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gnome-canvas-util

Name

gnome-canvas-util -- Canvas utility functions

Synopsis


#include <libgnomecanvas/libgnomecanvas.h>


struct      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);

Description

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().

Details

>struct GnomeCanvasPoints

struct GnomeCanvasPoints {

	double *coords;
	int num_points;
	int ref_count;
};

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.

double *coords

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.

int num_points

Read-only - Number of points in this array.

int ref_count

Read-only - Count of references to this array of points

>gnome_canvas_points_new ()

GnomeCanvasPoints* gnome_canvas_points_new  (int num_points);

Creates a structure that should be used to pass an array of points to items.

num_points :

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.

>gnome_canvas_points_ref ()

GnomeCanvasPoints* gnome_canvas_points_ref  (GnomeCanvasPoints *points);

Increases the reference count of the specified points structure.

points :

A canvas points structure.

Returns :

The canvas points structure itself.

>gnome_canvas_points_unref

#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.

>gnome_canvas_points_free ()

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.

points :

A canvas points structure.

>gnome_canvas_get_miter_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);

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.

x1 :

X coordinate of the first point

y1 :

Y coordinate of the first point

x2 :

X coordinate of the second (angle) point

y2 :

Y coordinate of the second (angle) point

x3 :

X coordinate of the third point

y3 :

Y coordinate of the third point

width :

Width of the line

mx1 :

The X coordinate of the first miter point is returned here.

my1 :

The Y coordinate of the first miter point is returned here.

mx2 :

The X coordinate of the second miter point is returned here.

my2 :

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.

>gnome_canvas_get_butt_points ()

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.

x1 :

X coordinate of first point in the line

y1 :

Y cooordinate of first point in the line

x2 :

X coordinate of second point (endpoint) of the line

y2 :

Y coordinate of second point (endpoint) of the line

width :

Width of the line

project :

Whether the butt points should project out by width/2 distance

bx1 :

X coordinate of first butt point is returned here

by1 :

Y coordinate of first butt point is returned here

bx2 :

X coordinate of second butt point is returned here

by2 :

Y coordinate of second butt point is returned here

>gnome_canvas_polygon_to_point ()

double      gnome_canvas_polygon_to_point   (double *poly,
                                             int num_points,
                                             double x,
                                             double y);

Computes the distance between a point and a polygon.

poly :

Vertices of the polygon. X coordinates are in the even indices, and Y coordinates are in the odd indices

num_points :

Number of points in the polygon

x :

X coordinate of the point

y :

Y coordinate of the point

Returns :

The distance from the point to the polygon, or zero if the point is inside the polygon.

>gnome_canvas_render_svp ()

void        gnome_canvas_render_svp         (GnomeCanvasBuf *buf,
                                             ArtSVP *svp,
                                             guint32 rgba);

Render the svp over the buf.

buf :

the canvas buffer to render over

svp :

the vector path to render

rgba :

the rgba color to render

>gnome_canvas_update_svp ()

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.

canvas :

the canvas containing the svp that needs updating.

p_svp :

a pointer to the existing svp

new_svp :

the new svp

>gnome_canvas_update_svp_clip ()

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.

canvas :

the canvas containing the svp that needs updating.

p_svp :

a pointer to the existing svp

new_svp :

the new svp

clip_svp :

a clip path, if non-null

>gnome_canvas_item_reset_bounds ()

void        gnome_canvas_item_reset_bounds  (GnomeCanvasItem *item);

Resets the bounding box of a canvas item to an empty rectangle.

item :

A canvas item

>gnome_canvas_item_update_svp ()

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.

item :

the canvas item containing the svp that needs updating.

p_svp :

a pointer to the existing svp

new_svp :

the new svp

>gnome_canvas_item_update_svp_clip ()

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.

item :

the canvas item containing the svp that needs updating.

p_svp :

a pointer to the existing svp

new_svp :

the new svp

clip_svp :

a clip path, if non-null

>gnome_canvas_item_request_redraw_svp ()

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.

item :

the item containing the svp

svp :

the svp that needs to be redrawn

>gnome_canvas_update_bbox ()

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.

item :

the canvas item needing update

x1 :

Left coordinate of the new bounding box

y1 :

Top coordinate of the new bounding box

x2 :

Right coordinate of the new bounding box

y2 :

Bottom coordinate of the new bounding box

>gnome_canvas_buf_ensure_buf ()

void        gnome_canvas_buf_ensure_buf     (GnomeCanvasBuf *buf);

Ensure that the buffer is in RGB format, suitable for compositing.

buf :

the buf that needs to be represened in RGB format

>gnome_canvas_join_gdk_to_art ()

ArtPathStrokeJoinType gnome_canvas_join_gdk_to_art
                                            (GdkJoinStyle gdk_join);

Convert from GDK line join specifier to libart.

gdk_join :

a join type, represented in GDK format

Returns :

The line join specifier in libart format.

>gnome_canvas_cap_gdk_to_art ()

ArtPathStrokeCapType gnome_canvas_cap_gdk_to_art
                                            (GdkCapStyle gdk_cap);

Convert from GDK line cap specifier to libart.

gdk_cap :

a cap type, represented in GDK format

Returns :

The line cap specifier in libart format.

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