_HINT_STYLE_DEFAULT: Use the default hint style for
 *   font backend and target device
 * @CAIRO_HINT_STYLE_NONE: Do not hint outlines
 * @CAIRO_HINT_STYLE_SLIGHT: Hint outlines slightly to improve
 *   contrast while retaining good fidelity to the original
 *   shapes.
 * @CAIRO_HINT_STYLE_MEDIUM: Hint outlines with medium strength
 *   giving a compromise between fidelity to the original shapes
 *   and contrast
 * @CAIRO_HINT_STYLE_FULL: Hint outlines to maximize contrast
 *
 * Specifies the type of hinting to do on font outlines. Hinting
 * is the process of fitting outlines to the pixel grid in order
 * to improve the appearance of the result. Since hinting outlines
 * involves distorting them, it also reduces the faithfulness
 * to the original outline shapes. Not all of the outline hinting
 * styles are supported by all font backends.
 *
 * New entries may be added in future versions.

 * 
 * @CAIRO_HINT_METRICS_DEFAULT: Hint metrics in the default
 *  manner for the font backend and target device
 * @CAIRO_HINT_METRICS_OFF: Do not hint font metrics
 * @CAIRO_HINT_METRICS_ON: Hint font metrics
 *
 * Specifies whether to hint font metrics; hinting font metrics
 * means quantizing them so that they are integer values in
 * device space. Doing this improves the consistency of
 * letter and line spacing, however it also means that text
 * will be laid out differently at different zoom factors.

 *
 * An opaque structure holding all options that are used when
 * rendering fonts.
 *
 * Individual features of a #cairo_font_options_t can be set or
 * accessed using functions named
 * cairo_font_options_set_feature_name and
 * cairo_font_options_get_feature_name, like
 * cairo_font_options_set_antialias() and
 * cairo_font_options_get_antialias().
 *
 * New features may be added to a #cairo_font_options_t in the
 * future.  For this reason, cairo_font_options_copy(),
 * cairo_font_options_equal(), cairo_font_options_merge(), and
 * cairo_font_options_hash() should be used to copy, check
 * for equality, merge, or compute a hash value of
 * #cairo_font_options_t objects.

 * 
 * @CAIRO_FONT_TYPE_TOY: The font was created using cairo's toy font api
 * @CAIRO_FONT_TYPE_FT: The font is of type FreeType
 * @CAIRO_FONT_TYPE_WIN32: The font is of type Win32
 * @CAIRO_FONT_TYPE_QUARTZ: The font is of type Quartz (Since: 1.6)
 * @CAIRO_FONT_TYPE_USER: The font was create using cairo's user font api (Since: 1.8)
 *
 * #cairo_font_type_t is used to describe the type of a given font
 * face or scaled font. The font types are also known as "font
 * backends" within cairo.
 *
 * The type of a font face is determined by the function used to
 * create it, which will generally be of the form
 * cairo_type_font_face_create(). The font face type can be queried
 * with cairo_font_face_get_type()
 *
 * The various #cairo_font_face_t functions can be used with a font face
 * of any type.
 *
 * The type of a scaled font is determined by the type of the font
 * face passed to cairo_scaled_font_create(). The scaled font type can
 * be queried with cairo_scaled_font_get_type()
 *
 * The various #cairo_scaled_font_t functions can be used with scaled
 * fonts of any type, but some font backends also provide
 * type-specific functions that must only be called with a scaled font
 * of the appropriate type. These functions have names that begin with
 * cairo_type_scaled_font() such as cairo_ft_scaled_font_lock_face().
 *
 * The behavior of calling a type-specific function with a scaled font
 * of the wrong type is undefined.
 *
 * New entries may be added in future versions.
 *
 * Since: 1.2

 * 
 * @CAIRO_PATH_MOVE_TO: A move-to operation
 * @CAIRO_PATH_LINE_TO: A line-to operation
 * @CAIRO_PATH_CURVE_TO: A curve-to operation
 * @CAIRO_PATH_CLOSE_PATH: A close-path operation
 *
 * #cairo_path_data_t is used to describe the type of one portion
 * of a path when represented as a #cairo_path_t.
 * See #cairo_path_data_t for details.

 *
 * #cairo_path_data_t is used to represent the path data inside a
 * #cairo_path_t.
 *
 * The data structure is designed to try to balance the demands of
 * efficiency and ease-of-use. A path is represented as an array of
 * #cairo_path_data_t, which is a union of headers and points.
 *
 * Each portion of the path is represented by one or more elements in
 * the array, (one header followed by 0 or more points). The length
 * value of the header is the number of array elements for the current
 * portion including the header, (ie. length == 1 + # of points), and
 * where the number of points for each element type is as follows:
 *
 * 
 *     %CAIRO_PATH_MOVE_TO:     1 point
 *     %CAIRO_PATH_LINE_TO:     1 point
 *     %CAIRO_PATH_CURVE_TO:    3 points
 *     %CAIRO_PATH_CLOSE_PATH:  0 points
 * 
 *
 * The semantics and ordering of the coordinate values are consistent
 * with cairo_move_to(), cairo_line_to(), cairo_curve_to(), and
 * cairo_close_path().
 *
 * Here is sample code for iterating through a #cairo_path_t:
 *
 * 
 *      int i;
 *      cairo_path_t *path;
 *      cairo_path_data_t *data;
 *  
 *      path = cairo_copy_path (cr);
 *  
 *      for (i=0; i < path->num_data; i += path->data[i].header.length) {
 *          data = &path->data[i];
 *          switch (data->header.type) {
 *          case CAIRO_PATH_MOVE_TO:
 *              do_move_to_things (data[1].point.x, data[1].point.y);
 *              break;
 *          case CAIRO_PATH_LINE_TO:
 *              do_line_to_things (data[1].point.x, data[1].point.y);
 *              break;
 *          case CAIRO_PATH_CURVE_TO:
 *              do_curve_to_things (data[1].point.x, data[1].point.y,
 *                                  data[2].point.x, data[2].point.y,
 *                                  data[3].point.x, data[3].point.y);
 *              break;
 *          case CAIRO_PATH_CLOSE_PATH:
 *              do_close_path_things ();
 *              break;
 *          }
 *      }
 *      cairo_path_destroy (path);
 * 
 *
 * As of cairo 1.4, cairo does not mind if there are more elements in
 * a portion of the path than needed.  Such elements can be used by
 * users of the cairo API to hold extra values in the path data
 * structure.  For this reason, it is recommended that applications
 * always use data->header.length to
 * iterate over the path data, instead of hardcoding the number of
 * elements for each element type.

 * 
 * @status: the current error status
 * @data: the elements in the path
 * @num_data: the number of elements in the data array
 *
 * A data structure for holding a path. This data structure serves as
 * the return value for cairo_copy_path() and
 * cairo_copy_path_flat() as well the input value for
 * cairo_append_path().
 *
 * See #cairo_path_data_t for hints on how to iterate over the
 * actual data within the path.
 *
 * The num_data member gives the number of elements in the data
 * array. This number is larger than the number of independent path
 * portions (defined in #cairo_path_data_type_t), since the data
 * includes both headers and coordinates for each portion.

 * 
 * cairo_device_type_t:
 * @CAIRO_DEVICE_TYPE_DRM: The surface is of type Direct Render Manager
 * @CAIRO_DEVICE_TYPE_GL: The surface is of type OpenGL
 * @CAIRO_DEVICE_TYPE_SCRIPT: The surface is of type script
 * @CAIRO_DEVICE_TYPE_XCB: The surface is of type xcb
 * @CAIRO_DEVICE_TYPE_XLIB: The surface is of type xlib
 * @CAIRO_DEVICE_TYPE_XML: The surface is of type XML
 *   cairo_surface_create_for_rectangle()
 *
 * #cairo_device_type_t is used to describe the type of a given
 * device. The devices types are also known as "backends" within cairo.
 *
 * The device type can be queried with cairo_device_get_type()
 *
 * The various #cairo_device_t functions can be used with surfaces of
 * any type, but some backends also provide type-specific functions
 * that must only be called with a device of the appropriate
 * type. These functions have names that begin with
 * cairo_type_device such as cairo_xcb_device_debug_set_render_version().
 *
 * The behavior of calling a type-specific function with a surface of
 * the wrong type is undefined.
 *
 * New entries may be added in future versions.
 *
 * Since: 1.10

 * 
 * @CAIRO_SURFACE_TYPE_IMAGE: The surface is of type image
 * @CAIRO_SURFACE_TYPE_PDF: The surface is of type pdf
 * @CAIRO_SURFACE_TYPE_PS: The surface is of type ps
 * @CAIRO_SURFACE_TYPE_XLIB: The surface is of type xlib
 * @CAIRO_SURFACE_TYPE_XCB: The surface is of type xcb
 * @CAIRO_SURFACE_TYPE_GLITZ: The surface is of type glitz
 * @CAIRO_SURFACE_TYPE_QUARTZ: The surface is of type quartz
 * @CAIRO_SURFACE_TYPE_WIN32: The surface is of type win32
 * @CAIRO_SURFACE_TYPE_BEOS: The surface is of type beos
 * @CAIRO_SURFACE_TYPE_DIRECTFB: The surface is of type directfb
 * @CAIRO_SURFACE_TYPE_SVG: The surface is of type svg
 * @CAIRO_SURFACE_TYPE_OS2: The surface is of type os2
 * @CAIRO_SURFACE_TYPE_WIN32_PRINTING: The surface is a win32 printing surface
 * @CAIRO_SURFACE_TYPE_QUARTZ_IMAGE: The surface is of type quartz_image
 * @CAIRO_SURFACE_TYPE_SCRIPT: The surface is of type script, since 1.10
 * @CAIRO_SURFACE_TYPE_QT: The surface is of type Qt, since 1.10
 * @CAIRO_SURFACE_TYPE_RECORDING: The surface is of type recording, since 1.10
 * @CAIRO_SURFACE_TYPE_VG: The surface is a OpenVG surface, since 1.10
 * @CAIRO_SURFACE_TYPE_GL: The surface is of type OpenGL, since 1.10
 * @CAIRO_SURFACE_TYPE_DRM: The surface is of type Direct Render Manager, since 1.10
 * @CAIRO_SURFACE_TYPE_TEE: The surface is of type 'tee' (a multiplexing surface), since 1.10
 * @CAIRO_SURFACE_TYPE_XML: The surface is of type XML (for debugging), since 1.10
 * @CAIRO_SURFACE_TYPE_SKIA: The surface is of type Skia, since 1.10
 * @CAIRO_SURFACE_TYPE_SUBSURFACE: The surface is a subsurface created with
 *   cairo_surface_create_for_rectangle(), since 1.10
 *
 * #cairo_surface_type_t is used to describe the type of a given
 * surface. The surface types are also known as "backends" or "surface
 * backends" within cairo.
 *
 * The type of a surface is determined by the function used to create
 * it, which will generally be of the form cairo_type_surface_create(),
 * (though see cairo_surface_create_similar() as well).
 *
 * The surface type can be queried with cairo_surface_get_type()
 *
 * The various #cairo_surface_t functions can be used with surfaces of
 * any type, but some backends also provide type-specific functions
 * that must only be called with a surface of the appropriate
 * type. These functions have names that begin with
 * cairo_type_surface such as cairo_image_surface_get_width().
 *
 * The behavior of calling a type-specific function with a surface of
 * the wrong type is undefined.
 *
 * New entries may be added in future versions.
 *
 * Since: 1.2

 * 
 * @CAIRO_FORMAT_INVALID: no such format exists or is supported.
 * @CAIRO_FORMAT_ARGB32: each pixel is a 32-bit quantity, with
 *   alpha in the upper 8 bits, then red, then green, then blue.
 *   The 32-bit quantities are stored native-endian. Pre-multiplied
 *   alpha is used. (That is, 50% transparent red is 0x80800000,
 *   not 0x80ff0000.)
 * @CAIRO_FORMAT_RGB24: each pixel is a 32-bit quantity, with
 *   the upper 8 bits unused. Red, Green, and Blue are stored
 *   in the remaining 24 bits in that order.
 * @CAIRO_FORMAT_A8: each pixel is a 8-bit quantity holding
 *   an alpha value.
 * @CAIRO_FORMAT_A1: each pixel is a 1-bit quantity holding
 *   an alpha value. Pixels are packed together into 32-bit
 *   quantities. The ordering of the bits matches the
 *   endianess of the platform. On a big-endian machine, the
 *   first pixel is in the uppermost bit, on a little-endian
 *   machine the first pixel is in the least-significant bit.
 * @CAIRO_FORMAT_RGB16_565: This format value is deprecated. It has
 *   never been properly implemented in cairo and should not be used
 *   by applications. (since 1.2)
 *
 * #cairo_format_t is used to identify the memory format of
 * image data.
 *
 * New entries may be added in future versions.

 * 
 * @CAIRO_PATTERN_TYPE_SOLID: The pattern is a solid (uniform)
 * color. It may be opaque or translucent.
 * @CAIRO_PATTERN_TYPE_SURFACE: The pattern is a based on a surface (an image).
 * @CAIRO_PATTERN_TYPE_LINEAR: The pattern is a linear gradient.
 * @CAIRO_PATTERN_TYPE_RADIAL: The pattern is a radial gradient.
 *
 * #cairo_pattern_type_t is used to describe the type of a given pattern.
 *
 * The type of a pattern is determined by the function used to create
 * it. The cairo_pattern_create_rgb() and cairo_pattern_create_rgba()
 * functions create SOLID patterns. The remaining
 * cairo_pattern_create functions map to pattern types in obvious
 * ways.
 *
 * The pattern type can be queried with cairo_pattern_get_type()
 *
 * Most #cairo_pattern_t functions can be called with a pattern of any
 * type, (though trying to change the extend or filter for a solid
 * pattern will have no effect). A notable exception is
 * cairo_pattern_add_color_stop_rgb() and
 * cairo_pattern_add_color_stop_rgba() which must only be called with
 * gradient patterns (either LINEAR or RADIAL). Otherwise the pattern
 * will be shutdown and put into an error state.
 *
 * New entries may be added in future versions.
 *
 * Since: 1.2

 * 
 * @CAIRO_EXTEND_NONE: pixels outside of the source pattern
 *   are fully transparent
 * @CAIRO_EXTEND_REPEAT: the pattern is tiled by repeating
 * @CAIRO_EXTEND_REFLECT: the pattern is tiled by reflecting
 *   at the edges (Implemented for surface patterns since 1.6)
 * @CAIRO_EXTEND_PAD: pixels outside of the pattern copy
 *   the closest pixel from the source (Since 1.2; but only
 *   implemented for surface patterns since 1.6)
 *
 * #cairo_extend_t is used to describe how pattern color/alpha will be
 * determined for areas "outside" the pattern's natural area, (for
 * example, outside the surface bounds or outside the gradient
 * geometry).
 *
 * The default extend mode is %CAIRO_EXTEND_NONE for surface patterns
 * and %CAIRO_EXTEND_PAD for gradient patterns.
 *
 * New entries may be added in future versions.

 * 
 * @CAIRO_FILTER_FAST: A high-performance filter, with quality similar
 *     to %CAIRO_FILTER_NEAREST
 * @CAIRO_FILTER_GOOD: A reasonable-performance filter, with quality
 *     similar to %CAIRO_FILTER_BILINEAR
 * @CAIRO_FILTER_BEST: The highest-quality available, performance may
 *     not be suitable for interactive use.
 * @CAIRO_FILTER_NEAREST: Nearest-neighbor filtering
 * @CAIRO_FILTER_BILINEAR: Linear interpolation in two dimensions
 * @CAIRO_FILTER_GAUSSIAN: This filter value is currently
 *     unimplemented, and should not be used in current code.
 *
 * #cairo_filter_t is used to indicate what filtering should be
 * applied when reading pixel values from patterns. See
 * cairo_pattern_set_source() for indicating the desired filter to be
 * used with a particular pattern.

 * 
 * @CAIRO_PDF_VERSION_1_4: The version 1.4 of the PDF specification.
 * @CAIRO_PDF_VERSION_1_5: The version 1.5 of the PDF specification.
 *
 * #cairo_pdf_version_t is used to describe the version number of the PDF
 * specification that a generated PDF file will conform to.
 *
 * Since 1.10

 * 
 * @CAIRO_PS_LEVEL_2: The language level 2 of the PostScript specification.
 * @CAIRO_PS_LEVEL_3: The language level 3 of the PostScript specification.
 *
 * #cairo_ps_level_t is used to describe the language level of the
 * PostScript Language Reference that a generated PostScript file will
 * conform to.

 * 
 * CAIRO_SCRIPT_MODE_BINARY
 * CAIRO_SCRIPT_MODE_ASCII

 * 
 * @CAIRO_SVG_VERSION_1_1: The version 1.1 of the SVG specification.
 * @CAIRO_SVG_VERSION_1_2: The version 1.2 of the SVG specification.
 *
 * #cairo_svg_version_t is used to describe the version number of the SVG
 * specification that a generated SVG file will conform to.
 

 *
 * @num_bytes: the number of bytes of UTF-8 text covered by cluster
 * @num_glyphs: the number of glyphs covered by cluster
 *
 * The #cairo_text_cluster_t structure holds information about a single
 * text cluster.  A text cluster is a minimal
 * mapping of some glyphs corresponding to some UTF-8 text.
 *
 * For a cluster to be valid, both @num_bytes and @num_glyphs should
 * be non-negative, and at least one should be non-zero.
 * Note that clusters with zero glyphs are not as well supported as
 * normal clusters.  For example, PDF rendering applications typically
 * ignore those clusters when PDF text is being selected.
 *
 * See cairo_show_text_glyphs() for how clusters are used in advanced
 * text operations.
 *
 * Since: 1.8
 

 *
 * @CAIRO_TEXT_CLUSTER_FLAG_BACKWARD: The clusters in the cluster array
 * map to glyphs in the glyph array from end to start.
 *
 * Specifies properties of a text cluster mapping.
 *
 * Since: 1.8
 

 * 
 * A #cairo_region_t represents a set of integer-aligned rectangles.
 *
 * It allows set-theoretical operations like cairo_region_union() and
 * cairo_region_intersect() to be performed on them.
 *
 * Memory management of #cairo_region_t is done with
 * cairo_region_reference() and cairo_region_destroy().
 *
 * Since: 1.10
 

 * 
 * @x: X coordinate of the left side of the rectangle
 * @y: Y coordinate of the the top side of the rectangle
 * @width: width of the rectangle
 * @height: height of the rectangle
 *
 * A data structure for holding a rectangle with integer coordinates.
 *
 * Since: 1.10
 

 * 
    CAIRO_REGION_OVERLAP_IN,		/* completely inside region */
    CAIRO_REGION_OVERLAP_OUT,		/* completely outside region */
    CAIRO_REGION_OVERLAP_PART		/* partly inside region */
 

 *
 * @scaled_font: the scaled-font being created
 * @cr: a cairo context, in font space
 * @extents: font extents to fill in, in font space
 *
 * #cairo_user_scaled_font_init_func_t is the type of function which is
 * called when a scaled-font needs to be created for a user font-face.
 *
 * The cairo context @cr is not used by the caller, but is prepared in font
 * space, similar to what the cairo contexts passed to the render_glyph
 * method will look like.  The callback can use this context for extents
 * computation for example.  After the callback is called, @cr is checked
 * for any error status.
 *
 * The @extents argument is where the user font sets the font extents for
 * @scaled_font.  It is in font space, which means that for most cases its
 * ascent and descent members should add to 1.0.  @extents is preset to
 * hold a value of 1.0 for ascent, height, and max_x_advance, and 0.0 for
 * descent and max_y_advance members.
 *
 * The callback is optional.  If not set, default font extents as described
 * in the previous paragraph will be used.
 *
 * Note that @scaled_font is not fully initialized at this
 * point and trying to use it for text operations in the callback will result
 * in deadlock.
 *
 * Returns: %CAIRO_STATUS_SUCCESS upon success, or an error status on error.
 *
 * Since: 1.8

typedef cairo_status_t (*cairo_user_scaled_font_init_func_t) (cairo_scaled_font_t  *scaled_font,
							      cairo_t              *cr,
							      cairo_font_extents_t *extents);

 * 
 * @scaled_font: user scaled-font
 * @glyph: glyph code to render
 * @cr: cairo context to draw to, in font space
 * @extents: glyph extents to fill in, in font space
 *
 * #cairo_user_scaled_font_render_glyph_func_t is the type of function which
 * is called when a user scaled-font needs to render a glyph.
 *
 * The callback is mandatory, and expected to draw the glyph with code @glyph to
 * the cairo context @cr.  @cr is prepared such that the glyph drawing is done in
 * font space.  That is, the matrix set on @cr is the scale matrix of @scaled_font,
 * The @extents argument is where the user font sets the font extents for
 * @scaled_font.  However, if user prefers to draw in user space, they can
 * achieve that by changing the matrix on @cr.  All cairo rendering operations
 * to @cr are permitted, however, the result is undefined if any source other
 * than the default source on @cr is used.  That means, glyph bitmaps should
 * be rendered using cairo_mask() instead of cairo_paint().
 *
 * Other non-default settings on @cr include a font size of 1.0 (given that
 * it is set up to be in font space), and font options corresponding to
 * @scaled_font.
 *
 * The @extents argument is preset to have x_bearing,
 * width, and y_advance of zero,
 * y_bearing set to -font_extents.ascent,
 * height to font_extents.ascent+font_extents.descent,
 * and x_advance to font_extents.max_x_advance.
 * The only field user needs to set in majority of cases is
 * x_advance.
 * If the width field is zero upon the callback returning
 * (which is its preset value), the glyph extents are automatically computed
 * based on the drawings done to @cr.  This is in most cases exactly what the
 * desired behavior is.  However, if for any reason the callback sets the
 * extents, it must be ink extents, and include the extents of all drawing
 * done to @cr in the callback.
 *
 * Returns: %CAIRO_STATUS_SUCCESS upon success, or
 * %CAIRO_STATUS_USER_FONT_ERROR or any other error status on error.
 *
 * Since: 1.8

typedef cairo_status_t (*cairo_user_scaled_font_render_glyph_func_t) (cairo_scaled_font_t  *scaled_font,
								      unsigned long         glyph,
								      cairo_t              *cr,
								      cairo_text_extents_t *extents);

 * 
 * @scaled_font: the scaled-font being created
 * @utf8: a string of text encoded in UTF-8
 * @utf8_len: length of @utf8 in bytes
 * @glyphs: pointer to array of glyphs to fill, in font space
 * @num_glyphs: pointer to number of glyphs
 * @clusters: pointer to array of cluster mapping information to fill, or %NULL
 * @num_clusters: pointer to number of clusters
 * @cluster_flags: pointer to location to store cluster flags corresponding to the
 *                 output @clusters
 *
 * #cairo_user_scaled_font_text_to_glyphs_func_t is the type of function which
 * is called to convert input text to an array of glyphs.  This is used by the
 * cairo_show_text() operation.
 *
 * Using this callback the user-font has full control on glyphs and their
 * positions.  That means, it allows for features like ligatures and kerning,
 * as well as complex shaping required for scripts like
 * Arabic and Indic.
 *
 * The @num_glyphs argument is preset to the number of glyph entries available
 * in the @glyphs buffer. If the @glyphs buffer is %NULL, the value of
 * @num_glyphs will be zero.  If the provided glyph array is too short for
 * the conversion (or for convenience), a new glyph array may be allocated
 * using cairo_glyph_allocate() and placed in @glyphs.  Upon return,
 * @num_glyphs should contain the number of generated glyphs.  If the value
 * @glyphs points at has changed after the call, the caller will free the
 * allocated glyph array using cairo_glyph_free().
 * The callback should populate the glyph indices and positions (in font space)
 * assuming that the text is to be shown at the origin.
 *
 * If @clusters is not %NULL, @num_clusters and @cluster_flags are also
 * non-%NULL, and cluster mapping should be computed. The semantics of how
 * cluster array allocation works is similar to the glyph array.  That is,
 * if @clusters initially points to a non-%NULL value, that array may be used
 * as a cluster buffer, and @num_clusters points to the number of cluster
 * entries available there.  If the provided cluster array is too short for
 * the conversion (or for convenience), a new cluster array may be allocated
 * using cairo_text_cluster_allocate() and placed in @clusters.  Upon return,
 * @num_clusters should contain the number of generated clusters.
 * If the value @clusters points at has changed after the call, the caller
 * will free the allocated cluster array using cairo_text_cluster_free().
 *
 * The callback is optional.  If @num_glyphs is negative upon
 * the callback returning or if the return value
 * is %CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED, the unicode_to_glyph callback
 * is tried.  See #cairo_user_scaled_font_unicode_to_glyph_func_t.
 *
 * Note: While cairo does not impose any limitation on glyph indices,
 * some applications may assume that a glyph index fits in a 16-bit
 * unsigned integer.  As such, it is advised that user-fonts keep their
 * glyphs in the 0 to 65535 range.  Furthermore, some applications may
 * assume that glyph 0 is a special glyph-not-found glyph.  User-fonts
 * are advised to use glyph 0 for such purposes and do not use that
 * glyph value for other purposes.
 *
 * Returns: %CAIRO_STATUS_SUCCESS upon success,
 * %CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED if fallback options should be tried,
 * or %CAIRO_STATUS_USER_FONT_ERROR or any other error status on error.
 *
 * Since: 1.8

typedef cairo_status_t (*cairo_user_scaled_font_text_to_glyphs_func_t) (cairo_scaled_font_t        *scaled_font,
									const char	           *utf8,
									int		            utf8_len,
									cairo_glyph_t	          **glyphs,
									int		           *num_glyphs,
									cairo_text_cluster_t      **clusters,
									int		           *num_clusters,
									cairo_text_cluster_flags_t *cluster_flags);

 * 
 * @scaled_font: the scaled-font being created
 * @unicode: input unicode character code-point
 * @glyph_index: output glyph index
 *
 * #cairo_user_scaled_font_unicode_to_glyph_func_t is the type of function which
 * is called to convert an input Unicode character to a single glyph.
 * This is used by the cairo_show_text() operation.
 *
 * This callback is used to provide the same functionality as the
 * text_to_glyphs callback does (see #cairo_user_scaled_font_text_to_glyphs_func_t)
 * but has much less control on the output,
 * in exchange for increased ease of use.  The inherent assumption to using
 * this callback is that each character maps to one glyph, and that the
 * mapping is context independent.  It also assumes that glyphs are positioned
 * according to their advance width.  These mean no ligatures, kerning, or
 * complex scripts can be implemented using this callback.
 *
 * The callback is optional, and only used if text_to_glyphs callback is not
 * set or fails to return glyphs.  If this callback is not set or if it returns
 * %CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED, an identity mapping from Unicode
 * code-points to glyph indices is assumed.
 *
 * Note: While cairo does not impose any limitation on glyph indices,
 * some applications may assume that a glyph index fits in a 16-bit
 * unsigned integer.  As such, it is advised that user-fonts keep their
 * glyphs in the 0 to 65535 range.  Furthermore, some applications may
 * assume that glyph 0 is a special glyph-not-found glyph.  User-fonts
 * are advised to use glyph 0 for such purposes and do not use that
 * glyph value for other purposes.
 *
 * Returns: %CAIRO_STATUS_SUCCESS upon success,
 * %CAIRO_STATUS_USER_FONT_NOT_IMPLEMENTED if fallback options should be tried,
 * or %CAIRO_STATUS_USER_FONT_ERROR or any other error status on error.
 *
 * Since: 1.8

typedef cairo_status_t (*cairo_user_scaled_font_unicode_to_glyph_func_t) (cairo_scaled_font_t *scaled_font,
									  unsigned long        unicode,
									  unsigned long       *glyph_index);

    [C]   cairo_surface_t * cairo_image_surface_create (cairo_format_t format, int width, int height);
    [Lua] surface_o = cairo.ImageSurface(format, width, height)
    

    [C]   void cairo_set_font_face (cairo_t *cr, cairo_font_face_t *font_face);
    [Lua] cr_o:set_font_face(font_face)  -- Context class
    
    [C]   void cairo_matrix_init_identity (cairo_matrix_t *matrix);
    [Lua] matrix_o:init_identity()
    

    [C]   cairo_surface_t * cairo_get_group_target (cairo_t *cr);
    [Lua] target_lud = cairo.get_group_target(cr)
          target_lud = cr:get_group_target()
          
          -- return value may wrapped as a Surface object
          target_o = cairo.SurfaceFromLUD(cr:get_group_target(), true) -- give ownership
          target_o = cairo.SurfaceFromLUD(cr:get_group_target())       -- by default ownership is not transferred
    

    [C]   cairo_format_t cairo_image_surface_get_format (cairo_surface_t *surface);
    [Lua] int = cairo.image_surface_get_format(surface_lud)
          int = cairo.image_surface_get_format(surface_o)
          
    [C]   void cairo_set_source_surface (cairo_t *cr, cairo_surface_t *surface, double x, double y);
    [Lua] cairo.set_source_surface(cr_lud, surface_lud, x, y)
          cairo.set_source_surface(cr_o, surface_o, x, y)
          cr:set_source_surface(surface_lud, x, y)
          cr:set_source_surface(surface_o, x, y)