Fix some issues with plots.pl and the graph tool.

First, fix the alt attribute for TikZ and GD image types for plots.pl.

The `image` method of `PGbasicmacros.pl` currently sets the
`aria_description` with the value of the `alt` option if it is passed to
the method, and it does so regardless of the plots image type.  However,
that is only used for `html` output with JSXGraph.  Thus for TikZ or GD
image types the alt attribute is lost.  This makes it so that the
`aria_description` is only set for `html` output, and for all other
outputs the given alt tag is left in the `@alt_list` so that the later
code that inserts the `<image>` tag can get it and add it as an
attribute to the `<image>` tag.

You can test this with the following MWE:

```perl
DOCUMENT();

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

$plot = Plot();
$plot->add_function('x^2', 'x', -10, 10, color => 'blue');
$plot->image_type('tikz');

BEGIN_PGML
[!graph of x^2!]{$plot}{300}
END_PGML

ENDDOCUMENT();
```

With that example and the current code, the image will not have an alt
attribute, but will with this pull request.  If you remove the line that
sets the image type to 'tikz', then the JSXGraph image will get the aria
description (with the second fix below).

Second, fix the aria description for both JSXGraph output of plots.pl
and the graph tool.

This is caused by the removal of the `description` option for the
`JXG.Board` object in the JSXGraph library. I must have missed this when
this happened three years ago. Although, it seems to have been done
rather quietly, as this is not listed in the change log for JSXGraph.

To fix this, I just do the same thing that the `description` option used
to do, and add a visually hidden span that the graph is `aria-describedby`.
Note that there is a new `aria-description` attribute that could be used
in the future for this, but it is in a future aria specification, and I
don't know how well supported it is at this point.

Finally, fix some issues with GD output of the plots.pl macro.  This is
caused when an Plots::Plot object does not have the height explicitly
set.  For TikZ and JSXGraph output, the `size` method is called which
determines the height if it is not set explicitly.  So GD output should
do the same.

Author: drgrice1

htdocs/js/GraphTool/graphtool.js

@@ -69,7 +69,6 @@ window.graphTool = (containerId, options) => {
 	if ('htmlInputId' in options) gt.html_input = document.getElementById(options.htmlInputId);
 	const cfgOptions = {
 		title: 'WeBWorK Graph Tool',
-		description: options.ariaDescription ?? 'Interactively graph objects',
 		showCopyright: false,
 		pan: { enabled: false },
 		zoom: { enabled: false },
@@ -116,6 +115,14 @@ window.graphTool = (containerId, options) => {
 
 	const setupBoard = () => {
 		gt.board = JXG.JSXGraph.initBoard(`${containerId}_graph`, cfgOptions);
+
+		const descriptionSpan = document.createElement('span');
+		descriptionSpan.id = `${containerId}_description`;
+		descriptionSpan.classList.add('visually-hidden');
+		descriptionSpan.textContent = options.ariaDescription ?? 'Interactively graph objects';
+		gt.board.containerObj.after(descriptionSpan);
+		gt.board.containerObj.setAttribute('aria-describedby', descriptionSpan.id);
+
 		gt.board.suspendUpdate();
 
 		// Move the axes defining points to the end so that the arrows go to the board edges.

lib/Plots/GD.pm

@@ -63,7 +63,8 @@ sub im_y {
 	return unless defined($y);
 	my $plots = $self->plots;
 	my ($ymin, $ymax) = ($plots->axes->yaxis('min'), $plots->axes->yaxis('max'));
-	return int(($ymax - $y) * $plots->{height} / ($ymax - $ymin));
+	(undef, my $height) = $plots->size;
+	return int(($ymax - $y) * $height / ($ymax - $ymin));
 }
 
 sub moveTo {
@@ -217,12 +218,11 @@ sub draw_circle_stamp {
 }
 
 sub draw {
-	my $self   = shift;
-	my $plots  = $self->plots;
-	my $axes   = $plots->axes;
-	my $grid   = $axes->grid;
-	my $width  = $plots->{width};
-	my $height = $plots->{height};
+	my $self  = shift;
+	my $plots = $self->plots;
+	my $axes  = $plots->axes;
+	my $grid  = $axes->grid;
+	my ($width, $height) = $plots->size;
 
 	# Initialize image
 	$self->im->interlaced('true');

lib/Plots/JSXGraph.pm

@@ -404,7 +404,6 @@ sub init_graph {
 
 	my $JSXOptions = Mojo::JSON::encode_json({
 		title          => $axes->style('aria_label'),
-		description    => $axes->style('aria_description'),
 		boundingBox    => [ $xmin, $ymax, $xmax, $ymin ],
 		axis           => 0,
 		showNavigation => $allow_navigation,
@@ -497,6 +496,12 @@ sub init_graph {
 	$self->{JSend} = '';
 	$self->{JS}    = <<~ "END_JS";
 			const board = JXG.JSXGraph.initBoard(id, $JSXOptions);
+			const descriptionSpan = document.createElement('span');
+			descriptionSpan.id = `\${id}_description`;
+			descriptionSpan.classList.add('visually-hidden');
+			descriptionSpan.textContent = '${\($axes->style('aria_description'))}';
+			board.containerObj.after(descriptionSpan);
+			board.containerObj.setAttribute('aria-describedby', descriptionSpan.id);
 			board.suspendUpdate();
 			board.create('axis', [[$xmin, $xaxis_pos], [$xmax, $xaxis_pos]], $XAxisOptions);
 			board.create('axis', [[$yaxis_pos, $ymin], [$yaxis_pos, $ymax]], $YAxisOptions);

macros/core/PGbasicmacros.pl

@@ -2928,9 +2928,9 @@ sub image {
 			$image_item->{width}    = $width    if $out_options{width};
 			$image_item->{height}   = $height   if $out_options{height};
 			$image_item->{tex_size} = $tex_size if $out_options{tex_size};
-			$image_item->axes->style(aria_description => shift @alt_list) if $out_options{alt};
 
 			if ($image_item->ext eq 'html') {
+				$image_item->axes->style(aria_description => shift @alt_list) if $out_options{alt};
 				$image_item->{description_details} = $description_details;
 				push(@output_list, $image_item->draw);
 				next;