Cairo Interaction: GDK 2 Reference Manual

Cairo Interaction

Cairo Interaction — Functions to support using Cairo

Functions

cairo_surface_t *	gdk_window_create_similar_surface ()
cairo_t *	gdk_cairo_create ()
void	gdk_cairo_set_source_color ()
void	gdk_cairo_set_source_pixbuf ()
void	gdk_cairo_set_source_pixmap ()
void	gdk_cairo_set_source_window ()
void	gdk_cairo_rectangle ()
void	gdk_cairo_region ()
void	gdk_cairo_reset_clip ()

Includes

#include <gdk/gdk.h>

Description

Cairo is a graphics library that supports vector graphics and image compositing that can be used with GDK. Since 2.8, GTK+ does most of its drawing using Cairo.

GDK does not wrap the Cairo API, instead it allows to create Cairo contexts which can be used to draw on GDK drawables. Additional functions allow to convert GDK's rectangles and regions into Cairo paths and to use pixbufs as sources for drawing operations.

Functions

gdk_window_create_similar_surface ()

cairo_surface_t *
gdk_window_create_similar_surface (GdkWindow *window,
                                   cairo_content_t content,
                                   int width,
                                   int height);

Create a new surface that is as compatible as possible with the given window . For example the new surface will have the same fallback resolution and font options as window . Generally, the new surface will also use the same backend as window , 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.)

Parameters

window	window to make new surface similar to
content	the content for the new surface
width	width of the new surface
height	height of the new surface

Returns

a pointer to the newly allocated surface. The caller owns the surface and should call cairo_surface_destroy() when done with it.

This function always returns a valid pointer, but it will return a pointer to a "nil" surface if other is already in an error state or any other error occurs.

Since: 2.22

gdk_cairo_create ()

cairo_t *
gdk_cairo_create (GdkDrawable *drawable);

Creates a Cairo context for drawing to drawable .

Note that due to double-buffering, Cairo contexts created in a GTK+ expose event handler cannot be cached and reused between different expose events.

Parameters

drawable

a GdkDrawable

Returns

A newly created Cairo context. Free with cairo_destroy() when you are done drawing.

Since: 2.8

gdk_cairo_set_source_color ()

void
gdk_cairo_set_source_color (cairo_t *cr,
                            const GdkColor *color);

Sets the specified GdkColor as the source color of cr .

Parameters

cr	a cairo_t
color	a GdkColor

Since: 2.8

gdk_cairo_set_source_pixbuf ()

void
gdk_cairo_set_source_pixbuf (cairo_t *cr,
                             const GdkPixbuf *pixbuf,
                             double pixbuf_x,
                             double pixbuf_y);

Sets the given pixbuf as the source pattern for the Cairo context. The pattern has an extend mode of CAIRO_EXTEND_NONE and is aligned so that the origin of pixbuf is pixbuf_x , pixbuf_y

Parameters

cr	a Cairo context
pixbuf	a GdkPixbuf
pixbuf_x	X coordinate of location to place upper left corner of `pixbuf`
pixbuf_y	Y coordinate of location to place upper left corner of `pixbuf`

Since: 2.8

gdk_cairo_set_source_pixmap ()

void
gdk_cairo_set_source_pixmap (cairo_t *cr,
                             GdkPixmap *pixmap,
                             double pixmap_x,
                             double pixmap_y);

gdk_cairo_set_source_pixmap has been deprecated since version 2.24 and should not be used in newly-written code.

This function is being removed in GTK+ 3 (together with GdkPixmap). Instead, use gdk_cairo_set_source_window() where appropriate.

Sets the given pixmap as the source pattern for the Cairo context. The pattern has an extend mode of CAIRO_EXTEND_NONE and is aligned so that the origin of pixmap is pixmap_x , pixmap_y

Parameters

cr	a Cairo context
pixmap	a GdkPixmap
pixmap_x	X coordinate of location to place upper left corner of `pixmap`
pixmap_y	Y coordinate of location to place upper left corner of `pixmap`

Since: 2.10

gdk_cairo_set_source_window ()

void
gdk_cairo_set_source_window (cairo_t *cr,
                             GdkWindow *window,
                             double x,
                             double y);

Sets the given window as the source pattern for the Cairo context. The pattern has an extend mode of CAIRO_EXTEND_NONE and is aligned so that the origin of window is x , y . The window contains all its subwindows when rendering.

Note that the contents of window are undefined outside of the visible part of window , so use this function with care.

Parameters

cr	a Cairo context
window	a GdkWindow
x	X coordinate of location to place upper left corner of `window`
y	Y coordinate of location to place upper left corner of `window`

Since: 2.24

gdk_cairo_rectangle ()

void
gdk_cairo_rectangle (cairo_t *cr,
                     const GdkRectangle *rectangle);

Adds the given rectangle to the current path of cr .

Parameters

cr	a cairo_t
rectangle	a GdkRectangle

Since: 2.8

gdk_cairo_region ()

void
gdk_cairo_region (cairo_t *cr,
                  const GdkRegion *region);

Adds the given region to the current path of cr .

Parameters

cr	a cairo_t
region	a GdkRegion

Since: 2.8

gdk_cairo_reset_clip ()

void
gdk_cairo_reset_clip (cairo_t *cr,
                      GdkDrawable *drawable);

Resets the clip region for a Cairo context created by gdk_cairo_create().

This resets the clip region to the "empty" state for the given drawable. This is required for non-native windows since a direct call to cairo_reset_clip() would unset the clip region inherited from the drawable (i.e. the window clip region), and thus let you e.g. draw outside your window.

This is rarely needed though, since most code just create a new cairo_t using gdk_cairo_create() each time they want to draw something.

Parameters

cr	a cairo_t
drawable	a GdkDrawable

Since: 2.18