By the way, the same sort of bug affects draw-ellipse and canvas%.<div> </div><div>-- Garrett Mitchener <div class="gmail_quote">On Thu, May 10, 2012 at 11:10 AM, Garrett Mitchener <<a href="mailto:garrett.mitchener@gmail.com" target="_blank">garrett.mitchener@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Okay, yes, using a dc-path% seems to work as intended. Thanks! -- Garrett Mitchener <div class="HOEnZb"><div class="h5"> <div class="gmail_quote">On Thu, May 10, 2012 at 11:04 AM, Matthew Flatt <<a href="mailto:mflatt@cs.utah.edu" target="_blank">mflatt@cs.utah.edu</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Although pixel alignment can be confusing, I think this one is just a bug. The `draw-rectangle' method tries to adjust the width of an outline so that in the simple case --- a width 0 or 1 pen in unsmoothed or aligned mode with a bitmap target --- the rectangle outline is the given width and height, instead of extending an extra pixel. That adjustment isn't implemented correctly, and the problem is particularly clear with a large scaling factor. You can work around the problem by creating a rectangle `dc-path%' and drawing it with `draw-path'. Meanwhile, I'll fix `draw-rectangle'. <div><div> At Thu, 10 May 2012 09:57:26 -0500, Robby Findler wrote: > The problem is that the coordinates are "between" the pixels. There is an > explanation of this in the context of another library, but the issues are > the same: > > > <a href="http://docs.racket-lang.org/teachpack/2htdpimage.html?q=2htdp/image#%28part._nitty-g" target="_blank">http://docs.racket-lang.org/teachpack/2htdpimage.html?q=2htdp/image#%28part._nitty-g</a> > ritty%29 > > hth, > Robby > > On Thu, May 10, 2012 at 8:29 AM, Garrett Mitchener < > <a href="mailto:garrett.mitchener@gmail.com" target="_blank">garrett.mitchener@gmail.com</a>> wrote: > > > Hi, I'm learning the racket GUI package, and I ran into something that > > doesn't make sense to me: > > > > #lang racket/gui > > > > (define black-pen > > (new pen% > > [width 1] > > [color "black"])) > > > > (define blue-brush > > (new brush% > > [color "blue"])) > > > > (define (draw-test-2 dc) > > (send dc scale 10 10) > > (send dc set-pen black-pen) > > (send dc set-brush blue-brush) > > (send dc draw-rectangle 7 2 4 4)) > > > > (define pic (make-bitmap 200 100)) > > > > (define dc (new bitmap-dc% [bitmap pic])) > > > > (draw-test-2 dc) > > > > And at the end, pic looks like this: > > > > [image: Inline image 1] > > The outline and the filling don't line up. What am I doing wrong? This > > is with DrRacket 5.2.1 on linux. > > > > Thanks, > > -- Garrett Mitchener > > > > ____________________ > > Racket Users list: > > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> > > > > > ____________________ > Racket Users list: > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </div></div></blockquote></div> </div></div></blockquote></div> </div>