Reland: Fix setComposingText with empty text when newCursorPosition != 1

content/renderer/render_widget.cc

 // 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/renderer/render_widget.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 1337 matching lines @@
     return pending_window_rect_;
   }
 
   return window_screen_rect_;
 }
 
 WebRect RenderWidget::windowResizerRect() {
   return resizer_rect_;
 }
 
+std::pair<int, int> RenderWidget::adjustSelectionForBoundary(
+    int selectionStart,
+    int selectionEnd,
+    const int textLength) const {
+  int compositionLength =
+      text_input_info_.compositionEnd - text_input_info_.compositionStart;
+  int beforeCompositionLength;
+  if (compositionLength != 0)
+    beforeCompositionLength = text_input_info_.compositionStart;
+  else
+    beforeCompositionLength = text_input_info_.selectionStart;
+  int afterCompositionLength =
+      static_cast<int>(text_input_info_.value.length()) - compositionLength -
+      beforeCompositionLength;
+
+  // In case of exceeding the left boundary.
+  selectionStart = std::max(selectionStart, -beforeCompositionLength);
+  selectionEnd = std::max(selectionEnd, selectionStart);
+
+  // In case of exceeding the right boundary.
+  selectionEnd = std::min(selectionEnd, textLength + afterCompositionLength);
+  selectionStart = std::min(selectionStart, selectionEnd);
+
+  return std::make_pair(selectionStart, selectionEnd);
+}
+
 void RenderWidget::OnImeSetComposition(
     const base::string16& text,
     const std::vector<WebCompositionUnderline>& underlines,
     const gfx::Range& replacement_range,
     int selection_start, int selection_end) {
   if (!ShouldHandleImeEvent())
     return;
   ImeEventGuard guard(this);
+
+  std::pair<int, int> selectionPair =
+      adjustSelectionForBoundary(selection_start, selection_end, text.length());
+
   if (!webwidget_->setComposition(
       text, WebVector<WebCompositionUnderline>(underlines),
-      selection_start, selection_end)) {
+      selectionPair.first, selectionPair.second)) {
     // If we failed to set the composition text, then we need to let the browser
     // process to cancel the input method's ongoing composition session, to make
     // sure we are in a consistent state.
     Send(new InputHostMsg_ImeCancelComposition(routing_id()));
   }
   UpdateCompositionInfo(true);
 }
 
 void RenderWidget::OnImeConfirmComposition(const base::string16& text,
                                            const gfx::Range& replacement_range,
@@ skipping 600 matching lines @@
 void RenderWidget::requestPointerUnlock() {
   mouse_lock_dispatcher_->UnlockMouse(webwidget_mouse_lock_target_.get());
 }
 
 bool RenderWidget::isPointerLocked() {
   return mouse_lock_dispatcher_->IsMouseLockedTo(
       webwidget_mouse_lock_target_.get());
 }
 
 }  // namespace content