From 995ba8e687cfc959aa69c23c9eb954f5ab153ff8 Mon Sep 17 00:00:00 2001
From: Glenn Rice <grice1@missouriwestern.edu>
Date: Tue, 24 Mar 2026 11:42:03 -0500
Subject: [PATCH] Fix `drawZero` for JSXGraph output of the plots macro.

Currently if the y axis location is 'center', 'left' (or 'box'), or
'right', then the determination that zero is drawn is made by checking
that the y axis min or max value.  That is incorrect.  It should be
checking the x axis min or max value.  The point is that if the y axis
is passing through x = 0, then zero should not be drawn, and otherwise
it should be.

Similarly, the y axis `drawZero` determination is fixed.

You can test this with the following problem code:

```
DOCUMENT();

loadMacros('PGstandard.pl', 'PGML.pl', 'plots.pl', 'PGcourse.pl');

$graph = Plot(
    xmin           => -2,
    xmax           => 10,
    xtick_distance => 1,
    xminor         => 0,
    xlocation      => 'bottom',
    ymin           => 0,
    ymax           => 10,
    ytick_distance => 1,
    yminor         => 0,
    ylocation      => 'left'
);

BEGIN_PGML
[!graph!]{$graph}{500}
END_PGML

ENDDOCUMENT();
```

With that example and the develop branch the zero on the x-axis is
incorrectly not drawn in JSXGraph output.  With this branch it is drawn
as it should be. Note that in TikZ output the zero is drawn with this
example. So this makes the two output formats consistent.
---
 htdocs/js/Plots/plots.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/htdocs/js/Plots/plots.js b/htdocs/js/Plots/plots.js
index 7e1c0416a..e53dc99fc 100644
--- a/htdocs/js/Plots/plots.js
+++ b/htdocs/js/Plots/plots.js
@@ -347,8 +347,8 @@ const PGplots = {
 									!options.yAxis?.visible ||
 									(options.yAxis.location === 'center' && (options.yAxis.position ?? 0) != 0) ||
 									((options.yAxis.location === 'left' || options.yAxis.location === 'box') &&
-										(options.yAxis.min ?? -5) != 0) ||
-									(options.yAxis.location === 'right' && (options.yAxis.max ?? 5) != 0)
+										(options.xAxis.min ?? -5) != 0) ||
+									(options.yAxis.location === 'right' && (options.xAxis.max ?? 5) != 0)
 										? true
 										: false,
 								insertTicks: false,
@@ -446,8 +446,8 @@ const PGplots = {
 									!options.xAxis?.visible ||
 									(options.xAxis.location === 'middle' && (options.xAxis.position ?? 0) != 0) ||
 									((options.xAxis.location === 'bottom' || options.xAxis.location === 'box') &&
-										(options.xAxis.min ?? -5) != 0) ||
-									(options.xAxis.location === 'top' && (options.xAxis.max ?? 5) != 0)
+										(options.yAxis.min ?? -5) != 0) ||
+									(options.xAxis.location === 'top' && (options.yAxis.max ?? 5) != 0)
 										? true
 										: false,
 								insertTicks: false,