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This part instructs you how to use the configuration to resize the gadget by adding the height attribute (for example, height="300")
to the <ModulePrefs> tag in the HelloGadget.xml file:
<ModulePrefs author="eXoPlatform"
title="Hello World"
directory_title="Hello World"
description="The simplest gadget"
height="300">
</ModulePrefs>
You can also resize a gadget through the web console as described in Editing a gadget.