GnomeCanvas

typedef struct _GnomeCanvas GnomeCanvas;

This should not be accessed directly. Use the accessor functions as described below.

GNOME_CANVAS_EPSILON

#define GNOME_CANVAS_EPSILON 1e-10

A tiny value used by internal canvas operations.

GNOME_CANVAS_COLOR()

#define     GNOME_CANVAS_COLOR(r, g, b)

Macro for creating a canvas 32 bit RGBA color from red, green and blue components.

GNOME_CANVAS_COLOR_A()

#define     GNOME_CANVAS_COLOR_A(r, g, b, a)

Macro for creating a canvas 32 bit RGBA color from red, green, blue and alpha components.

GnomeCanvasBuf

typedef struct {
	/* 24-bit RGB buffer for rendering */
	guchar *buf;

	/* Rectangle describing the rendering area */
	ArtIRect rect;

	/* Rowstride for the buffer */
	int buf_rowstride;

	/* Background color, given as 0xrrggbb */
	guint32 bg_color;

	/* Invariant: at least one of the following flags is true. */

	/* Set when the render rectangle area is the solid color bg_color */
	unsigned int is_bg : 1;

	/* Set when the render rectangle area is represented by the buf */
	unsigned int is_buf : 1;
} GnomeCanvasBuf;

A buffer used for rendering for antialiased mode canvas widgets.

gnome_canvas_new ()

GtkWidget*  gnome_canvas_new                (void);

Creates a new empty canvas in non-antialiased mode.

gnome_canvas_new_aa ()

GtkWidget*  gnome_canvas_new_aa             (void);

Creates a new empty canvas in antialiased mode.

gnome_canvas_root ()

GnomeCanvasGroup* gnome_canvas_root         (GnomeCanvas *canvas);

Queries the root group of a canvas.

gnome_canvas_set_scroll_region ()

void        gnome_canvas_set_scroll_region  (GnomeCanvas *canvas,
                                             double x1,
                                             double y1,
                                             double x2,
                                             double y2);

Sets the scrolling region of a canvas to the specified rectangle. The canvas will then be able to scroll only within this region. The view of the canvas is adjusted as appropriate to display as much of the new region as possible.

gnome_canvas_get_scroll_region ()

void        gnome_canvas_get_scroll_region  (GnomeCanvas *canvas,
                                             double *x1,
                                             double *y1,
                                             double *x2,
                                             double *y2);

Queries the scrolling region of a canvas.

gnome_canvas_set_center_scroll_region ()

void        gnome_canvas_set_center_scroll_region
                                            (GnomeCanvas *canvas,
                                             gboolean center_scroll_region);

When the scrolling region of the canvas is smaller than the canvas window, e.g. the allocation of the canvas, it can be either centered on the window or simply made to be on the upper-left corner on the window. This function lets you configure this property.

gnome_canvas_get_center_scroll_region ()

gboolean    gnome_canvas_get_center_scroll_region
                                            (GnomeCanvas *canvas);

Returns whether the canvas is set to center the scrolling region in the window if the former is smaller than the canvas' allocation.

gnome_canvas_set_pixels_per_unit ()

void        gnome_canvas_set_pixels_per_unit
                                            (GnomeCanvas *canvas,
                                             double n);

Sets the zooming factor of a canvas by specifying the number of pixels that correspond to one canvas unit.

The anchor point for zooming, i.e. the point that stays fixed and all others zoom inwards or outwards from it, depends on whether the canvas is set to center the scrolling region or not. You can control this using the gnome_canvas_set_center_scroll_region() function. If the canvas is set to center the scroll region, then the center of the canvas window is used as the anchor point for zooming. Otherwise, the upper-left corner of the canvas window is used as the anchor point.

gnome_canvas_scroll_to ()

void        gnome_canvas_scroll_to          (GnomeCanvas *canvas,
                                             int cx,
                                             int cy);

Makes a canvas scroll to the specified offsets, given in canvas pixel units. The canvas will adjust the view so that it is not outside the scrolling region. This function is typically not used, as it is better to hook scrollbars to the canvas layout's scrolling adjusments.

gnome_canvas_get_scroll_offsets ()

void        gnome_canvas_get_scroll_offsets (GnomeCanvas *canvas,
                                             int *cx,
                                             int *cy);

Queries the scrolling offsets of a canvas. The values are returned in canvas pixel units.

gnome_canvas_update_now ()

void        gnome_canvas_update_now         (GnomeCanvas *canvas);

Forces an immediate update and redraw of a canvas. If the canvas does not have any pending update or redraw requests, then no action is taken. This is typically only used by applications that need explicit control of when the display is updated, like games. It is not needed by normal applications.

gnome_canvas_get_item_at ()

GnomeCanvasItem* gnome_canvas_get_item_at   (GnomeCanvas *canvas,
                                             double x,
                                             double y);

Looks for the item that is under the specified position, which must be specified in world coordinates.

gnome_canvas_request_redraw_uta ()

void        gnome_canvas_request_redraw_uta (GnomeCanvas *canvas,
                                             ArtUta *uta);

Informs a canvas that the specified area, given as a microtile array, needs to be repainted. To be used only by item implementations.

gnome_canvas_request_redraw ()

void        gnome_canvas_request_redraw     (GnomeCanvas *canvas,
                                             int x1,
                                             int y1,
                                             int x2,
                                             int y2);

Convenience function that informs a canvas that the specified rectangle needs to be repainted. This function converts the rectangle to a microtile array and feeds it to gnome_canvas_request_redraw_uta(). The rectangle includes x1 and y1, but not x2 and y2. To be used only by item implementations.

gnome_canvas_w2c_affine ()

void        gnome_canvas_w2c_affine         (GnomeCanvas *canvas,
                                             double affine[6]);

Gets the affine transform that converts from world coordinates to canvas pixel coordinates.

gnome_canvas_w2c ()

void        gnome_canvas_w2c                (GnomeCanvas *canvas,
                                             double wx,
                                             double wy,
                                             int *cx,
                                             int *cy);

Converts world coordinates into canvas pixel coordinates.

gnome_canvas_w2c_d ()

void        gnome_canvas_w2c_d              (GnomeCanvas *canvas,
                                             double wx,
                                             double wy,
                                             double *cx,
                                             double *cy);

Converts world coordinates into canvas pixel coordinates. This version returns coordinates in floating point coordinates, for greater precision.

gnome_canvas_c2w ()

void        gnome_canvas_c2w                (GnomeCanvas *canvas,
                                             int cx,
                                             int cy,
                                             double *wx,
                                             double *wy);

Converts canvas pixel coordinates to world coordinates.

gnome_canvas_window_to_world ()

void        gnome_canvas_window_to_world    (GnomeCanvas *canvas,
                                             double winx,
                                             double winy,
                                             double *worldx,
                                             double *worldy);

Converts window-relative coordinates into world coordinates. You can use this when you need to convert mouse coordinates into world coordinates, for example.

gnome_canvas_world_to_window ()

void        gnome_canvas_world_to_window    (GnomeCanvas *canvas,
                                             double worldx,
                                             double worldy,
                                             double *winx,
                                             double *winy);

Converts world coordinates into window-relative coordinates.

gnome_canvas_get_color ()

int         gnome_canvas_get_color          (GnomeCanvas *canvas,
                                             const char *spec,
                                             GdkColor *color);

Allocates a color based on the specified X color specification. As a convenience to item implementations, it returns TRUE if the color was allocated, or FALSE if the specification was NULL. A NULL color specification is considered as "transparent" by the canvas.

gnome_canvas_get_color_pixel ()

gulong      gnome_canvas_get_color_pixel    (GnomeCanvas *canvas,
                                             guint rgba);

Allocates a color from the RGBA value passed into this function. The alpha opacity value is discarded, since normal X colors do not support it.

gnome_canvas_set_stipple_origin ()

void        gnome_canvas_set_stipple_origin (GnomeCanvas *canvas,
                                             GdkGC *gc);

Sets the stipple origin of the specified GC as is appropriate for the canvas, so that it will be aligned with other stipple patterns used by canvas items. This is typically only needed by item implementations.

gnome_canvas_set_dither ()

void        gnome_canvas_set_dither         (GnomeCanvas *canvas,
                                             GdkRgbDither dither);

Controls dithered rendering for antialiased canvases. The value of dither should be GDK_RGB_DITHER_NONE, GDK_RGB_DITHER_NORMAL, or GDK_RGB_DITHER_MAX. The default canvas setting is GDK_RGB_DITHER_NORMAL.

gnome_canvas_get_dither ()

GdkRgbDither gnome_canvas_get_dither        (GnomeCanvas *canvas);

Returns the type of dithering used to render an antialiased canvas.

The "aa" property

  "aa"                   gboolean              : Read / Write / Construct Only

Enable anti-aliasing mode?

Note that this parameter can only be set at the time of object construction. The same effect can be achieved by calling gnome_canvas_new() to create new non-aa canvas or gnome_canvas_new_aa() for an anti-aliased canvas.

Default value: FALSE

The "draw-background" signal

void        user_function                  (GnomeCanvas *canvas,
                                            GdkDrawable *arg1,
                                            gint arg2,
                                            gint arg3,
                                            gint arg4,
                                            gint arg5,
                                            gpointer user_data);

This signal is emitted to draw the background for non-antialiased mode canvas widgets. The default method uses the canvas widget's style to draw the background.

The "render-background" signal

void        user_function                  (GnomeCanvas *canvas,
                                            gpointer arg1,
                                            gpointer user_data);

This signal is emitted for antialiased mode canvas widgets to render the background. The buf data structure contains both a pointer to a packed 24-bit RGB array and the coordinates.