doc, test, fix that style curve option can be 0

Author: mohawk2

README.pod

@@ -467,7 +467,7 @@ number supported by the backend.  The styles are generally defined by
 a mix of color and dash pattern, but the particular color and dash
 pattern depend on the engine in use. The first 30 styles are
 guaranteed to be distinguishable. This is useful to produce, e.g.,
-multiple traces with the same style.
+multiple traces with the same style. C<0> is a valid value.
 
 =back
 

lib/PDL/Graphics/Simple.pm

@@ -628,7 +628,7 @@ number supported by the backend.  The styles are generally defined by
 a mix of color and dash pattern, but the particular color and dash
 pattern depend on the engine in use. The first 30 styles are
 guaranteed to be distinguishable. This is useful to produce, e.g.,
-multiple traces with the same style.
+multiple traces with the same style. C<0> is a valid value.
 
 =back
 

lib/PDL/Graphics/Simple/PGPLOT.pm

@@ -234,8 +234,8 @@ sub plot {
     while (@_) {
 	my ($co, @data) = @{shift()};
 	my @extra_opts = ();
-	if ( defined($co->{style}) and $co->{style} ) {
-	    $me->{curvestyle} = int($co->{style});
+	if ( defined $co->{style} ) {
+	    $me->{curvestyle} = int($co->{style}) + 1;
 	} else {
 	    $me->{curvestyle}++;
 	}

lib/PDL/Graphics/Simple/PLplot.pm

@@ -330,7 +330,7 @@ sub plot {
     while (@_) {
 	my ($co, @data) = @{shift()};
 	my @extra_opts = ();
-	if ( $co->{style}) {
+	if (defined $co->{style}) {
 	    $me->{style} = $co->{style};
 	} else {
 	    $me->{style}++;

lib/PDL/Graphics/Simple/Prima.pm

@@ -506,7 +506,7 @@ sub plot {
 	my $co = shift @$block;
 
 	# Parse out curve style (for points type selection)
-	if ($co->{style}) {
+	if (defined $co->{style}) {
 	    $me->{curvestyle} = $co->{style};
 	} else {
 	    $me->{curvestyle}++;

t/simple.t

@@ -156,8 +156,8 @@ for my $engine (@engines) {
 # Simple line & bin plot
 {
 my @args = PDL::Graphics::Simple::_translate_plot(@$w{qw(held keys)},
-  with=>'line', $x10, $x10sqrt,
-  with=>'line', $x10, $x10_12,
+  with=>'line', style=>0, $x10, $x10sqrt,
+  with=>'line', style=>0, $x10, $x10_12,
   with=>'bins', $x10, $sin10,
   {title=>"PDL: $engine engine, line & bin plots"}
 );
@@ -173,11 +173,11 @@ is_deeply \@args, [
     'xrange' => [ 0, 9 ],
   },
   [
-    { 'key' => undef, 'style' => undef, 'width' => undef, 'with' => 'lines' },
+    { 'key' => undef, 'style' => 0, 'width' => undef, 'with' => 'lines' },
     $x10, $x10sqrt,
   ],
   [
-    { 'key' => undef, 'style' => undef, 'width' => undef, 'with' => 'lines' },
+    { 'key' => undef, 'style' => 0, 'width' => undef, 'with' => 'lines' },
     $x10, $x10_12,
   ],
   [
@@ -186,9 +186,9 @@ is_deeply \@args, [
   ]
 ];
 }
-      eval { $w->plot(with=>'line', $x10, $x10sqrt,
-		      with=>'line', $x10, $x10_12,
-		      with=>'bins', $sin10,
+      eval { $w->plot(with=>'line', style=>0, $x10, $x10sqrt,
+		      with=>'line', style=>0, $x10, $x10_12,
+		      with=>'bins', style=>3, $sin10,
 		 {title=>"PDL: $engine engine, line & bin plots"}),
       };
       is($@, '', "plot succeeded\n");
@@ -364,8 +364,8 @@ is_deeply \@args, [
 
       ask_yn qq{
 Testing $engine engine: You should see in a 3x2 grid:
-1) 2 superposed line plots and a bin plot, with x range from 0 to 9 and
-yrange from 0 to 9. The three plots should have different line styles.
+1) 2 superposed line plots with same style and a bin plot with different,
+with x range from 0 to 9 and yrange from 0 to 9.
 2) error bars (symmetric relative to each plotted point) and limit bars
 (asymmetric about each plotted point).
 3) a radial 11x11 "target" image and some superimposed "circles".