Been looking at a premium theme and see that for various text and elements on the page, when inspected - many have inherit and 0 for the values.
Why would these not be left blank if they are not required and automatically inherited from the parent? Does it perhaps save on load time?
margin: 0;
padding: 0;
border: 0;
outline: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
font-family: inherit;
font-size: 100%;
font-style: inherit;
font-weight: inherit;
This is done to override browser defaults.
Most browsers themselves apply their own style declarations to make basic HTML pages look prettier. Unfortunately these style declarations often clash with how a designer wants a web page to look. The way to overcome this is to reset the styles to what they should be by default.
Example
A good example of this is with heading and p tags. Take the following example:
<h1>Hello, world!</h1>
<p>Woah, that's a big heading!</p>
Without any custom styling applied, these elements use styles provided by the browser. One of the styles used here is margin, and that's what's putting the large gaps between each element.
We can reset these ourselves by setting the margin to 0:
* {
margin: 0;
}
<h1>Hello, world!</h1>
<p>Woah, that's a big heading!</p>
Because of the need to reset such styles public stylesheets like Normalize.css exist, whose intention is to do nothing more than reset (and normalize) all elements to look the same across different browsers.
Related
I wrote a Google Chrome extension, which popups a dialog with an autocomplete field and it's own style, but there are some sites where my CSS gets totally broken, which doesn't look very nice.
I know about isolating styles with iFrames, but in Google Chrome extension there is no way to isolate my HTML and CSS in this way. Another method is to wrap all my stuff into a separated div with it's own id and relative styles for that id, and I do so, but it seems that it doesn't work on some sites with "hard" tags style overloading or "!important" directives in the CSS code.
So, I want to know is there any way to really isolate my styles in z convenient way or it's my bad carma to overload every little CSS property to fix one or another style issue for each site?
By the way: I set up my manifest to load all the things at the "document_end", but I see it's not being applied to the stylesheets which is every time loaded whenever the DOM is ready.
At the time of asking the question, your only option was to either use iframes, or stylesheets with a very high specificity and explicitly set all properties that might affect styles. The last method is very cumbersome, because there will always be some property that is overlooked by you. Consequently, the only usable method for isolating stylesheets was to use iframes.
The solution to this problem -isolation of styles without iframes- is Shadow DOM (since Chrome 25). You can find a tutorial at HTML5 Rocks. For a real-world Chrome extension that uses Shadow DOM to isolate styles, see Display #Anchors (source code here).
As I've recently gone through the gauntlet of this issue, I want to share some information I think is valuable.
First, Rob W's answer is correct. Shadow DOM is the correct solution to this problem. However, in my case not only did I need CSS isolation, I also needed JavaScript events. For example, what happens if the user clicks a button that lives within the isolated HTML? This gets really ugly with just Shadow DOM, but we have another Web Components technology, Custom Elements, to the rescue. Except that as of this writing there is a bug in chrome that prevents custom element in chrome extensions. See my questions here and here and the bug here.
So where does that leave us? I believe the best solution today is IFrames, which is what I went with. The article shahalpk linked is great but it only describes part of the process. Here's how I did it:
First, create an html file and js file for your isolated widget. Everything inside these files will run in an isolated environment in an iframe. Be sure to source your js file from the html file.
//iframe.js
var button = document.querySelector('.my-button');
button.addEventListener('click', function() {
// do useful things
});
//iframe.html
<style>
/* css */
</style>
<button class='my-button'>Hi there</button>
<script src='iframe.js'></script>
Next, inside your content script create an iframe element in javascript. You need to do it in javascript because you have to use chrome.extension.getURL in order to grab your iframe html file:
var iframe = document.createElement('iframe');
iframe.src = chrome.extension.getURL("iframe.html");
document.body.appendChild(iframe);
And that's it.
One thing to keep in mind: If you need to communicated between the iframe and the rest of the content script, you need to chrome.runtime.sendMessage() to the background page, and then chrome.tabs.sendMessage from the background page back to the tab. They can't communicate directly.
EDIT: I wrote a blog post detailing everything I learned through my process, including a complete example chrome extension and lots of links to different information:
https://apitman.com/3/#chrome-extension-content-script-stylesheet-isolation
In case my blog goes down, here's the sources to the original post:
Blog post
Example source
Either use all
.some-selector {
all: initial;
}
.some-selector * {
all: unset;
}
or use Shadow DOM
Library
function Widget(nodeName, appendTo){
this.outer = document.createElement(nodeName || 'DIV');
this.outer.className = 'extension-widget-' + chrome.runtime.id;
this.inner = this.outer.createShadowRoot();
(appendTo || document.body).appendChild(this.outer);
}
Widget.prototype.show = function(){
this.outer.style.display = 'block';
return this;
};
Widget.prototype.hide = function(){
this.outer.style.display = 'none';
return this;
};
Usage
var myWidget = new Widget();
myWidget.inner.innerHTML = '<h1>myWidget</h1>';
You can access the widget contents via myWidget.inner and the outer via myWidget.outer.
Styles
/*
* Reset Widget Wrapper Element
*/
.extension-widget-__MSG_##extension_id__ {
background: none;
border: none;
bottom: auto;
box-shadow: none;
color: black;
cursor: auto;
display: inline;
float: none;
font-family : "Helvetica Neue", "Helvetica", "Arial", sans-serif;
font-size: inherit;
font-style: normal;
font-variant: normal;
font-weight: normal;
height: auto;
left: auto;
letter-spacing: 0;
line-height: 100%;
margin: 0;
max-height: none;
max-width: none;
min-height: 0;
min-width: 0;
opacity: 1;
padding: 0;
position: static;
right: auto;
text-align: left;
text-decoration: none;
text-indent: 0;
text-shadow: none;
text-transform: none;
top: auto;
vertical-align: baseline;
white-space: normal;
width: auto;
z-index: 2147483648;
}
/*
* Add your own styles here
* but always prefix them with:
*
* .extension-widget-__MSG_##extension_id__
*
*/
.extension-widget-__MSG_##extension_id__{
position: fixed;
top: 100px;
margin: 0 auto;
left: 0;
right: 0;
width: 500px;
}
.extension-widget-__MSG_##extension_id__::shadow h1 {
display: block;
margin: 0 auto;
padding: 20px;
background-color: yellow;
border: 10px solid green;
font-size: 20px;
text-align: center;
}
I recently created Boundary, a CSS+JS library to solve problems just like this. Boundary creates elements that are completely separate from the existing webpage's CSS.
Take creating a dialog for example. After installing Boundary, you can do this in your content script
var dialog = Boundary.createBox("yourDialogID", "yourDialogClassName");
Boundary.loadBoxCSS("#yourDialogID", "style-for-elems-in-dialog.css");
Boundary.appendToBox(
"#yourDialogID",
"<button id='submit_button'>submit</button>"
);
Boundary.find("#submit_button").click(function() {
// some js after button is clicked.
});
Elements within #yourDialogID will not be affected by the existing webpage. And find() function returns a regular jQuery DOM element so you can do whatever you want with it.
Hope this helps. Please let me know if you have any question.
https://github.com/liviavinci/Boundary
Use iframes. It's a workaround, but works fine.
Maxime has written an article on it.
I wrote a Google Chrome extension, which popups a dialog with an autocomplete field and it's own style, but there are some sites where my CSS gets totally broken, which doesn't look very nice.
I know about isolating styles with iFrames, but in Google Chrome extension there is no way to isolate my HTML and CSS in this way. Another method is to wrap all my stuff into a separated div with it's own id and relative styles for that id, and I do so, but it seems that it doesn't work on some sites with "hard" tags style overloading or "!important" directives in the CSS code.
So, I want to know is there any way to really isolate my styles in z convenient way or it's my bad carma to overload every little CSS property to fix one or another style issue for each site?
By the way: I set up my manifest to load all the things at the "document_end", but I see it's not being applied to the stylesheets which is every time loaded whenever the DOM is ready.
At the time of asking the question, your only option was to either use iframes, or stylesheets with a very high specificity and explicitly set all properties that might affect styles. The last method is very cumbersome, because there will always be some property that is overlooked by you. Consequently, the only usable method for isolating stylesheets was to use iframes.
The solution to this problem -isolation of styles without iframes- is Shadow DOM (since Chrome 25). You can find a tutorial at HTML5 Rocks. For a real-world Chrome extension that uses Shadow DOM to isolate styles, see Display #Anchors (source code here).
As I've recently gone through the gauntlet of this issue, I want to share some information I think is valuable.
First, Rob W's answer is correct. Shadow DOM is the correct solution to this problem. However, in my case not only did I need CSS isolation, I also needed JavaScript events. For example, what happens if the user clicks a button that lives within the isolated HTML? This gets really ugly with just Shadow DOM, but we have another Web Components technology, Custom Elements, to the rescue. Except that as of this writing there is a bug in chrome that prevents custom element in chrome extensions. See my questions here and here and the bug here.
So where does that leave us? I believe the best solution today is IFrames, which is what I went with. The article shahalpk linked is great but it only describes part of the process. Here's how I did it:
First, create an html file and js file for your isolated widget. Everything inside these files will run in an isolated environment in an iframe. Be sure to source your js file from the html file.
//iframe.js
var button = document.querySelector('.my-button');
button.addEventListener('click', function() {
// do useful things
});
//iframe.html
<style>
/* css */
</style>
<button class='my-button'>Hi there</button>
<script src='iframe.js'></script>
Next, inside your content script create an iframe element in javascript. You need to do it in javascript because you have to use chrome.extension.getURL in order to grab your iframe html file:
var iframe = document.createElement('iframe');
iframe.src = chrome.extension.getURL("iframe.html");
document.body.appendChild(iframe);
And that's it.
One thing to keep in mind: If you need to communicated between the iframe and the rest of the content script, you need to chrome.runtime.sendMessage() to the background page, and then chrome.tabs.sendMessage from the background page back to the tab. They can't communicate directly.
EDIT: I wrote a blog post detailing everything I learned through my process, including a complete example chrome extension and lots of links to different information:
https://apitman.com/3/#chrome-extension-content-script-stylesheet-isolation
In case my blog goes down, here's the sources to the original post:
Blog post
Example source
Either use all
.some-selector {
all: initial;
}
.some-selector * {
all: unset;
}
or use Shadow DOM
Library
function Widget(nodeName, appendTo){
this.outer = document.createElement(nodeName || 'DIV');
this.outer.className = 'extension-widget-' + chrome.runtime.id;
this.inner = this.outer.createShadowRoot();
(appendTo || document.body).appendChild(this.outer);
}
Widget.prototype.show = function(){
this.outer.style.display = 'block';
return this;
};
Widget.prototype.hide = function(){
this.outer.style.display = 'none';
return this;
};
Usage
var myWidget = new Widget();
myWidget.inner.innerHTML = '<h1>myWidget</h1>';
You can access the widget contents via myWidget.inner and the outer via myWidget.outer.
Styles
/*
* Reset Widget Wrapper Element
*/
.extension-widget-__MSG_##extension_id__ {
background: none;
border: none;
bottom: auto;
box-shadow: none;
color: black;
cursor: auto;
display: inline;
float: none;
font-family : "Helvetica Neue", "Helvetica", "Arial", sans-serif;
font-size: inherit;
font-style: normal;
font-variant: normal;
font-weight: normal;
height: auto;
left: auto;
letter-spacing: 0;
line-height: 100%;
margin: 0;
max-height: none;
max-width: none;
min-height: 0;
min-width: 0;
opacity: 1;
padding: 0;
position: static;
right: auto;
text-align: left;
text-decoration: none;
text-indent: 0;
text-shadow: none;
text-transform: none;
top: auto;
vertical-align: baseline;
white-space: normal;
width: auto;
z-index: 2147483648;
}
/*
* Add your own styles here
* but always prefix them with:
*
* .extension-widget-__MSG_##extension_id__
*
*/
.extension-widget-__MSG_##extension_id__{
position: fixed;
top: 100px;
margin: 0 auto;
left: 0;
right: 0;
width: 500px;
}
.extension-widget-__MSG_##extension_id__::shadow h1 {
display: block;
margin: 0 auto;
padding: 20px;
background-color: yellow;
border: 10px solid green;
font-size: 20px;
text-align: center;
}
I recently created Boundary, a CSS+JS library to solve problems just like this. Boundary creates elements that are completely separate from the existing webpage's CSS.
Take creating a dialog for example. After installing Boundary, you can do this in your content script
var dialog = Boundary.createBox("yourDialogID", "yourDialogClassName");
Boundary.loadBoxCSS("#yourDialogID", "style-for-elems-in-dialog.css");
Boundary.appendToBox(
"#yourDialogID",
"<button id='submit_button'>submit</button>"
);
Boundary.find("#submit_button").click(function() {
// some js after button is clicked.
});
Elements within #yourDialogID will not be affected by the existing webpage. And find() function returns a regular jQuery DOM element so you can do whatever you want with it.
Hope this helps. Please let me know if you have any question.
https://github.com/liviavinci/Boundary
Use iframes. It's a workaround, but works fine.
Maxime has written an article on it.
Is there a way to apply a font style or any other style to an element inside CSS?
For instance
You defined a certain font style
.impact {
font-family: "Impact";
letter-spacing: 16px;
line-height: 72%;
}
Now apply this style to an element inside css:
#certainElement {
font-family: Impact (the one we defined)
width: 400px;
}
Unfortunately, CSS does not support this kind of composition. However, you can use SASS or LESS to get similar behavior.
Is there any reason that defining a class on your element with id certainElement isn't desirable?
<div id="certainElement" class="impact"></div>
I have some CSS for a Wordpress blog. I want paragraphs to indent, but blocks of code to align left to the margin. This is the code that I have---all of these elements appear with a <div class="postContent" tag, and Wordpress automatically wraps post text blocks in <p> tags.
First, I've set all paragraphs within the div tags to indent:
.postContent p {
font-size: 1.2em;
text-indent: 2.5em;
text-align: justify;
line-height: 1.6em;
margin: 1em;
}
Then, Wordpress sets aside the first paragraph as a .lead paragraph. I want that to indent, provided it's not code:
.postContent p.lead code {
margin: 0;
text-indent: 0;
}
That works just fine. However, all the other code paragraphs are still indenting, so I added this to the stylesheet:
.postContent p code {
text-indent: 0;
padding: 0;
padding-top: 2em;
padding-bottom: 2em;
}
No dice. The code blocks are still indenting according to the .postContent p rule.
Setting text-indent on a code element inside a p element does not affect the indentation of the p element. It does not affect anything, really, since text-indent applies to block containers only.
If the markup is <p><code>...</code></p> so that the p contains nothing but the code, you can add
.postContent p code { display: block; }
and then consider what to do with vertical spacing, which may be a bit excessive after the addition (namely margins of p plus padding of code).
It's really hard to say without seeing both the source for the html and the actual css code, but I'm guessing your styles are being overridden by a more specific style.
The best thing for you to do is install Firebug in Firefox (really, the best development tools for a browser, IMHO) and inspect the targeted elements. The inspector should display all the styles being applied to the element. The overridden styles will have a strikethrough it. If you see they are being overridden, make your styles more specific. Otherwise, if you don't see your style listed, then you're not correctly targeting it.
Hope that helps. Good luck.
When I set the font family, font size, color etc. it seems that some nested elements override these with ugly browser defaults.
Must I really specify those a dozens of times for any kind of element on my page, or is there a way to set them globally once and forever?
How to do that?
* {
font-size: 100%;
font-family: Arial;
}
The asterisk implies all elements.
If you're using IE, chances are it will revert to the browser defaults for certain elements, like tables. You can counter that with something like the following CSS:
html, body, form, fieldset, table, tr, td, img {
margin: 0;
padding: 0;
font: 100%/150% calibri,helvetica,sans-serif;
}
input, button, select, textarea, optgroup, option {
font-family: inherit;
font-size: inherit;
font-style: inherit;
font-weight: inherit;
}
/* rest of your styles; like: */
body {
font-size: 0.875em;
}
Edit: you may want to read up on CSS resets; see threads like this one
I can't stress this advice enough: use a reset stylesheet, then set everything explicitly. It'll cut your cross-browser CSS development time in half.
Try Eric Meyer's reset.css.
you can set them in the body tag
body
{
font-size:xxx;
font-family:yyyy;
}
If you specify CSS attributes for your body element it should apply to anything within <body></body> so long as you don't override them later in the stylesheet.
If you want to set styles of all elements in body you should use next code^
body{
color: green;
}