resolve #84 [rt.cpan.org #67100] - document default charset

being nonsensical in some situations and the workaround being to pass
in -charset => '' in those cases. this is the path of least disruption
as there is currently no way to tell if the default charset is one
set by the user or the module, and the alternative of checking the
content type against the charset is a no go IMO

Changes

@@ -1,3 +1,10 @@
+4.08 2014-11-01
+
+    [ DOCUMENTATION ]
+    - note that calling headers without a -charset may lead to a nonsensical
+      charset being added to certain content types due to the default and the
+      workaround
+
 4.07 2014-10-12
 
     [ RELEASE NOTES ]

lib/CGI.pm

@@ -5238,7 +5238,13 @@ to use with certain servers that expect all their scripts to be NPH.
 
 The B<-charset> parameter can be used to control the character set
 sent to the browser.  If not provided, defaults to ISO-8859-1.  As a
-side effect, this sets the charset() method as well.
+side effect, this sets the charset() method as well. B<Note> that the
+default being ISO-8859-1 may not make sense for all content types, e.g.:
+
+    Content-Type: image/gif; charset=ISO-8859-1
+
+In the above case you need to pass -charset => '' to prevent the default
+being used.
 
 The B<-attachment> parameter can be used to turn the page into an
 attachment.  Instead of displaying the page, some browsers will prompt

t/headers/type.t

@@ -68,4 +68,34 @@ use Test::More;
     is $got, $expected, 'type and charset, type defines charset';
 }
 
+{
+    my $cgi = CGI->new;
+    my $got = $cgi->header( -type => 'image/gif' );
+    my $expected = 'Content-Type: image/gif; charset=ISO-8859-1'
+                 . $CGI::CRLF x 2;
+    is $got, $expected, 'image type, no charset';
+}
+
+{
+    my $cgi = CGI->new;
+    my $got = $cgi->header(
+		-type    => 'image/gif',
+		-charset => '',
+	);
+    my $expected = 'Content-Type: image/gif'
+                 . $CGI::CRLF x 2;
+    is $got, $expected, 'image type, no charset';
+}
+
+{
+    my $cgi = CGI->new;
+    my $got = $cgi->header(
+        -type    => 'image/gif',
+        -charset => 'utf-8',
+    );
+    my $expected = 'Content-Type: image/gif; charset=utf-8'
+                 . $CGI::CRLF x 2;
+    is $got, $expected, 'image type, forced charset';
+}
+
 done_testing;