scx/scheme/xlib/region.scm

;; create-region creates a new empty region. See XCreateRegion.

(define (create-region)
  (make-region (%create-region) #t))

(import-lambda-definition %create-region ()
  "scx_Create_Region")

;; clip-box returns the smalles rectangle enclosing the specified
;; region. The resulting rectangle is a list of four elements: x, y,
;; width and height. See XClipBox.

(define (clip-box region)
  (vector->list (%clip-box (region-Xregion region))))

(import-lambda-definition %clip-box (Xregion)
  "scx_Clip_Box")

;; region-empty? returns true if the region is empty. See XEmptyRegion

(define (region-empty? region)
  (%region-empty? (region-Xregion region)))

(import-lambda-definition %region-empty? (Xregion)
  "scx_Region_Empty")

;; region-equal? returns true if the two regions have the same offset,
;; size, and shape. See XEqualRegion.

(define (region-equal? r1 r2)
  (%region-equal? (region-Xregion r1)
		  (region-Xregion r2)))

(import-lambda-definition %region-equal? (Xr1 Xr2)
  "scx_Region_Equal")

;; point-in-region? function returns true if the point (x, y) is
;; contained in the region r. See XPointInRegion.

(define (point-in-region? region x y)
  (%point-in-region? (region-Xregion region)
		     x y))

(import-lambda-definition %point-in-region? (Xregion x y)
  "scx_Point_In_Region")

;; rectangle-in-region? returns 'in if the rectangle is entirely in
;; the specified region, #f if the rectangle is entirely out of the
;; specified region, and 'part if the rectangle is partially in the
;; specified region. rectangle is a list '(x y width height). See
;; XRectInRegion.

(define (rectangle-in-region? region rectangle)
  (case (%rectanlge-in-region? (region-Xregion region)
			       (car rectangle) (cadr rectangle)
			       (caddr rectangle) (cadddr rectangle))
    ((0) #f)
    ((1) 'in)
    ((2) 'part)))

(import-lambda-definition %rectangle-in-region? (Xregion x y w h)
  "scx_Rect_In_Region")

;; intersect-region returns the intersection of two regions. See
;; XIntersectRegion.

(define (intersect-region r1 r2)
  (make-region (%intersect-region (region-Xregion r1)
				  (region-Xregion r1))
	       #t))

(import-lambda-definition %intersect-region (Xr1 Xr2)
  "scx_Intersect_Region")

;; union-region returns the union of two regions. See XUnionRegion.

(define (union-region r1 r2)
  (make-region (%union-region (region-Xregion r1)
			      (region-Xregion r1))
	       #t))

(import-lambda-definition %union-region (Xr1 Xr2)
  "scx_Union_Region")

;; union-rectangle-with-region returns the union of the specified
;; rectangle and the specified region. The rectangle is a list (x y
;; width height) See XUnionRectWithRegion.

(define (union-rectangle-with-region rectangle region)
  (make-region (%union-rectangle-with-region
		(car rectangle) (cadr rectangle)
		(caddr rectangle) (cadddr rectangle)
		(region-Xregion region))
	       #t))

(import-lambda-definition %union-rectangle-with-region (x y w h Xregion)
  "scx_Union_Rect_With_Region")

;; subtract-region subtracts r2 from r1 and returns the resulting
;; region. See XSubtractRegion.

(define (subtract-region r1 r2)
  (make-region (%subtract-region (region-Xregion r1)
				 (region-Xregion r2))
	       #t))

(import-lambda-definition %subtract-region (Xr1 Xr2)
  "scx_Subtract_Region")

;; xor-region calculates the difference between the union and
;; intersection of two regions and returns the resulting region. See
;; XXorRegion.

(define (xor-region r1 r2)
  (make-region (%xor-region (region-Xregion r1)
			    (region-Xregion r2))
	       #t))

(import-lambda-definition %xor-region (Xr1 Xr2)
  "scx_Xor_Region")

;; offset-region! moves the specified region by a dx and dy. See
;; XOffsetRegion.

(define (offset-region! region dx dy)
  (%offset-region! (region-Xregion region)
		   dx dy))

(import-lambda-definition %offset-region (Xregion dx dy)
  "scx_Offset_Region")

;; shrink-region! reduces the specified region by specified
;; amount. Positive values shrink the size of the region, and negative
;; values expand the region.

(define (shrink-region! region dx dy)
  (%shrink-region! (region-Xregion region)
		   dx dy))

(import-lambda-definition %shrink-region! (Xregion dx dy)
  "scx_Shrink_Region")

;; polygon-region returns a region for the polygon defines by
;; points. points has to a list of pairs (x . y). For an explanation
;; of fill-rule see create-gcontext. See XPolygonRegion.

(define (polygon-region points fill-rule)
  (make-region (%polygon-region (list->vector points)
				fill-rule)
	       #t))

(import-lambda-definition %polygon-region (points fillrule)
  "scx_Polygon_Region")

;; set-region sets the clip-mask in the GC to the specified region.
;; The region is specified relative to the drawable's origin. The
;; resulting GC clip origin is implementation-dependent. Once it is
;; set in the GC, the region can be destroyed. See XSetRegion.

(define (set-region gcontext region)
  (%set-region (display-Xdisplay (gcontext-display gcontext))
	       (gcontext-Xgcontext gcontext)
	       (region-Xregion region)))

(import-lambda-definition %set-region (Xdisplay Xgontext Xregion)
  "scx_Set_Region")

;;** Additional functions to support the more "scheme-like" functions
;;** above

;; copy-region! mutates to-region so that it is identical to
;; from-region. In fact this function uses XUnionRegion to create an
;; identical region. See "region.c".

(define (copy-region! from-region to-region)
  (%copy-region (region-Xregion from-region)
		(region-Xregion to-region)))

(import-lambda-definition %copy-region (Xfrom Xto)
  "scx_Copy_Region")

;; duplicate-region returns a new region that is identical to the
;; specified one.

(define (duplicate-region region)
  (let ((r (create-region)))
    (copy-region! region r)
    r))

;; offset-region returns a new region that is identical to the
;; specified one except that it is moved by dx and dy. See
;; offset-region!.

(define (offset-region region dx dy)
  (let ((r (duplicate-region region)))
    (offset-region! r dx dy)
    r))

;; shrink-region returns a new region that is identical to the
;; specified one except that it is shrunk by dx and dy. See
;; shrink-region!.

(define (shrink-region region dx dy)
  (let ((r (duplicate-region region)))
    (shrink-region! r dx dy)
    r))