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1.If it is 1.2.0, modify <mantis directory> / plugins / MantisGraph / pages / config.php
$ t_current_font_selected = array (
'arial' => false,
'verdana' => false,
'trebuchet' => false,
'verasans' => false,
'chinese_gbk' => false, / / newly added
'times' => false,
'georgia' => false,
'veraserif' => false,
'courier' => false,
'veramono' => false,
);

Also a need to modify the local (the last one label, and on top of the br)
<td style="vertical-align: top">
Sans-serif:

<label> <input type = "radio" name = "font" value = "arial" <? php echo print_font_checked ( 'arial' )?>/> Arial </ label>

<label> <input type = "radio" name = "font" value = "verdana" <? php echo print_font_checked ( 'verdana' )?>/> Verdana </ label>

<label> <input type = "radio" name = "font" value = "trebuchet" <? php echo print_font_checked ( 'trebuchet' )?>/> Trebuchet </ label>

<label> <input type = "radio" name = "font" value = "verasans" <? php echo print_font_checked ( 'verasans' )?>/> Vera Sans </ label>

<label> <input type = "radio" name = "font" value = "chinese_gbk" <? php echo print_font_checked ( 'chinese_gbk' )?>/> chinese_gbk </ label>
</ td>

2.If it is 1.2.0, modify <mantis directory> / plugins / MantisGraph / pages / config_edit.php
if (plugin_config_get ( 'font')! = $ f_font) (
switch ($ f_font) (
case 'arial':
case 'verdana':
case 'trebuchet':
case 'verasans':
case 'chinese_gbk': / / newly added
case 'times':
case 'georgia':
case 'veraserif':
case 'courier':
case 'veramono':
plugin_config_set ( 'font', $ f_font);
break;
default:
plugin_config_set ( 'font', 'chinese_gbk'); / / where to change the default values, do not change, then you can manually select what
)
)

After completing these steps, to system management - plug-in management-Mantis Graphs 1.0, went in to see should have been set to chinese_gbk