I spent some time today with Lit trying to make a simple WebComponent that makes a HTTP GET to a URI, which returns a fully formed HTML document, and I want to inject said HTML document into the WebComponent's shadow DOM; basically this WebComponent acts as a simple proxy for embedding an externally hosted (but trusted) web snippet on my web page. I ran into a few problems:
Lit considers all HTML unsafe, so i had to mark it with Lit's unsafeHTML directive.
Then, I noticed none of the script or link tags in the injected HTML were being followed, so I parsed the incoming HTML as a HtmlDocument, located all the script/link tags, and "re-created" them using document.createElement(...) and returned them in my render(). I'm now noticing that images arent showing up either.
I don't like scraping scripts/links and re-creating them and jamming them into my web component anyhow, but I'm curious - what's the right way to approach this syndicating/consuming syndicated HTML pages/fragments?
Is this a solved problem w/ oEmbed already?
Is this simpler to do with a different WebComponent library?
This seems way harder than it should be at this point.
I think that it has little to do with WebComponents but rather with the HTML5 specs. lit-html uses innerHTML to create elements.
Script elements inserted using innerHTML do not execute when they are inserted
There are still ways to execute JS but this has little to do with your question.
unsafeHTML(`<img src="triggerError" onerror="alert('BOOM')">`)
Regarding the images, it may be a path issue?
This should work:
unsafeHTML(`<img src='http://placehold.it/350x350'>`)
Related
i'm trying to improve speed of my website. i'm using PageSpeed Insights to check my site performance and it was telling me to remove render blocking java script and css. so i did it and know its causing problem in my website design. so what should i do to remove rendering blocking without causing problem in my website design.
Render Blocking CSS
Render blocking CSS will always show on Google Page Speed Insights if you are using external resources for your CSS.
What you need to do is to inline all of your 'above the fold' styles in <style></style> tags in the head of your web page.
I will warn you, this is NOT easy and plugins that claim to do this often do not work, it requires effort.
To explain what is happening:-
A user navigates to your site and the HTML starts downloading.
As the HTML downloads the browser is trying to work out how to render that HTML correctly and it expects styling on those elements.
Once the HTML has downloaded if it hasn't found styles for the elements that appear above the fold (the initial part of the visible page) then it cannot render anything yet.
The browser looks for your style sheets and once they have downloaded it can render the page.
Point 4. is the render blocking as those resources are stopping the page from rendering the initial view.
To achieve this you need to work out every element that displays without scrolling the page and then find all the styles associated with those elements and inline them.
Render Blocking JS
This one is simpler to fix.
If you are able to use the async attribute on your external JS then use that.
However be warned that in a lot of cases this will break your site if you have not designed for it in the first place.
This is because async will download and execute your JS files as fast as possible. If a script requires another script to function (i.e. you are using jQuery) then if it loads before the other script it will throw an error. (i.e. your main.js file uses jQuery but downloads before it. You call $('#element') and you get a $ is undefined error as jQuery is not downloaded yet.)
The better tag to use if you do not have the knowledge required to implement async without error is to use the defer attribute instead.
This will not start downloading the script until the HTML has finished parsing. However it will still download and execute scripts in the order specified in the HTML.
Add async in the script tag and put the css and js in the last of the page
Is there a way in code to determine if a Web control contains server blocks (other than, for example, parsing out the file, grabbing the contents of the tag, and scanning for <% ... %>)?
My reason for wanting this is because I have a lot of old Web forms that were designed without any regard whatsoever to HTML conformance. The header control (which is included on every page but is inside the body tag) contains the link tag referencing the site's main stylesheet. As long as the page's head tag does not contain server blocks, I can programmatically insert the link tag into Page.Controls.OfType(Of HtmlHead).First(), then set the visibility of the "bad" link tag to false.
Again, this is all legacy stuff (it's in 3.5 now, but most was written in the .NET 1.1 days), so changing everything over to use a master page is something for which I simply do not have the time and budget. Regardless, it would be nice to see the pages come up with the stylesheet pre-loaded, rather than having the browser begin rendering with no styling, then applying the stylesheet once it reaches the reference to it in the body.
Seems like a silly work around but could you change the name of your CSS file so that when the legacy code goes to load, it can't find it?
Although Mufasa entered his response as a comment, this question has been sitting unresolved too long. Therefore, I will surmise that the only solution is his -- to wrap it in a try/catch black.
I have a dynamic PHP stylesheet, but I can't find a way to send variables to it so I used sessions instead. Figured this kinda sucked, so I'm going to give it another try but could need some help. It's an external stylesheet where a variable has effect through the whole document.
You probably want to use an embedded stylesheet (a <style> block) in the page: it increases the size of the main page, but solves the variable access issue without needing sessions and reduces your number of requests. You can just load your dynamic stylesheet into the main page's view using load->view.
EDIT: Ah, massive amounts of CSS would be one problem. Well, two alternatives are to:
Turn on the $_GET support in your CI install, you COULD pass in a request parameter in the CSS link and then check for the request parameter in the PHP controller or view file that generates the actual CSS. Not visually the tidiest option, but it does work.
Put in a cookie that you check in the controller that gets called for the CSS: you can then check that in the controller or view and do the right thing. Visually much tidier than the request parameter option, but a bit more involved.
What is the best way to handle style that that is user-customized? Just as an example of the result I'm looking for, this would suffice:
body {
color: {{ user.profile.text_color }};
}
However, serving CSS as a view seems like it would cause a significant amount of overhead in a file that is constantly requested, so this is probably not a good solution.
The user does not have access to the CSS files and we must assume that they have no web development knowledge.
However, serving CSS as a view seems like it would cause a significant amount of overhead in a file that is constantly requested, so this is probably not a good solution.
And what if you would generate that CSS once?
Default CSS is: /common/css.css
Member customize CSS, now <link /> elements points to /user-specific/123.css?ts=123123123. 123 is of course an identifier of the member, and ts parameter contains a timestamp - a date of last CSS modification
Make sure that your CSS generator sets proper HTTP headers responsible for client-side caching
User browser request a CSS file - server replies with simple 304 Not Modified header - there is no need for any script execution or contents download
When member modifies his CSS then you just update ts - once again just a single request is needed
Do the CSS dynamically via a view as normal, but use aggressive caching so that it loads quickly.
You can try django mediagenerato, actually I read this Q and I was searching for solution like you, then I found that Django-mediagenerator
I didn't tried it yet but it seams to be a solution.
I use an AJAX-Request to load a part of a Webpage, the request is handled by a framework, which delivers the content. After that, I use jquery to insert the delivered content into the DOM-Tree. So far, so good.
But I use background-images for links in the delivered content, which are generated while processing the AJAX-Request. Normally I would place the path to the background-image into a style-attribute in the link-tags, what works perfectly, until I want to use pseudo-classes for i.e. :hover (you know, to display an alternative image while the mouse hovers)
The solution would be to create a custom CSS-file, which will be inserted into the HTML-Head, but until it is an AJAX-Request, the HTML-Head is already sent.
Do you have any idea, how to attach CSS-properties to links, which will be generated on AJAX-Call-Time?
not possible with inline style.
as s jones says, you can have the style in your existing CSS and it should pick it up.
the other option is to do it using jquery..
$('div.ajax a').hover(function(){$(this).css('color','red')});