Bug 21625 – drop down box and button are wrapped to new line because containing <span> tag does not inherit parent's <div> width

• Status: RESOLVED
• Resolution: WONTFIX
• Component: Layout and Rendering

[jasneet]

I Steps:
Go to http://edu.sina.com.cn/
Scroll down to module with title "考试书架"

II Issue:
drop down box and button are wrapped to new line 

III Conclusion:
The outermost <div> (with blue border) has a <span> which has a <div>  (with green border) that contains the dropdown and the button. While the outermost <div> has a width defined, the <span> doesn't have any width defined nor does the inner <div> and this is what's causing the issue.
It seems that the <span> does not inherit the width of the <div>. Defining a width for either  the <span> or the inner <div> resolves the issue.

IV Other Browsers:
IE7: ok
FF3: not ok

V Nightly tested: 37604

[jasneet]

Created attachment 24376 [details]
reduced testcase

[Robert Hogan]

Created attachment 205415 [details]
Reduction

[Robert Hogan]

This is one of those pathological cases where the presence of floats means you need to do a full layout in order to establish the true preferred width of the container. Previously dhyatt has r-'d attempts to fix this kind of bug as there's no way of fixing it properly without adopting a two-pass widths calculation model.