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:
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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;
}
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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。
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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;
}
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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：
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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;
}
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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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