In the attached test case, there's a popup with two items. In the menu that pops up, both items have the word "English" on the left and the Hebrew word on the right. However, in TOT, when the second item is selected, the popup button shows the words in reverse order: Hebrew on the left and English on the right. The problem is that AppKit uses "natural" writing direction for the popup menu items, roughly meaning that the first character with strong directionality determines the paragraph directionality to use. CSS (and WebKit) do not have a notion of "direction: natural", so everything has the same direction (LTR now, the <select>'s direction prior to <http://trac.webkit.org/projects/webkit/changeset/21541>). I think it may be possible for the popup button to fake "natural" directionality for this specific case.
Created attachment 14607 [details] Test case
<rdar://problem/5213488>
Created attachment 14748 [details] Natural directionality patch This is a patch that works as far as I can tell, but I think that both the left alignment and the "natural" directionality are very Mac-specific quirks that have to do with the Mac popup implementation, so it doesn't feel right to do them in cross-platform code. Those style adjustments are really something that the popup dictates, so it might make sense to do them in a PopupMenu static method (since you don't want to create a popup just for that) or a RenderTheme method.
Or you could do this in cross-platform code but have a PopupMenu method that asks whether or not you should do it.
Created attachment 14770 [details] Natural directionality patch
Comment on attachment 14770 [details] Natural directionality patch I think we should refactor the loop that figures out the TextDirection of a run of text into a helper function. r=me
Created attachment 14771 [details] Updated patch Factored out the loop.
Comment on attachment 14771 [details] Updated patch +TextDirection textDirectionForParagraph(StringImpl* paragraph) Should be marked "static" so it gets internal linkage. r=me
Landed in r21900 with "static" added as requested.