[webkit-dev] Question on Inline element

Eric Seidel eric at webkit.org
Tue May 17 11:18:46 PDT 2011

On Tue, May 17, 2011 at 4:12 AM, Mustafizur Rahaman
<mustaf.here at gmail.com>wrote:

> Hi Eric,
> Thanks for your patient & detailed answer :-) So based on your explanation,
> I understand that a paragraph element can contain an image (inline) & text
> (inline) element altogether.
> Am i correct?
> If that is so, as per my understanding the m_framerect of Renderblock
> corresponding to Paragraph element will contain both the image & text
> element.
> Is this understanding correct?

>From RenderBox.h:


    // The width/height of the contents + borders + padding.  The x/y
location is relative to our container (which is not always our parent).

    IntRect m_frameRect;

So yes, I would expect that to include the rects of all kids, including the
text and image.

I wrote the below html to draw a border around the paragraph element, but
> the border is drawn around the text element only as can be seen in Safari
> browser too, which brings to the conclusion that the framerect calculation
> of paragraph element is not taking into consideration the children image
> element.
> <html>
> <head>
> <style type="text/css">
> p.one
> {
> border-style:solid;
> border-width:5px;
> }
> </style>
> </head>
> <p class="one"> <img src="titan.jpg" alt="RSS" width="256" border="0"
> height="256" align="left">Subscribe</p>
> </html>

A slightly modified example:
p { border: 5px solid black; }
img { border: 2px solid red }
<p><img src="invalid.jpg" alt="alt" width="256" height="256"

You can see that the <img> overflows the paragraph in both Firefox and
WebKit.  This seems to be caused by the align="left", which I believe
implies the CSS style "float: left;".  I suspect that floats do not get
counted towards the height of a block, but I'd have to check.  I suspect
that if we cleared the float (adding something with style="float: clear")
after the <img> we would see the p (block) expand so that the img did not

> I have also debugged the WebKit code & found that while doing layout
> calculation for Paragraph element, it goes inside
> RenderBlock::layoutInlineChildren==> Inside this we are doing the layout
> for each of the children. As per my understanding, the size of paragraph
> element would be the largest of its children & I dont see any such
> calculation. Could you please suggest where I should look to fix this issue
> appropriately?

As far as I can tell, there is no issue to fix. :)  I suggest that you read
the CSS 2.1 spec and this will all become much clearer.

As to where the height of a block is calculated? I would have to dig around,
but I would start with methods like computeContentBoxLogicalHeight The
height is going to be calculated as part of layout() through a series of
setLogicalHeight(foo) calls I would imagine.

> Thanks,
> Rahaman
> On Fri, May 13, 2011 at 11:25 PM, Eric Seidel <eric at webkit.org> wrote:
>> On Thu, May 12, 2011 at 10:52 PM, Mustafizur Rahaman <
>> mustaf.here at gmail.com> wrote:
>>> So my question is
>>>    - Can a paragraph element contain an image element=> the html spec
>>>    does not say NO.
>>> Yes.  There are two specs at play here.  HTML and CSS. Ignore anything
>> prior to HTML5 as it was proscriptive rather than descriptive and does not
>> match what browsers and web authors actually use!   <image> (aka <img>) is
>> just an inline element.  (Like span or b or i, etc.) and flows with inline
>> children per the CSS spec.  (See CSS 2.1).  So Paragraph, which is a block,
>> can contain as many inline children as its little heart desires.  <img>
>> happens to be a "replaced" element, so it has intrinsic size (again see CSS
>> 2.1).  Inline children (with the exception of inline blocks, which are
>> blocks which flow as inlines) CANNOT contain box children (blocks are
>> boxes), so for example <span><p></p></span> would be invalid and cause a
>> special type of craziness called a "continuation", where the spans inline
>> contents are split in two, wrapped in anonymous blocks, and the two
>> anonymous wrappers and the P are all children off the parent instead of the
>> P being a child of the span.
>>>    - If we make the image element neither float/nor positioned, it
>>>    creates an anomynous block & everything is rendered properly. But I am not
>>>    sure whether that is the right approach.
>>> Images will only end up getting wrapped in anonymous blocks when they're
>> in a block with other box children.  For example:
>> <div><img><div></div></div> will cause the <img> to get wrapped in an
>> anonymous block.
>> This is due to he CSS rule that blocks may contain either all inline
>> children OR all box/block children.  Thus since it has one block child (the
>> <div>) the img has to get wrapped in an anymous block to keep with the rule.
>> http://www.w3.org/TR/CSS21/visuren.html#anonymous-block-level
>>> Can any one please throw some light here & help us out.
>>> Thanks.
>>> _______________________________________________
>>> webkit-dev mailing list
>>> webkit-dev at lists.webkit.org
>>> http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
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