Truncate the Javascript alert message if the length is too long on Mac port

chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.mm

 // Copyright (c) 2012 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 "chrome/browser/ui/cocoa/javascript_app_modal_dialog_cocoa.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/i18n/rtl.h"
 #include "base/logging.h"
 #import "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 #import "chrome/browser/chrome_browser_application_mac.h"
 #include "chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h"
 #include "grit/generated_resources.h"
 #include "grit/ui_strings.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 #include "ui/base/ui_base_types.h"
 
+const int kSlotsPerLine = 50;
+const int kMessageTextMaxSlots = 2000;
+
 // Helper object that receives the notification that the dialog/sheet is
 // going away. Is responsible for cleaning itself up.
 @interface JavaScriptAppModalDialogHelper : NSObject<NSAlertDelegate> {
  @private
   base::scoped_nsobject<NSAlert> alert_;
   NSTextField* textField_;  // WEAK; owned by alert_
 }
 
 - (NSAlert*)alert;
 - (NSTextField*)textField;
@@ skipping 109 matching lines @@
   alert_ = [helper_ alert];
   NSTextField* field = nil;
   if (text_field) {
     field = [helper_ textField];
     [field setStringValue:base::SysUTF16ToNSString(
         dialog_->default_prompt_text())];
   }
   [alert_ setDelegate:helper_];
   NSString* informative_text =
       base::SysUTF16ToNSString(dialog_->message_text());
+
+  // Truncate long JS alerts - crbug.com/331219
+  NSCharacterSet* newline_char_set = [NSCharacterSet newlineCharacterSet];
+  for (size_t index = 0, slots_count = 0; index < informative_text.length;
+      ++index) {
+    unichar current_char = [informative_text characterAtIndex:index];
+    if ([newline_char_set characterIsMember:current_char])
+      slots_count += kSlotsPerLine;
+    else
+      slots_count++;
+    if (slots_count > kMessageTextMaxSlots) {
+      informative_text = [informative_text substringToIndex:index - 1];

[Avi (use Gerrit), 2014/01/24 20:08:08]

But that's what you're doing here with -substringToIndex:! It, as well as
TruncateString, takes a length to truncate to. You could easily put in
TruncateString here with i as the length.

+      informative_text = [informative_text stringByAppendingString:@"\n..."];
+      break;
+    }
+  }
+
   [alert_ setInformativeText:informative_text];
   NSString* message_text =
       base::SysUTF16ToNSString(dialog_->title());
   [alert_ setMessageText:message_text];
   [alert_ addButtonWithTitle:default_button];
   if (!one_button) {
     NSButton* other = [alert_ addButtonWithTitle:other_button];
     [other setKeyEquivalent:@"\e"];
   }
   if (dialog_->display_suppress_checkbox()) {
@@ skipping 139 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeAppModalDialog, public:
 
 // static
 NativeAppModalDialog* NativeAppModalDialog::CreateNativeJavaScriptPrompt(
     JavaScriptAppModalDialog* dialog,
     gfx::NativeWindow parent_window) {
   return new JavaScriptAppModalDialogCocoa(dialog);
 }