Re: about css style in gwt

ton123123,

The intent is to prevent CSS namespace pollution. It is common
practice to use a makeshift namespace for your CSS selectors so as not
to break existing CSS selectors. Say for example you had a rule for
".closeButton" . If anyone else used that selector in their module,
you might be overriding and breaking their CSS. So, you use a
makeshift namespace. Let's say everything in your module is inside a
container, then you could make that selector
".myModuleContainer .closeButton" and now it will only apply to your
module and not break any others.

This is why ".gwt-MenuBar .gwt-MenuItem" is used. There could be ".gwt-
MenuItem" items that appear in places other than the menubar, so use
this more specific selector to only apply to the menu items of
interest.

A better step is to use the CSSResource feature of GWT, and then
you'll never need to worry about these collisions as each selector can
have a unique name, and your CSS will parse faster.
https://code.google.com/p/google-web-toolkit/wiki/CssResourceCookbook

Hope that helps.

Sincerely,
Joseph

On Feb 29, 10:43 pm, tong123123 <tong123...@gmail.com> wrote:
> in gwt developer guildehttp://code.google.com/webtoolkit/doc/latest/DevGuideUiCss.html
> complex style section:
>
>  .gwt-MenuBar {>        /* properties applying to the menu bar itself */
> >    }
> >    .gwt-MenuBar .gwt-MenuItem {
> >        /* properties applying to the menu bar's menu items */
> >    }
> >    .gwt-MenuBar .gwt-MenuItem-selected {
> >        /* properties applying to the menu bar's selected menu items */
> >    }
>
> I cannout underatand, why the css rule is
>
> .gwt-MenuBar .gwt-MenuItem
>
> but not
>
> .gwt-MenuItem
> ?
> I am not good in css, is
> .gwt-MenuBar .gwt-MenuItem
>  is equal to just one css class? not any special meaning for the prefix .gwt-MenuBar, that is
> we can rename it as
> .gwt-MenuBargwt-MenuItem will not any different?

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