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GocItem

GocItem — Base canvas item.

Synopsis

                    GocItem;
                    GocItemClass;
GocItem *           goc_item_new                        (GocGroup *parent,
                                                         GType type,
                                                         const gchar *first_arg_name,
                                                         ...);
void                goc_item_destroy                    (GocItem *item);
void                goc_item_set                        (GocItem *item,
                                                         const gchar *first_arg_name,
                                                         ...);
double              goc_item_distance                   (GocItem *item,
                                                         double x,
                                                         double y,
                                                         GocItem **near_item);
void                goc_item_draw                       (GocItem const *item,
                                                         cairo_t *cr);
gboolean            goc_item_draw_region                (GocItem const *item,
                                                         cairo_t *cr,
                                                         double x0,
                                                         double y0,
                                                         double x1,
                                                         double y1);
void                goc_item_invalidate                 (GocItem *item);
void                goc_item_show                       (GocItem *item);
void                goc_item_hide                       (GocItem *item);
gboolean            goc_item_is_visible                 (GocItem *item);
void                goc_item_get_bounds                 (GocItem const *item,
                                                         double *x0,
                                                         double *y0,
                                                         double *x1,
                                                         double *y1);
void                goc_item_bounds_changed             (GocItem *item);
void                goc_item_grab                       (GocItem *item);
void                goc_item_ungrab                     (GocItem *item);
void                goc_item_raise                      (GocItem *item,
                                                         int n);
void                goc_item_lower                      (GocItem *item,
                                                         int n);
void                goc_item_lower_to_bottom            (GocItem *item);
void                goc_item_raise_to_top               (GocItem *item);

Object Hierarchy

  GObject
   +----GocItem
         +----GocStyledItem
         +----GocGraph
         +----GocGroup
         +----GocPixbuf
         +----GocWidget

Properties

  "canvas"                   GocCanvas*            : Read
  "parent"                   GocGroup*             : Read

Description

GocItem is the virtual base object for canvas items.

Details

GocItem

typedef struct _GocItem GocItem;

GocItem contains the following fields:

double x0; The lowest horizontal bound of the item.
double y0; The lowest vertical bound of the item.
double x1; The highest horizontal bound of the item.
double y1; The highest vertical bound of the item.

The various fields should not be accessed directly except from children objects which must update x0, y0, x1, and y1 from their update_bounds method. All other fields are read-only and not documented.


GocItemClass

typedef struct {
	GObjectClass	 base;

	double			(*distance) (GocItem *item,
					     double x, double y, GocItem **near_item);
	void			(*draw) (GocItem const *item, cairo_t *cr);
	gboolean		(*draw_region) (GocItem const *item, cairo_t *cr,
						double x0, double y0, double x1, double y1);
	void			(*update_bounds) (GocItem *item);
	/* events related functions */
	gboolean		(*button_pressed) (GocItem *item, int button, double x, double y);
	gboolean		(*button2_pressed) (GocItem *item, int button, double x, double y);
	gboolean		(*button_released) (GocItem *item, int button, double x, double y);
	gboolean		(*motion) (GocItem *item, double x, double y);
	gboolean		(*enter_notify) (GocItem *item, double x, double y);
	gboolean		(*leave_notify) (GocItem *item, double x, double y);
	void			(*realize) (GocItem *item);
	void			(*unrealize) (GocItem *item);
	gboolean		(*key_pressed) (GocItem *item, GdkEventKey* ev);
	gboolean		(*key_released) (GocItem *item, GdkEventKey* ev);
	void			(*notify_scrolled) (GocItem *item);
} GocItemClass;

The base class for all canvas items.

GObjectClass base;

the parent class

distance ()

returns the distance between the item and the point defined by x and y. When the distance is larger than a few pixels, the result is not relevant, so an approximate value or even G_MAXDOUBLE might be returned.

draw ()

draws the item to the cairo context.

draw_region ()

draws the item in the region defined by x0, y0, x1 and y1. Should return TRUE when successfull. If FALSE is returned, draw will be called. There is no need to implement both methods for an item. Large items should implement draw_region.

update_bounds ()

updates the bounds stored in GocItem as fields x0, y0, x1,and y1.

button_pressed ()

callback for a button press event.

button2_pressed ()

callback for a double click event.

button_released ()

callback for a button release event.

motion ()

callback for a motion event.

enter_notify ()

callback for an enter notify event.

leave_notify ()

callback for a leave notify event.

realize ()

callback for a realizes event.

unrealize ()

callback for an unrealize event.

key_pressed ()

callback for a key press event.

key_released ()

callback for a key release event.

notify_scrolled ()

callback for a notify scrolled event. This is useful to reposition children of the GtkLayout parent of the canvas to their new position.

goc_item_new ()

GocItem *           goc_item_new                        (GocGroup *parent,
                                                         GType type,
                                                         const gchar *first_arg_name,
                                                         ...);

Creates a new item of type type in group group. Properties can be set just the same way they are in g_object_new.

parent :

parent GocGroup for the new item

type :

GType of the new item

first_arg_name :

property name or NULL

... :

value for the first property, followed optionally by more name/value pairs, followed by NULL

Returns :

the newly created GocItem.

goc_item_destroy ()

void                goc_item_destroy                    (GocItem *item);

Destroys item, removes it from its parent group and updates the canvas accordingly.

item :

GocItem

goc_item_set ()

void                goc_item_set                        (GocItem *item,
                                                         const gchar *first_arg_name,
                                                         ...);

Set properties and updates the canvas. Using g_object_set instead would set the properties, but not update the canvas.

item :

GocItem

first_arg_name :

property name or NULL

... :

value for the first property, followed optionally by more name/value pairs, followed by NULL

goc_item_distance ()

double              goc_item_distance                   (GocItem *item,
                                                         double x,
                                                         double y,
                                                         GocItem **near_item);

Evaluates the distance between the point with canvas coordinates x,y and the nearest point of item. near_item is set with either item or its appropriate child.

item :

GocItem

x :

horizontal position

y :

vertical position

near_item :

where to store the nearest item

Returns :

the evaluated distance.

goc_item_draw ()

void                goc_item_draw                       (GocItem const *item,
                                                         cairo_t *cr);

Renders item using cr. There is no need to call this function directly. Invalidating the item is the way to go.

item :

GocItem

cr :

cairo_t

goc_item_draw_region ()

gboolean            goc_item_draw_region                (GocItem const *item,
                                                         cairo_t *cr,
                                                         double x0,
                                                         double y0,
                                                         double x1,
                                                         double y1);

Renders item using cr, limiting all drawings to the region limited by x0, y0, x1, and y1. If this function returns FALSE, goc_item_draw should be called. There is no need to call this function directly. Invalidating the item is the way to go.

item :

GocItem

cr :

cairo_t

x0 :

the lowest horizontal bound of the region to draw

y0 :

the lowest vertical bound of the region to draw

x1 :

the highest horizontal bound of the region to draw

y1 :

the highest vertical bound of the region to draw

Returns :

TRUE if successful.

goc_item_invalidate ()

void                goc_item_invalidate                 (GocItem *item);

Force a redraw of item bounding region.

item :

GocItem

goc_item_show ()

void                goc_item_show                       (GocItem *item);

Makes item visible.

item :

GocItem

goc_item_hide ()

void                goc_item_hide                       (GocItem *item);

Hides item.

item :

GocItem

goc_item_is_visible ()

gboolean            goc_item_is_visible                 (GocItem *item);

item :

GocItem

Returns :

TRUE if item is visible.

goc_item_get_bounds ()

void                goc_item_get_bounds                 (GocItem const *item,
                                                         double *x0,
                                                         double *y0,
                                                         double *x1,
                                                         double *y1);

Retrieves the bounds of item in canvas coordinates.

item :

GocItem

x0 :

where to store the lowest horizontal bound

y0 :

where to store the lowest vertical bound

x1 :

where to store the highest horizontal bound

y1 :

where to store the highest vertical bound

goc_item_bounds_changed ()

void                goc_item_bounds_changed             (GocItem *item);

This function needs to be called each time the bounds of item change. It is normally called from inside the implementation of items derived classes.

item :

GocItem

goc_item_grab ()

void                goc_item_grab                       (GocItem *item);

Grabs the item. This function will fail if another item is grabbed.

item :

GocItem

goc_item_ungrab ()

void                goc_item_ungrab                     (GocItem *item);

Ungrabs the item. This function will fail if item is not grabbed.

item :

GocItem

goc_item_raise ()

void                goc_item_raise                      (GocItem *item,
                                                         int n);

Raises item by n steps inside its parent GocGroup (or less if the list is too short) in the item list so that it is displayed nearer the top of the items stack.

item :

GocItem

n :

the rank change

goc_item_lower ()

void                goc_item_lower                      (GocItem *item,
                                                         int n);

Lowers item by n steps inside its parent GocGroup (or less if the list is too short) in the item list so that it is displayed more deeply in the items stack.

item :

GocItem

n :

the rank change

goc_item_lower_to_bottom ()

void                goc_item_lower_to_bottom            (GocItem *item);

Lowers item to bottom inside its parent GocGroup so that it will be at least partly hidden by any overlapping item.

item :

GocItem

goc_item_raise_to_top ()

void                goc_item_raise_to_top               (GocItem *item);

Raises item to front so that it becomes the toplevel item inside its parent GocGroup.

item :

GocItem

Property Details

The "canvas" property

  "canvas"                   GocCanvas*            : Read

The canvas object on which the item resides.


The "parent" property

  "parent"                   GocGroup*             : Read

The group in which the item resides.

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