Implement Pango RenderText for Linux.

views/controls/textfield/textfield_views_model.cc

Index: views/controls/textfield/textfield_views_model.cc
===================================================================
--- views/controls/textfield/textfield_views_model.cc	(revision 97884)
+++ views/controls/textfield/textfield_views_model.cc	(working copy)
@@ -611,10 +611,10 @@
 void TextfieldViewsModel::CancelCompositionText() {
   DCHECK(HasCompositionText());
   ui::Range range = render_text_->GetCompositionRange();
+  ClearComposition();

[msw, 2011/08/29 20:38:05]

Why did you make this change?
I have a vague feeling that I tried this before and it caused problems, but I
don't remember exactly what. Perhaps oshima can take a look.

[xji, 2011/08/30 00:39:41]

Inside SetCursorPosition(), we will need to get the previous grapheme of the
last index, which depends on pango layout is set up. During set up layout, pango
attribute is set up, including styles of composition text.  
Without ClearComposition(), we will be accessing the Composition range of
previous text during the setup of current text.

BTW, should not we reset composition_range_ inside SetText()?

[msw, 2011/08/30 01:17:07]

OK.
Perhaps, I'm not an expert with the IME code.

[xji, 2011/08/31 19:01:06]

From suzhe
"The caller should make sure that the composition text has been committed or
cancelled before calling RenderText::SetText(), so it's probably reasonable to
do a DCHECK in RenderText::SetText() to make sure the composition range has been
cleared."

   string16 new_text = GetText();
   render_text_->SetText(new_text.erase(range.start(), range.length()));
   render_text_->SetCursorPosition(range.start());
-  ClearComposition();
   if (delegate_)
     delegate_->OnCompositionTextConfirmedOrCleared();
 }