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Points, Rectangles and Regions

Points, Rectangles and Regions — Simple graphical data types

Types and Values

struct GdkPoint
struct GdkRectangle
  GdkRegion
enum GdkFillRule
enum GdkOverlapType
struct GdkSpan

Includes

#include <gdk/gdk.h>

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().

Functions

gdk_rectangle_intersect ()

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

Calculates the intersection of two rectangles. It is allowed for dest to be the same as either src1 or src2 . If the rectangles do not intersect, dest 's width and height is set to 0 and its x and y values are undefined. If you are only interested in whether the rectangles intersect, but not in the intersecting area itself, pass NULL for dest .

Parameters

src1

a GdkRectangle

 

src2

a GdkRectangle

 

dest

return location for the intersection of src1 and src2 , or NULL.

[out caller-allocates][allow-none]

Returns

TRUE if the rectangles intersect.


gdk_rectangle_union ()

void
gdk_rectangle_union (const GdkRectangle *src1,
                     const 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 .

Parameters

src1

a GdkRectangle

 

src2

a GdkRectangle

 

dest

return location for the union of src1 and src2 .

[out]

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 (const GdkPoint *points,
                    gint n_points,
                    GdkFillRule fill_rule);

gdk_region_polygon has been deprecated since version 2.22 and should not be used in newly-written code.

There is no replacement. For working with paths, please use Cairo.

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

Parameters

points

an array of GdkPoint structs

 

n_points

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


gdk_region_copy ()

GdkRegion *
gdk_region_copy (const GdkRegion *region);

Copies region , creating an identical new region.

Parameters

region

a GdkRegion

 

Returns

a new region identical to region


gdk_region_rectangle ()

GdkRegion *
gdk_region_rectangle (const GdkRectangle *rectangle);

Creates a new region containing the area rectangle .

Parameters

rectangle

a GdkRectangle

 

Returns

a new region


gdk_region_destroy ()

void
gdk_region_destroy (GdkRegion *region);

Destroys a GdkRegion.

Parameters

region

a GdkRegion

 

gdk_region_get_clipbox ()

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

Obtains the smallest rectangle which includes the entire GdkRegion.

Parameters

region

a GdkRegion

 

rectangle

return location for the clipbox

 

gdk_region_get_rectangles ()

void
gdk_region_get_rectangles (const 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().

Parameters

region

a GdkRegion

 

rectangles

return location for an array of rectangles.

[array length=n_rectangles][transfer container]

n_rectangles

length of returned array

 

gdk_region_empty ()

gboolean
gdk_region_empty (const GdkRegion *region);

Finds out if the GdkRegion is empty.

Parameters

region

a GdkRegion

 

Returns

TRUE if region is empty.


gdk_region_equal ()

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

Finds out if the two regions are the same.

Parameters

region1

a GdkRegion

 

region2

a GdkRegion

 

Returns

TRUE if region1 and region2 are equal.


gdk_region_rect_equal ()

gboolean
gdk_region_rect_equal (const GdkRegion *region,
                       const GdkRectangle *rectangle);

gdk_region_rect_equal has been deprecated since version 2.22 and should not be used in newly-written code.

Use gdk_region_new_rect() and gdk_region_equal() to achieve the same effect.

Finds out if a regions is the same as a rectangle.

Parameters

region

a GdkRegion

 

rectangle

a GdkRectangle

 

Returns

TRUE if region and rectangle are equal.

Since: 2.18


gdk_region_point_in ()

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

Finds out if a point is in a region.

Parameters

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 (const GdkRegion *region,
                    const GdkRectangle *rectangle);

Tests whether a rectangle is within a region.

Parameters

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.


gdk_region_offset ()

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

Moves a region the specified distance.

Parameters

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);

gdk_region_shrink has been deprecated since version 2.22 and should not be used in newly-written code.

There is no replacement for this function.

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

Parameters

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,
                            const 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 .

Parameters

region

a GdkRegion.

 

rect

a GdkRectangle.

 

gdk_region_intersect ()

void
gdk_region_intersect (GdkRegion *source1,
                      const 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 .

Parameters

source1

a GdkRegion

 

source2

another GdkRegion

 

gdk_region_union ()

void
gdk_region_union (GdkRegion *source1,
                  const 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 .

Parameters

source1

a GdkRegion

 

source2

a GdkRegion

 

gdk_region_subtract ()

void
gdk_region_subtract (GdkRegion *source1,
                     const 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 .

Parameters

source1

a GdkRegion

 

source2

another GdkRegion

 

gdk_region_xor ()

void
gdk_region_xor (GdkRegion *source1,
                const 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.

Parameters

source1

a GdkRegion

 

source2

another GdkRegion

 

GdkSpanFunc ()

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

GdkSpanFunc is deprecated and should not be used in newly-written code.

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

Parameters

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,
                                    const GdkSpan *spans,
                                    int n_spans,
                                    gboolean sorted,
                                    GdkSpanFunc function,
                                    gpointer data);

gdk_region_spans_intersect_foreach has been deprecated since version 2.22 and should not be used in newly-written code.

There is no replacement.

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

Parameters

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

 

Types and Values

struct GdkPoint

struct GdkPoint {
  gint x;
  gint y;
};

GdkPoint is deprecated and should not be used in newly-written code.

Defines the x and y coordinates of a point.

Members

gint x;

the x coordinate of the point.

 

gint y;

the 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.

Members

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.

 

GdkRegion

typedef struct _GdkRegion GdkRegion;

A GdkRegion represents a set of pixels on the screen.

In GTK3, GdkRegion will be replaced by cairo_region_t. All the functions listed in this section will go away and you will have to use the relevant Cairo functions. The conversion can be done using simple serch and replace.


enum GdkFillRule

GdkFillRule is deprecated and should not be used in newly-written code.

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.

Members

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.

 

enum GdkOverlapType

Specifies the possible values returned by gdk_region_rect_in().

Members

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.

 

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.

Members

gint x;

x coordinate of the first pixel.

 

gint y;

y coordinate of the first pixel.

 

gint width;

number of pixels in the span.

 
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