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() {
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// Record our state.
记录当前已经输入的字符串。
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text_before_change_ = GetText();
记录当前选中的字符位置。
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GetSelection(sel_before_change_);
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select_all_before_change_ = IsSelectAll(sel_before_change_);
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}
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：
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bool AutocompleteEdit::OnAfterPossibleChange() {
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// Prevent the user from selecting the "phantom newline" at the end of the
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// edit.
If they try, we just silently move the end of the selection back to
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// the end of the real text.
判断用户新选中状态。
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CHARRANGE new_sel;
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GetSelection(new_sel);
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const int length = GetTextLength();
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if ((new_sel.cpMin > length) || (new_sel.cpMax > length)) {
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if (new_sel.cpMin > length)
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new_sel.cpMin = length;
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if (new_sel.cpMax > length)
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new_sel.cpMax = length;
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SetSelectionRange(new_sel);
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}
判断用户是否输入字符有变化。
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const bool selection_differs = (new_sel.cpMin != sel_before_change_.cpMin) ||
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(new_sel.cpMax != sel_before_change_.cpMax);
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// See if the text or selection have changed since OnBeforePossibleChange().
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const std::wstring new_text(GetText());
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const bool text_differs = (new_text != text_before_change_);
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// Update the paste state as appropriate: if we're just finishing a paste
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// that replaced all the text, preserve that information; otherwise, if we've
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// made some other edit, clear paste tracking.
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if (paste_state_ == REPLACING_ALL)
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paste_state_ = REPLACED_ALL;
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else if (text_differs)
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paste_state_ = NONE;
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如果输入没有任何变化，就返回去。
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// If something has changed while the control key is down, prevent
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// "ctrl-enter" until the control key is released.
When we do this, we need
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// to update the popup if it's open, since the desired_tld will have changed.
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if ((text_differs || selection_differs) &&
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(control_key_state_ == DOWN_WITHOUT_CHANGE)) {
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control_key_state_ = DOWN_WITH_CHANGE;
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if (!text_differs && !popup_->is_open())
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return false;
// Don't open the popup for no reason.
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} else if (!text_differs &&
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(inline_autocomplete_text_.empty() || !selection_differs)) {
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return false;
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}
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const bool had_keyword = !is_keyword_hint_ && !keyword_.empty();
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下面开始设置新的显示字符串。
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// Modifying the selection counts as accepting the autocompleted text.
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InternalSetUserText(UserTextFromDisplayText(new_text));
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has_temporary_text_ = false;
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if (text_differs) {
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// When the user has deleted text, don't allow inline autocomplete.
Make
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// sure to not flag cases like selecting part of the text and then pasting
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// (or typing) the prefix of that selection.
(We detect these by making
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// sure the caret, which should be after any insertion, hasn't moved
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// forward of the old selection start.)
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just_deleted_text_ = (text_before_change_.length() > new_text.length()) &&
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(new_sel.cpMin <= std::min(sel_before_change_.cpMin,
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sel_before_change_.cpMax));
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// When the user doesn't have a selected keyword, deleting text or replacing
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// all of it with something else should reset the provider affinity.
The
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// typical use case for deleting is that the user starts typing, sees that
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// some entry is close to what he wants, arrows to it, and then deletes some
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// unnecessary bit from the end of the string.
In this case the user didn't
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// actually want "provider X", he wanted the string from that entry for
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// editing purposes, and he's no longer looking at the popup to notice that,
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// despite deleting some text, the action we'll take on enter hasn't changed
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// at all.
这里删除已经选择的提示。
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if (!had_keyword && (just_deleted_text_ || select_all_before_change_)) {
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popup_->manually_selected_match_.Clear();
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}
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}
#072
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// Disable the fancy keyword UI if the user didn't already have a visible
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// keyword and is not at the end of the edit.
This prevents us from showing
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// the fancy UI (and interrupting the user's editing) if the user happens to
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// have a keyword for 'a', types 'ab' then puts a space between the 'a' and
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// the 'b'.
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disable_keyword_ui_ = (is_keyword_hint_ || keyword_.empty()) &&
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((new_sel.cpMax != length) || (new_sel.cpMin != length));
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更新智能提示菜单。
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UpdatePopup();
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if (!had_keyword && !is_keyword_hint_ && !keyword_.empty()) {
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// Went from no selected keyword to a selected keyword. Set the affinity to
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// the keyword provider.
This forces the selected keyword to persist even
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// if the user deletes all the text.
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popup_->manually_selected_match_.Clear();
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popup_->manually_selected_match_.provider_affinity =
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popup_->autocomplete_controller()->keyword_provider();
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}
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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)
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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。
