Avoid sync IPCs for firstRectForCharacterRange/attributedSubstringForProposedRange.

content/browser/renderer_host/render_widget_host_view_mac.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 "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
 #include "base/debug/crash_logging.h"
 #include "base/logging.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/mac/sdk_forward_declarations.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/sys_info.h"
 #include "base/trace_event/trace_event.h"
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 #include "content/browser/accessibility/browser_accessibility_manager_mac.h"
 #include "content/browser/bad_message.h"
 #import "content/browser/cocoa/system_hotkey_helper_mac.h"
@@ skipping 1186 matching lines @@
     [cocoa_view_ setMarkedRange:range.ToNSRange()];
   }
 
   RenderWidgetHostViewBase::SelectionChanged(text, offset, range);
 }
 
 void RenderWidgetHostViewMac::SelectionBoundsChanged(
     const ViewHostMsg_SelectionBounds_Params& params) {
   if (params.anchor_rect == params.focus_rect)
     caret_rect_ = params.anchor_rect;
+  first_selection_rect_ = params.anchor_rect;
 }
 
 void RenderWidgetHostViewMac::SetShowingContextMenu(bool showing) {
   RenderWidgetHostViewBase::SetShowingContextMenu(showing);
 
   // Create a fake mouse event to inform the render widget that the mouse
   // left or entered.
   NSWindow* window = [cocoa_view_ window];
   // TODO(asvitkine): If the location outside of the event stream doesn't
   // correspond to the current event (due to delayed event processing), then
@@ skipping 200 matching lines @@
 
 bool RenderWidgetHostViewMac::GetCachedFirstRectForCharacterRange(
     NSRange range,
     NSRect* rect,
     NSRange* actual_range) {
   DCHECK(rect);
   // This exists to make IMEs more responsive, see http://crbug.com/115920
   TRACE_EVENT0("browser",
                "RenderWidgetHostViewMac::GetFirstRectForCharacterRange");
 
+  const gfx::Range requested_range(range);
   // If requested range is same as caret location, we can just return it.
-  if (selection_range_.is_empty() && gfx::Range(range) == selection_range_) {
+  if (selection_range_.is_empty() && requested_range == selection_range_) {
     if (actual_range)
       *actual_range = range;
     *rect = NSRectFromCGRect(caret_rect_.ToCGRect());
     return true;
   }
 
+  if (composition_range_.is_empty()) {
+    if (!selection_range_.Contains(requested_range))
+      return false;
+    if (actual_range)
+      *actual_range = selection_range_.ToNSRange();
+    *rect = NSRectFromCGRect(first_selection_rect_.ToCGRect());
+    return true;
+  }
+
   const gfx::Range request_range_in_composition =
-      ConvertCharacterRangeToCompositionRange(gfx::Range(range));
+      ConvertCharacterRangeToCompositionRange(requested_range);
   if (request_range_in_composition == gfx::Range::InvalidRange())
     return false;
 
   // If firstRectForCharacterRange in WebFrame is failed in renderer,
   // ImeCompositionRangeChanged will be sent with empty vector.
   if (composition_bounds_.empty())
     return false;
   DCHECK_EQ(composition_bounds_.size(), composition_range_.length());
 
   gfx::Range ui_actual_range;
@@ skipping 1419 matching lines @@
   // there. (When this method returns an empty range, the input method doesn't
   // call the setMarkedText method.)
   return hasMarkedText_ ? markedRange_ : NSMakeRange(NSNotFound, 0);
 }
 
 - (NSAttributedString*)attributedSubstringForProposedRange:(NSRange)range
     actualRange:(NSRangePointer)actualRange {
   // TODO(thakis): Pipe |actualRange| through TextInputClientMac machinery.
   if (actualRange)
     *actualRange = range;
-  NSAttributedString* str =
-      TextInputClientMac::GetInstance()->GetAttributedSubstringFromRange(
-          renderWidgetHostView_->render_widget_host_, range);
-  return str;
+
+  const gfx::Range requested_range(range);
+  if (requested_range.is_reversed())
+    return nil;
+  size_t requested_len = requested_range.length();
+  // Avoid integer overflow.

[palmer, 2015/09/03 23:03:59]

This check is OK, but it's easy for people to get wrong in other contexts. And
later maintainers might get it wrong too. It's better to use our standard
defense, base::CheckedNumeric.

And, put this down near line 2938, i.e. immediately where it's used.

base::CheckedNumeric<size_t> requested_len = requested_range.length();
requested_len *= sizeof(base::char16);
NSUInteger bytes_len = base::strict_cast<NSUInteger,
size_t>(requested_len.ValueOrDefault(0));

[Shu Chen, 2015/09/04 01:36:47]

Done.

+  if (requested_len > NSUIntegerMax / sizeof(base::char16))
+    return nil;
+
+  gfx::Range expected_range;
+  const base::string16* expected_text;
+
+  if (!renderWidgetHostView_->composition_range().is_empty()) {
+    expected_text = &markedText_;
+    expected_range = renderWidgetHostView_->composition_range();
+  } else {
+    expected_text = &renderWidgetHostView_->selection_text();
+    size_t offset = renderWidgetHostView_->selection_text_offset();
+    expected_range = gfx::Range(offset, offset + expected_text->size());
+  }
+
+  if (!expected_range.Contains(requested_range))
+    return nil;
+
+  // Gets the raw bytes to avoid unnecessary string copies for generating
+  // NSString.
+  const base::char16* bytes =
+      &(*expected_text)[requested_range.start() - expected_range.start()];
+  NSUInteger bytes_len = base::strict_cast<NSUInteger, size_t>(
+      requested_len * sizeof(base::char16));
+  base::scoped_nsobject<NSString> ns_string(
+      [[NSString alloc] initWithBytes:bytes
+                               length:bytes_len
+                             encoding:NSUTF16LittleEndianStringEncoding]);
+  return [[[NSAttributedString alloc] initWithString:ns_string] autorelease];
 }
 
 - (NSInteger)conversationIdentifier {
   return reinterpret_cast<NSInteger>(self);
 }
 
 // Each RenderWidgetHostViewCocoa has its own input context, but we return
 // nil when the caret is in non-editable content or password box to avoid
 // making input methods do their work.
 - (NSTextInputContext *)inputContext {
@@ skipping 411 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end