[Octave-bug-tracker] [bug #51938] Contour lines of meshc disappear when calling axis

[Dan Sebald]

Follow-up Comment #7, bug #51938 (project octave):

I've attached a simple patch that adds a listener to the axes that passes the
contour handle into the function so it may be used to adjust the zlim.

The following works about right:


graphics_toolkit qt
figure
[X,Y] = meshgrid(-3:.125:3);
Z = peaks(X,Y);
meshc(X,Y,Z)
axis('equal')


albeit a little clunky.

However, pressing "Autoscale" has a problem.  Although the listener is called,
the placement of the contour seems to affect auto-zlim range.  I've lessened
the effect by de-activating zlimmode adjustment temporarily, but once it gets
turned back on the range readjusts.  In the patch I've printed out the actual
value of zlim minimum to illustrate.  I suppose the autoscale is designed to
leave a bit of space beyond the data limit even if that data limit falls at a
nice whole number.  (Without turning off auto-adjust, the code will get into a
short feedback loop where it keeps adjusting until finding a stopping point.) 
If someone can think of a way around this auto-adjusted zlim caused by the
placement of the contour, let me know (e.g., is there a way to take the
particular contour object out of the list of data elements used to determine
auto-range?).

(file #41742)
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Additional Item Attachment:

File name: octave-contour_listener-djs2017aug05.patch Size:1 KB


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