Hi Matthew, On 05/24/11 05:02, Matthew Flatt wrote: > At Mon, 23 May 2011 16:04:24 +0200, Marijn wrote: >> I'm trying to implement a toy graphical list editor program to get a >> feel for GUI programming in racket. Basic idea is a graphical >> representation of a list with text-field%s alternated with buttons to >> insert items and on the side of each text-field% a button to remove that >> item. When the program is destroyed it should print the constructed list >> on the console (when started from one). My understanding so far calls >> for a doubly-linked list to hold the items (and their graphical >> manifestation), although this seems very unlispy... Is there a better way? > > My preference for this sort of problem is to abandon MVC and let the > GUI represent the model. That is, to build the result list in this > case, I'd traverse the GUI hierarchy to extract the elements. > > To keep the model separate, though, I don't have a better suggestion > than a doubly-linked list. > >> Sample code showing graphical layout and rudimentary functioning of the >> program is attached. >> >> Side-question: why does pressing an insert-button resize the top-level >> frame%? > > When a text field has a non-empty string as its initial value, the > minimum width is based on the string. If the initial value is an empty > string, then a default is used, and the default turns out to be wider > than one character. The "insert" buttons create empty fields, while the > three initial fields have non-empty initial content.
After changing all the values to "1", when pressing an insert-button *sometimes* the window is resized horizontally (slightly larger width) and *sometimes* the window flickers to slightly larger horizontally, but remains the same width. According to `get-graphical-min-size' the horizontal width stays constant at, for me, 58. I wrote another program which exhibits this flickering behavior for me which I attached. Again the size output seems to be fine, at least on the granularity instrumented. Is this expected behavior? Thanks, Marijn
#lang racket/gui
(define (get-size)
(call-with-values (lambda ()(send items get-graphical-min-size))
(λ (a b) (write a)(display " , ")(write b)(newline)) ))
(define f (new frame% [label "List Editor"]))
(define items (new vertical-pane% (parent f))) (get-size)
;(un)comment this line to change the smaller size of the flicker
;(new text-field% (parent f) (label "") (init-value "1")) (get-size)
(send f show #t) (get-size)
(for-each (λ (v)
(get-size)
(new text-field% (parent items) (label "") (init-value
(number->string v))))
'(1 2 2 3 4 4 5 2 2 3 4 3 4 2 3 4 2 5 1 2 4 1 5 2 3 4 3 3 4))
signature.asc
Description: OpenPGP digital signature
_________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
