如何在GWT / Bootstrap中覆盖CSS样式？

Question

I just started to port twitter's bootstrap to GWT (see the github project here and a very ugly demo here ), but, I was having a log of issues with bootstrap styles vs Gwt styles.

Bootstrap put a border-top in tr/td elements, and GWT components basically use tables everywhere. In the demo you can see that bug in the left VerticalPanel.

So, I was looking for a way to make GWT components ignore bootstrap styles, and I have no idea how to do this.

Is there a simple way to make it work right?

Thanks in advance.

Answer 1

You can simply add a style to one of your root GWT objects and then simply override the bootstrap styles to remove those messy borders:

<div class="gwt">
   ... some other GWT-content
</div>

and in your CSS:

.gwt tr, .gwt td {
    border-top: 0px;
}

Of course if you need to embed some bootstrap elements in your GWT elements then you will have to hack around and do:

<div class="gwt">
   ... some other GWT-content
   <div class="bootstrap">...
        ... Bootstrap elements
   </div>
</div>

and in your CSS:

.bootstrap tr, .bootstrap td {
    border-top: 1px; // Whatever bootstrap style puts
}

Answer 2

It's possible, but somewhat complex to do something with a Linker in GWT. The high-level idea would be:

1. Put all your GWT components in a <div id="gwt">...</div>
2. Add a linker to the GWT Module file that will process CSS files.
3. In the linker, transform the GWT CSS (eg, standard.css) to insert a #gwt before each selector rule.

The first part is easy, just add an id to your root element.

The second part is also easy, simply add code that looks like this to your Module.gwt.xml file:

<define-linker name="cssLinker" class="com.you.bootstrap.linker.CssRenamingLinker" />
<add-linker name="cssLinker"/>

The hard part is implementing the Linker. It's possible to do parse it by hand, but you might find it easier to use something like SAC .

Using the Linker, you can transform your CSS by inserting a #gwt before each selector. Using SAC, you might do that by overriding all the DocumentHandler methods to simply emit each of their arguments to an OutputStream. In DocumentHandler.startSelector() you would first emit "#gwt " before each selector.

[Edit] This assumes that GWT's standard.css defines styles that override the bootstrap styles. If not, you might have to 'enhance' the GWT CSS with defaults. There's a list of W3C recommended defaults here .

The benefit is that this is future-resistant - if GWT styles change or if bootstrap styles change, this should be robust.

Hope that helps,

Adam