srfi-203

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srfi-203
- Introduction
- Author
- Repository
- API
  - Canvas manipulation
  - Painters
- Example
- Licenses
- Version history
  - 0.1

Introduction

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

Author

Vasilij Schneidermann

Repository

https://depp.brause.cc/srfi-203

API

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

canvas-pathparameter: Obtain or set the path the canvas should be rendered to.

canvas-widthparameter
canvas-heightparameter: Obtain or set the width and height of the canvas measured in pixels.

canvas-frameprocedure: Obtain a frame corresponding to the canvas width and height.

canvas-resetprocedure: Reset the canvas to its initial state.

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

canvas-cleanupprocedure: Delete the current canvas, including its backing file.

Painters

draw-line start endprocedure: 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.

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

image-file->painter file-nameprocedure

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.

jpeg-file->painter file-nameprocedure: Alias for image-file->painter.

Example

(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))

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