differences between css and equivalent xpath in selenium 2.0 - css

Question

Still new to selenium and css/xpath locators. I stumbled across a problem where CSS works but the equivalent XPath doesn't, and I'd really like to know why. I'm using Scala in the examples but it's still the normal Java Selenium2 library. I also use the FirefoxDriver
Here's the interesting part of the HTML:
...
<li class="k-item k-filter-item k-state-default k-last" role="menuitem" style="z-index: auto;">
...
<form class="k-filter-menu k-secondary">
<div>
<div class="k-filter-help-text">Show items with value that:</div>
<span class="k-widget k-dropdown k-header" style="" unselectable="on" role="listbox" aria-haspopup="true" aria-expanded="false" tabindex="0" aria-owns="" aria-disabled="false" aria-readonly="false" aria-busy="false">
<span class="k-widget k-datetimepicker k-header" style="">
<div>
<button class="k-button" type="submit">Filter</button>
<button class="k-button" type="reset">Clear</button>
</div>
</div>
</form>
</li>
...
I'm getting the li with
val filter = driver.findElement(By.cssSelector("li.k-filter-item"))
which works for me.
Then, I want to find the button. It's a dynamic menu thingy sliding out and what not, so I need to wait for it to appear:
new WebDriverWait(driver, selectorTimeout).until(
new ExpectedCondition[Boolean] {
override def apply(d: WebDriver) = {
filter.findElement(By.cssSelector("button[type=submit]")).isDisplayed
}
})
And that works nicely, too. My question is, why doesn't the xpath equivalent work:
new WebDriverWait(driver, selectorTimeout).until(
new ExpectedCondition[Boolean] {
override def apply(d: WebDriver) = {
filter.findElement(By.xpath("//button[#type='submit']")).isDisplayed
}
})
Anybody?
[EDIT]
Selenium version: 2.35.0
FireFox driver: 2.35.0
I will try it with Opera now.

Answer 1

You'll need the . in front of the XPath selector anyway, so that it'll search the current element's descendants/children:
.//button[#type='submit']
Sometimes, a more elaborate XPath can also help:
.//descendant::button[#type='submit']