[plt-scheme] MrEd Graphics Questions

From: Robby Findler (robby at cs.uchicago.edu)
Date: Sat Apr 14 09:38:39 EDT 2007

On 4/13/07, Williams, M. Douglas <M.DOUGLAS.WILLIAMS at saic.com> wrote:
> First, does the basic structure of the graphical
> elements makes sense?  For example, I am using an editor-canvas% instance to
> the main output.  It works fine, but, for instance,  I would like to make it
> not editable since I am using it just for output.

Try calling the `lock' message with #t. (note you'll need to unlock it
when you insert something and then re-lock it when you're done)

>  Also, in the Options... menu item (under Edit), I am using text-field%
> instances and string->number to input simulation parameters.  Is there a
> better method for doing this that would make checking values easier.  In the
> same light, I would like to check the values when the field is exited.  Is
> there a way to do that?

You can pass a callback method to a text-field% that gets called on
each keystroke. You can use that to do some checking. If the text is
bad, you might just use something like this (where `e' is bound to the
text% object in the text-field%).

    (send e change-style
          (send (make-object style-delta%) set-delta-background (if on? "yellow"
 "white"))
          0 (send e last-position)))

to turn the text yellow, instead of rejecting it outright (then use
the ok button callback to reject the input when it is malformed).

hth,
Robby


Posted on the users mailing list.