谷歌浏览器的源码分析(7)

添加时间：2013-12-7

相关阅读: 谷歌

副标题#e#

　　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。

#p#副标题#e#

#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。