1. srfi-203
    1. Introduction
    2. Author
    3. Repository
    4. API
      1. Canvas manipulation
      2. Painters
    5. Example
    6. Licenses
    7. Version history
      1. 0.1


This egg implements SRFI-203 using code from the sicp egg.


Vasilij Schneidermann



The procedures listed below expect a proper list of numbers for their data representation. Vector and frame accessors are therefore defined as follows:

(define origin-frame car)
(define edge1-frame cadr)
(define edge2-frame caddr)
(define xcor-vect car)
(define ycor-vect cadr)

If you chose to use a different internal representation, you'll need to define appropriate conversion procedures. For example a pair representation can be transformed as follows:

(define (fixup-vector vector)
  (list (xcor-vect vector) (ycor-vect vector)))

(draw-line (fixup-vector start) (fixup-vector end))

Canvas manipulation

[parameter] (canvas-path)

Obtain or set the path the canvas should be rendered to.

[parameter] (canvas-width)
[parameter] (canvas-height)

Obtain or set the width and height of the canvas measured in pixels.

[procedure] (canvas-frame)

Obtain a frame corresponding to the canvas width and height.

[procedure] (canvas-reset)

Reset the canvas to its initial state.

[procedure] (canvas-refresh)

Commit all pending drawing operations and return a file:// URL to the file backing the canvas. This will call canvas-reset if needed.

[procedure] (canvas-cleanup)

Delete the current canvas, including its backing file.


[procedure] (draw-line start end)

Draws a line from start to end on the canvas. This should be used in combination with a procedure that adjusts the coordinates of start and end to fit the canvas.

[procedure] (rogers frame)

A built-in painter that paints an image of William Rogers into frame.

[procedure] (image-file->painter file-name)

Returns a painter that will paint the image at file-name.

Note that file-name is interpreted relative to the path returned by canvas-refresh. Therefore only absolute paths are guaranteed to work.

[procedure] (jpeg-file->painter file-name)

Alias for image-file->painter.


(import scheme)
(import (srfi 203))

(define (flip-vert painter) ...)
(define (beside painter1 painter2) ...)
(define (below painter1 painter2) ...)

(define rogers2 (beside rogers (flip-vert rogers)))
(define rogers4 (below rogers2 rogers2))

(rogers4 (canvas-frame))
(print (canvas-refresh))


BSD-3-Clause, CC0-1.0

Version history