Points, Rectangles and Regions

Points, Rectangles and Regions — Simple graphical data types

Synopsis


#include <gdk/gdk.h>


            GdkPoint;

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

            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 *rectangle);
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);

            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

GdkPoint

typedef struct {
  gint x;
  gint y;
} GdkPoint;

Defines the x and y coordinates of a point.

gint x; the x coordinate of the point.
gint y; the y coordinate of the point.

GdkRectangle

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

Defines the position and size of a rectangle.

gint x; the x coordinate of the left edge of the rectangle.
gint y; the y coordinate of the top of the rectangle.
gint width; the width of the rectangle.
gint height; the height of the rectangle.

gdk_rectangle_intersect ()

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

Calculates the intersection of two rectangles. It is allowed for dest to be the same as either src1 or src2.

src1 : a GdkRectangle
src2 : a GdkRectangle
dest : return location for 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. It is allowed for dest to be the same as either src1 or src2.

src1 : a GdkRectangle
src2 : a GdkRectangle
dest : return location for the union of src1 and src2

GdkRegion

typedef struct _GdkRegion GdkRegion;

A GdkRegion represents a set of pixels on the screen.

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_RULE areas 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_RULE overlapping 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);

Obtains the smallest rectangle which includes the entire GdkRegion.

region : a GdkRegion
rectangle : return location for the clipbox

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);

Finds out 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);

Finds out 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);

Finds out 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 *rectangle);

Tests whether a rectangle is within a region.

region : a GdkRegion.
rectangle : 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_IN if the rectangle is inside the GdkRegion.
GDK_OVERLAP_RECTANGLE_OUT if the rectangle is outside the GdkRegion.
GDK_OVERLAP_RECTANGLE_PART if 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);

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 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);

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

GdkSpan

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

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

gint x; x coordinate of the first pixel.
gint y; y coordinate of the first pixel.
gint width; number 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