Adding a block to login onepage checkout

Question

I try to add an additional login option during the checkout process. At the moment, you have the username/password way. I want to add a button image to login via an OAuth process (in my case Github).

I found a way but it's not the best way. There is in the checkout/onepage/login.phtml template file, a call to get a block child named form.additional.info.

I tried to insert my own block in it in this way but it didn't work.

<checkout_onepage_index>
        <reference name="form.additional.info">
            <block type="core/template" name="login_github_button" as="login.github.button">
                <action method="setTemplate" ifconfig="github/config/enabled">
                    <template>github/customer/login.phtml</template>
                </action>
            </block>
        </reference>
</checkout_onepage_index>

I found a different way like it is done by the captcha module:

<checkout_onepage_index>
    <reference name="checkout.onepage.login">
        <block type="core/text_list" name="form.additional.info">
            <block type="core/template" name="login_github_button" as="login.github.button">
                <action method="setTemplate" ifconfig="github/config/enabled">
                    <template>github/customer/login.phtml</template>
                </action>
            </block>
        </block>
    </reference>
</checkout_onepage_index>

In this case, it works BUT the captcha won't be displayed. How can I insert several blocks into form.additional.info block?

Thanks for your help

EDIT:

I found some reasons why the button is not displayed under the login fields when using the reference form.additional.info method. It is displayed in the checkout billing view instead.

1. The block form.additional.info is created by the captcha module for the block checkout.onepage.login then it is also created for the block checkout.onepage.billing
2. While generating the block in Mage_Core_Model_Layout::_generateBlock() it searches the parent block object of the block login_github_button. Instead of finding the one of checkout.onepage.login, it finds one of the latest created: checkout.onepage.billing. The block is attached to this last one, instead of the log in one. Then I find my login button in the billing address view instead of the login view!!!
3. If I comment into the layout captcha.xml file the part about checkout.onepage.billing my first solution works.

It's still not ok but I begin to find the reasons.

Answer 1

Well, the only solution I see is to create into the layout module the block, add the code of the captcha and add as reference my customized code. In this case it is accepted.

Unfortunately, it will still be difficult to insert a block into the form.additional.info block.

Here is the solution I implemented:

<checkout_onepage_index>
    <reference name="checkout.onepage.login">
        <block type="core/text_list" name="form.additional.info">
            <block type="captcha/captcha" name="captcha">
                <reference name="head">
                    <action method="addJs"><file>mage/captcha.js</file></action>
                </reference>
                <action method="setFormId"><formId>user_login</formId></action>
                <action method="setImgWidth"><width>230</width></action>
                <action method="setImgHeight"><width>50</width></action>
            </block>
        </block>

        <reference name="form.additional.info">
            <block type="core/template" name="login_github_button" as="login.github.button">
                <action method="setTemplate" ifconfig="github/config/enabled">
                    <template>github/customer/login.phtml</template>
                </action>
            </block>
        </reference>
    </reference>
</checkout_onepage_index> 

Answer 2

the captcha.xml generates the block, so it should be useable. Did you add a

<depends>
    <Mage_Captcha />
</depends>

to be sure, that your block already exists, when you try to add a child to it?