Draw an arrow in racket

Question

How to draw an arrow in a frame in racket (DrRacket)? For example between two objects: a circle and a rectangle obtained by:

(send dc draw-ellipse 50 50 30 30) and (send dc draw-rectangle 200 200 30 6)

Depending on the goal of the program, it might be easier to draw a `pict` and then send the pict to the frame as a bitmap because it would avoid all the message passing semantics. `pict` is also easier to use in general. — ben rudgers, Jan 28 '15 at 19:48

score 2 · Answer 1 · answered Jan 29 '15 at 23:28

2

You can use picts to do such things.

First, you define your picts.

(define pict-a (rectangle 40 40))

(define pict-b (circle 40))

Then you combine them to be able to use rc-find or lc-find, which are the procedures that will help you connect those picts.

(define combined (hc-append 200 pict-a pict-b))

Finally

> (pin-arrows-line 30 combined
                   pict-a rc-find
                   pict-b lc-find
                   #:start-angle (/ pi 11)
                   #:end-angle (- (/ pi 11))
                   #:solid? #f)

Will produce this: Two picts connected

You can find more information in the docs! Tell us if that solved your problem!

answered Jan 29 '15 at 23:28

David Merinos

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I agree with you. But I want to do the same on a frame (GUI). It's possible? – chsms Feb 19 '15 at 10:48
I'm not used to GUI with Racket but I'm pretty sure you can send pics to a frame (?) and display it. – David Merinos Feb 20 '15 at 00:08
Can you try please David? – chsms Feb 22 '15 at 17:48
As I said I'm not used to GUI with Racket, I've never done it before, but since Racket uses Lambda programming you can pass a function to generate the pict and display it later. – David Merinos Feb 22 '15 at 23:32

score 1 · Answer 2 · edited Jan 28 '15 at 19:59

1

What kind of arrows?

For simple arrows use draw-line directly.
For bended arrows use draw-spline. Use a filled triangle as a simple arrow head.

If you need a prettier arrow head shape, one option is to adapt the arrow shape from MetaPict.

You can find other examples of arrows in MetaPict's documentation.

An example with a non-straight arrow which shows how to draw a state machine with MetaPict.

edited Jan 28 '15 at 19:59

ben rudgers

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answered Jan 28 '15 at 09:50

soegaard

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An arrow as in oriented graphs or Petri nets to connect two nodes. A bit like too pin-line-arrow but in frame. – chsms Jan 28 '15 at 10:09

Draw an arrow in racket

2 Answers2