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AMP Form

jeudi 16 février 2017

Once I had the authorization working and could display the comment form properly the next step was to get the form submitting properly. First of all, to use forms in AMP you need to include the following script:

<script async custom-element="amp-form" src="https://cdn.ampproject.org/v0/amp-form-0.1.js"></script>

AMP forms work mostly the same way as normal HTML5 forms, but there are a few differences. With AMP you have to either use GET forms or you can use POST forms but you need to use action-xhr instead of action. For POST forms you also need to include a target of either _blank or _top. Using action-xhr means that the page will basically post an AJAX request which expects a JSON response instead of reloading the whole page. If you want to reload the whole page you should use method="get". 

The response from the request needs to include the same headers as the authorization request, which are detailed in this post. The response doesn't need to contain any specific data, you can put whatever you want in there. You can use the response data to update the page after a successful post, but I have not done that yet.

In this case, the controller function action for my new comment just adds the comment and then returns the id and body of the new comment in JSON along with the necessary headers. I would like to display the new comment on the page, but the syntax to display the JSON data is {{ var }} which is the same syntax blade uses. I know there is a workaround for this, but I haven't looked for it yet.

The two big issues I had with this form were how to update the page after a successful post. I wanted to do two things: hide the form to leave a comment and display a success message. There are AMP components to accomplish both of these tasks.

To hide the form after a successful post you can add the following CSS:

form.amp-form-submit-success > input {
  display: none

And set the form's class to "hide-inputs." When the success message comes back the form's class is updated to included amp-form-submit-success which will cascade down to hide any child inputs. I had my inputs in a panel inside the form and the inputs were not hidden because the input was not a direct child of the form. This was fixed by rearranging the elements so that the form was inside the divs so that the inputs were children of the form. Before I arrived at this solution I first tried to hide the entire form, which worked great, but also hid the success message. Since my form field was a textarea I had to add another item to the CSS for textareas, otherwise identical to that above.

The next step was displaying a success message, which I did by following the instructions here. The block of sample code from this page is:


  <form class="hide-inputs" method="post" action-xhr="https://ampbyexample.com/components/amp-form/submit-form-input-text-xhr" target="_top">
    <input type="text" class="data-input" name="name" placeholder="Name..." required>
    <input type="submit" value="Subscribe" class="button button-primary">
    <div submit-success>
    <template type="amp-mustache">
    Success! Thanks {{name}} for trying the
    <code>amp-form</code> demo! Try to insert the word "error" as a name input in the form to see how
    <code>amp-form</code> handles errors.
    <div submit-error>
    <template type="amp-mustache">
    Error! Thanks {{name}} for trying the
    <code>amp-form</code> demo with an error response.
The div submit-success is hidden until the form submission comes back with a success message at which point it is display, and likewise with the submit-error block. To use the amp-mustache templates you need to include the following in a script tag:

script custom-template="amp-mustache" src="https://cdn.ampproject.org/v0/amp-mustache-0.1.js"

In the submit-success section the {{ name }} will substitute in the "name" element from the JSON data returned from the post. In my case I have left this out for now and just display a success message and hide the form. 

To see this in action you can look at the AMP version of this blog here. When you submit a comment the form disappears and is replaced by a success message. Ideally the new comment would show up, but I'll get to that at some point in the future.

Update - the blade syntax to display the "{{ }}" for Javascript is "@{{ whatever }}". So I updated my code to actually display the comment after it is posted.

Libellés: coding, laravel, amp
1 commentaires

AMP Authentication

mercredi 15 février 2017

I finally got the AMP forms working as expected. It was a bit tricky to figure out so I will outline the issues I encountered and how I solved them. The situation I was working with was making a comments form for the AMP version of my blog pages.

The first issue I had to deal with was that a user can't leave a comment unless they are logged in. In the rest of the app I use the session to determine if the user is logged in, but AMP has it's own protocol for doing that, which involves making AJAX requests to a page which returns a JSON response to determine if the user is logged in. In this case, in the controller I simply do an Auth::check() and return a JSON response depending on the results of the check(). 

The issues arose from the fact that AMP requires specific response headers, which took me a while to figure out how to set properly. I wasn't able to find much documentation on the values of these headers, but I was able to figure out the proper values.

The headers required were:

  • Access-Control-Allow-Credentials: true
  • Access-Control-Expose-Headers: AMP-Access-Control-Allow-Source-Origin
  • Access-Control-Allow-Origin
  • AMP-Access-Control-Allow-Source-Origin

The latter two headers need to have specific values, and although they ended up being the same in most cases, I set them to the separate values to make sure errors won't occur.

The value for Access-Control-Allow-Origin needs to be the "origin" header made in the request, which I get with:


The value for the AMP-Access-Control-Allow-Source-Origin needs reflect the value passed in the URL to the request, which is a parameter named:  __amp_source_origin.

The authorization page can return a variety of values to indicate whether the user has a subscription, if they can view a specific number of free articles, and what they have access to. But in my case all I need to know is whether they are logged in or not, so I just return the JSON data:

{loggedIn: true}

To enable content being displayed differently based on authorization you need to include the following scripts:

<script async custom-element="amp-access" src="https://cdn.ampproject.org/v0/amp-access-0.1.js"></script>
<script async custom-element="amp-analytics" src="https://cdn.ampproject.org/v0/amp-analytics-0.1.js"></script>

You also need to include the following in a script to tell the scripts what to do and where to get the info from:
    "authorization": "[Auth URI]",
    "noPingback": "true",
    "login": {
        "sign-in": "[Login URI]",
        "sign-out": "[Logout URI]"
    "authorizationFallbackResponse": {
        "error": true,
        "loggedIn": false

Where [Auth URI] is the URI detailed above which returns whether the user is logged in or not; [login URI] is the URI to allow the user to login; and [logout URI] is the URI to allow the user to logout. All URIs must either be HTTPS or // or AMP will complain about them and won't function properly.

Then the following code is included in the template:

<span amp-access="NOT loggedIn" role="button" tabindex="0" amp-access-hide>
    <button on="tap:amp-access.login-sign-in" class="btn btn-xs btn-primary comment-button">Login</button>
    Please login to comment<br><BR>
<span amp-access="loggedIn">

The amp-access attribute in the span tells the page NOT to display the section if the user is loggedIn - presumably you could vary this to reference other data returned by the auth page. The on attribute of the button tells the page to reference the login:sign-in attribute of the amp-access script when it is tapped, so it will launch the [login URI] when the button is clicked. And finally the amp-access="loggedIn" attribute says that if the user IS logged in the commentForm will be included.

For me the most complicated part was figuring out the response headers required and their values, once I got that figured out the rest worked pretty easily. The next step was getting the actual form to submit and update the page properly. I'll write about that in the next post.

Libellés: coding, laravel, amp
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Accelerated Mobile Pages

mardi 14 février 2017

Over the last week I have been messing around with adding Structured Data to my pages so that Google can display Rich Cards. Google hasn't yet indexed my pages with structured data so there's not much I can say about that so far. I have also been playing with Accelerated Mobile Pages (AMP), which are lightweight pages designed specifically for mobile devices.

The two resources for AMP which I've found to be useful are AMP Project and AMP By Example. Unfortunately neither of them goes into a whole lot of detail about how to implement this stuff and I haven't been able to find very good explanations online. However I've been able to solve most of the issues I've encountered by trial and error.

The biggest difference between AMP and normal HTML is that AMP does not allow Javascript, nor does it allow linked CSS. All CSS must be inline, must total less than 50kB, and the only Javascript you can use is special Javascript from AMP Project. All images must have sizes defined and forms work a bit differently. The reason for this is to avoid any blocking resources that could slow the load of the page. I have been using Bootstrap CSS which I thought would be compatible as it is responsive and displays great on mobile devices, but it's too big and uses Javascript. I ended up using Bootstrap's Customizer to only output the elements I needed and then minified that and included it into my page. At some point I will clean out unused styles from the CSS to trim it down even more, but I was able to get my CSS to just barely fit the maximum size requirements by only using the bare minimum.

AMP isn't really all that complicated - it really just restricts what you can use in the page, but there were a couple things that I really struggled with. Those were, in order of difficulty:

  1. Creating a menu bar - my Bootstrap nav uses drop-downs which use Javascript so would not work. I had to create a simplified menu bar, but luckily amp has specific tags for this which were pretty easy to figure out.
  2. Creating a comments form on my blog - AMP does not support normal forms. You can use GET forms as usual, but for post you need to use XHR. 
  3. Forcing the user to login before they can post a comment - AMP has very specific requirements for validation which requires you to make XML requests to certain pages and which requires the pages to return certain responses. I have this working right now, but there are still some kinks I need to iron out.

I will post more articles on each of these three issues and my solutions to them over the next few days, as I get the kinks worked out.

Libellés: coding, laravel, amp
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