Move gfx::ElideText functionality to RenderText.

ui/gfx/text_elider.cc

Index: ui/gfx/text_elider.cc
diff --git a/ui/gfx/text_elider.cc b/ui/gfx/text_elider.cc
index 8c07bdecd5f581d2e88b3bf20f1947bd94fe1c6b..947027887b02c92791a3296fcfb23ddb0f949b12 100644
--- a/ui/gfx/text_elider.cc
+++ b/ui/gfx/text_elider.cc
@@ -24,6 +24,7 @@
 #include "third_party/icu/source/common/unicode/rbbi.h"
 #include "third_party/icu/source/common/unicode/uloc.h"
 #include "ui/gfx/font_list.h"
+#include "ui/gfx/render_text.h"
 #include "ui/gfx/text_utils.h"
 
 using base::ASCIIToUTF16;
@@ -34,16 +35,13 @@ namespace gfx {
 
 namespace {
 
-// Elides a well-formed email address (e.g. username@domain.com) to fit into
-// |available_pixel_width| using the specified |font_list|.
-// This function guarantees that the string returned will contain at least one
-// character, other than the ellipses, on either side of the '@'. If it is
-// impossible to achieve these requirements: only an ellipsis will be returned.
-// If possible: this elides only the username portion of the |email|. Otherwise,
-// the domain is elided in the middle so that it splits the available width
-// equally with the elided username (should the username be short enough that it
-// doesn't need half the available width: the elided domain will occupy that
-// extra width).
+#if !defined(OS_WIN) && !defined(OS_LINUX)
+// The returned string will have at least one character besides the ellipsis
+// on either side of '@'; if that's impossible, a single ellipsis is returned.
+// If possible, only the username is elided. Otherwise, the domain is elided
+// in the middle, splitting available width equally with the elided username.
+// If the username is short enough that it doesn't need half the available
+// width, the elided domain will occupy that extra width.
 base::string16 ElideEmail(const base::string16& email,
                           const FontList& font_list,
                           float available_pixel_width) {
@@ -51,10 +49,8 @@ base::string16 ElideEmail(const base::string16& email,
     return email;
 
   // Split the email into its local-part (username) and domain-part. The email
-  // spec technically allows for @ symbols in the local-part (username) of the
-  // email under some special requirements. It is guaranteed that there is no @
-  // symbol in the domain part of the email however so splitting at the last @
-  // symbol is safe.
+  // spec allows for @ symbols in the username under some special requirements,
+  // but not in the domain part, so splitting at the last @ symbol is safe.
   const size_t split_index = email.find_last_of('@');
   DCHECK_NE(split_index, base::string16::npos);
   base::string16 username = email.substr(0, split_index);
@@ -99,6 +95,7 @@ base::string16 ElideEmail(const base::string16& email,
   username = ElideText(username, font_list, available_pixel_width, ELIDE_TAIL);
   return username + kAtSignUTF16 + domain;
 }
+#endif
 
 }  // namespace
 
@@ -205,36 +202,32 @@ base::string16 ElideText(const base::string16& text,
                          const FontList& font_list,
                          float available_pixel_width,
                          ElideBehavior behavior) {
+#if defined(OS_WIN) || defined(OS_LINUX)

[Alexei Svitkine (slow), 2014/07/03 20:12:34]

I understand why it wouldn't work on platforms that don't have RenderText (e.g.
iOS), but why not Mac? afaik, eliding shouldn't be using any things
unimplemented by RenderTextMac.

[msw, 2014/07/08 19:07:36]

RenderText doesn't support RectF values for the display rect and failed some
unit tests. I ceil'ed the available  width and made GetContentWidth return float
values. That gets the tests passing, but might cause a non-integral available
width elision to assume use of the full pixel. Do you think I should attempt to
support RectF display rects in this CL (or as a prerequisite CL)?

+  DCHECK_NE(behavior, FADE_TAIL);
+  scoped_ptr<RenderText> render_text(RenderText::CreateInstance());
+  render_text->SetCursorEnabled(false);
+  // Do not bother accurately sizing strings over 5000 characters here, for
+  // performance purposes. This matches the behavior of Canvas::SizeStringFloat.
+  render_text->set_truncate_length(5000);
+  render_text->SetFontList(font_list);
+  render_text->SetDisplayRect(gfx::Rect(gfx::Size(available_pixel_width, 1)));
+  render_text->SetElideBehavior(behavior);
+  render_text->SetText(text);
+  return render_text->layout_text();
+#else
   DCHECK_NE(behavior, FADE_TAIL);
-  if (text.empty() || behavior == FADE_TAIL)
+  if (text.empty() || behavior == FADE_TAIL || behavior == NO_ELIDE ||
+      GetStringWidthF(text, font_list) <= available_pixel_width)

[Alexei Svitkine (slow), 2014/07/03 20:12:34]

Nit: {}'s

[msw, 2014/07/08 19:07:36]

Done.

     return text;
   if (behavior == ELIDE_EMAIL)
     return ElideEmail(text, font_list, available_pixel_width);
 
-  const float current_text_pixel_width = GetStringWidthF(text, font_list);
   const bool elide_in_middle = (behavior == ELIDE_MIDDLE);
   const bool elide_at_beginning = (behavior == ELIDE_HEAD);
   const bool insert_ellipsis = (behavior != TRUNCATE);
   const base::string16 ellipsis = base::string16(kEllipsisUTF16);
   StringSlicer slicer(text, ellipsis, elide_in_middle, elide_at_beginning);
 
-  // Pango will return 0 width for absurdly long strings. Cut the string in
-  // half and try again.
-  // This is caused by an int overflow in Pango (specifically, in
-  // pango_glyph_string_extents_range). It's actually more subtle than just
-  // returning 0, since on super absurdly long strings, the int can wrap and
-  // return positive numbers again. Detecting that is probably not worth it
-  // (eliding way too much from a ridiculous string is probably still
-  // ridiculous), but we should check other widths for bogus values as well.
-  if (current_text_pixel_width <= 0) {
-    const base::string16 cut =
-      slicer.CutString(text.length() / 2, insert_ellipsis);
-    return ElideText(cut, font_list, available_pixel_width, behavior);
-  }
-
-  if (current_text_pixel_width <= available_pixel_width)
-    return text;
-
   if (insert_ellipsis &&
       GetStringWidthF(ellipsis, font_list) > available_pixel_width)
     return base::string16();
@@ -254,8 +247,7 @@ base::string16 ElideText(const base::string16& text,
       break;
     if (guess_width > available_pixel_width) {
       hi = guess - 1;
-      // Move back if we are on loop terminating condition, and guess is wider
-      // than available.
+      // Move back on the loop terminating condition when the guess is too wide.
       if (hi < lo)
         lo = hi;
     } else {
@@ -264,6 +256,7 @@ base::string16 ElideText(const base::string16& text,
   }
 
   return slicer.CutString(guess, insert_ellipsis);
+#endif
 }
 
 bool ElideString(const base::string16& input,