630163 - Changing element.style attribute overflow-x forces reload of Java applet

Status: RESOLVED INVALID

(Firefox :: General, defect)

Description

[Marek Slama]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.13) Gecko/20101206 Ubuntu/10.10 (maverick) Firefox/3.6.13
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.13) Gecko/20101206 Ubuntu/10.10 (maverick) Firefox/3.6.13

When I change element.style attribute overflow-x on body element FF forces reload of our Java applet. I change value eg. from auto to hidden or back from hidden to auto. Our applet is used as editor so user can loose unsaved data. Of course real use case is different: User can open modal HTML window which changes element.style.

Reproducible: Always

Comment 1

[dacrazycoder]

There may be related to this issue:  

When you are trying to calculate a scrollWidth vs clientWidth equation using an element that does not have overflow set to hidden/auto, you have to flip the overflow value to hidden/auto then make the calculation and then flip it back. This is done ONLY for firefox.. no other browser forces this equation. 

The problem with this equation is that flipping overflow causes two major side effects:  

(1) Firefox will re-render fonts embedded with @Font-Family for anything inside an Iframe. So, if you have a dashboarding type of application or any legacy application filled with iframes and custom fonts - this will cause the fonts to flicker heavily. This becomes increasingly painful if it is inside a timeout style calculation where the ScrollWidth is being evaluated on a consistent basis. 

(2) Modifying the overflow attribute will cause any input text element to lose focus. If you have an end user trying to select text in an input field and you modify the overflow - the user will be unable to select the text as the selection breaks upon losing focus. 

This deviation from the behavior imposed by other browsers has made it very difficult to implement custom scrollbars inside of FireFox, especially when working with legacy applications.

Using 16.0.2 - I've created a jsfiddle project to show the behavior that flipping the overflow produces.

http://jsfiddle.net/dacrazycoder/635J7/11/

In order to test - attempt to select the text inside the text input box. Focus will break as the overflow flips every 500 ms in order to calculate the scrollHeight.

It seems modifying the overflow can cause some unforseen flow/redraw issues - I ahve also noticed that it will cause @font-face fonts to be reloaded inside an iframe - though I would expect those to be cached.

Comment 2

[Kyle Machulis [:qdot] [:kmachulis] (INACTIVE)]

The HTML <applet> element and related java functionality was removed from Gecko in Bug 1279218. Marking related bugs as invalid.