谷歌浏览器的源码分析 9

Posted 2021-02-07 skiwnchh

 

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。

 

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