cairo.h

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

		double	 offset);

cairo_public void
cairo_set_miter_limit (cairo_t *cr, double limit);

cairo_public void
cairo_translate (cairo_t *cr, double tx, double ty);

cairo_public void
cairo_scale (cairo_t *cr, double sx, double sy);

cairo_public void
cairo_rotate (cairo_t *cr, double angle);

cairo_public void
cairo_transform (cairo_t	      *cr,
		 const cairo_matrix_t *matrix);

cairo_public void
cairo_set_matrix (cairo_t	       *cr,
		  const cairo_matrix_t *matrix);

cairo_public void
cairo_identity_matrix (cairo_t *cr);

cairo_public void
cairo_user_to_device (cairo_t *cr, double *x, double *y);

cairo_public void
cairo_user_to_device_distance (cairo_t *cr, double *dx, double *dy);

cairo_public void
cairo_device_to_user (cairo_t *cr, double *x, double *y);

cairo_public void
cairo_device_to_user_distance (cairo_t *cr, double *dx, double *dy);

/* Path creation functions */
cairo_public void
cairo_new_path (cairo_t *cr);

cairo_public void
cairo_move_to (cairo_t *cr, double x, double y);

cairo_public void
cairo_new_sub_path (cairo_t *cr);

cairo_public void
cairo_line_to (cairo_t *cr, double x, double y);

cairo_public void
cairo_curve_to (cairo_t *cr,
		double x1, double y1,
		double x2, double y2,
		double x3, double y3);

cairo_public void
cairo_arc (cairo_t *cr,
	   double xc, double yc,
	   double radius,
	   double angle1, double angle2);

cairo_public void
cairo_arc_negative (cairo_t *cr,
		    double xc, double yc,
		    double radius,
		    double angle1, double angle2);

/* XXX: NYI
cairo_public void
cairo_arc_to (cairo_t *cr,
	      double x1, double y1,
	      double x2, double y2,
	      double radius);
*/

cairo_public void
cairo_rel_move_to (cairo_t *cr, double dx, double dy);

cairo_public void
cairo_rel_line_to (cairo_t *cr, double dx, double dy);

cairo_public void
cairo_rel_curve_to (cairo_t *cr,
		    double dx1, double dy1,
		    double dx2, double dy2,
		    double dx3, double dy3);

cairo_public void
cairo_rectangle (cairo_t *cr,
		 double x, double y,
		 double width, double height);

/* XXX: NYI
cairo_public void
cairo_stroke_to_path (cairo_t *cr);
*/

cairo_public void
cairo_close_path (cairo_t *cr);

/* Painting functions */
cairo_public void
cairo_paint (cairo_t *cr);

cairo_public void
cairo_paint_with_alpha (cairo_t *cr,
			double   alpha);

cairo_public void
cairo_mask (cairo_t         *cr,
	    cairo_pattern_t *pattern);

cairo_public void
cairo_mask_surface (cairo_t         *cr,
		    cairo_surface_t *surface,
		    double           surface_x,
		    double           surface_y);

cairo_public void
cairo_stroke (cairo_t *cr);

cairo_public void
cairo_stroke_preserve (cairo_t *cr);

cairo_public void
cairo_fill (cairo_t *cr);

cairo_public void
cairo_fill_preserve (cairo_t *cr);

cairo_public void
cairo_copy_page (cairo_t *cr);

cairo_public void
cairo_show_page (cairo_t *cr);

/* Insideness testing */
cairo_public cairo_bool_t
cairo_in_stroke (cairo_t *cr, double x, double y);

cairo_public cairo_bool_t
cairo_in_fill (cairo_t *cr, double x, double y);

/* Rectangular extents */
cairo_public void
cairo_stroke_extents (cairo_t *cr,
		      double *x1, double *y1,
		      double *x2, double *y2);

cairo_public void
cairo_fill_extents (cairo_t *cr,
		    double *x1, double *y1,
		    double *x2, double *y2);

/* Clipping */
cairo_public void
cairo_reset_clip (cairo_t *cr);

cairo_public void
cairo_clip (cairo_t *cr);

cairo_public void
cairo_clip_preserve (cairo_t *cr);

/* Font/Text functions */

/**
 * cairo_scaled_font_t:
 *
 * 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.
 */
typedef struct _cairo_scaled_font cairo_scaled_font_t;

/**
 * cairo_font_face_t:
 *
 * 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().
 */
typedef struct _cairo_font_face cairo_font_face_t;

/**
 * cairo_glyph_t:
 * @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 <firstterm>ligature</firstterm> 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
 **/
typedef struct {
  unsigned long        index;
  double               x;
  double               y;
} cairo_glyph_t;

/**
 * cairo_text_extents_t:
 * @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
 * <literal>cairo_scale(cr, 2.0, 2.0)</literal>, 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.
 */
typedef struct {
    double x_bearing;
    double y_bearing;
    double width;
    double height;
    double x_advance;
    double y_advance;
} cairo_text_extents_t;

/**
 * cairo_font_extents_t:
 * @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 <firstterm>line spacing</firstterm>
 *          or <firstterm>external leading</firstterm>. 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_text_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 <literal>cairo_scale(cr, 2.0, 2.0)</literal>,
 * 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.
 */
typedef struct {
    double ascent;
    double descent;
    double height;
    double max_x_advance;
    double max_y_advance;
} cairo_font_extents_t;

typedef enum _cairo_font_slant {
  CAIRO_FONT_SLANT_NORMAL,
  CAIRO_FONT_SLANT_ITALIC,
  CAIRO_FONT_SLANT_OBLIQUE
} cairo_font_slant_t;

typedef enum _cairo_font_weight {
  CAIRO_FONT_WEIGHT_NORMAL,
  CAIRO_FONT_WEIGHT_BOLD
} cairo_font_weight_t;

/**
 * cairo_subpixel_order_t:
 * @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.
 **/
typedef enum _cairo_subpixel_order {
    CAIRO_SUBPIXEL_ORDER_DEFAULT,
    CAIRO_SUBPIXEL_ORDER_RGB,
    CAIRO_SUBPIXEL_ORDER_BGR,
    CAIRO_SUBPIXEL_ORDER_VRGB,
    CAIRO_SUBPIXEL_ORDER_VBGR
} cairo_subpixel_order_t;

/**
 * cairo_hint_style_t:
 * @CAIRO_HINT_STYLE_DEFAULT: Use the default hint style for
 *   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.
 */
typedef enum _cairo_hint_style {
    CAIRO_HINT_STYLE_DEFAULT,
    CAIRO_HINT_STYLE_NONE,
    CAIRO_HINT_STYLE_SLIGHT,
    CAIRO_HINT_STYLE_MEDIUM,
    CAIRO_HINT_STYLE_FULL
} cairo_hint_style_t;

/**
 * cairo_hint_metrics_t:
 * @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.
 */
typedef enum _cairo_hint_metrics {
    CAIRO_HINT_METRICS_DEFAULT,
    CAIRO_HINT_METRICS_OFF,
    CAIRO_HINT_METRICS_ON
} cairo_hint_metrics_t;

typedef struct _cairo_font_options cairo_font_options_t;

cairo_public cairo_font_options_t *
cairo_font_options_create (void);

cairo_public cairo_font_options_t *
cairo_font_options_copy (const cairo_font_options_t *original);

cairo_public void
cairo_font_options_destroy (cairo_font_options_t *options);

cairo_public cairo_status_t
cairo_font_options_status (cairo_font_options_t *options);

cairo_public void
cairo_font_options_merge (cairo_font_options_t       *options,
			  const cairo_font_options_t *other);
cairo_public cairo_bool_t
cairo_font_options_equal (const cairo_font_options_t *options,
			  const cairo_font_options_t *other);

cairo_public unsigned long
cairo_font_options_hash (const cairo_font_options_t *options);

cairo_public void
cairo_font_options_set_antialias (cairo_font_options_t *options,
				  cairo_antialias_t     antialias);
cairo_public cairo_antialias_t
cairo_font_options_get_antialias (const cairo_font_options_t *options);

cairo_public void