?

為了處理字符消息實現自動完成的功能，這是怎么樣實現的呢？其實是先記錄字符消息響應前的字符串以及選中狀態，接著再處理消息，最后才查詢可能的輸入，做出智能提示。

#001 ? void AutocompleteEdit::OnBeforePossibleChange() {

#002 ??? // Record our state.

?

記錄當前已經輸入的字符串。

#003 ??? text_before_change_ = GetText();

?

記錄當前選中的字符位置。

#004 ??? GetSelection(sel_before_change_);

#005 ??? select_all_before_change_ = IsSelectAll(sel_before_change_);

#006 ? }

?

上面就保存字符消息響應前的狀態，接著下來就是消息響應后的處理了，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.

?

判斷用戶新選中狀態。

#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 ??? }

?

判斷用戶是否輸入字符有變化。

#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 ?

?

如果輸入沒有任何變化，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 ?

?

下面開始設置新的顯示字符串。

#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.

?

這里刪除已經選擇的提示。

#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 ?

?

更新智能提示菜單。

#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 ?

?

當自動完成框字符串發生變化，就需要更新 URL 重點顯示。

#092 ??? if (text_differs)

#093 ????? TextChanged();

#094 ?

#095 ??? return true;

#096 ? }

?

在這個函數里，先判斷字符串是否發生變化，然后根據變化來決定是否更新編輯框的顯示，同時還需要 UpdatePopup 更新智能提示菜單，最后判斷是否有一個 URL 地址，如果有就重點顯示出來。

?

其實這里最關鍵的問題就是智能菜單的數據從那里來的呢？怎么樣根據用戶的輸入查找到最合適的提示呢？下一次我們再來分析這方面的問題。

谷歌瀏覽器的源碼分析(9)