[rendertext,i18n] Added flag to force RTL rendering

base/i18n/rtl.cc

 // Copyright (c) 2011 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 "base/i18n/rtl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 37 matching lines @@
   if (variant != NULL && *variant != '\0')
     result += '@' + base::ToLowerASCII(variant);
 
   return result;
 }
 
 // Returns LEFT_TO_RIGHT or RIGHT_TO_LEFT if |character| has strong
 // directionality, returns UNKNOWN_DIRECTION if it doesn't. Please refer to
 // http://unicode.org/reports/tr9/ for more information.
 base::i18n::TextDirection GetCharacterDirection(UChar32 character) {
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();

[msw, 2017/04/28 22:04:03]

This function is called heavily, cache the value (or at least the presence of a
value, so the typical production codepath isn't hit with commandline checks for
each call), maybe:

namespace {

bool HasForcedTextDirection() {
  static bool value =
base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kForceTextDirection);
  return value;  
}

}  // namespace

...

  if (HasForcedTextDirection()) {
    std::string force_flag = ...
  }

[Kevin Bailey, 2017/04/29 04:24:03]

Done.

+  if (command_line->HasSwitch(switches::kForceTextDirection)) {
+    std::string force_flag =
+        command_line->GetSwitchValueASCII(switches::kForceTextDirection);
+
+    if (force_flag == switches::kForceUIDirectionRTL)
+      return base::i18n::RIGHT_TO_LEFT;
+    if (force_flag == switches::kForceUIDirectionLTR)
+      return base::i18n::LEFT_TO_RIGHT;
+  }
   // Now that we have the character, we use ICU in order to query for the
   // appropriate Unicode BiDi character type.
   int32_t property = u_getIntPropertyValue(character, UCHAR_BIDI_CLASS);
   if ((property == U_RIGHT_TO_LEFT) ||
       (property == U_RIGHT_TO_LEFT_ARABIC) ||
       (property == U_RIGHT_TO_LEFT_EMBEDDING) ||
       (property == U_RIGHT_TO_LEFT_OVERRIDE)) {
     return base::i18n::RIGHT_TO_LEFT;
   } else if ((property == U_LEFT_TO_RIGHT) ||
              (property == U_LEFT_TO_RIGHT_EMBEDDING) ||
@@ skipping 376 matching lines @@
       begin == kRightToLeftOverride)
     ++begin_index;
   size_t end_index = text.length() - 1;
   if (text[end_index] == kPopDirectionalFormatting)
     --end_index;
   return text.substr(begin_index, end_index - begin_index + 1);
 }
 
 }  // namespace i18n
 }  // namespace base