4 Draw, Clear, and Flip Operations

The following are the basic graphics operations for drawing to a viewport. Each function takes a viewport as its argument and returns a function operating within that viewport. Further arguments, if any, are curried. For example, (draw-line viewport) returns a function, that can then be applied to the proper arguments to draw a line in the viewport corresponding to viewport descriptor viewport.

In general, draw- functions make pixels black or colored, clear- functions make them white, and flip- commands invert pixels (which makes black white, white black, and is otherwise ill-defined).

4.1 Viewports

((draw-viewport viewport) [color]) → void?

viewport : viewport?

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Colors the entire contents of viewport with color.

((clear-viewport viewport)) → void?

viewport : viewport?

Whitens the entire contents of viewport.

((flip-viewport viewport)) → void?

viewport : viewport?

Inverts the entire contents of viewport.

(copy-viewport source dest) → void?

source : viewport?

dest : viewport?

Copies the content of source into dest.

4.2 Pixels

((draw-pixel viewport) p [color]) → void?

viewport : viewport?

p : posn?

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Colors the pixel in viewport at p.

((clear-pixel viewport) p) → void?

viewport : viewport?

p : posn?

Whitens the pixel in viewport at p.

((flip-pixel viewport) p) → void?

viewport : viewport?

p : posn?

Inverts the pixel in viewport at p.

4.3 Lines

((draw-line viewport) p1 p2 [color]) → void?

viewport : viewport?

p1 : posn?

p2 : posn?

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a line in viewport connecting positions p1 and p2.

((clear-line viewport) p1 p2) → void?

viewport : viewport?

p1 : posn?

p2 : posn?

Whitens a line in viewport connecting positions p1 and p2.

((flip-line viewport) p1 p2) → void?

viewport : viewport?

p1 : posn?

p2 : posn?

Inverts a line in viewport connecting positions p1 and p2.

4.4 Rectangles

((draw-rectangle   viewport)             p             width             height            [ color])   →   void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a rectangle border in the viewport with the top-left of the rectangle at the position p and with sides width across and height tall.

((clear-rectangle viewport) p width height) → void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Whitens a rectangle border in the viewport, analogous to draw-rectangle.

((flip-rectangle viewport) p width height) → void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Inverts a rectangle border in the viewport, analogous to draw-rectangle.

((draw-solid-rectangle   viewport)             p             width             height            [ color])   →   void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a solid rectangle in the viewport with the top-left of the rectangle at the position p and with sides width across and height tall.

((clear-solid-rectangle   viewport)             p             width             height)   →   void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Whitens a rectangle border in the viewport, analogous to draw-solid-rectangle.

((flip-solid-rectangle   viewport)             p             width             height)   →   void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Inverts a rectangle border in the viewport, analogous to draw-solid-rectangle.

4.5 Ellipses

((draw-ellipse viewport) p width height [color]) → void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a ellipse border in the viewport. The ellipse is inscribed with a rectangle whose top-left is at position p and with sides width across and height tall.

((clear-ellipse viewport) p width height) → void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Whitens a ellipse border in the viewport, analogous to draw-ellipse.

((flip-ellipse viewport) p width height) → void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Inverts a ellipse border in the viewport, analogous to draw-ellipse.

((draw-solid-ellipse   viewport)             p             width             height            [ color])   →   void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a solid ellipse in the viewport. The ellipse is inscribed with a rectangle whose top-left is at position p and with sides width across and height tall.

((clear-solid-ellipse   viewport)             p             width             height)   →   void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Whitens a ellipse border in the viewport, analogous to draw-solid-ellipse.

((flip-solid-ellipse   viewport)             p             width             height)   →   void?

viewport : viewport?

p : posn?

width : (and/c real? (not/c negative?))

height : (and/c real? (not/c negative?))

Inverts a ellipse border in the viewport, analogous to draw-solid-ellipse.

4.6 Polygons

((draw-polygon viewport) points offset [color]) → void?

viewport : viewport?

points : (listof posn?)

offset : posn?

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a polygon border in viewport using points for the polygon vertices and offset as an offset added to all points.

((clear-polygon viewport) points offset) → void?

viewport : viewport?

points : (listof posn?)

offset : posn?

Whitens a polygon border in viewport, analogous to draw-polygon.

((flip-polygon viewport) points offset) → void?

viewport : viewport?

points : (listof posn?)

offset : posn?

Inverts a polygon border in viewport, analogous to draw-polygon.

((draw-solid-polygon   viewport)             points             offset            [ color])   →   void?

viewport : viewport?

points : (listof posn?)

offset : posn?

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a solid polygon in viewport using points for the polygon vertices and offset as an offset added to all points.

((clear-solid-polygon   viewport)             points             offset)   →   void?

viewport : viewport?

points : (listof posn?)

offset : posn?

Whitens a polygon border in viewport, analogous to draw-solid-polygon.

((flip-solid-polygon   viewport)             points             offset)   →   void?

viewport : viewport?

points : (listof posn?)

offset : posn?

Inverts a polygon border in viewport, analogous to draw-solid-polygon.

4.7 Strings

((draw-string viewport) p str [color]) → void?

viewport : viewport?

p : posn?

str : string?

color   :   (or/c (integer-in 0 299)       string?       rgb?)   =   "black"

Draws a string at a specified location in the viewport. The lower left of the string begins at p.

((clear-string viewport) p str) → void?

viewport : viewport?

p : posn?

str : string?

Whitens a string at a specified location in the viewport. The lower left of the string begins at p.

((flip-string viewport) p str) → void?

viewport : viewport?

p : posn?

str : string?

Inverts a string at a specified location in the viewport. The lower left of the string begins at p.

4.8 Pixmaps

(((draw-pixmap-posn