No, I didn't see this message, but I think we arrived at the same conclusion. I think the solution is just to calculate the width and height in the same way in both places (copy_to_bbox and the Qt blitting code in Python). We can't change bbox.bounds, since many other parts of the code rely on that calculation being in pure floating point. But there's only two places (in Qt and Qt4) that rely on the rounding behavior of copy_to_bbox, and IMHO, the way it does the rounding is the sanest way given that the edges must be integer-aligned.
I've committed these changes in r4995. Cheers, Mike Darren Dale wrote: > Hi Mike, > > On Monday 10 March 2008 08:24:27 am you wrote: > >> Sorry, I didn't see this latest e-mail before I replied before. I see >> the shearing now that I've adjusted window size. Maybe it could be >> related to the fact that width != span? Anyway, I'll investigated >> further and get back. >> > > Thanks for having a look. But before you dig to deep, did you see my last > post > to this thread?: > > ----- > I think this problem is due to a loss of precision in _backend_agg's > copy_from_bbox. That method takes a bbox with double precision as input, and > constructs a rect with ints as input: > > agg::rect_i rect((int)l, height - (int)t, (int)r, height - (int)b); > > A rendering buffer is created with a width based on that rect. Half of the > time, the width of that buffer disagrees with the width reported by the > original bbox. For example, I can kludge the bbox width so it agrees with the > output of copy_from_bbox: > > l, b, w, h = bbox.bounds > r = int(l+w) > w_mod = r-int(l) > > I can use w_mod instead of w as a workaround for the blitting issue I > reported, but I wonder if there might be a better solution? > ------ > > >> Darren Dale wrote: >> >>> On Friday 07 March 2008 4:58:03 pm Darren Dale wrote: >>> >>>> I am having some trouble with the Cursor widget with the qt4agg backend. >>>> Here is a short script which works with the gtkagg backend with useblit >>>> either true or false: >>>> >>>> ---------- >>>> from matplotlib import rcParams >>>> rcParams['backend']='gtkagg' >>>> from pylab import * >>>> from matplotlib.widgets import Cursor >>>> >>>> t = arange(0.0, 1.0, 0.01) >>>> s = sin(2*2*pi*t) >>>> ax = subplot(111) >>>> >>>> cursor = Cursor(ax, useblit=True) >>>> >>>> ax.plot(t, s, 'o') >>>> axis([0,1,-1,1]) >>>> show() >>>> ------------ >>>> >>>> If I use the qt4agg backend, with useblit False, the cursor lines do not >>>> render. If useblit is True, the lines render but the pixmap inside the >>>> axes is sheared. I've been looking at the backend_qt4agg code, the >>>> widgets.Cursor code, and the working animation_blit_qt4 example, but I'm >>>> stuck. Does anyone have any ideas? >>>> >>> Here is an additional wrinkle, sometimes the pixmap is sheared, and >>> sometimes it is not. The behavior seems to shift back and forth when I >>> change the horizontal size of the figure window, bu I don't see a pattern >>> emerging that would explain why: 556-559 pixels wide is sheared, 560-564 >>> looks ok, 565-567 is sheared, 568 is normal, 569 and 570 are sheared, >>> etc. The >>> animation_blit_qt4 demo also has the same problem, depending on the >>> horizontal size. So confusing. >>> -- Michael Droettboom Science Software Branch Operations and Engineering Division Space Telescope Science Institute Operated by AURA for NASA ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Matplotlib-devel mailing list Matplotlib-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-devel
