Make styled-label trimming less agressive, allowing whitespace

ui/views/controls/styled_label.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/styled_label.h"
 
 #include <stddef.h>
 
 #include <limits>
 #include <vector>
@@ skipping 241 matching lines @@
   int total_height = 0;
   // The width that was actually used. Guaranteed to be no larger than |width|.
   int used_width = 0;
 
   base::string16 remaining_string = text_;
   StyleRanges::const_iterator current_range = style_ranges_.begin();
 
   // Iterate over the text, creating a bunch of labels and links and laying them
   // out in the appropriate positions.
   while (!remaining_string.empty()) {
-    // Don't put whitespace at beginning of a line with an exception for the
-    // first line (so the text's leading whitespace is respected).
     if (x == 0 && line > 0) {
-      base::TrimWhitespace(remaining_string, base::TRIM_LEADING,
-                           &remaining_string);
+      if (remaining_string.front() == L'\n') {
+        // Wrapped to the next line on \n, remove it. Other whitespace,
+        // eg, spaces to indent next line, are preserved.
+        remaining_string.erase(0, 1);
+      } else {
+        // Wrapped on whitespace character or characters in the middle of the
+        // line - none of them are needed at the beginning of the next line.
+        base::TrimWhitespace(remaining_string, base::TRIM_LEADING,
+                             &remaining_string);
+      }
     }
 
     gfx::Range range(gfx::Range::InvalidRange());
     if (current_range != style_ranges_.end())
       range = current_range->range;
 
     const size_t position = text_.size() - remaining_string.size();
 
     const gfx::Rect chunk_bounds(x, 0, width - x, 2 * line_height);
     std::vector<base::string16> substrings;
     gfx::FontList text_font_list = font_list_;
     // If the start of the remaining text is inside a styled range, the font
     // style may differ from the base font. The font specified by the range
     // should be used when eliding text.
     if (position >= range.start()) {
       text_font_list =
           text_font_list.Derive(0, current_range->style_info.font_style,
                                 current_range->style_info.weight);
     }
     gfx::ElideRectangleText(remaining_string,
                             text_font_list,
                             chunk_bounds.width(),
                             chunk_bounds.height(),
                             gfx::WRAP_LONG_WORDS,
                             &substrings);
 
     if (substrings.empty() || substrings[0].empty()) {
       // Nothing fits on this line. Start a new line.
       // If x is 0, first line may have leading whitespace that doesn't fit in a
-      // single line, so try trimming those. Otherwise there is no room for
-      // anything; abort.
+      // single line, so try trimming those. When first remaining char is \n,
+      // otput it as an empty line.
+      // Otherwise there is no room for anything; abort.

[Evan Stade, 2016/12/09 18:41:58]

When I rewrite this portion of the function (L299-319) to this[1], all tests
still pass. Is this a valid rewrite or is the test coverage incomplete?

[1]
    if (substrings.empty())
      break;

    if (substrings[0].empty()) {
      x = 0;
      ++line;
      continue;
    }

       if (x == 0) {
         if (line == 0) {
           base::TrimWhitespace(remaining_string, base::TRIM_LEADING,
                                &remaining_string);
           continue;
+        } else if (remaining_string.empty() ||
+                   remaining_string.front() != L'\n') {
+          break;
         }
-        break;
       }
 
       x = 0;
-      line++;
+      ++line;
       continue;
     }
 
     base::string16 chunk = substrings[0];
 
     std::unique_ptr<Label> label;
     if (position >= range.start()) {
       const RangeStyleInfo& style_info = current_range->style_info;
 
       if (style_info.disable_line_wrapping && chunk.size() < range.length() &&
           position == range.start() && x != 0) {
         // If the chunk should not be wrapped, try to fit it entirely on the
         // next line.
         x = 0;
-        line++;
+        ++line;
         continue;
       }
 
       if (chunk.size() > range.end() - position)
         chunk = chunk.substr(0, range.end() - position);
 
       label = CreateLabelRange(chunk, font_list_, style_info, this);
 
       if (style_info.is_link && !dry_run)
         link_targets_[label.get()] = range;
@@ skipping 39 matching lines @@
 
     remaining_string = remaining_string.substr(chunk.size());
   }
 
   DCHECK_LE(used_width, width);
   calculated_size_ = gfx::Size(used_width + GetInsets().width(), total_height);
   return calculated_size_;
 }
 
 }  // namespace views