为了处理字符消息实现自动完成的功能，这是怎么样实现的呢？其实是先记录字符消息响应前的字符串以及选中状态，接着再处理消息，最后才查询可能的输入，做出智能提示。<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
#001 void AutocompleteEdit::OnBeforePossibleChange() {
#002 // Record our state.
记录当前已经输入的字符串。
#003 text_before_change_ = GetText();
记录当前选中的字符位置。
#004 GetSelection(sel_before_change_);
#005 select_all_before_change_ = IsSelectAll(sel_before_change_);
#006 }
上面就保存字符消息响应前的状态，接着下来就是消息响应后的处理了，如下：
#001 bool AutocompleteEdit::OnAfterPossibleChange() {
#002 // Prevent the user from selecting the "phantom newline" at the end of the
#003 // edit. If they try, we just silently move the end of the selection back to
#004 // the end of the real text.
判断用户新选中状态。
#005 CHARRANGE new_sel;
#006 GetSelection(new_sel);
#007 const int length = GetTextLength();
#008 if ((new_sel.cpMin > length) || (new_sel.cpMax > length)) {
#009 if (new_sel.cpMin > length)
#010 new_sel.cpMin = length;
#011 if (new_sel.cpMax > length)
#012 new_sel.cpMax = length;
#013 SetSelectionRange(new_sel);
#014 }
判断用户是否输入字符有变化。
#015 const bool selection_differs = (new_sel.cpMin != sel_before_change_.cpMin) ||
#016 (new_sel.cpMax != sel_before_change_.cpMax);
#017
#018 // See if the text or selection have changed since OnBeforePossibleChange().
#019 const std::wstring new_text(GetText());
#020 const bool text_differs = (new_text != text_before_change_);
#021
#022 // Update the paste state as appropriate: if we're just finishing a paste
#023 // that replaced all the text, preserve that information; otherwise, if we've
#024 // made some other edit, clear paste tracking.
#025 if (paste_state_ == REPLACING_ALL)
#026 paste_state_ = REPLACED_ALL;
#027 else if (text_differs)
#028 paste_state_ = NONE;
#029
如果输入没有任何变化，就返回去。
#030 // If something has changed while the control key is down, prevent
#031 // "ctrl-enter" until the control key is released. When we do this, we need
#032 // to update the popup if it's open, since the desired_tld will have changed.
#033 if ((text_differs || selection_differs) &&
#034 (control_key_state_ == DOWN_WITHOUT_CHANGE)) {
#035 control_key_state_ = DOWN_WITH_CHANGE;
#036 if (!text_differs && !popup_->is_open())
#037 return false; // Don't open the popup for no reason.
#038 } else if (!text_differs &&
#039 (inline_autocomplete_text_.empty() || !selection_differs)) {
#040 return false;
#041 }
#042
#043 const bool had_keyword = !is_keyword_hint_ && !keyword_.empty();
#044
下面开始设置新的显示字符串。
#045 // Modifying the selection counts as accepting the autocompleted text.
#046 InternalSetUserText(UserTextFromDisplayText(new_text));
#047 has_temporary_text_ = false;
#048
#049 if (text_differs) {
#050 // When the user has deleted text, don't allow inline autocomplete. Make
#051 // sure to not flag cases like selecting part of the text and then pasting
#052 // (or typing) the prefix of that selection. (We detect these by making
#053 // sure the caret, which should be after any insertion, hasn't moved
#054 // forward of the old selection start.)
#055 just_deleted_text_ = (text_before_change_.length() > new_text.length()) &&
#056 (new_sel.cpMin <= std::min(sel_before_change_.cpMin,
#057 sel_before_change_.cpMax));
#058
#059 // When the user doesn't have a selected keyword, deleting text or replacing
#060 // all of it with something else should reset the provider affinity. The
#061 // typical use case for deleting is that the user starts typing, sees that
#062 // some entry is close to what he wants, arrows to it, and then deletes some
#063 // unnecessary bit from the end of the string. In this case the user didn't
#064 // actually want "provider X", he wanted the string from that entry for
#065 // editing purposes, and he's no longer looking at the popup to notice that,
#066 // despite deleting some text, the action we'll take on enter hasn't changed
#067 // at all.
这里删除已经选择的提示。
#068 if (!had_keyword && (just_deleted_text_ || select_all_before_change_)) {
#069 popup_->manually_selected_match_.Clear();
#070 }
#071 }
#072
#073 // Disable the fancy keyword UI if the user didn't already have a visible
#074 // keyword and is not at the end of the edit. This prevents us from showing
#075 // the fancy UI (and interrupting the user's editing) if the user happens to
#076 // have a keyword for 'a', types 'ab' then puts a space between the 'a' and
#077 // the 'b'.
#078 disable_keyword_ui_ = (is_keyword_hint_ || keyword_.empty()) &&
#079 ((new_sel.cpMax != length) || (new_sel.cpMin != length));
#080
更新智能提示菜单。
#081 UpdatePopup();
#082
#083 if (!had_keyword && !is_keyword_hint_ && !keyword_.empty()) {
#084 // Went from no selected keyword to a selected keyword. Set the affinity to
#085 // the keyword provider. This forces the selected keyword to persist even
#086 // if the user deletes all the text.
#087 popup_->manually_selected_match_.Clear();
#088 popup_->manually_selected_match_.provider_affinity =
#089 popup_->autocomplete_controller()->keyword_provider();
#090 }
#091
当自动完成框字符串发生变化，就需要更新URL重点显示。
#092 if (text_differs)
#093 TextChanged();
#094
#095 return true;
#096 }
在这个函数里，先判断字符串是否发生变化，然后根据变化来决定是否更新编辑框的显示，同时还需要UpdatePopup更新智能提示菜单，最后判断是否有一个URL地址，如果有就重点显示出来。
其实这里最关键的问题就是智能菜单的数据从那里来的呢？怎么样根据用户的输入查找到最合适的提示呢？下一次我们再来分析这方面的问题。
再分享一下我老师大神的人工智能教程吧。零基础！通俗易懂！风趣幽默！还带黄段子！希望你也加入到我们人工智能的队伍中来！https://blog.csdn.net/jiangjunshow