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[Octave-bug-tracker] [bug #52260] Axes appear upside down with Qt5

From: Dan Sebald
Subject: [Octave-bug-tracker] [bug #52260] Axes appear upside down with Qt5
Date: Mon, 23 Oct 2017 16:44:51 -0400 (EDT)
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:55.0) Gecko/20100101 Firefox/55.0

Follow-up Comment #10, bug #52260 (project octave):

I'm attaching a diff file that adds a few lines to print out information to
stderr.  Here's what it looks like for me:

 h_axes3 = subplot (2, 2, 4);
  h_surf2 = surf (h_axes3, peaks, "LineStyle", "none");
  view (3);
  title ("Surface without lighting");

VW = 0 0 560 420
Mat1 = 1.000000 0.000000 0.000000 0.000000
Mat2 = 180.997043 0.000000 0.000000 0.000000

and I'm curious what is shown for your system (when in the mode that plots
axes upside down).  To apply, try something like

patch -p1 < dump_opengl_transform_info-djs2017oct23.diff

I guess what I'm most curious about is what VW looks like and whether yours
indicates 0 420 in the first two locations as opposed to 0 0.  The value back

    glGetIntegerv (GL_VIEWPORT, vw);

is supposed to be the lower left corner.  A 0 420 would then mean that the
coordinate system has 0,0 at the top left.

Notice in this line of code:

    glOrtho (0, vw[2], vw[3], 0, xZ1, xZ2);

only vw[2] and vw[3] get used.  I don't see anywhere that vw[0] and vw[1] are
used.  Hence, I'm wondering if there is an inherent assumption in the Octave
code that the coordinate system is bottom left 0,0.

I can't explain why ticks and annotation come out correctly if the
orthographic projection is wrong.


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