Set your input language to Katakana. Type 'ka<return>' in the input and in the textarea. In the input, the "value" field updates as you type. In the textarea, the value doesn't update until you hit 'return'. The former is consistent with other browser and is the desired behavior. This happens on OSX and Windows.
I think this bug would be clearer if it the title talked about <input> and not <textarea>, since <textarea> is behaving as desired. The bug here isn't that it's inconsistent, but rather that it's wrong for <input>! I'm going to take a cut at retitling the bug.
Is this a change from previous versions of WebKit, or has it always been this way? Is this the same on Windows, or is this Mac-specific?
It's actually the other way around - input has the desired behavior, textarea does not. It happens on Mac and Windows.
That is, all other browsers give the intermediate value (which is what input does in WebKit). This is helpful for autocomplete.
Retitling the bug again. I see how this can be desired behavior, but do all other browsers work like this? In Firefox 3.1b3 on Mac OS X, nether textareas nor inputs have their value affected by unconfirmed text.
Firefox 3.08 on the Mac definitely works like this. IE works like this, as does current FF on Windows. This is definitely the desired behavior. If FF 3.1 doesn't work like this, I'll file a bug over there too.
FYI - for contentEditable, on Chrome, I'm seeing the input behavior (fetching innerHTML rather than value).
Created attachment 30441 [details] Make unconfirmed IME text affect textarea's value.
Comment on attachment 30441 [details] Make unconfirmed IME text affect textarea's value. Please make an automated test for this (at least Mac-only, if it cannot be made cross-platform).
Comment on attachment 30441 [details] Make unconfirmed IME text affect textarea's value. Marking r- per Alexey's comment about tests. Someone should review the substance of the code change as well.
Created attachment 31911 [details] Ojan's fix with an automated test. This change just replaces Ojan's manual tests with an automated test. Since I'm wondering if textInputController.setMarkedText() works on all platforms, this automated test is put under "LayoutTest/platform/mac/editing/input".
Comment on attachment 31911 [details] Ojan's fix with an automated test. Looks good. r=me
Landed as r45567.