Points, Rectangles and Regions

Name

Points, Rectangles and Regions -- simple graphical data types.

Synopsis


#include <gdk/gdk.h>


struct      GdkPoint;

struct      GdkRectangle;
gboolean    gdk_rectangle_intersect         (GdkRectangle *src1,
                                             GdkRectangle *src2,
                                             GdkRectangle *dest);
void        gdk_rectangle_union             (GdkRectangle *src1,
                                             GdkRectangle *src2,
                                             GdkRectangle *dest);

struct      GdkRegion;
GdkRegion*  gdk_region_new                  (void);
GdkRegion*  gdk_region_polygon              (GdkPoint *points,
                                             gint npoints,
                                             GdkFillRule fill_rule);
enum        GdkFillRule;
GdkRegion*  gdk_region_copy                 (GdkRegion *region);
GdkRegion*  gdk_region_rectangle            (GdkRectangle *rectangle);
void        gdk_region_destroy              (GdkRegion *region);

void        gdk_region_get_clipbox          (GdkRegion *region,
                                             GdkRectangle *rectangle);
void        gdk_region_get_rectangles       (GdkRegion *region,
                                             GdkRectangle **rectangles,
                                             gint *n_rectangles);
gboolean    gdk_region_empty                (GdkRegion *region);
gboolean    gdk_region_equal                (GdkRegion *region1,
                                             GdkRegion *region2);
gboolean    gdk_region_point_in             (GdkRegion *region,
                                             int x,
                                             int y);
GdkOverlapType gdk_region_rect_in           (GdkRegion *region,
                                             GdkRectangle *rect);
enum        GdkOverlapType;

void        gdk_region_offset               (GdkRegion *region,
                                             gint dx,
                                             gint dy);
void        gdk_region_shrink               (GdkRegion *region,
                                             gint dx,
                                             gint dy);
void        gdk_region_union_with_rect      (GdkRegion *region,
                                             GdkRectangle *rect);
void        gdk_region_intersect            (GdkRegion *source1,
                                             GdkRegion *source2);
void        gdk_region_union                (GdkRegion *source1,
                                             GdkRegion *source2);
void        gdk_region_subtract             (GdkRegion *source1,
                                             GdkRegion *source2);
void        gdk_region_xor                  (GdkRegion *source1,
                                             GdkRegion *source2);

struct      GdkSpan;
void        (*GdkSpanFunc)                  (GdkSpan *span,
                                             gpointer data);
void        gdk_region_spans_intersect_foreach
                                            (GdkRegion *region,
                                             GdkSpan *spans,
                                             int n_spans,
                                             gboolean sorted,
                                             GdkSpanFunc function,
                                             gpointer data);

Description

GDK provides the GdkPoint, GdkRectangle, GdkRegion and GdkSpan data types for representing pixels and sets of pixels on the screen.

GdkPoint is a simple structure containing an x and y coordinate of a point.

GdkRectangle is a structure holding the position and size of a rectangle. The intersection of two rectangles can be computed with gdk_rectangle_intersect(). To find the union of two rectangles use gdk_rectangle_union().

GdkRegion is an opaque data type holding a set of arbitrary pixels, and is usually used for clipping graphical operations (see gdk_gc_set_clip_region()).

GdkSpan is a structure holding a spanline. A spanline is a horizontal line that is one pixel wide. It is mainly used when rasterizing other graphics primitives. It can be intersected to regions by using gdk_region_spans_intersect_foreach().

Details

struct GdkPoint

struct GdkPoint
{
  gint x;
  gint y;
};

Defines the x and y coordinates of a point. Note that both are defined as gint16 values, so the coordinates are limited to between -32,768 and 32,767.

gint xthe x coordinate of the point.
gint ythe y coordinate of the point.


struct GdkRectangle

struct GdkRectangle
{
  gint x;
  gint y;
  gint width;
  gint height;
};

Defines the position and size of a rectangle.

gint xthe x coordinate of the left edge of the rectangle.
gint ythe y coordinate of the top of the rectangle.
gint widththe width of the rectangle.
gint heightthe height of the rectangle.


gdk_rectangle_intersect ()

gboolean    gdk_rectangle_intersect         (GdkRectangle *src1,
                                             GdkRectangle *src2,
                                             GdkRectangle *dest);

Calculates the intersection of two rectangles.

src1 :a GdkRectangle.
src2 :a GdkRectangle.
dest :the intersection of src1 and src2.
Returns :TRUE if the rectangles intersect.


gdk_rectangle_union ()

void        gdk_rectangle_union             (GdkRectangle *src1,
                                             GdkRectangle *src2,
                                             GdkRectangle *dest);

Calculates the union of two rectangles. The union of rectangles src1 and src2 is the smallest rectangle which includes both src1 and src2 within it.

src1 :a GdkRectangle.
src2 :a GdkRectangle.
dest :the union of src1 and src2.


struct GdkRegion

struct GdkRegion;

A GdkRegion represents a set of pixels on the screen. The only user-visible field of the structure is the user_data member, which can be used to attach arbitrary data to the GdkRegion.


gdk_region_new ()

GdkRegion*  gdk_region_new                  (void);

Creates a new empty GdkRegion.

Returns :a new empty GdkRegion.


gdk_region_polygon ()

GdkRegion*  gdk_region_polygon              (GdkPoint *points,
                                             gint npoints,
                                             GdkFillRule fill_rule);

Creates a new GdkRegion using the polygon defined by a number of points.

points :an array of GdkPoint structs.
npoints :the number of elements in the points array.
fill_rule :specifies which pixels are included in the region when the polygon overlaps itself.
Returns :a new GdkRegion based on the given polygon.


enum GdkFillRule

typedef enum
{
  GDK_EVEN_ODD_RULE,
  GDK_WINDING_RULE
} GdkFillRule;

The method for determining which pixels are included in a region, when creating a GdkRegion from a polygon. The fill rule is only relevant for polygons which overlap themselves.

GDK_EVEN_ODD_RULEareas which are overlapped an odd number of times are included in the region, while areas overlapped an even number of times are not.
GDK_WINDING_RULEoverlapping areas are always included.


gdk_region_copy ()

GdkRegion*  gdk_region_copy                 (GdkRegion *region);

Copies region, creating an identical new region.

region : a GdkRegion
Returns : a new region identical to region


gdk_region_rectangle ()

GdkRegion*  gdk_region_rectangle            (GdkRectangle *rectangle);

Creates a new region containing the area rectangle.

rectangle : a GdkRectangle
Returns : a new region


gdk_region_destroy ()

void        gdk_region_destroy              (GdkRegion *region);

Destroys a GdkRegion.

region :a GdkRegion.


gdk_region_get_clipbox ()

void        gdk_region_get_clipbox          (GdkRegion *region,
                                             GdkRectangle *rectangle);

Returns the smallest rectangle which includes the entire GdkRegion.

region :a GdkRegion.
rectangle :returns the smallest rectangle which includes all of region.


gdk_region_get_rectangles ()

void        gdk_region_get_rectangles       (GdkRegion *region,
                                             GdkRectangle **rectangles,
                                             gint *n_rectangles);

Obtains the area covered by the region as a list of rectangles. The array returned in rectangles must be freed with g_free().

region : a GdkRegion
rectangles : return location for an array of rectangles
n_rectangles : length of returned array


gdk_region_empty ()

gboolean    gdk_region_empty                (GdkRegion *region);

Returns TRUE if the GdkRegion is empty.

region :a GdkRegion.
Returns :TRUE if region is empty.


gdk_region_equal ()

gboolean    gdk_region_equal                (GdkRegion *region1,
                                             GdkRegion *region2);

Returns TRUE if the two regions are the same.

region1 :a GdkRegion.
region2 :a GdkRegion.
Returns :TRUE if region1 and region2 are equal.


gdk_region_point_in ()

gboolean    gdk_region_point_in             (GdkRegion *region,
                                             int x,
                                             int y);

Returns TRUE if a point is in a region.

region :a GdkRegion.
x :the x coordinate of a point.
y :the y coordinate of a point.
Returns :TRUE if the point is in region.


gdk_region_rect_in ()

GdkOverlapType gdk_region_rect_in           (GdkRegion *region,
                                             GdkRectangle *rect);

Tests whether a rectangle is within a region.

region :a GdkRegion.
rect :a GdkRectangle.
Returns :GDK_OVERLAP_RECTANGLE_IN, GDK_OVERLAP_RECTANGLE_OUT, or GDK_OVERLAP_RECTANGLE_PART, depending on whether the rectangle is inside, outside, or partly inside the GdkRegion, respectively.


enum GdkOverlapType

typedef enum
{
  GDK_OVERLAP_RECTANGLE_IN,
  GDK_OVERLAP_RECTANGLE_OUT,
  GDK_OVERLAP_RECTANGLE_PART
} GdkOverlapType;

Specifies the possible values returned by gdk_region_rect_in().

GDK_OVERLAP_RECTANGLE_INif the rectangle is inside the GdkRegion.
GDK_OVERLAP_RECTANGLE_OUTif the rectangle is outside the GdkRegion.
GDK_OVERLAP_RECTANGLE_PARTif the rectangle is partly inside the GdkRegion.


gdk_region_offset ()

void        gdk_region_offset               (GdkRegion *region,
                                             gint dx,
                                             gint dy);

Moves a region the specified distance.

region :a GdkRegion.
dx :the distance to move the region horizontally.
dy :the distance to move the region vertically.


gdk_region_shrink ()

void        gdk_region_shrink               (GdkRegion *region,
                                             gint dx,
                                             gint dy);

Resizes a region by the specified amount. Positive values shrink the region. Negative values expand it.

region :a GdkRegion.
dx :the number of pixels to shrink the region horizontally.
dy :the number of pixels to shrink the region vertically.


gdk_region_union_with_rect ()

void        gdk_region_union_with_rect      (GdkRegion *region,
                                             GdkRectangle *rect);

Sets the area of region to the union of the areas of region and rect. The resulting area is the set of pixels contained in either region or rect.

region :a GdkRegion.
rect :a GdkRectangle.


gdk_region_intersect ()

void        gdk_region_intersect            (GdkRegion *source1,
                                             GdkRegion *source2);

Converts source1 into the intersection between source1 and source2. That is, after calling this function source2 will be unchanged and source1 will be the areas the two regions have in common.

Sets the area of source1 to the intersection of the areas of source1 and source2. The resulting area is the set of pixels contained in both source1 and source2.

source1 : a GdkRegion
source2 : another GdkRegion


gdk_region_union ()

void        gdk_region_union                (GdkRegion *source1,
                                             GdkRegion *source2);

Sets the area of source1 to the union of the areas of source1 and source2. The resulting area is the set of pixels contained in either source1 or source2.

source1 :a GdkRegion
source2 :a GdkRegion


gdk_region_subtract ()

void        gdk_region_subtract             (GdkRegion *source1,
                                             GdkRegion *source2);

Subtracts any area in source2 from the area in source1.

Subtracts the area of source2 from the area source1. The resulting area is the set of pixels contained in source1 but not in source2.

source1 : a GdkRegion
source2 : another GdkRegion


gdk_region_xor ()

void        gdk_region_xor                  (GdkRegion *source1,
                                             GdkRegion *source2);

XORs the two regions, placing the result in source1. The XOR of two regions contains all areas which were not overlapping. That is, it's the union of the regions minus the intersection of the regions.

Sets the area of source1 to the exclusive-OR of the areas of source1 and source2. The resulting area is the set of pixels contained in one or the other of the two sources but not in both.

source1 : a GdkRegion
source2 : another GdkRegion


struct GdkSpan

struct GdkSpan
{
  gint x;
  gint y;
  gint width;
};

A GdkSpan represents a horizontal line of pixels starting at the pixel with coordinates x, y and ending before x + width, y.

gint xx coordinate of the first pixel.
gint yy coordinate of the first pixel.
gint widthnumber of pixels in the span.


GdkSpanFunc ()

void        (*GdkSpanFunc)                  (GdkSpan *span,
                                             gpointer data);

This defines the type of the function passed to gdk_region_spans_intersect_foreach().

span :a GdkSpan.
data :the user data passed to gdk_region_spans_intersect_foreach().


gdk_region_spans_intersect_foreach ()

void        gdk_region_spans_intersect_foreach
                                            (GdkRegion *region,
                                             GdkSpan *spans,
                                             int n_spans,
                                             gboolean sorted,
                                             GdkSpanFunc function,
                                             gpointer data);

Calls a function on each span in the intersection of region and spans.

region :a GdkRegion.
spans :an array of GdkSpans.
n_spans :the length of spans.
sorted :TRUE if spans is sorted wrt. the y coordinate.
function :function to call on each span in the intersection.
data :data to pass to function.