cairo_t

cairo_t — The cairo drawing context

Synopsis

typedef             cairo_t;
cairo_t*            cairo_create                        (cairo_surface_t *target);
cairo_t*            cairo_reference                     (cairo_t *cr);
void                cairo_destroy                       (cairo_t *cr);
cairo_status_t      cairo_status                        (cairo_t *cr);
void                cairo_save                          (cairo_t *cr);
void                cairo_restore                       (cairo_t *cr);
cairo_surface_t*    cairo_get_target                    (cairo_t *cr);
void                cairo_push_group                    (cairo_t *cr);
void                cairo_push_group_with_content       (cairo_t *cr,
                                                         cairo_content_t content);
cairo_pattern_t*    cairo_pop_group                     (cairo_t *cr);
void                cairo_pop_group_to_source           (cairo_t *cr);
cairo_surface_t*    cairo_get_group_target              (cairo_t *cr);
void                cairo_set_source_rgb                (cairo_t *cr,
                                                         double red,
                                                         double green,
                                                         double blue);
void                cairo_set_source_rgba               (cairo_t *cr,
                                                         double red,
                                                         double green,
                                                         double blue,
                                                         double alpha);
void                cairo_set_source                    (cairo_t *cr,
                                                         cairo_pattern_t *source);
void                cairo_set_source_surface            (cairo_t *cr,
                                                         cairo_surface_t *surface,
                                                         double x,
                                                         double y);
cairo_pattern_t*    cairo_get_source                    (cairo_t *cr);
enum                cairo_antialias_t;
void                cairo_set_antialias                 (cairo_t *cr,
                                                         cairo_antialias_t antialias);
cairo_antialias_t   cairo_get_antialias                 (cairo_t *cr);
void                cairo_set_dash                      (cairo_t *cr,
                                                         double *dashes,
                                                         int num_dashes,
                                                         double offset);
enum                cairo_fill_rule_t;
void                cairo_set_fill_rule                 (cairo_t *cr,
                                                         cairo_fill_rule_t fill_rule);
cairo_fill_rule_t   cairo_get_fill_rule                 (cairo_t *cr);
enum                cairo_line_cap_t;
void                cairo_set_line_cap                  (cairo_t *cr,
                                                         cairo_line_cap_t line_cap);
cairo_line_cap_t    cairo_get_line_cap                  (cairo_t *cr);
enum                cairo_line_join_t;
void                cairo_set_line_join                 (cairo_t *cr,
                                                         cairo_line_join_t line_join);
cairo_line_join_t   cairo_get_line_join                 (cairo_t *cr);
void                cairo_set_line_width                (cairo_t *cr,
                                                         double width);
double              cairo_get_line_width                (cairo_t *cr);
void                cairo_set_miter_limit               (cairo_t *cr,
                                                         double limit);
double              cairo_get_miter_limit               (cairo_t *cr);
enum                cairo_operator_t;
void                cairo_set_operator                  (cairo_t *cr,
                                                         cairo_operator_t op);
cairo_operator_t    cairo_get_operator                  (cairo_t *cr);
void                cairo_set_tolerance                 (cairo_t *cr,
                                                         double tolerance);
double              cairo_get_tolerance                 (cairo_t *cr);
void                cairo_clip                          (cairo_t *cr);
void                cairo_clip_preserve                 (cairo_t *cr);
void                cairo_reset_clip                    (cairo_t *cr);
void                cairo_fill                          (cairo_t *cr);
void                cairo_fill_preserve                 (cairo_t *cr);
void                cairo_fill_extents                  (cairo_t *cr,
                                                         double *x1,
                                                         double *y1,
                                                         double *x2,
                                                         double *y2);
cairo_bool_t        cairo_in_fill                       (cairo_t *cr,
                                                         double x,
                                                         double y);
void                cairo_mask                          (cairo_t *cr,
                                                         cairo_pattern_t *pattern);
void                cairo_mask_surface                  (cairo_t *cr,
                                                         cairo_surface_t *surface,
                                                         double surface_x,
                                                         double surface_y);
void                cairo_paint                         (cairo_t *cr);
void                cairo_paint_with_alpha              (cairo_t *cr,
                                                         double alpha);
void                cairo_stroke                        (cairo_t *cr);
void                cairo_stroke_preserve               (cairo_t *cr);
void                cairo_stroke_extents                (cairo_t *cr,
                                                         double *x1,
                                                         double *y1,
                                                         double *x2,
                                                         double *y2);
cairo_bool_t        cairo_in_stroke                     (cairo_t *cr,
                                                         double x,
                                                         double y);
void                cairo_copy_page                     (cairo_t *cr);
void                cairo_show_page                     (cairo_t *cr);

Description

cairo_t is the main object used when drawing with cairo. To draw with cairo, you create a cairo_t, set the target surface, and drawing options for the cairo_t, create shapes with functions like cairo_move_to() and cairo_line_to(), and then draw shapes with cairo_stroke() or cairo_fill().

cairo_t's can be pushed to a stack via cairo_save(). They may then safely be changed, without loosing the current state. Use cairo_restore() to restore to the saved state.

Details

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.

target :

target surface for the context

Returns :

a newly allocated cairo_t with a reference count of 1. The initial reference count should be released with cairo_destroy() when you are done using the cairo_t. This function never returns NULL. If memory cannot be allocated, a special cairo_t object will be returned on which cairo_status() returns CAIRO_STATUS_NO_MEMORY. You can use this object normally, but no drawing will be done.

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.

cr :

a cairo_t

Returns :

the referenced cairo_t.

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().

cr :

a cairo_t

cairo_status ()

cairo_status_t      cairo_status                        (cairo_t *cr);

Checks whether an error has previously occurred for this context.

cr :

a cairo context

Returns :

the current status of this context, see cairo_status_t

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.

cr :

a 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.

cr :

a cairo_t

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.

cr :

a cairo context

Returns :

the target surface. This object is owned by cairo. To keep a reference to it, you must call cairo_surface_reference().

cairo_push_group ()

void                cairo_push_group                    (cairo_t *cr);

Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to cairo_pop_group() or cairo_pop_group_to_source(). These calls provide the result of any drawing to the group as a pattern, (either as an explicit object, or set as the source pattern).

This group functionality can be convenient for performing intermediate compositing. One common use of a group is to render objects as opaque within the group, (so that they occlude each other), and then blend the result with translucence onto the destination.

Groups can be nested arbitrarily deep by making balanced calls to cairo_push_group()/cairo_pop_group(). Each call pushes/pops the new target group onto/from a stack.

The cairo_push_group() function calls cairo_save() so that any changes to the graphics state will not be visible outside the group, (the pop_group functions call cairo_restore()).

By default the intermediate group will have a content type of CAIRO_CONTENT_COLOR_ALPHA. Other content types can be chosen for the group by using cairo_push_group_with_content() instead.

As an example, here is how one might fill and stroke a path with translucence, but without any portion of the fill being visible under the stroke:

cairo_push_group (cr);
cairo_set_source (cr, fill_pattern);
cairo_fill_preserve (cr);
cairo_set_source (cr, stroke_pattern);
cairo_stroke (cr);
cairo_pop_group_to_source (cr);
cairo_paint_with_alpha (cr, alpha);

cr :

a cairo context

Since 1.2


cairo_push_group_with_content ()

void                cairo_push_group_with_content       (cairo_t *cr,
                                                         cairo_content_t content);

Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to cairo_pop_group() or cairo_pop_group_to_source(). These calls provide the result of any drawing to the group as a pattern, (either as an explicit object, or set as the source pattern).

The group will have a content type of content. The ability to control this content type is the only distinction between this function and cairo_push_group() which you should see for a more detailed description of group rendering.

cr :

a cairo context

content :

a cairo_content_t indicating the type of group that will be created

Since 1.2


cairo_pop_group ()

cairo_pattern_t*    cairo_pop_group                     (cairo_t *cr);

Terminates the redirection begun by a call to cairo_push_group() or cairo_push_group_with_content() and returns a new pattern containing the results of all drawing operations performed to the group.

The cairo_pop_group() function calls cairo_restore(), (balancing a call to cairo_save() by the push_group function), so that any changes to the graphics state will not be visible outside the group.

cr :

a cairo context

Returns :

a newly created (surface) pattern containing the results of all drawing operations performed to the group. The caller owns the returned object and should call cairo_pattern_destroy() when finished with it.

Since 1.2


cairo_pop_group_to_source ()

void                cairo_pop_group_to_source           (cairo_t *cr);

Terminates the redirection begun by a call to cairo_push_group() or cairo_push_group_with_content() and installs the resulting pattern as the source pattern in the given cairo context.

The behavior of this function is equivalent to the sequence of operations:

cairo_pattern_t *group = cairo_pop_group (cr);
cairo_set_source (cr, group);
cairo_pattern_destroy (group);

but is more convenient as their is no need for a variable to store the short-lived pointer to the pattern.

The cairo_pop_group() function calls cairo_restore(), (balancing a call to cairo_save() by the push_group function), so that any changes to the graphics state will not be visible outside the group.

cr :

a cairo context

Since 1.2


cairo_get_group_target ()

cairo_surface_t*    cairo_get_group_target              (cairo_t *cr);

Gets the target surface for the current group as started by the most recent call to cairo_push_group() or cairo_push_group_with_content().

This function will return NULL if called "outside" of any group rendering blocks, (that is, after the last balancing call to cairo_pop_group() or cairo_pop_group_to_source()).

cr :

a cairo context

Returns :

the target group surface, or NULL if none. This object is owned by cairo. To keep a reference to it, you must call cairo_surface_reference().

Since 1.2


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.

cr :

a cairo context

red :

red component of color

green :

green component of color

blue :

blue component of color

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.

cr :

a cairo context

red :

red component of color

green :

green component of color

blue :

blue component of color

alpha :

alpha component of color

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).

cr :

a cairo context

source :

a cairo_pattern_t to be used as the source for subsequent drawing operations.

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()).

cr :

a cairo context

surface :

a surface to be used to set the source pattern

x :

User-space X coordinate for surface origin

y :

User-space Y coordinate for surface origin

cairo_get_source ()

cairo_pattern_t*    cairo_get_source                    (cairo_t *cr);

Gets the current source pattern for cr.

cr :

a cairo context

Returns :

the current source pattern. This object is owned by cairo. To keep a reference to it, you must call cairo_pattern_reference().

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_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

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().

cr :

a cairo_t

antialias :

the new antialiasing mode

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().

cr :

a cairo context

Returns :

the current shape antialiasing mode.

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 length of alternate "on" and "off" portions of the stroke. The offset specifies an offset into the pattern at which the stroke begins.

Each "on" segment will have caps applied as if the segment were a separate sub-path. In particular, it is valid to use an "on" length of 0.0 with CAIRO_LINE_CAP_ROUND or CAIRO_LINE_CAP_SQUARE in order to distributed dots or squares along a path.

Note: The length values are in user-space units as evaluated at the time of stroking. This is not necessarily the same as the user space at the time of cairo_set_dash().

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.

cr :

a cairo context

dashes :

an array specifying alternate lengths of on and off stroke portions

num_dashes :

the length of the dashes array

offset :

an offset into the dash pattern at which the stroke should start

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_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_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.

cr :

a cairo_t

fill_rule :

a fill rule, specified as a cairo_fill_rule_t

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().

cr :

a cairo context

Returns :

the current 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_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

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.

cr :

a cairo context, as a cairo_t

line_cap :

a line cap style, as a cairo_line_cap_t

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().

cr :

a cairo context

Returns :

the current line cap style.

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.

cr :

a cairo context, as a cairo_t

line_join :

a line joint style, as a cairo_line_join_t

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().

cr :

a cairo context

Returns :

the current line join style.

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 value specifies the diameter of a pen that is circular in user space, (though device-space pen may be an ellipse in general due to scaling/shear/rotation of the CTM).

Note: When the description above refers to user space and CTM it refers to the user space and CTM in effect at the time of the stroking operation, not the user space and CTM in effect at the time of the call to cairo_set_line_width(). The simplest usage makes both of these spaces identical. That is, if there is no change to the CTM between a call to cairo_set_line_with() and the stroking operation, then one can just pass user-space values to cairo_set_line_width() and ignore this note.

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

The default line width value is 2.0.

cr :

a cairo_t

width :

a line width

cairo_get_line_width ()

double              cairo_get_line_width                (cairo_t *cr);

cr :

a cairo context

Returns :

the current line width value exactly as set by cairo_set_line_width(). Note that the value is unchanged even if the CTM has changed between the calls to cairo_set_line_width() and cairo_get_line_width().

cairo_set_miter_limit ()

void                cairo_set_miter_limit               (cairo_t *cr,
                                                         double limit);

cr :

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().

cr :

a cairo context

Returns :

the current 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).

cr :

a cairo_t

op :

a compositing operator, specified as a cairo_operator_t

cairo_get_operator ()

cairo_operator_t    cairo_get_operator                  (cairo_t *cr);

Gets the current compositing operator for a cairo context.

cr :

a cairo context

Returns :

the current compositing operator.

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.)

cr :

a cairo_t

tolerance :

the tolerance, in device units (typically pixels)

cairo_get_tolerance ()

double              cairo_get_tolerance                 (cairo_t *cr);

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

cr :

a cairo context

Returns :

the current tolerance value.

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().

cr :

a cairo context

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().

cr :

a cairo context

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.

cr :

a cairo context

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().

cr :

a cairo context

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().

cr :

a cairo context

cairo_fill_extents ()

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

cr :

x1 :

y1 :

x2 :

y2 :


cairo_in_fill ()

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

cr :

x :

y :

Returns :


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.)

cr :

a cairo context

pattern :

a cairo_pattern_t

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.)

cr :

a cairo context

surface :

a cairo_surface_t

surface_x :

X coordinate at which to place the origin of surface

surface_y :

Y coordinate at which to place the origin of surface

cairo_paint ()

void                cairo_paint                         (cairo_t *cr);

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

cr :

a cairo context

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.

cr :

a cairo context

alpha :

alpha value, between 0 (transparent) and 1 (opaque)

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().

Note: Degenerate segments and sub-paths are treated specially and provide a useful result. These can result in two different situations:

1. Zero-length "on" segments set in cairo_set_dash(). If the cap style is CAIRO_LINE_CAP_ROUND or CAIRO_LINE_CAP_SQUARE then these segments will be drawn as circular dots or squares respectively. In the case of CAIRO_LINE_CAP_SQUARE, the orientation of the squares is determined by the direction of the underlying path.

2. A sub-path created by cairo_move_to() followed by either a cairo_close_path() or one or more calls to cairo_line_to() to the same coordinate as the cairo_move_to(). If the cap style is CAIRO_LINE_CAP_ROUND then these sub-paths will be drawn as circular dots. Note that in the case of CAIRO_LINE_CAP_SQUARE a degenerate sub-path will not be drawn at all, (since the correct orientation is indeterminate).

In no case will a cap style of CAIRO_LINE_CAP_BUTT cause anything to be drawn in the case of either degenerate segments or sub-paths.

cr :

a cairo context

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().

cr :

a cairo context

cairo_stroke_extents ()

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

cr :

x1 :

y1 :

x2 :

y2 :


cairo_in_stroke ()

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

cr :

x :

y :

Returns :


cairo_copy_page ()

void                cairo_copy_page                     (cairo_t *cr);

cr :


cairo_show_page ()

void                cairo_show_page                     (cairo_t *cr);

cr :