| GNOME Canvas Library Reference Manual | ||||
|---|---|---|---|---|
| Top | Description | ||||
#include <libgnomecanvas/libgnomecanvas.h>
GnomeCanvasPoints;
GnomeCanvasPoints * gnome_canvas_points_new (int num_points);
GnomeCanvasPoints * gnome_canvas_points_ref (GnomeCanvasPoints *points);
#define gnome_canvas_points_unref
void gnome_canvas_points_free (GnomeCanvasPoints *points);
int gnome_canvas_get_miter_points (double x1,
double y1,
double x2,
double y2,
double x3,
double y3,
double width,
double *mx1,
double *my1,
double *mx2,
double *my2);
void gnome_canvas_get_butt_points (double x1,
double y1,
double x2,
double y2,
double width,
int project,
double *bx1,
double *by1,
double *bx2,
double *by2);
double gnome_canvas_polygon_to_point (double *poly,
int num_points,
double x,
double y);
void gnome_canvas_render_svp (GnomeCanvasBuf *buf,
ArtSVP *svp,
guint32 rgba);
void gnome_canvas_update_svp (GnomeCanvas *canvas,
ArtSVP **p_svp,
ArtSVP *new_svp);
void gnome_canvas_update_svp_clip (GnomeCanvas *canvas,
ArtSVP **p_svp,
ArtSVP *new_svp,
ArtSVP *clip_svp);
void gnome_canvas_item_reset_bounds (GnomeCanvasItem *item);
void gnome_canvas_item_update_svp (GnomeCanvasItem *item,
ArtSVP **p_svp,
ArtSVP *new_svp);
void gnome_canvas_item_update_svp_clip (GnomeCanvasItem *item,
ArtSVP **p_svp,
ArtSVP *new_svp,
ArtSVP *clip_svp);
void gnome_canvas_item_request_redraw_svp
(GnomeCanvasItem *item,
const ArtSVP *svp);
void gnome_canvas_update_bbox (GnomeCanvasItem *item,
int x1,
int y1,
int x2,
int y2);
void gnome_canvas_buf_ensure_buf (GnomeCanvasBuf *buf);
ArtPathStrokeJoinType gnome_canvas_join_gdk_to_art (GdkJoinStyle gdk_join);
ArtPathStrokeCapType gnome_canvas_cap_gdk_to_art (GdkCapStyle gdk_cap);
Some useful canvas utility functions.
The GnomeCanvasPoints structure manages an array of points (X and Y coordinates) and is used by GnomeCanvasLine and GnomeCanvasPolygon canvas items.
To create a GnomeCanvasPoints structure call gnome_canvas_points_new() and
when finished using it call gnome_canvas_points_free().
Of note is that the GnomeCanvasPoints structure is actually managed
by a reference count, so it won't be freed until this count reaches
0. To increment its reference count call gnome_canvas_points_ref() and
to decrement it call gnome_canvas_points_unref().
typedef struct {
double *coords;
int num_points;
int ref_count;
} GnomeCanvasPoints;
A structure to manage an array of points (X and Y coordinates). The memory
management of this structure is handled with functions below, but the point
coordinates are meant to be written directly into the array pointed to by
the coords field.
| Array of coordinates (num_points * 2 in size), X coordinates are stored in the even-numbered indices, and Y coordinates are stored in the odd-numbered indices. | |
| Read-only - Number of points in this array. | |
| Read-only - Count of references to this array of points |
GnomeCanvasPoints * gnome_canvas_points_new (int num_points);
Creates a structure that should be used to pass an array of points to items.
|
The number of points to allocate space for in the array. |
Returns : |
A newly-created array of points. It should be filled in by the user. |
GnomeCanvasPoints * gnome_canvas_points_ref (GnomeCanvasPoints *points);
Increases the reference count of the specified points structure.
|
A canvas points structure. |
Returns : |
The canvas points structure itself. |
#define gnome_canvas_points_unref
A synonym for gnome_canvas_points_free(). It decrements a GnomeCanvasPoints
reference by 1 and frees it when there are no more references.
void gnome_canvas_points_free (GnomeCanvasPoints *points);
Decreases the reference count of the specified points structure. If it reaches zero, then the structure is freed.
|
A canvas points structure. |
int gnome_canvas_get_miter_points (double x1, double y1, double x2, double y2, double x3, double y3, double width, double *mx1, double *my1, double *mx2, double *my2);
Given three points forming an angle, computes the coordinates of the inside and outside points of the mitered corner formed by a line of a given width at that angle.
|
X coordinate of the first point |
|
Y coordinate of the first point |
|
X coordinate of the second (angle) point |
|
Y coordinate of the second (angle) point |
|
X coordinate of the third point |
|
Y coordinate of the third point |
|
Width of the line |
|
The X coordinate of the first miter point is returned here. |
|
The Y coordinate of the first miter point is returned here. |
|
The X coordinate of the second miter point is returned here. |
|
The Y coordinate of the second miter point is returned here. |
Returns : |
FALSE if the angle is less than 11 degrees (this is the same threshold as X uses. If this occurs, the return points are not modified. Otherwise, returns TRUE. |
void gnome_canvas_get_butt_points (double x1, double y1, double x2, double y2, double width, int project, double *bx1, double *by1, double *bx2, double *by2);
Computes the butt points of a line segment.
|
X coordinate of first point in the line |
|
Y cooordinate of first point in the line |
|
X coordinate of second point (endpoint) of the line |
|
Y coordinate of second point (endpoint) of the line |
|
Width of the line |
|
Whether the butt points should project out by width/2 distance |
|
X coordinate of first butt point is returned here |
|
Y coordinate of first butt point is returned here |
|
X coordinate of second butt point is returned here |
|
Y coordinate of second butt point is returned here |
double gnome_canvas_polygon_to_point (double *poly, int num_points, double x, double y);
Computes the distance between a point and a polygon.
|
Vertices of the polygon. X coordinates are in the even indices, and Y coordinates are in the odd indices |
|
Number of points in the polygon |
|
X coordinate of the point |
|
Y coordinate of the point |
Returns : |
The distance from the point to the polygon, or zero if the point is inside the polygon. |
void gnome_canvas_render_svp (GnomeCanvasBuf *buf, ArtSVP *svp, guint32 rgba);
Render the svp over the buf.
|
the canvas buffer to render over |
|
the vector path to render |
|
the rgba color to render |
void gnome_canvas_update_svp (GnomeCanvas *canvas, ArtSVP **p_svp, ArtSVP *new_svp);
Sets the svp to the new value, requesting repaint on what's changed. This function takes responsibility for freeing new_svp.
|
the canvas containing the svp that needs updating. |
|
a pointer to the existing svp |
|
the new svp |
void gnome_canvas_update_svp_clip (GnomeCanvas *canvas, ArtSVP **p_svp, ArtSVP *new_svp, ArtSVP *clip_svp);
Sets the svp to the new value, clipping if necessary, and requesting repaint on what's changed. This function takes responsibility for freeing new_svp.
|
the canvas containing the svp that needs updating. |
|
a pointer to the existing svp |
|
the new svp |
|
a clip path, if non-null |
void gnome_canvas_item_reset_bounds (GnomeCanvasItem *item);
Resets the bounding box of a canvas item to an empty rectangle.
|
A canvas item |
void gnome_canvas_item_update_svp (GnomeCanvasItem *item, ArtSVP **p_svp, ArtSVP *new_svp);
Sets the svp to the new value, requesting repaint on what's changed. This function takes responsibility for freeing new_svp. This routine also adds the svp's bbox to the item's.
|
the canvas item containing the svp that needs updating. |
|
a pointer to the existing svp |
|
the new svp |
void gnome_canvas_item_update_svp_clip (GnomeCanvasItem *item, ArtSVP **p_svp, ArtSVP *new_svp, ArtSVP *clip_svp);
Sets the svp to the new value, clipping if necessary, and requesting repaint on what's changed. This function takes responsibility for freeing new_svp.
|
the canvas item containing the svp that needs updating. |
|
a pointer to the existing svp |
|
the new svp |
|
a clip path, if non-null |
void gnome_canvas_item_request_redraw_svp (GnomeCanvasItem *item, const ArtSVP *svp);
Request redraw of the svp if in aa mode, or the entire item in in xlib mode.
|
the item containing the svp |
|
the svp that needs to be redrawn |
void gnome_canvas_update_bbox (GnomeCanvasItem *item, int x1, int y1, int x2, int y2);
Sets the bbox to the new value, requesting full repaint.
|
the canvas item needing update |
|
Left coordinate of the new bounding box |
|
Top coordinate of the new bounding box |
|
Right coordinate of the new bounding box |
|
Bottom coordinate of the new bounding box |
void gnome_canvas_buf_ensure_buf (GnomeCanvasBuf *buf);
Ensure that the buffer is in RGB format, suitable for compositing.
|
the buf that needs to be represened in RGB format |
ArtPathStrokeJoinType gnome_canvas_join_gdk_to_art (GdkJoinStyle gdk_join);
Convert from GDK line join specifier to libart.
|
a join type, represented in GDK format |
Returns : |
The line join specifier in libart format. |