> #lang racket > (require racket/gui/base) > > #|Hello all, > Patrick here- > First, my apologies for posting a non-working example-I hope I didn't > waste anyone's time. Secondly, thanks to Matthias and Robby for the > corrections-I will certainly refer to these when I use eventspaces again. > > I found the issue I had seen, and it had nothing to do with eventspaces-it > occurred even without the call-with-eventspace machinery. Rather, the > message% used truncated all text whose length exceeded that of the original > init field [Label]. I think there is either a docs bug or a bug in the > Windows implementation. |# > > #|Problem: I have a message% control called x-pos parented by a frame% > called parent1. I have a canvas% subclass called canvas parented under > frame% parent2. I would like x-pos to always show the current x coordinate > of the mouse position over canvas, and for this to be kept up to date as > the mouse moves.|# > > #|Setting up the first frame and parent.|# > > (define parent1 (new frame% > [label "Parent1"] > [width 200] > [height 200] > [enabled #t])) > > #|Upon further investigation, I found that the label was indeed showing > the first digit of the number, and truncating the remaining. This was of > course dependent on the length of the label set on message% init. message% > does not resize automatically, and I needed to set the auto-resize field to > #t. It also didn't show in my original test-sort of a heisenbug because I > used a really long initial label in my test scenario. > > > From > http://docs.racket-lang.org/gui/message_.html > "If auto-resize is not #f, then automatic resizing is initially enanbled > (see auto-resize), and the message% object’s graphical minimum size is as > small as possible." -> this doesn't appear to be the case here. Windows XP, > Racket 5.1 > > I don't have a linux box to test atm, but I wonder if the default for the > auto-size field is #t there. If so, either the docs are incorrect, or the > windows implementation. If not, docs need to be updated. I'd be glad to > help in any way possible.|# > > (define x-pos (new message% > [parent parent1] > [label "0"])) > > #|This variant of x-pos works, resizing with new set-label requests and > thus avoiding the truncation. |# > #;(define x-pos (new message% > [parent parent1] > [label "0"]#|Setting the label to say, "Long label!" > avoids the behavior.|# > [auto-resize #t])) > > (send parent1 show #t) > > #|The second frame*pos combo-|# > > (define parent2 (new frame% > [label "Parent2"] > [width 200] > [height 200] > [enabled #t])) > > #|Here comes the canvas subclass-I'm looking to override on-event method > to grab the x-component of the mouse pos, and I want to have that > constantly updating the x-pos message%. I really want reactive behavior, > but I ran into some issues with the frtime-namely, differences in bindings > due to the mzscheme bindings. the require spec (prefix-in ..) doesn't > appear to be in the language. I'm probably doing something wrong. |# > (define my-canvas% (class canvas% > > (inherit get-dc) > > (define/override (on-event mouse-event) > (define x (send mouse-event get-x)) > (send x-pos set-label (number->string x))) > (super-new))) > > (define canvas (new my-canvas% [parent parent2] > [label "Nothing yet."])) > > (send parent2 show #t) > > > #|There you have it kids-message% objects don't auto-resize, and will > truncate the text that is longer than the [label] that they are init-ed > with. Sorry for the noise. |# > > > > On 20 April 2012 10:34, Matthias Felleisen <matth...@ccs.neu.edu> wrote: > >> >> Here is a solution in the DrRacket beginner language: >> >> (require 2htdp/universe) >> (require 2htdp/image) >> >> (define (bundle x) (make-bundle x '() '())) >> >> (launch-many-worlds >> (universe 'n/a (on-new (λ (u nw) (bundle u))) (on-msg (λ (u w m) (bundle >> m))) (state #t)) >> (big-bang 'n/a (to-draw (λ (w) (empty-scene 200 200))) >> (register LOCALHOST) >> (on-mouse (λ (w x y ke) (make-package w x))))) >> >> Here is a solution in Racket derived from yours: >> >> #lang racket >> >> (require racket/gui/base) >> >> (define show-x >> (new frame% >> [label "frame for displaying the current x coordinate"] >> [width 200] >> [height 200] >> [enabled #t])) >> >> (define x-pos >> (new message% >> [parent show-x] >> [label "No x-pos yet."])) >> >> (define discover-x >> (new frame% >> [label "frame for noticing mouse evets and their current x >> coordinates"] >> [width 200] >> [height 200] >> [enabled #t])) >> >> (define y-pos >> (new (class canvas% >> (inherit get-dc) >> (super-new) >> (define/override (on-event mouse-event) >> (define x-pos (send mouse-event get-x)) >> (define y-pos (send mouse-event get-y)) >> (set! *x x-pos) >> (refresh))) >> [parent discover-x])) >> >> ;; for communicating between the two frams >> (define *x 'n/a) >> >> (define (refresh) >> (send x-pos set-label (format "~a" *x))) >> >> ;; run program run >> (send show-x show #t) >> (send discover-x show #t) >> >> ;; you were creating way too many event spaces. No need for that. >> >> >> >> >> On Apr 19, 2012, at 2:32 PM, Patrick Mahoney wrote: >> >> > #lang racket >> > #|Hello all, I'm PMah. |# >> > (require racket/gui/base) >> > >> > #|Problem: I have a message% control called x-pos parented by a frame% >> called parent1. I have a canvas% called canvas parented under frame% >> parent2. I would like x-pos to always show the current x coordinate of the >> mouse position over canvas, and for this to be kept up to date as the mouse >> moves. Ultimately I'd love to move to a reactive semantics. |# >> > >> > >> > #|Setting up the first frame and parent. I'm also going to grab the >> eventspace for this frame while I'm at it.|# >> > (define parent1 (new frame% >> > [label "Parent1"] >> > [width 200] >> > [height 200] >> > [enabled #t])) >> > >> > (define x-pos (new message% >> > [parent parent1] >> > [label "No x-pos yet."])) >> > >> > (send parent1 show #t) >> > >> > (define eventspace1 (send parent1 get-eventspace)) >> > >> > >> > #|The second eventspace*frame*pos combo-|# >> > (define parent2 (new frame% >> > [label "Parent2"] >> > [width 200] >> > [height 200] >> > [enabled #t])) >> > >> > >> > #|Here comes the canvas subclass-I'm looking to override on-event >> method to grab the x-component of the mouse pos, and I want to have that >> constantly updating the x-pos message%. I really want reactive behavior, >> but I ran into some issues with the frtime-namely, differences in bindings >> due to the mzscheme bindings. the require spec (prefix-in ..) doesn't >> appear to be in the language. I'm probably doing something wrong. |# >> > (define y-pos (class canvas% >> > >> > (inherit get-dc) >> > #|My notion of scope in objects is not precise. With those defines >> within the scope of the on-event bindings, do the defines recalculate each >> time on-event receives a message? lo, I wish I had some sort of channel >> protocol to pass messages between threads, along with control. >> > The mushrooms kick in now. >> > PFFFT MIND >> > |# >> > (define/override (on-event mouse-event) >> > (define min-x (dc:min-x (get-dc))) >> > (define max-x (dc:max-x (get-dc))) >> > (define min-y (dc:min-y (get-dc))) >> > (define max-y (dc:max-y (get-dc))) >> > (define x-pos (send mouse-event get-x)) >> > (define y-pos (send mouse-event get-y)) >> > (call-in-other-eventspace (make-eventspace) (draw-diagnostics >> max-x max-y x-pos y-pos))) >> > >> > (super-new))) >> > >> > (define >> > (send parent2 show #t) >> > >> > >> > #|I have tried some of the examples on >> http://groups.google.com/group/plt-scheme/browse_thread/thread/28af25a01200bc3c/7937bb0314cc231e?lnk=raot >> > Basically, one using a channel, probably incorrectly and the second >> without. Now what I believe I've done is to add the thunk to the queue in >> the frame% parent1's eventspace, but I haven't transferred control. The >> other eventspace's thread still has control. Kind of? >> > |# >> > (define (call-in-other-eventspace e thunk) >> > (let ([ch (make-channel)]) >> > (parameterize ([current-eventspace e]) >> > (queue-callback (lambda () >> > (channel-put ch (thunk))))) >> > (channel-get ch))) >> > #|This blocks both frames updating in some way-im not able to >> transfer control smoothly to the thread in the message% message1 workspace, >> and so the x-pos label updates only sporadically when the other eventspace >> thread yields? |# >> > (define (call-in-other-eventspace e thunk) >> > (parameterize ([current-eventspace e]) >> > (queue-callback thunk))) >> > >> > >> > #|How can I get x-pos to update automatically on each on-event send >> here? (draw-diagnostics max-x max-y x-pos y-pos) appears to terminate here >> in all cases. Part 2: how can I apply frtime to make the update >> relationship I want between canvas mouse position and message text (or >> other racket reactive work if it exists.). I really would like to >> understand this idiom and get it in my toolchest for gui programming. >> Thanks all! Racket is an impressive contribution to computer science. |# >> > >> > >> > >> > ____________________ >> > Racket Users list: >> > http://lists.racket-lang.org/users >> >> >
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