webkit linux 方向键移动焦点

webkit linux 方向键移动焦点
本文章只使用与在linux平台下基于GTK的Webkit浏览器，其他平台可以参考。

总所周知，刚编译的浏览器或者PC上的浏览器，如果按方向键一般都是操作滚轮事件，想要获取某一元素焦点，要么就是鼠标移动上去，要么就是按TAB键一个一个移动。下面我将介绍如何修改代码实现上下左右键移动焦点；（其实很简单）
webkit事件处理不管port如何实现，最后其实都是调用EventHandler这个类来处理各种事件，对应EventHandler.cpp和EventHandler.h。一般一个事件从port层发给浏览器，都是先交给页面做处理，页面不处理则会交给浏览器默认处理。
这里有个关键方法keyEvent(),这个方法是处理事件的入口，一般不同的port层接收按键都会调用EventHandler类下的keyEvent方法传递按键，具体流程大家可以去Windows工程慢慢调试。
废话不多说，直接看EventHandler类的defaultKeyboardEventHandler方法：

void EventHandler::defaultKeyboardEventHandler(KeyboardEvent* event)
{
if (event->type() == eventNames().keydownEvent) {
m_frame.editor().handleKeyboardEvent(event);
if (event->defaultHandled())
return;
if (event->keyIdentifier() == "U+0009")
defaultTabEventHandler(event);
else if (event->keyIdentifier() == "U+0008")
defaultBackspaceEventHandler(event);
else {
FocusDirection direction = focusDirectionForKey(event->keyIdentifier());
if (direction != FocusDirectionNone)
<span style="color:#ff0000;">defaultArrowEventHandler</span>(direction, event);
}
handleKeyboardSelectionMovementForAccessibility(event);
}
if (event->type() == eventNames().keypressEvent) {
m_frame.editor().handleKeyboardEvent(event);
if (event->defaultHandled())
return;
if (event->charCode() == ' ')
defaultSpaceEventHandler(event);
}
}

这就是浏览器内部默认处理按键的地方，该方法里面调用了defaultArrowEventHandler方法，这个方法就是处理锚点移动的，在实际调试中，发现在调用handleKeyboardEvent方法的时候，事件居然被处理了WebEditorClientGtk.cpp下的handleKeyboardEvent方法当成字符串处理了，处理办法也很简单，见下红色部分：

void WebEditorClient::handleKeyboardEvent(KeyboardEvent* event)
{
Node* node = event->target()->toNode();
ASSERT(node);
Frame* frame = node->document().frame();
ASSERT(frame);

const PlatformKeyboardEvent* platformEvent = event->keyEvent();
if (!platformEvent)
return;

// If this was an IME event don't do anything.
if (platformEvent->windowsVirtualKeyCode() == VK_PROCESSKEY ||
platformEvent->windowsVirtualKeyCode() ==VK_UP ||
platformEvent->windowsVirtualKeyCode() == VK_DOWN ||
platformEvent->windowsVirtualKeyCode() == VK_LEFT ||
platformEvent->windowsVirtualKeyCode() == VK_RIGHT)
return;

Vector<WTF::String> pendingEditorCommands;
getEditorCommandsForKeyEvent(event, pendingEditorCommands);
if (!pendingEditorCommands.isEmpty()) {

// During RawKeyDown events if an editor command will insert text, defer
// the insertion until the keypress event. We want keydown to bubble up
// through the DOM first.
if (platformEvent->type() == PlatformEvent::RawKeyDown) {
if (executePendingEditorCommands(frame, pendingEditorCommands, false))
event->setDefaultHandled();

return;
}

// Only allow text insertion commands if the current node is editable.
if (executePendingEditorCommands(frame, pendingEditorCommands, frame->editor().canEdit())) {
event->setDefaultHandled();
return;
}
}

// Don't allow text insertion for nodes that cannot edit.
if (!frame->editor().canEdit())
return;

// This is just a normal text insertion, so wait to execute the insertion
// until a keypress event happens. This will ensure that the insertion will not
// be reflected in the contents of the field until the keyup DOM event.
if (event->type() != eventNames().keypressEvent)
return;

// Don't insert null or control characters as they can result in unexpected behaviour
if (event->charCode() < ' ')
return;

// Don't insert anything if a modifier is pressed
if (platformEvent->ctrlKey() || platformEvent->altKey())
return;

if (frame->editor().insertText(platformEvent->text(), event))
event->setDefaultHandled();
}

终于可以进defaultArrowEventHandler函数了

void EventHandler::defaultArrowEventHandler(FocusDirection focusDirection, KeyboardEvent* event)
{
ASSERT(event->type() == eventNames().keydownEvent);

if (event->ctrlKey() || event->metaKey() || event->altGraphKey() || event->shiftKey())
return;

Page* page = m_frame.page();
if (!page)
return;

if (!<span style="color:#ff0000;">isSpatialNavigationEnabled</span>(&m_frame))
return;

// Arrows and other possible directional navigation keys can be used in design
// mode editing.
if (m_frame.document()->inDesignMode())
return;

if (page->focusController().advanceFocus(focusDirection, event))
event->setDefaultHandled();
}

可是在isSpatialNavigationEnabled返回了，不过这个就简单了，这个配置是通过Settings类设置的，你只要找到这个类，调用它的setSpatialNavigationEnabled(bool Enable)方法就可以了

经过一系列修改，哈哈，方向键就可以移动焦点了