ADDPT(2)                                                 ADDPT(2)

          addpt, subpt, mulpt, divpt, rectaddpt, rectsubpt, insetrect,
          canonrect, eqpt, eqrect, ptinrect, rectinrect, rectXrect,
          rectclip, combinerect, badrect, Dx, Dy, Pt, Rect, Rpt -
          arithmetic on points and rectangles

          #include <u.h>
          #include <libc.h>
          #include <draw.h>

          Point     addpt(Point p, Point q)

          Point     subpt(Point p, Point q)

          Point     mulpt(Point p, int a)

          Point     divpt(Point p, int a)

          Rectangle rectaddpt(Rectangle r, Point p)

          Rectangle rectsubpt(Rectangle r, Point p)

          Rectangle insetrect(Rectangle r, int n)

          Rectangle canonrect(Rectangle r)

          int       eqpt(Point p, Point q)

          int       eqrect(Rectangle r, Rectangle s)

          int       ptinrect(Point p, Rectangle r)

          int       rectinrect(Rectangle r, Rectangle s)

          int       rectXrect(Rectangle r, Rectangle s)

          int       rectclip(Rectangle *rp, Rectangle b)

          void      combinerect(Rectangle *rp, Rectangle b)

          int       badrect(Rectangle r)

          int       Dx(Rectangle r)

          int       Dy(Rectangle r)

          Point     Pt(int x, int y)

          Rectangle Rect(int x0, int y0, int x1, int y1)

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     ADDPT(2)                                                 ADDPT(2)

          Rectangle Rpt(Point p, Point q)

          The functions Pt, Rect and Rpt construct geometrical data
          types from their components.

          Addpt returns the Point sum of its arguments: Pt(p.x+q.x,
          p.y+q.y).  Subpt returns the Point difference of its argu-
          ments: Pt(p.x-q.x, p.y-q.y).  Mulpt returns the Point
          Pt(p.x*a, p.y*a).  Divpt returns the Point Pt(p.x/a, p.y/a).

          Rectaddpt returns the Rectangle Rect(add(r.min, p),
          add(r.max, p)); rectsubpt returns the Rectangle
          Rpt(sub(r.min, p), sub(r.max, p)).

          Insetrect returns the Rectangle Rect(r.min.x+n, r.min.y+n,
          r.max.x-n, r.max.y-n).

          Canonrect returns a rectangle with the same extent as r,
          canonicalized so that min.x ≤ max.x, and min.y ≤ max.y.

          Eqpt compares its argument Points and returns 0 if unequal,
          1 if equal.  Eqrect does the same for its argument Rectan-

          Ptinrect returns 1 if p is a point within r, and 0 other-

          Rectinrect returns 1 if all the pixels in r are also in s,
          and 0 otherwise.

          RectXrect returns 1 if r and s share any point, and 0 other-

          Rectclip clips in place the Rectangle pointed to by rp so
          that it is completely contained within b. The return value
          is 1 if any part of *rp is within b. Otherwise, the return
          value is 0 and *rp is unchanged.

          Combinerect overwrites *rp with the smallest rectangle suf-
          ficient to cover all the pixels of *rp and b.

          Badrect returns 1 if r is zero, negative size or insanely
          huge rectangle.  It returns 0 otherwise.

          The functions Dx and Dy give the width (Δx) and height (Δy)
          of a Rectangle.  They are implemented as macros.



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     ADDPT(2)                                                 ADDPT(2)


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