cairo_surface_t

typedef struct _cairo_surface cairo_surface_t;

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().

enum cairo_content_t

typedef enum _cairo_content {
    CAIRO_CONTENT_COLOR		= 0x1000,
    CAIRO_CONTENT_ALPHA		= 0x2000,
    CAIRO_CONTENT_COLOR_ALPHA	= 0x3000
} cairo_content_t;

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.

cairo_surface_create_similar ()

cairo_surface_t*    cairo_surface_create_similar        (cairo_surface_t *other,
                                                         cairo_content_t content,
                                                         int width,
                                                         int height);

Create a new surface that is as compatible as possible with an existing surface. For example the new surface will have the same fallback resolution and font options as other. Generally, the new surface will also use the same backend as other, unless that is not possible for some reason. The type of the returned surface may be examined with cairo_surface_get_type().

Initially the surface contents are all 0 (transparent if contents have transparency, black otherwise.)

cairo_surface_reference ()

cairo_surface_t*    cairo_surface_reference             (cairo_surface_t *surface);

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

The number of references to a cairo_surface_t can be get using cairo_surface_get_reference_count().

cairo_surface_destroy ()

void                cairo_surface_destroy               (cairo_surface_t *surface);

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

cairo_surface_status ()

cairo_status_t      cairo_surface_status                (cairo_surface_t *surface);

Checks whether an error has previously occurred for this surface.

cairo_surface_finish ()

void                cairo_surface_finish                (cairo_surface_t *surface);

This function finishes the surface and drops all references to external resources. For example, for the Xlib backend it means that cairo will no longer access the drawable, which can be freed. After calling cairo_surface_finish() the only valid operations on a surface are getting and setting user data and referencing and destroying it. Further drawing to the surface will not affect the surface but will instead trigger a CAIRO_STATUS_SURFACE_FINISHED error.

When the last call to cairo_surface_destroy() decreases the reference count to zero, cairo will call cairo_surface_finish() if it hasn't been called already, before freeing the resources associated with the surface.

cairo_surface_flush ()

void                cairo_surface_flush                 (cairo_surface_t *surface);

Do any pending drawing for the surface and also restore any temporary modification's cairo has made to the surface's state. This function must be called before switching from drawing on the surface with cairo to drawing on it directly with native APIs. If the surface doesn't support direct access, then this function does nothing.

cairo_surface_get_font_options ()

void                cairo_surface_get_font_options      (cairo_surface_t *surface,
                                                         cairo_font_options_t *options);

Retrieves the default font rendering options for the surface. This allows display surfaces to report the correct subpixel order for rendering on them, print surfaces to disable hinting of metrics and so forth. The result can then be used with cairo_scaled_font_create().

cairo_surface_get_content ()

cairo_content_t     cairo_surface_get_content           (cairo_surface_t *surface);

This function returns the content type of surface which indicates whether the surface contains color and/or alpha information. See cairo_content_t.

Since 1.2

cairo_surface_mark_dirty ()

void                cairo_surface_mark_dirty            (cairo_surface_t *surface);

Tells cairo that drawing has been done to surface using means other than cairo, and that cairo should reread any cached areas. Note that you must call cairo_surface_flush() before doing such drawing.

cairo_surface_mark_dirty_rectangle ()

void                cairo_surface_mark_dirty_rectangle  (cairo_surface_t *surface,
                                                         int x,
                                                         int y,
                                                         int width,
                                                         int height);

Like cairo_surface_mark_dirty(), but drawing has been done only to the specified rectangle, so that cairo can retain cached contents for other parts of the surface.

Any cached clip set on the surface will be reset by this function, to make sure that future cairo calls have the clip set that they expect.

cairo_surface_set_device_offset ()

void                cairo_surface_set_device_offset     (cairo_surface_t *surface,
                                                         double x_offset,
                                                         double y_offset);

Sets an offset that is added to the device coordinates determined by the CTM when drawing to surface. One use case for this function is when we want to create a cairo_surface_t that redirects drawing for a portion of an onscreen surface to an offscreen surface in a way that is completely invisible to the user of the cairo API. Setting a transformation via cairo_translate() isn't sufficient to do this, since functions like cairo_device_to_user() will expose the hidden offset.

Note that the offset affects drawing to the surface as well as using the surface in a source pattern.

cairo_surface_get_device_offset ()

void                cairo_surface_get_device_offset     (cairo_surface_t *surface,
                                                         double *x_offset,
                                                         double *y_offset);

This function returns the previous device offset set by cairo_surface_set_device_offset().

Since 1.2

cairo_surface_set_fallback_resolution ()

void                cairo_surface_set_fallback_resolution
                                                        (cairo_surface_t *surface,
                                                         double x_pixels_per_inch,
                                                         double y_pixels_per_inch);

Set the horizontal and vertical resolution for image fallbacks.

When certain operations aren't supported natively by a backend, cairo will fallback by rendering operations to an image and then overlaying that image onto the output. For backends that are natively vector-oriented, this function can be used to set the resolution used for these image fallbacks, (larger values will result in more detailed images, but also larger file sizes).

Some examples of natively vector-oriented backends are the ps, pdf, and svg backends.

For backends that are natively raster-oriented, image fallbacks are still possible, but they are always performed at the native device resolution. So this function has no effect on those backends.

NOTE: The fallback resolution only takes effect at the time of completing a page (with cairo_show_page() or cairo_copy_page()) so there is currently no way to have more than one fallback resolution in effect on a single page.

Since 1.2

enum cairo_surface_type_t

typedef enum _cairo_surface_type {
    CAIRO_SURFACE_TYPE_IMAGE,
    CAIRO_SURFACE_TYPE_PDF,
    CAIRO_SURFACE_TYPE_PS,
    CAIRO_SURFACE_TYPE_XLIB,
    CAIRO_SURFACE_TYPE_XCB,
    CAIRO_SURFACE_TYPE_GLITZ,
    CAIRO_SURFACE_TYPE_QUARTZ,
    CAIRO_SURFACE_TYPE_WIN32,
    CAIRO_SURFACE_TYPE_BEOS,
    CAIRO_SURFACE_TYPE_DIRECTFB,
    CAIRO_SURFACE_TYPE_SVG,
    CAIRO_SURFACE_TYPE_OS2
} cairo_surface_type_t;

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 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_surface_get_type ()

cairo_surface_type_t cairo_surface_get_type             (cairo_surface_t *surface);

This function returns the type of the backend used to create a surface. See cairo_surface_type_t for available types.

Since 1.2

cairo_surface_get_reference_count ()

unsigned int        cairo_surface_get_reference_count   (cairo_surface_t *surface);

Returns the current reference count of surface.

Since 1.4

cairo_surface_set_user_data ()

cairo_status_t      cairo_surface_set_user_data         (cairo_surface_t *surface,
                                                         const cairo_user_data_key_t *key,
                                                         void *user_data,
                                                         cairo_destroy_func_t destroy);

Attach user data to surface. To remove user data from a surface, call this function with the key that was used to set it and NULL for data.

cairo_surface_get_user_data ()

void*               cairo_surface_get_user_data         (cairo_surface_t *surface,
                                                         const cairo_user_data_key_t *key);

Return user data previously attached to surface using the specified key. If no user data has been attached with the given key this function returns NULL.