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#1 Nick Brunt

Nick Brunt

    Neowinian

  • Joined: 03-September 09
  • Location: England

Posted 21 February 2011 - 02:23

Here's the problem in the form of a fancy picture (isn't it beautiful?):

demo.jpg

Each rectangle is a div tag and I'll refer to them by their colours. Black is the main content of the page and has to be below red which is the footer. However I have an image (green) within red which extends over the text in black but must always lie below the text. The text in black is contained within a span tag (but this could be a div as well if it needs to be).

My question is, is it possible to give black a z-index of, say, 1; red a z-index of 2; green a z-index of 3; and the text a z-index of 4?

This would make the above picture possible. However, browsers won't allow a child element to have a higher z-index than its parent so the above is not possible. The text always has an inherited z-index of 1, and therefore lies below green.

Is there a workaround?

P.S. I realise this can be a bit confusing to understand, hence the picture.


#2 sweetsam

sweetsam

    Developer

  • Joined: 21-July 04

Posted 21 February 2011 - 04:03

This is possible if you wrap the text in a separate tag with the highest z index.

#3 OP Nick Brunt

Nick Brunt

    Neowinian

  • Joined: 03-September 09
  • Location: England

Posted 21 February 2011 - 14:25

Yeah unforunately it's actually not - assuming that the text is inside the black div. It doesn't matter what the z-index of the text is set to, it will always inherit the z-index of its parent div and will therefore have a lower z-index than the green div.

This is my example code which outputs the diagram above but shows that the text always lies below the green div even though it has a higher z-index:

<html>
  <head>
    <style type="text/css">
      #black {
        position: relative;
        width: 400px;
        height: 400px;
        background-color: black;
        z-index: 1;
      }

      #text {
        color: white;
        z-index: 4;
      }

      #red {
        position: relative;
        margin-top: -100px;
        margin-left: 25px;
        width: 350px;
        height: 200px;
        background-color: red;
        z-index: 2;
      }

      #green {
        position: absolute;
        top: -150px;
        right: 50px;
        width: 50px;
        height: 200px;
        background-color: green; 
        z-index: 3;
      }
    </style>
  </head>
  <body>
    <div id="black">
      <span id="text">
        Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum
      </span>
    </div>

    <div id="red">
      <div id="green"></div>
    </div>
  </body>
</html>


#4 wctaiwan

wctaiwan

    Neowinian

  • Joined: 07-March 05
  • Location: Taiwan

Posted 21 February 2011 - 14:37

Would it be possible to separate the text in the black div from the div itself, put it into a div of its own as a child of <body> or whatever, and then give that a higher z-index, background: transparent; and absolute position things to line them up? Just a thought.

#5 OP Nick Brunt

Nick Brunt

    Neowinian

  • Joined: 03-September 09
  • Location: England

Posted 21 February 2011 - 14:46

Yeah I thought of that, and it's basically a good idea, but the content of the black div is loaded by AJAX and so the length is undetermined. I'd have to use javascript to measure the height of the div containing the text and then make the black div that same height. Perfectly possible, yes. But is it really necessary?

#6 Calculator

Calculator

    Neowinian

  • Joined: 13-May 05
  • Location: Belgium

Posted 21 February 2011 - 16:35

I found this to be an intriguing question, so I gave this a try. Have a look at it here.

Here's how it's done:
  • There's no background set on #black, the background is simply transparent. Instead, the background color is done by adding an extra element (#black:before) and absolutely positioning it so that it has the same position and size as its parent. This element then gets the black background color set.
  • To make the black background layer #black:before go behind the text, its z-index is set to a negative value. Since the text is separate from the background, this z-index causes the text to be on top of the background layer.
  • #red and #green can now assume negative z-indexes between the z-indexes of #black and #black:after to make them appear between the background and the text.
    If only one background box is needed, you might want to consider using #black:after instead and get rid of the meaningless HTML.
Known issues:
  • Doesn't work in Internet Explorer. :pinch:
    It appears that in IE, the :after element is created as a child rather than a sibling and as such, #red and #green cannot be placed between those two z-indexes.
The problem lies in setting the position and size of the background layer when this layer is not a child of the text layer. If the text layer has a fixed position and size, you can simply copy these over to the background layer. However, with flexible layer heights, I don't see a way to match the size of a sibling.
We couldn't do it for layout columns and so we had to use techniques like faux columns or floats with clears to make two columns appears to have equal heights. It appears that this problem is very similar to the columns issue.

Perhaps someone finds a better solution?

#7 sweetsam

sweetsam

    Developer

  • Joined: 21-July 04

Posted 21 February 2011 - 16:54

It is possible just like I mentioned earlier. Don't need js height calculations. Need to assign z index only to one element.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head>
	<title></title>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<style type="text/css">

*	{
	margin: 0;
	padding: 0;
}
body	{
	padding: 20px;
}
#wrap	{
	width: 920px;
	margin: 0 auto;
}
#content	{
	color: #fff;
	background: #000;
	padding-bottom: 20px;
}
#content p	{
	z-index: 2;
	padding: 50px;
	position: relative;
}
#footer	{
	padding: 20px;
	height: 150px;
	background: #f00;
	margin: -50px 50px 0 50px;
}
#green	{
	width: 50px;
	float: right;
	height: 240px;
	display: block;
	margin-top: -150px;
	background: green;
}

	</style>
</head>

<body>

<div id="wrap">
	<div id="content">
		<p>Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.</p>
	</div>
	<div id="footer">
		<span id="green">
		</span>
	</div>
</div>

</body>

</html>


#8 OP Nick Brunt

Nick Brunt

    Neowinian

  • Joined: 03-September 09
  • Location: England

Posted 21 February 2011 - 17:54

It is possible just like I mentioned earlier. Don't need js height calculations. Need to assign z index only to one element.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

...


Your version is very good, but I'm having trouble recreating it with my demo... This is my new code:

<html>
  <head>
    <style type="text/css">
      #black {
        position: relative;
        width: 400px;
        height: 400px;
        background-color: black;
      }

      #text {
        color: white;
        z-index: 5;
      }

      #red {
        position: relative;
        margin-top: -100px;
        margin-left: 25px;
        width: 350px;
        height: 200px;
        background-color: red;
      }

      #green {
        position: absolute;
        top: -150px;
        right: 50px;
        width: 50px;
        height: 200px;
        background-color: green;
      }
    </style>
  </head>
  <body>
    <div id="black">
      <span id="text">
        Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum
      </span>
    </div>

    <div id="red">
      <div id="green"></div>
    </div>
  </body>
</html>

The green div is still above the text.

Ah don't worry, it works now. I just added "position: relative" under #text and it works now - thanks a lot!