谷歌浏览器的源码分析(9)

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。

#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。