cairo_t

typedef struct _cairo cairo_t;

A cairo_t contains the current state of the rendering device, including coordinates of yet to be drawn shapes.

cairo_create ()

cairo_t*            cairo_create                        (cairo_surface_t *target);

Creates a new cairo_t with all graphics state parameters set to default values and with target as a target surface. The target surface should be constructed with a backend-specific function such as cairo_image_surface_create() (or any other cairo_<backend>_surface_create variant).

This function references target, so you can immediately call cairo_surface_destroy() on it if you don't need to maintain a separate reference to it.

cairo_reference ()

cairo_t*            cairo_reference                     (cairo_t *cr);

Increases the reference count on cr by one. This prevents cr from being destroyed until a matching call to cairo_destroy() is made.

cairo_destroy ()

void                cairo_destroy                       (cairo_t *cr);

Decreases the reference count on cr by one. If the result is zero, then cr and all associated resources are freed. See cairo_reference().

cairo_save ()

void                cairo_save                          (cairo_t *cr);

Makes a copy of the current state of cr and saves it on an internal stack of saved states for cr. When cairo_restore() is called, cr will be restored to the saved state. Multiple calls to cairo_save() and cairo_restore() can be nested; each call to cairo_restore() restores the state from the matching paired cairo_save().

It isn't necessary to clear all saved states before a cairo_t is freed. If the reference count of a cairo_t drops to zero in response to a call to cairo_destroy(), any saved states will be freed along with the cairo_t.

cairo_restore ()

void                cairo_restore                       (cairo_t *cr);

Restores cr to the state saved by a preceding call to cairo_save() and removes that state from the stack of saved states.

cairo_status ()

cairo_status_t      cairo_status                        (cairo_t *cr);

Checks whether an error has previously occurred for this context.

cairo_get_target ()

cairo_surface_t*    cairo_get_target                    (cairo_t *cr);

Gets the target surface for the cairo context as passed to cairo_create().

This function will always return a valid pointer, but the result can be a "nil" surface if cr is already in an error state, (ie. cairo_status() != CAIRO_STATUS_SUCCESS). A nil surface is indicated by cairo_surface_status() != CAIRO_STATUS_SUCCESS.

cairo_set_source_rgb ()

void                cairo_set_source_rgb                (cairo_t *cr,
                                                         double red,
                                                         double green,
                                                         double blue);

Sets the source pattern within cr to an opaque color. This opaque color will then be used for any subsequent drawing operation until a new source pattern is set.

The color components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

cairo_set_source_rgba ()

void                cairo_set_source_rgba               (cairo_t *cr,
                                                         double red,
                                                         double green,
                                                         double blue,
                                                         double alpha);

Sets the source pattern within cr to a translucent color. This color will then be used for any subsequent drawing operation until a new source pattern is set.

The color and alpha components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

cairo_set_source ()

void                cairo_set_source                    (cairo_t *cr,
                                                         cairo_pattern_t *source);

Sets the source pattern within cr to source. This pattern will then be used for any subsequent drawing operation until a new source pattern is set.

Note: The pattern's transformation matrix will be locked to the user space in effect at the time of cairo_set_source(). This means that further modifications of the current transformation matrix will not affect the source pattern. See cairo_pattern_set_matrix().

XXX: I'd also like to direct the reader's attention to some (not-yet-written) section on cairo's imaging model. How would I do that if such a section existed? (cworth).

cairo_set_source_surface ()

void                cairo_set_source_surface            (cairo_t *cr,
                                                         cairo_surface_t *surface,
                                                         double x,
                                                         double y);

This is a convenience function for creating a pattern from surface and setting it as the source in cr with cairo_set_source().

The x and y parameters give the user-space coordinate at which the surface origin should appear. (The surface origin is its upper-left corner before any transformation has been applied.) The x and y patterns are negated and then set as translation values in the pattern matrix.

Other than the initial translation pattern matrix, as described above, all other pattern attributes, (such as its extend mode), are set to the default values as in cairo_pattern_create_for_surface(). The resulting pattern can be queried with cairo_get_source() so that these attributes can be modified if desired, (eg. to create a repeating pattern with cairo_pattern_set_extend()).

cairo_get_source ()

cairo_pattern_t*    cairo_get_source                    (cairo_t *cr);

Gets the current source pattern for cr.

enum cairo_antialias_t

typedef enum _cairo_antialias {
    CAIRO_ANTIALIAS_DEFAULT,
    CAIRO_ANTIALIAS_NONE,
    CAIRO_ANTIALIAS_GRAY,
    CAIRO_ANTIALIAS_SUBPIXEL
} cairo_antialias_t;

Specifies the type of antialiasing to do when rendering text or shapes.

cairo_set_antialias ()

void                cairo_set_antialias                 (cairo_t *cr,
                                                         cairo_antialias_t antialias);

Set the antialiasing mode of the rasterizer used for drawing shapes. This value is a hint, and a particular backend may or may not support a particular value. At the current time, no backend supports CAIRO_ANTIALIAS_SUBPIXEL when drawing shapes.

Note that this option does not affect text rendering, instead see cairo_font_options_set_antialias().

cairo_get_antialias ()

cairo_antialias_t   cairo_get_antialias                 (cairo_t *cr);

Gets the current shape antialiasing mode, as set by cairo_set_shape_antialias().

cairo_set_dash ()

void                cairo_set_dash                      (cairo_t *cr,
                                                         double *dashes,
                                                         int num_dashes,
                                                         double offset);

Sets the dash pattern to be used by cairo_stroke(). A dash pattern is specified by dashes, an array of positive values. Each value provides the user-space length of altenate "on" and "off" portions of the stroke. The offset specifies an offset into the pattern at which the stroke begins.

If num_dashes is 0 dashing is disabled.

If num_dashes is 1 a symmetric pattern is assumed with alternating on and off portions of the size specified by the single value in dashes.

If any value in dashes is negative, or if all values are 0, then cairo_t will be put into an error state with a status of CAIRO_STATUS_INVALID_DASH.

enum cairo_fill_rule_t

typedef enum _cairo_fill_rule {
    CAIRO_FILL_RULE_WINDING,
    CAIRO_FILL_RULE_EVEN_ODD
} cairo_fill_rule_t;

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.)

cairo_set_fill_rule ()

void                cairo_set_fill_rule                 (cairo_t *cr,
                                                         cairo_fill_rule_t fill_rule);

Set the current fill rule within the cairo context. The fill rule is used to determine which regions are inside or outside a complex (potentially self-intersecting) path. The current fill rule affects both cairo_fill and cairo_clip. See cairo_fill_rule_t for details on the semantics of each available fill rule.

cairo_get_fill_rule ()

cairo_fill_rule_t   cairo_get_fill_rule                 (cairo_t *cr);

Gets the current fill rule, as set by cairo_set_fill_rule().

enum cairo_line_cap_t

typedef enum _cairo_line_cap {
    CAIRO_LINE_CAP_BUTT,
    CAIRO_LINE_CAP_ROUND,
    CAIRO_LINE_CAP_SQUARE
} cairo_line_cap_t;

enumeration for style of line-endings

cairo_set_line_cap ()

void                cairo_set_line_cap                  (cairo_t *cr,
                                                         cairo_line_cap_t line_cap);

Sets the current line cap style within the cairo context. See cairo_line_cap_t for details about how the available line cap styles are drawn.

As with the other stroke parameters, the current line cap style is examined by cairo_stroke(), cairo_stroke_extents(), and cairo_stroke_to_path(), but does not have any effect during path construction.

cairo_get_line_cap ()

cairo_line_cap_t    cairo_get_line_cap                  (cairo_t *cr);

Gets the current line cap style, as set by cairo_set_line_cap().

enum cairo_line_join_t

typedef enum _cairo_line_join {
    CAIRO_LINE_JOIN_MITER,
    CAIRO_LINE_JOIN_ROUND,
    CAIRO_LINE_JOIN_BEVEL
} cairo_line_join_t;

cairo_set_line_join ()

void                cairo_set_line_join                 (cairo_t *cr,
                                                         cairo_line_join_t line_join);

Sets the current line join style within the cairo context. See cairo_line_join_t for details about how the available line join styles are drawn.

As with the other stroke parameters, the current line join style is examined by cairo_stroke(), cairo_stroke_extents(), and cairo_stroke_to_path(), but does not have any effect during path construction.

cairo_get_line_join ()

cairo_line_join_t   cairo_get_line_join                 (cairo_t *cr);

Gets the current line join style, as set by cairo_set_line_join().

cairo_set_line_width ()

void                cairo_set_line_width                (cairo_t *cr,
                                                         double width);

Sets the current line width within the cairo context. The line width specifies the diameter of a pen that is circular in user-space.

As with the other stroke parameters, the current line cap style is examined by cairo_stroke(), cairo_stroke_extents(), and cairo_stroke_to_path(), but does not have any effect during path construction.

cairo_get_line_width ()

double              cairo_get_line_width                (cairo_t *cr);

Gets the current line width, as set by cairo_set_line_width().

cairo_set_miter_limit ()

void                cairo_set_miter_limit               (cairo_t *cr,
                                                         double limit);

cairo_get_miter_limit ()

double              cairo_get_miter_limit               (cairo_t *cr);

Gets the current miter limit, as set by cairo_set_miter_limit().

enum cairo_operator_t

typedef enum _cairo_operator {
    CAIRO_OPERATOR_CLEAR,

    CAIRO_OPERATOR_SOURCE,
    CAIRO_OPERATOR_OVER,
    CAIRO_OPERATOR_IN,
    CAIRO_OPERATOR_OUT,
    CAIRO_OPERATOR_ATOP,

    CAIRO_OPERATOR_DEST,
    CAIRO_OPERATOR_DEST_OVER,
    CAIRO_OPERATOR_DEST_IN,
    CAIRO_OPERATOR_DEST_OUT,
    CAIRO_OPERATOR_DEST_ATOP,

    CAIRO_OPERATOR_XOR,
    CAIRO_OPERATOR_ADD,
    CAIRO_OPERATOR_SATURATE
} cairo_operator_t;

cairo_set_operator ()

void                cairo_set_operator                  (cairo_t *cr,
                                                         cairo_operator_t op);

Sets the compositing operator to be used for all drawing operations. See cairo_operator_t for details on the semantics of each available compositing operator.

XXX: I'd also like to direct the reader's attention to some (not-yet-written) section on cairo's imaging model. How would I do that if such a section existed? (cworth).

cairo_get_operator ()

cairo_operator_t    cairo_get_operator                  (cairo_t *cr);

Gets the current compositing operator for a cairo context.

cairo_set_tolerance ()

void                cairo_set_tolerance                 (cairo_t *cr,
                                                         double tolerance);

Sets the tolerance used when converting paths into trapezoids. Curved segments of the path will be subdivided until the maximum deviation between the original path and the polygonal approximation is less than tolerance. The default value is 0.1. A larger value will give better performance, a smaller value, better appearance. (Reducing the value from the default value of 0.1 is unlikely to improve appearance significantly.)

cairo_get_tolerance ()

double              cairo_get_tolerance                 (cairo_t *cr);

Gets the current tolerance value, as set by cairo_set_tolerance().

cairo_clip ()

void                cairo_clip                          (cairo_t *cr);

Establishes a new clip region by intersecting the current clip region with the current path as it would be filled by cairo_fill() and according to the current fill rule (see cairo_set_fill_rule()).

After cairo_clip, the current path will be cleared from the cairo context.

The current clip region affects all drawing operations by effectively masking out any changes to the surface that are outside the current clip region.

Calling cairo_clip() can only make the clip region smaller, never larger. But the current clip is part of the graphics state, so a temporary restriction of the clip region can be achieved by calling cairo_clip() within a cairo_save()/cairo_restore() pair. The only other means of increasing the size of the clip region is cairo_reset_clip().

cairo_clip_preserve ()

void                cairo_clip_preserve                 (cairo_t *cr);

Establishes a new clip region by intersecting the current clip region with the current path as it would be filled by cairo_fill() and according to the current fill rule (see cairo_set_fill_rule()).

Unlike cairo_clip(), cairo_clip_preserve preserves the path within the cairo context.

The current clip region affects all drawing operations by effectively masking out any changes to the surface that are outside the current clip region.

Calling cairo_clip() can only make the clip region smaller, never larger. But the current clip is part of the graphics state, so a temporary restriction of the clip region can be achieved by calling cairo_clip() within a cairo_save()/cairo_restore() pair. The only other means of increasing the size of the clip region is cairo_reset_clip().

cairo_reset_clip ()

void                cairo_reset_clip                    (cairo_t *cr);

Reset the current clip region to its original, unrestricted state. That is, set the clip region to an infinitely large shape containing the target surface. Equivalently, if infinity is too hard to grasp, one can imagine the clip region being reset to the exact bounds of the target surface.

Note that code meant to be reusable should not call cairo_reset_clip() as it will cause results unexpected by higher-level code which calls cairo_clip(). Consider using cairo_save() and cairo_restore() around cairo_clip() as a more robust means of temporarily restricting the clip region.

cairo_fill ()

void                cairo_fill                          (cairo_t *cr);

A drawing operator that fills the current path according to the current fill rule, (each sub-path is implicitly closed before being filled). After cairo_fill, the current path will be cleared from the cairo context. See cairo_set_fill_rule() and cairo_fill_preserve().

cairo_fill_preserve ()

void                cairo_fill_preserve                 (cairo_t *cr);

A drawing operator that fills the current path according to the current fill rule, (each sub-path is implicitly closed before being filled). Unlike cairo_fill(), cairo_fill_preserve preserves the path within the cairo context.

See cairo_set_fill_rule() and cairo_fill().

cairo_fill_extents ()

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

cairo_in_fill ()

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

cairo_mask ()

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

A drawing operator that paints the current source using the alpha channel of pattern as a mask. (Opaque areas of mask are painted with the source, transparent areas are not painted.)

cairo_mask_surface ()

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

A drawing operator that paints the current source using the alpha channel of surface as a mask. (Opaque areas of surface are painted with the source, transparent areas are not painted.)

cairo_paint ()

void                cairo_paint                         (cairo_t *cr);

A drawing operator that paints the current source everywhere within the current clip region.

cairo_paint_with_alpha ()

void                cairo_paint_with_alpha              (cairo_t *cr,
                                                         double alpha);

A drawing operator that paints the current source everywhere within the current clip region using a mask of constant alpha value alpha. The effect is similar to cairo_paint(), but the drawing is faded out using the alpha value.

cairo_stroke ()

void                cairo_stroke                        (cairo_t *cr);

A drawing operator that strokes the current path according to the current line width, line join, line cap, and dash settings. After cairo_stroke, the current path will be cleared from the cairo context. See cairo_set_line_width(), cairo_set_line_join(), cairo_set_line_cap(), cairo_set_dash(), and cairo_stroke_preserve().

cairo_stroke_preserve ()

void                cairo_stroke_preserve               (cairo_t *cr);

A drawing operator that strokes the current path according to the current line width, line join, line cap, and dash settings. Unlike cairo_stroke(), cairo_stroke_preserve preserves the path within the cairo context.

See cairo_set_line_width(), cairo_set_line_join(), cairo_set_line_cap(), cairo_set_dash(), and cairo_stroke_preserve().

cairo_stroke_extents ()

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

cairo_in_stroke ()

cairo_bool_t        cairo_in_stroke                     (cairo_t *cr,
                                                         double x,
                                                         double y);

cairo_copy_page ()

void                cairo_copy_page                     (cairo_t *cr);

cairo_show_page ()

void                cairo_show_page                     (cairo_t *cr);