Ogre中的Overlay第一个TextArea首次渲染时不能显示的问题

项目中使用Ogre画一些物件的tag时遇到一些tag不能正常显示的问题。几经折腾，感觉应该是属于Ogre的bug。

Google之，找到官网论坛上的一个report：

http://www.ogre3d.org/forums/viewtopic.php?f=4&t=59197

看来蛮多同学遇到了一样的问题。目前对ogre不熟，不敢确定是否自己的原因。该bug的表现就是第一次加入的TextArea不能正常渲染，不管你有多少个overlay。必须场景被刷新（viewport改变，拉伸一下窗口），才能看到该tag。

report中提到bug可能的所在代码。有人给了一个dirty fix，在渲染循环中强制提前刷新一次。

  bool first = true;

    while(mRunning)
    {
        //Pump messages in all registered RenderWindow windows
        Ogre::WindowEventUtilities::messagePump();
        mRoot->renderOneFrame(); // Ignore whatever the frame listeners return basically.

        if(first)
        {
            first = false;

            // Simple hack to make sure all text area overlay elements are shown correctly..

            Ogre::OverlayManager& om = Ogre::OverlayManager::getSingleton();

            Ogre::OverlayManager::OverlayMapIterator omi = om.getOverlayIterator();
            while(omi.hasMoreElements())
            {
                Ogre::Overlay* overlay = omi.getNext();
                Ogre::Overlay::Overlay2DElementsIterator o2dei = overlay->get2DElementsIterator();
                while(o2dei.hasMoreElements())
                {
                    Ogre::OverlayElement* oe = o2dei.getNext();
                    oe->setCaption(oe->getCaption());
                }

            }
        }
    }

我自己的选择是建了一个“空白”节点，加入一个“空白”的overlay并添加textArea。这个overlay中最好载入所有你需要用到的字体，一个textArea一个字体。

惭愧，今后有时间再追这个bug。

备忘，测试代码。

#ifndef __OgreApplication_H__
#define __OgreApplication_H__
#include "stdafx.h"

using namespace Ogre;
using namespace std;


class MyAapplicaton : public RenderTargetListener
{
public:
    class MyRenderListener : public Ogre::RenderTargetListener
    {
    public:
        std::vector<Overlay*> m_overlayList;
    public:
        MyRenderListener() {}
        void preViewportUpdate(const RenderTargetViewportEvent& evt)
        {
            std::vector<Overlay*>::iterator it;
            for (it = m_overlayList.begin(); it != m_overlayList.end(); ++it)
            {
                (*it)->show();
            }
        }
        void postViewportUpdate(const RenderTargetViewportEvent& evt)
        { 

        }
        void addOverlay(Overlay* _overlay)
        {
            m_overlayList.push_back(_overlay);
        }
    };


protected:
    Root* m_root;
    SceneManager* m_sceneManger;
    Ogre::RenderWindow* m_window;
    Ogre::Viewport* m_viewport;
    Ogre::Camera* m_camera;
    Ogre::Overlay* m_overlay;
    MyRenderListener m_preViewportRenderListener;


public:
    MyAapplicaton()
    {
        m_root = NULL;
        m_sceneManger = NULL;
    }
    ~MyAapplicaton()
    {
        delete m_root;
    }

public:
    void LoadResources()
    {
        ConfigFile cf;
        cf.load("resources_d.cfg");
        Ogre::String sectionName, typeName, dataname;
        ConfigFile::SectionIterator sectionIter = cf.getSectionIterator();
        
        while (sectionIter.hasMoreElements())
        {
            sectionName = sectionIter.peekNextKey();
            Ogre::ConfigFile::SettingsMultiMap *settings = sectionIter.getNext();
            Ogre::ConfigFile::SettingsMultiMap::iterator i;
            for (i = settings->begin(); i != settings->end(); ++i)
            {
                typeName = i->first;
                dataname = i->second;
                Ogre::ResourceGroupManager::getSingleton().addResourceLocation(dataname, typeName, sectionName);
            }
        }
        Ogre::ResourceGroupManager::getSingleton().initialiseAllResourceGroups();
    }

    int startup()
    {
        m_root = new Root("plugins_d.cfg");
        if (!m_root->showConfigDialog())
        {
            return -1;
        }

        m_window = m_root->initialise(true, "My Application");
        m_sceneManger = m_root->createSceneManager(ST_GENERIC);

        m_camera = m_sceneManger->createCamera("Camera");
        m_camera->setPosition(Vector3(0, 0, 50));
        m_camera->lookAt(Vector3(0, 0, 0));
        m_camera->setNearClipDistance(5);

        m_viewport = m_window->addViewport(m_camera);
        //m_viewport->setBackgroundColour(ColourValue(0.0, 0.0, 0.0));
        m_viewport->setOverlaysEnabled(true);
        m_camera->setAutoAspectRatio( Real( m_viewport->getActualWidth()) / Real(m_viewport->getActualHeight()) );

        LoadResources();
        createScene();
        m_root->startRendering();
        return 0;

    }

    void createScene( void )
    {
        //Entity* ent = m_sceneManger->createEntity("sinbad.mesh");
        //SceneNode* node = m_sceneManger->createSceneNode("node1");
        //m_sceneManger->getRootSceneNode()->addChild(node);
        //node->attachObject(ent);

        OverlayManager* pOverlayManager = OverlayManager::getSingletonPtr();
        Ogre::String name = "MyPanel";

        //TextAreaOverlayElement *nameArea, *valuesArea;
        //OverlayElement* element = pOverlayManager->createOverlayElementFromTemplate("SdkTrays/ParamsPanel","BorderPanel", name);
        //OverlayContainer* container = (OverlayContainer*)element;
        //nameArea = (TextAreaOverlayElement*)container->getChild(container->getName()+"/ParamsPanelNames");
        //valuesArea = (TextAreaOverlayElement*)container->getChild(container->getName() + "/ParamsPanelValues");
        //element->setHeight(nameArea->getTop()*2*10+10);
        //element->setWidth(200);
        ////element->setColour(ColourValue(0, 0, 0));
        //nameArea->setLeft(10);
        //nameArea->setTop(10);
        //nameArea->setCaption("i am very very very  am very very very  am very very very  am very very very  am very very very sleepy");
        //nameArea->show();

        //Overlay* pOverlay = OverlayManager::getSingletonPtr()->create("overlay");
        //
        //pOverlay->add2D(container);
        //pOverlay->show();
    //////////////////////////////////////////////////////////////////////////
        
        OverlayContainer* container_root = (OverlayContainer*)pOverlayManager->createOverlayElementFromTemplate("SdkTrays/TextBox", "BorderPanel", name);
    
        container_root->setHeight(480);
        container_root->setWidth(480);


        TextAreaOverlayElement* element_textarea = (TextAreaOverlayElement*)container_root->getChild(container_root->getName()+ "/TextBoxText");
        element_textarea->setFontName("StarWars");
        element_textarea->setCaption("hi, girl! my name is god");
        element_textarea->setWidth(320);
        element_textarea->setHeight(320);
        element_textarea->setTop(100);
        element_textarea->setCharHeight(19);
        element_textarea->setSpaceWidth(8);
        //
        //cout<<"=========================="<<endl;
        //cout<<element_textarea->getName()<<endl;
        //cout<<element_textarea->getWidth() <<endl;
        //cout<<element_textarea->getHeight()<<endl;
        //cout<<element_textarea->getTop() <<endl;
        //cout<<element_textarea->getTypeName() <<endl;
        //cout<<element_textarea->getFontName() <<endl;
        //cout<<element_textarea->getZOrder() <<endl;
        element_textarea->show();

        OverlayContainer* container_TextBoxCaptionBar = (OverlayContainer*)container_root->getChild(container_root->getName() + "/TextBoxCaptionBar");
        container_TextBoxCaptionBar->setWidth(480);
        TextAreaOverlayElement* element_texbar = (TextAreaOverlayElement*)container_TextBoxCaptionBar->getChild(container_TextBoxCaptionBar->getName() + "/TextBoxCaption");
        element_texbar->setCaption(DisplayString("oh, my god"));

        //Overlay* pOverlay = OverlayManager::getSingletonPtr()->create("overlay");
        //pOverlay->add2D(container_root);
        //pOverlay->show();
//////////////////////////////////////////////////////////////////////////

        OverlayManager& overlayManager = OverlayManager::getSingleton();

        // Create a panel
        OverlayContainer* panel = static_cast<OverlayContainer*>(
        overlayManager.createOverlayElement("Panel", "PanelTest"));
        panel->setMetricsMode(Ogre::GMM_PIXELS);
        panel->setPosition(10, 10);
        panel->setDimensions(100, 100);
        //panel->setMaterialName("MaterialName"); // Optional background material

        // Create a text area
        TextAreaOverlayElement* textArea = static_cast<TextAreaOverlayElement*>(
            overlayManager.createOverlayElement("TextArea", "TextAreaTest"));
        textArea->setMetricsMode(Ogre::GMM_PIXELS);
        textArea->setPosition(0, 0);
        textArea->setDimensions(100, 100);
        textArea->setCaption("Hello, World!");
        textArea->setCharHeight(16);
        textArea->setFontName("SdkTrays/Caption");
        /*textArea->setFontName("StarWars");*/
        textArea->setColourBottom(ColourValue(0.3, 0.5, 0.3));
        textArea->setColourTop(ColourValue(0.5, 0.7, 0.5));

        panel->addChild(textArea);

        TextAreaOverlayElement* textArea1 = static_cast<TextAreaOverlayElement*>(
            overlayManager.createOverlayElement("TextArea", "TextAreaTest1"));
        textArea1->setMetricsMode(Ogre::GMM_PIXELS);
        textArea1->setPosition(50, 50);
        textArea1->setDimensions(100, 100);
        textArea1->setCaption("hi, god!");
        textArea1->setCharHeight(16);
        textArea1->setFontName("StarWars");
        textArea1->setColourBottom(ColourValue(0.3, 0.5, 0.3));
        textArea1->setColourTop(ColourValue(0.5, 0.7, 0.5));
        
        panel->addChild(textArea1);

        // Create an overlay, and add the panel
        m_overlay = overlayManager.create("OverlayTest");
        
               /*-----------------------------------------------
               更换这2行的顺序
               -----------------------------------------------*/
        m_overlay->add2D(container_root);   
        m_overlay->add2D(panel);
        
        

        // Add the text area to the panel

        // Show the overlay
        //m_overlay->show();
        //m_preViewportRenderListener.addOverlay(m_overlay);
        m_overlay->show();
        m_viewport->getTarget()->addListener(&m_preViewportRenderListener);
    }

};



#endif