499565 - select size=1 can be displayed outside the window when opened while the page still loads

Status: RESOLVED WORKSFORME

(Core :: Layout: Form Controls, defect)

Description

[Andreas Jung]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1pre) Gecko/20090620 Shiretoko/3.5pre
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1pre) Gecko/20090620 Shiretoko/3.5pre

A drop-down menu (select with size set to 1) may be displayed at a wrong position or even outside the window or screen if it is opened before the page finished loading and the page is intended to scroll down as soon as it is loaded completely.
In this case you can open a drop-down menu at the top of the document, the browser continues loading, finds a anchor it should jump to, scrolls down, the drop-down menu stays open but is displayed at the wrong position...

Reproducible: Always

Steps to Reproduce:
(0. Install Greasemonkey)
1. Install http://userscripts.org/scripts/show/52059
2. Open the URL provided (or any other page on mangafox)
3. Open the chapter drop-down menu before(!) the image loaded

Important: It only works if the image isn't loaded yet and is not in the cache.

(You can use the next button to go to the next page and repeat step 3 to reproduce the bug on another page, or clear the cache to see the bug again)
Actual Results:  
Drop-down menu is displayed at the wrong position (partly outside the window).

Expected Results:  
Not sure what the right thing to do here is.
Close the drop-down as soon as the content scrolls down?
Cancel the scrolling?

Comment 1

[Andreas Jung]

Attachment: Screenshot

Comment 2

[Andreas Jung]

Attachment: testcase (read comment 2)

There are two cases (that I know of) that reproduce the misplaced select menu.

The first case is the one described above (that is still reproducible in the latest nightly). I tried to create a simple testcase for this case, but failed because it is only reproducible if a certain order of events is true:
1) the page starts loading
2) as soon as the DOM is ready the (user-)script runs and changes the location hash, it doesn't scroll the page immediately because the (large) image isn't loaded yet and therefore the page's height is smaller than the window's (inner) height.
3) the user opens the select menu
4) the (large) image is loaded completely; the page's height increases, therefore the page is scrolled and the select menu becomes misplaced

When you change the location hash while a select menu is opened or insert a large element (to cause scrolling) and the page finished loading before, it seems it is not reproducible. The select menu flickers shortly and then closes in this case.

I found a second case while trying to create a testcase for the first case and it is much easier to reproduce / create a testcase for it.

The bug is also reproducible by using window.scroll while a select menu is opened.
This is what the attached testcase does.

Comment 3

[Andreas Jung]

can't reproduce this anymore.