Which CSS rules explain the following sceanrio:
Assuming I have the following HTML CSS snippets
HTML:
<div id="main">
<div id="first">
first div float left
</div>
<div id="second">
second div does not have a float property set
and appears in a new line instead of next to
the first div
</div>
</div>
CSS:
#first
float: left
What I am wondering about is, why the second div floats next to the first div, only when its width is set. If I replace the second div with a paragraph, it also floats next the first div. So why does the second div only position next to the first one when its width is set or its own float property is set to float left?
By the way. I am not trying to achieve any sort of layout here. I am just trying to understand these particular behaviours of the div element and other block elements.
EDIT:
OK. First of all thanks for the answers. The problem I had was based on the fact that I did set the width of the first and the second div to the same value, so that the content of the second could not float around the first one. To sum things up, I guess it is important to know that elements with the float property set are taken put of the page flow and dont take up any space. Secondly one should remember only the content can flow around, not the actual div.
A <div> is a block level element which is 100% wide and has a line break before & after when it's within the normal content flow.
Technically, when you float a <div>, you're taking the element out of the normal flow so it no longer has a line-break before & after and also the other page content flows around it.
So why does the second div only position next to the first one when
its width is set or its own float property is set to float left?
Floated <div>'s will always appear side-by-side only if there's enough room to contain them side-by-side. Otherwise, the next floated <div> will wrap to a new line. This is because floated <div>'s are outside the content flow and defined to behave this way in the spec.
However, you've made some incorrect assumptions in your question about what happens when you set the width of the second (non-floated) <div>.
The second <div>, itself, is always underneath (meaning behind) the floated <div>. Whereas, the "content" of the second <div> always flows around the floated <div>. (see three examples below)
So whether or not you set the width of the second div, its content will still flow around the left floated div as you can see illustrated here in three examples. (For illustration purposes, the first <div> is red with 50% opacity and the second is blue with a thick green border.)
Fiddle with second div wider than first
Fiddle with no set width (100%) on second div
Fiddle with second div narrower than first
As you can see from all three examples above, despite the existence of the floated first <div>...
the second <div> always starts on the left edge of the screen despite the width of the second <div>.
the second <div> always starts on the top edge of the screen because there's no other page flow content above the second <div>.
the actual content of the second <div> flows around (to the right of) the floated first <div> only where there is enough room inside its container to allow it to flow around the floated <div>. Otherwise, it appears as if it's starting a new line where really only its content is continuing to flow around the bottom of the floated <div>.
W3C Spec: 9 Visual formatting model, 9.5 Floats
A float is a box that is shifted to the left or right on the current
line. The most interesting characteristic of a float (or "floated" or
"floating" box) is that content may flow along its side (or be
prohibited from doing so by the 'clear' property). Content flows down
the right side of a left-floated box and down the left side of a
right-floated box. The following is an introduction to float
positioning and content flow; the exact rules governing float behavior
are given in the description of the 'float' property.
A floated box is shifted to the left or right until its outer edge
touches the containing block edge or the outer edge of another float.
If there is a line box, the outer top of the floated box is aligned
with the top of the current line box.
If there is not enough horizontal room for the float, it is shifted
downward until either it fits or there are no more floats present.
Since a float is not in the flow, non-positioned block boxes created
before and after the float box flow vertically as if the float did not
exist. However, the current and subsequent line boxes created next to
the float are shortened as necessary to make room for the margin box
of the float.
And here are a whole bunch of examples...
W3C Spec: 9 Visual formatting model, 9.8 Comparison of normal flow, floats, and absolute positioning
What makes you believe the div's are floated next to each other? In reality they are not. It's only that their content shows up next to each other but that's not because DIV #second is to the left of the floated DIV. It doesn't matter if you set the width or not.
What in fact is happening is that the floated DIV #first is floated to the left. Because it's floated, it's taken out of the normal flow. This means that DIV #second is actually on the same place as where DIV #first is appearing. The content of DIV #second though is inline content and inline content always flows around floated elements. Even floated elements that are outside of the container. So DIV #second is underneath DIV #first but the content of DIV #second is floating around DIV #first.
To illustrate that, I've create this CSS:
#first { float: left; background-color: rgba(255,0,0,0.3); }
#second { background-color: rgba(0,255,0,1); }
Play with the alpha value of the RGBA() value (i.e. the last parameter, it can range from 0 to 1) of the background-color of DIV #first and you will see that DIV #second is in fact below DIV #first all the time
Unless you clear your floats, the next block level element will float next to the last float by default.
I'm not sure what you're trying to achieve here, but if you want #first to float, and #second to NOT float, the rule you'd want to add to #first is : clear:both
But, that's pretty silly, you might as well just remove the float properties completely if you want to stack them.
Block elements take 100% of the width of their parent element, so even if your first div is floated, the second div will take the width of his parent, thus falling on a second line. This is why if you specify a smaller width, it stands next to the first floated div.
The reason why it also works if you float the two divs is that floated element behave a bit more like inline-block elements, wich means they will only take the space needed for the content inside of them.
Bottom line is, if you want these two divs to stand next to each other, you should probably just float the two of them.
Related
While investigating this question about clearing floats, I came across a peculiar situation with margins and clearance with a non-floating box.
According to section 8.3.1 of the spec, margin collapse should not occur when either
at least one of the elements generating the margins is a float, or
clearance is in the way.
But, consider a series of floating boxes, the last of which clears the rest:
<div class="container">
<div></div>
<div></div>
<div></div>
<div></div>
</div>
div.container > div {
float: left;
width: 50px;
height: 50px;
margin: 10px;
}
div.container > div:last-child {
clear: left;
}
As you would expect, both the horizontal and vertical gaps between each box are 20 pixels wide. The vertical margins do not collapse.
However, when the clearing element is not floated, it jumps up by 10 pixels as though its top margin were collapsing with that of the float directly above it.
This behavior completely defies both conditions listed above:
There is clearance.
For clearance to occur, there must be some other float to clear in the first place. The fact that the clearing element itself is not floated shouldn't be relevant.
This behavior also seems to be consistent across all browsers, including less-than-recent versions of IE.
That said, I don't claim to know the CSS float model like the back of my hand, so... Can somebody else explain why this happens?
Never mind, I think I found it myself. Looks like the following assumption in my question was wrong (told you I don't fully grok the CSS float model):
The fact that the clearing element itself is not floated shouldn't be relevant.
In section 9.5.2, which describes the clear property, it says:
Computing the clearance of an element on which 'clear' is set is done by first determining the hypothetical position of the element's top border edge. This position is where the actual top border edge would have been if the element's 'clear' property had been 'none'.
If this hypothetical position of the element's top border edge is not past the relevant floats, then clearance is introduced, and margins collapse according to the rules in 8.3.1.
Then the amount of clearance is set to the greater of:
The amount necessary to place the border edge of the block even with the bottom outer edge of the lowest float that is to be cleared.
The amount necessary to place the top border edge of the block at its hypothetical position.
And further down that section, it says:
When the property is set on floating elements, it results in a modification of the rules for positioning the float. An extra constraint (#10) is added:
The top outer edge of the float must be below the bottom outer edge of all earlier left-floating boxes (in the case of 'clear: left'), or all earlier right-floating boxes (in the case of 'clear: right'), or both ('clear: both').
(Emphasis mine. Note that "outer edge" is synonymous with "margin edge", as described in section 8.1.)
Essentially, this means if the clearing element is not floated and its top margin alone does not push it far enough away from the floats, then the element is pushed just enough for its top border to sit right underneath the bottom margin of the float being cleared. While it would appear as if its top margin was collapsing with the bottom margin of the float, in reality the top margin doesn't have any meaningful effect because it doesn't reach the border edge of the clearing element.
Otherwise if the clearing element is floated, then its top margin is taken into account, so to speak (as consistent with the rules stated in 8.3.1).
And as I write this, I recall that in-flow non-floating elements are positioned as if the floats were never there to begin with, because floats are taken out of the normal flow. In other words, any top margin that is set on a non-floating clearing element does not take into account any floats, regardless of whether it is enough for clearance. For example, when both clear and float are set to none on the last element, it sits flush with the edges of its container in the exact same position as the first floating element, albeit behind it (note that the borders on the container block margin collapse between it and the container).
Lastly, the fact that clearance is introduced is actually not relevant in this specific situation, because clearance blocks margin collapse only when the element's margins would normally have collapsed had its clear property been set to none. Since we're talking about floats here, margin collapse should indeed never happen normally, and so whether or not the last element has clearance isn't relevant (not directly, anyway).
Here goes the code:
<style>
.thumbnail
{
float:left;
width:110px;
height:90px;
margin:5px;
}
</style>
<body>
<img src="klematis_small.jpg" style="width:107px; height:140px">
<img class="thumbnail" src="klematis_small.jpg" style="width:107px; height:150px">
The confusing is why the second img which is floated appering before the first img.If we place the first img to second img everything works as expected.
Floated elements are taken out of the normal document flow:
Since a float is not in the flow, non-positioned block boxes created before and after the float box flow vertically as if the float did not exist. However, the current and subsequent line boxes created next to the float are shortened as necessary to make room for the margin box of the float.
Only line boxes (elements in the inline formatting context) respect floats, usually this is in the form of text. Also remember that floats will always be positioned on top (in the stacking order) when colliding with in-flow block level elements, but it will appear behind all lines boxes ..
The contents of floats are stacked as if floats generated new stacking contexts, except that any positioned elements and elements that actually create new stacking contexts take part in the float's parent stacking context. A float can overlap other boxes in the normal flow (e.g., when a normal flow box next to a float has negative margins). When this happens, floats are rendered in front of non-positioned in-flow blocks, but behind in-flow inlines.
The section on floats in the Visual Formatting Model is helpful if you're interested in learning the specifics
References: Section 9.4, Floats, CSS 2.1 Specification
You copy example from W3Schools but didn't read:
How Elements Float
Elements are floated horizontally, this means that an element can only be floated left or right, not up or down.
A floated element will move as far to the left or right as it can.
Usually this means all the way to the left or right of the containing
element.
Yes. This is normal and expected. If you want the first one first, you need to float them both.
I wouldnt use floats, just use display: inline-block; which will display your items exactly in the same order as the code is written.
I have a quandary. I have an application where CSS seems to do what it is supposed to do, but does not show results as you would expect and I can find no solution to get the "expected" results. The issue is how content is flowed when there is a float element to the left of the content and the content styles use padding or margins.
In my application, users can enter text in a DIV. There may or may not be a float left element so that the div with the text can either be at the left of the body area or shifted to the right (i.e. after the floating element).
When there is no floating element, the text is fine with paragraphs (i.e. with divs and appropriate classes) that are left, indented, first line indented, or hanging.
The CSS for the paragraphs are:
.firstindent { text-indent:30px; }
.indent { padding-left:30px; }
.hanging { padding-left:30px; text-indent:-30px; }
However, when a a float left element is added, only the standard and first indent show properly. This is because padding, borders, and margins are outside the box model "content" and only items in the "content" area are adjusted for the float.
Floats. In the float model, a box is first laid out according to the normal flow, then >taken out of the flow and shifted to the left or right as far as possible. Content may
flow along the side of a float.
If you use Firefox with Firebug, you can highlight the divs and you will find that the padding is shown at the left edge, i.e. "underneath" the floating element, not adjusted to the right of the floating element.
As a result, the paragraphs with a float left element look like this:
(Note that the float element also effects the presentation of lists.)
So far, I have not been able to come up with a CSS solution that lets me set the main text contents and then have them properly display whether or not there is a float left element to the left.
I have posted a full HTML sample so please feel free to snag the source and see if you can find a solution! Sample Page
Thank you - I should have included the "what you expect". Here it is with the float left and the float left spacer.
To correct, set overflow: hidden on all your paragraph elements (and lists, etc.) See fiddle.
I was playing around with a floated div example, where I have a floated container and some floated child divs except one non-floated child
You can see the example on;
http://jsfiddle.net/emeRJ/7/
Now I wanted to understand the behavior or rendering for this non-floated child div...
2 questions:
Could you please explain how it renders currently and what difference does it make if I have it coded after all the child divs (i.e. it is the last child element)
Also will it have any impact on the non-floated child if I make the container as overflow:hidden ?
Answer 1
At the moment the un-floated div right at the top with the red border is displaying block so it spans the whole width of it's containing div. It is unaffected by the other divs in the containing element
If you move it to the last position in the containing div the other floated divs do affect the un-floated one so you need to clear: both; (which clears the float and places the un-floated div under the floated divs) with CSS, otherwise any text contained within the un-floated one will be floated to the left and then would proceed to wrap around the floated elements (it doesn't do this at the moment because the text isn't long enough). Unless that's what you are trying to achieve?
Answer 2
It shouldn't make any difference as nothing is actually overflowing the containing div which would be set to overflow: hidden;
Hope this helps
I have 1 span within a container div. I want the span floated to the right. The content within the div and the span should be on one line.
In Firefox, that's how it displays.
But in IE, the span is displayed on a new line:
http://i48.tinypic.com/etzg5f.png
Why do the browsers display the content differently?
You should float the other content to the left. So have two floats; left and right.
Another approach could be using position absolute on the span, andposition relative on the surrounding div. Then you could put the positions (top, left, right and bottom) and position the elements as you should!
You could probably get away with specifying a width on your .catalogSelection#top #rss style definition. When setting the element to float it considers it a block level element and since your existing text is not floated, it wraps to the next line. Either this, or you need to float your Choose Catalog text to the left as well. Or as Kevin suggested, you can just put your Floated elements to the left of the non-floated, but this can be an issue when it comes to screen readers as it reads from left to right in your code, and is not semantically correct.