Magento widget doesn't show custom template

Question

I set up a custom module with one custom widget in Magento. The widget should render some HTML in frontend. Therefore I created a custom .phtml file and configured it in widget.xml

<?xml version="1.0"?>
<widgets>
    <startslider_slider type="startslider/slider ">
        <name>Slider Startpage</name>
        <description type="desc">Adds a slider</description>
        <parameters>
            <the_text>
                <label>myTestText</label>
                <visible>1</visible>
                <required>1</required>
                <type>text</type>
            </the_text>
            <template translate="label">
                <label>Frontend Template</label>
                <visible>1</visible>
                <required>1</required>
                <type>select</type>
                <values>
                    <three translate="label">
                        <value>startslider/slider-3.phtml</value>
                        <label>Slider with three blocks</label>
                    </three>
                    <four translate="label">
                        <value>startslider/slider-4.phtml</value>
                        <label>Slider with four blocks</label>
                    </four>
                </values>
            </template>
        </parameters>       
    </startslider_slider>
</widgets>

I can insert and configure the widget in backend ( {widget type="startslider/slider" the_text="blabla" template="startslider/slider-3.phtml"} ) and in frontend the _toHtml() method of the block class is executed and some text is output, just for testing. But the content of the .phtml template is never shown. I'm wondering if Magento is unable to find the .phtml?

I put the .phtml in the following locations:

magento-vhost/app/design/frontend/default/myCustomTheme/template/startslider/slider-3.phtml
magento-vhost/app/design/frontend/default/default/template/startslider/slider-3.phtml
magento-vhost/app/design/frontend/base/default/template/startslider/slider-3.phtml 

Did I forget something? Do I have to configure sth. else to use custom .phtml?

Answer 1

Too many possible things it could be, but here's some stuff to try.

What class does your startslider/slider widget inherit from? If it's not Mage_Core_Block_Template then you don't have a template widget block.

You created a _toHtml method for your widget — does this widget still call parent::_toHtml();. If not the template rendering code will never be run.

What does

var_dump($this->getData());
var_dump($this->getTemplate());
var_dump($this->getTemplateFile());

render from the _toHtml method? Do these paths match up exactly (including letter case) with the file system?