OSG源代码部分剖析（待续）？？？？？？？？？？？？？？？？？？？？？？？？？？？？？_osg updatecallback eventcallback drawablecullcallb-优快云博客

本文链接：https://blog.youkuaiyun.com/tmljs1988/article/details/7545799

本文深入剖析了osg::Drawable中的DrawCallback、UpdateCallback、EventCallback和CullCallback，以及NodeCallback和CameraUpdateCallback的使用。重点讨论了如何设置用户事件回调，如通过osgViewer::viewer和osgGA::GUIEventHandler处理鼠标和键盘操作。同时，讲解了osgGA::EventVisitor在事件处理中的核心作用。

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class DrawableDrawCallback : public osg::Drawable::DrawCallback

{

virtual voiddrawImplementation(osg::RenderInfo& renderInfo,const osg::Drawable* drawable)const

{

std::cout<<"draw call back - pre drawImplementation"<<drawable<<std::endl;

drawable->drawImplementation(renderInfo);

std::cout<<"draw call back - post drawImplementation"<<drawable<<std::endl;

}

};

struct DrawableUpdateCallback :public osg::Drawable::UpdateCallback

{

virtual voidupdate(osg::NodeVisitor*, osg::Drawable* drawable)

{

std::cout<<"Drawable update callback "<<drawable<<std::endl;

}

};

struct DrawableCullCallback : public osg::Drawable::CullCallback

{

/** do customized cull code.*/

virtual boolcull(osg::NodeVisitor*, osg::Drawable* drawable, osg::State*/*state*/) const

{

std::cout<<"Drawable cull callback "<<drawable<<std::endl;

return false;

}

};

osg::Drawable类中：

structEventCallback : public virtual osg::Object

{

EventCallback() {}

EventCallback(const EventCallback&,const CopyOp&) {}

META_Object(osg,EventCallback);

virtual void event(osg::NodeVisitor*, osg::Drawable*) {}

};

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osg::Drawable::DrawCallback、osg::Drawable::UpdateCallback、osg::Drawable::EventCallback、osg::Drawable::CullCallback、osg::NodeCallback都继承自osg::Object:

struct DrawCallback : public virtual osg::Object{}

struct UpdateCallback : public virtual osg::Object{}

struct EventCallback : public virtual osg::Object{}

struct CullCallback : public virtual osg::Object

class OSG_EXPORT NodeCallback : public virtual Object{}

――――――――――――――――――――

class CameraUpdateCallback : public osg::NodeCallback

{

virtual voidoperator()(osg::Node* node, osg::NodeVisitor* nv)

{

std::cout<<"Camera update callback - pre traverse"<<node<<std::endl;

traverse(node,nv);

std::cout<<"Camera update callback - post traverse"<<node<<std::endl;

}

};

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Group->setEventCallback(osg::NodeCallback);或者

osgViewer::viewer->addEventhandler(osgGA::GUIEventHandler)可以设置用户事件回调（如用户鼠标、键盘操作）。

GUIEventHandler继承自NodeCallback和Drawable::EventCallback：

class OSGGA_EXPORT GUIEventHandler : public osg::NodeCallback, public osg::Drawable::EventCallback

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osgViewer::view:

class OSGVIEWER_EXPORT View : public osg::View, public osgGA::GUIActionAdapter

osgViewer::viewer:

void Viewer::constructorInit()

{

_eventVisitor = new osgGA::EventVisitor;

_eventVisitor->setActionAdapter(this);

}

void Viewer::eventTraversal()

{

……

for(osgGA::EventQueue::Events::iterator itr = events.begin();

itr != events.end();

++itr)

{

osgGA::GUIEventAdapter* event = itr->get();

_eventVisitor->reset();

_eventVisitor->addEvent( event );

getSceneData()->accept(*_eventVisitor);

}

virtualvoid operator()(osg::Node* node, osg::NodeVisitor* nv)

{

。。。。。。

{

osgGA::EventVisitor* ev = dynamic_cast<osgGA::EventVisitor*>(nv);

if (ev && ev->getActionAdapter() && !ev->getEvents().empty())

{

for(osgGA::EventQueue::Events::iterator itr = ev->getEvents().begin();

itr != ev->getEvents().end();

++itr)

{

handleWithCheckAgainstIgnoreHandledEventsMask(*(*itr), *(ev->getActionAdapter()), node, nv);

}

traverse(node, nv);

}

osg::NodeCallback最终调用的是operator()。而的核心函数是handle()，可以获取当前viewer:

bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa)

{

osgViewer::Viewer* viewer = dynamic_cast<osgViewer::Viewer*>(&aa);

}

――――――

void GUIEventHandler::operator()(osg::Node* node, osg::NodeVisitor* nv)

{

osgGA::EventVisitor* ev = dynamic_cast<osgGA::EventVisitor*>(nv);

if (ev && ev->getActionAdapter() && !ev->getEvents().empty())

{

for(osgGA::EventQueue::Events::iterator itr = ev->getEvents().begin();

itr != ev->getEvents().end();

++itr)

{

handleWithCheckAgainstIgnoreHandledEventsMask(*(*itr), *(ev->getActionAdapter()), node, nv);

}

if (node->getNumChildrenRequiringEventTraversal()>0)traverse(node,nv);

}

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GUIEventHandler:: inline bool handleWithCheckAgainstIgnoreHandledEventsMask(const GUIEventAdapter& ea,GUIActionAdapter& aa, osg::Object* object, osg::NodeVisitor* nv)

{

if (!ea.getHandled() ||

(ea.getEventType() & _ignoreHandledEventsMask)==0)

{

bool handled = handle(ea,aa,object,nv);

if (handled) ea.setHandled(true);

return handled;

}

else

{

return false;

}