Bug 17994 – REGRESSION (523-525+) View not updated when changing CSS size via JavaScript

• Status: VERIFIED
• Resolution: FIXED
• Component: Layout and Rendering

[Andrea Baron]

I could not figure out the real cause of the bug, but I made a reduction that is to the bare minimum: changing, removing or even adding things makes the bug disappear. The css stylings involved are all needed to exhibit the bug.
There's an element with an onmouseover event that changes the size of its first child to follow the mouse (like a progress bar that always ends where the mouse is). With Firefox and Safari 3.0.4 all works fine, the bar enlarges and reduces as needed; with Safari 3.1 and the latest WebKit (r31201) the view is not updated. If I add another change (like a changed text) the view is updated. I also saw that if I move the mouse in a certain position, change application and then return to Safari the bar appear in the right position, even if before changing app it was not.
This is true for width and height, but trying to do the same thing with the background color, it works in the right way.

I uploaded three reductions: one show the bug with width, one with height and the third shows that with backgroundColor it works right; in the first two I left commented the line that changes a text in a div, and this forces the rendering of the page, so the width/height changes.

For now on my website (I use this technique for voting) I modify a div adding a comment with the width as a workaround. The bug shown on my website was even stranger: the page was updated only if the content of the div really changed, if I simply put the same text in the div the page was not refreshed.

Hope this will be useful.

[Andrea Baron]

Created attachment 19942 [details]
Test case for width

[Andrea Baron]

Created attachment 19943 [details]
Test case for height

[Andrea Baron]

Created attachment 19944 [details]
Test case for backgroundColor

Layout is updated but the view is not repainted.

Created attachment 19955 [details]
Patch, including change log and pixel test

Comment on attachment 19955 [details]
Patch, including change log and pixel test

The patch attached to bug 18063 addresses this bug as well.

Fixed in <http://trac.webkit.org/projects/webkit/changeset/31313>.

[Andrea Baron]

I verified the problem that I reported is now fixed, even the one that I had on my website.

Thanks