在minimo中用方向键切换焦点

 

在minimo中用方向键切换焦点

 

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作者联系方式：李先静 <xianjimli at hotmail dot com>

 

用XUL编写的minimo实在太慢了，起动过程足足要40秒钟，我对它已经完全失去信心了。前几天发现用GTK+编写的minimo则要快得多，第二次起动仅仅花了7秒钟时间，这要让我精神大振，可惜mozilla中所带的GTK+编写的minimo已经没有人维护了，代码很凌乱，很多功能也都不支持。

 

最后我们决定用GTK+重新编写minimo，而界面完全模仿Windows Mobile5.0 中的IE。经过一周时间的努力，基本功能已经完成，只是还有少数功能需要完善。其中方向键切换焦点就是其中的问题之一，在firefox里，默认情况是不能用方向键在网页中切换焦点的，切换焦点只能用tab键，而普通手机根本没有tab键，我们希望能用方向键代替tab实现焦点切换。

 

以前在阅读mozilla代码时，我记得有个扩展可以实现这个功能，不过忘了具体是哪个扩展了，今天在extension目录里找了一下，很快确认是spatialnavigation扩展，spatial取得真不怎么样，我还以为是什么3D相关的东西的呢，还好navigation给了一些提示。

 

Spatialnavigation的实现原理很简单:

 

NS_IMETHODIMP nsSpatialNavigation::Init(nsIDOMWindow *aWindow) {   mTopWindow = aWindow;   nsCOMPtr<nsIDOM3EventTarget> target;   nsCOMPtr<nsIDOMEventGroup> systemGroup;   nsresult rv = getEventTargetFromWindow(aWindow, getter_AddRefs(target), getter_AddRefs(systemGroup));   if (NS_FAILED(rv))     return rv;        target->AddGroupedEventListener(NS_LITERAL_STRING("keypress"),                                   static_cast<nsIDOMKeyListener*>(this),                                   PR_FALSE,                                   systemGroup);      return NS_OK; }

 

这个函数向DOMWindow注册按键事件，当有按键发生时，nsSpatialNavigation相关虚函数就会被调用。

 

NS_IMETHODIMP nsSpatialNavigation::KeyDown(nsIDOMEvent* aEvent) {   nsCOMPtr<nsIPrefBranch> prefBranch = do_GetService(NS_PREFSERVICE_CONTRACTID);   PRBool enabled;   prefBranch->GetBoolPref("snav.enabled", &enabled);   if (!enabled) //  this doesn't work.  wtf? if (!mService->mEnabled)     return NS_OK;     nsCOMPtr<nsIDOMNSUIEvent> uiEvent(do_QueryInterface(aEvent));   if (uiEvent)   {     // If a web page wants to use the keys mapped to our     // move, they have to use evt.preventDefault() after     // they get the key     PRBool preventDefault;     uiEvent->GetPreventDefault(&preventDefault);     if (preventDefault)       return NS_OK;   }   PRInt32 formControlType = -1;   // check to see if we are in a text field.   // based on nsTypeAheadFind.        //nsEvent should be renamed.   nsCOMPtr<nsIDOMNSEvent> nsEvent = do_QueryInterface(aEvent);   if (!nsEvent)     return NS_ERROR_FAILURE;      nsCOMPtr<nsIDOMEventTarget> domEventTarget;   nsEvent->GetOriginalTarget(getter_AddRefs(domEventTarget));      nsCOMPtr<nsIContent> targetContent = do_QueryInterface(domEventTarget);   if (targetContent->IsNodeOfType(nsINode::eXUL))     return NS_OK;      if (targetContent->IsNodeOfType(nsINode::eHTML_FORM_CONTROL))   {       nsCOMPtr<nsIFormControl> formControl(do_QueryInterface(targetContent));       formControlType = formControl->GetType();              if (mService->mIgnoreTextFields)       {         if (formControlType == NS_FORM_TEXTAREA ||             formControlType == NS_FORM_INPUT_TEXT ||             formControlType == NS_FORM_INPUT_PASSWORD ||             formControlType == NS_FORM_INPUT_FILE)         {           return NS_OK;         }       }   }   else if (mService->mIgnoreTextFields && targetContent->IsNodeOfType(nsINode::eHTML))   {     // Test for isindex, a deprecated kind of text field. We're using a string     // compare because <isindex> is not considered a form control, so it does     // not support nsIFormControl or eHTML_FORM_CONTROL, and it's not worth     // having a table of atoms just for it.            if (isContentOfType(targetContent, "isindex"))         return NS_OK;   } …     if (formControlType == NS_FORM_INPUT_TEXT ||         formControlType == NS_FORM_INPUT_PASSWORD)     {       PRInt32 selectionStart, textLength;       nsCOMPtr<nsIDOMNSHTMLInputElement> input = do_QueryInterface(targetContent);       if (input) {         input->GetSelectionStart (&selectionStart);         input->GetTextLength (&textLength);       } else {         nsCOMPtr<nsIDOMNSHTMLTextAreaElement> textArea = do_QueryInterface(targetContent);         if (textArea) {           textArea->GetSelectionStart (&selectionStart);           textArea->GetTextLength (&textLength);         }       }                  if (textLength != 0 && selectionStart != 0)         return NS_OK;     }     // We're using this key, no one else should     aEvent->StopPropagation();         aEvent->PreventDefault();              return Left();   }      if (keyCode == mService->mKeyCodeRight)   {     // ************************************************************************************     // NS_FORM_TEXTAREA cases:     // ************************************************************************************     // NS_FORM_INPUT_TEXT | NS_FORM_INPUT_PASSWORD | NS_FORM_INPUT_FILE cases     if (formControlType == NS_FORM_INPUT_TEXT ||         formControlType == NS_FORM_INPUT_PASSWORD)     {       PRInt32 selectionEnd, textLength;       nsCOMPtr<nsIDOMNSHTMLInputElement> input = do_QueryInterface(targetContent);       if (input) {         input->GetSelectionEnd (&selectionEnd);         input->GetTextLength (&textLength);       } else {         nsCOMPtr<nsIDOMNSHTMLTextAreaElement> textArea = do_QueryInterface(targetContent);         if (textArea) {           textArea->GetSelectionEnd (&selectionEnd);           textArea->GetTextLength (&textLength);         }       }              // going down.       if (textLength  != selectionEnd)         return NS_OK;     }              aEvent->StopPropagation();         aEvent->PreventDefault();     return Right();   }      if (keyCode == mService->mKeyCodeUp)   {     // If we are going up or down, in a select, lets not     // navigate.     //     // FIX: What we really want to do is determine if we are     // at the start or the end fo the form element, and     // based on the selected position we decide to nav. or     // not.     // ************************************************************************************     // NS_FORM_SELECT cases:     // * if it is a select form of 'size' attr != than '1' then we do as above.     // * if it is a select form of 'size' attr == than '1', snav can take care of it.     // if (formControlType == NS_FORM_SELECT)     //   return NS_OK;     aEvent->StopPropagation();     aEvent->PreventDefault();     return Up();   }      if (keyCode == mService->mKeyCodeDown)   {     // If we are going up or down, in a select, lets not     // navigate.     //     // FIX: What we really want to do is determine if we are     // at the start or the end fo the form element, and     // based on the selected position we decide to nav. or     // not.     // ************************************************************************************     // NS_FORM_SELECT cases:     // * if it is a select form of 'size' attr != than '1' then we do as above.     // * if it is a select form of 'size' attr == than '1', snav can take care of it.     // if (formControlType == NS_FORM_SELECT)     //   return NS_OK;     aEvent->StopPropagation();  // We're using this key, no one else should     aEvent->PreventDefault();     return Down();   }      return NS_OK; }

 

以上函数负责对按键事件的处理。我发现该函数被调用了，但是就是没有切换焦点，调试了好一会才发现，原来是两个设置没有设，后来加了一个函数，在初始时调用，一切正常了：

 

gboolean mozilla_pref_init(void) {     nsresult rv;     nsCOMPtr<nsIPrefBranch> pref = do_GetService(NS_PREFSERVICE_CONTRACTID, &rv);     if(NS_SUCCEEDED(rv) && pref != nsnull)     {         pref->SetIntPref("snav.keyCode.modifier", 0);         pref->SetBoolPref("snav.enabled", true);     }     return TRUE; }

 

Spatialnavigation是一个非常典型的扩展，对于实现自己的扩展很有参考价值，特别是添加自己的快捷键处理。

 

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