1、实现一个应用程序插架框架关键点有：
一个插件的标准接口，在主程序中存在一个插件的集合。主程序通过循环读取每个插件，将插件对象通过多态的机制转换为插件接口，实现插件的装载。
主程序对象或者主程序接口需要作为参数传递到插件对象中，以方便插件对象调用主程序的内容，如主视图、工具栏、树视图、状态栏等。
2、开源点云处理软件CloudCompare也是一个插件框架，因此也必然包括这些内容。
插件接口：ccPluginInterface，每个插件对象有在ccPluginInterface基础上定义了一个新的接口类class ccStdPluginInterface : public ccPluginInterface
具体的插件则继承自ccStdPluginInterface 累，比如这样，class qMyPlugin : public QObject, public ccStdPluginInterface
主程序对象：class ccMainAppInterface，MainWindow主窗体类实现了ccMainAppInterface接口。
MainWindow::loadPlugins()方法负责插件的调用。（mainwindow.cpp文件中）
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1 void MainWindow::loadPlugins()
2 {
3 menuPlugins->setEnabled(false);
4 menuShadersAndFilters->setEnabled(false);
5 toolBarPluginTools->setVisible(false);
6 toolBarGLFilters->setVisible(false);
7
8 //“static” plugins
9 foreach (QObject plugin, QPluginLoader::staticInstances())
10 dispatchPlugin(plugin);
11
12 ccConsole::Print(QString(“Application path: “)+QCoreApplication::applicationDirPath());
13
14 #if defined(Q_OS_MAC)
15 // plugins are in the bundle
16 QString path = QCoreApplication::applicationDirPath();
17 path.remove( “MacOS” );
18 m_pluginsPath = path + “Plugins/ccPlugins”;
19 #else
20 //plugins are in bin/plugins
21 m_pluginsPath = QCoreApplication::applicationDirPath()+QString(”/plugins”);
22 #endif
23
24 ccConsole::Print(QString(“Plugins lookup dir.: %1”).arg(m_pluginsPath));
25
26 QStringList filters;
27 #if defined(Q_OS_WIN)
28 filters << ".dll";
29 #elif defined(Q_OS_LINUX)
30 filters << “.so";
31 #elif defined(Q_OS_MAC)
32 filters << ".dylib”;
33 #endif
34 QDir pluginsDir(m_pluginsPath);
35 pluginsDir.setNameFilters(filters);
36 foreach (QString filename, pluginsDir.entryList(filters))
37 {
38 QPluginLoader loader(pluginsDir.absoluteFilePath(filename));
39 QObject* plugin = loader.instance();
40 if (plugin)
41 {
42 ccConsole::Print(QString(“Found new plugin: ‘%1’”).arg(filename));
43 if (dispatchPlugin(plugin))
44 {
45 m_pluginFileNames += filename;
46 }
47 else
48 {
49 delete plugin;
50 plugin = 0;
51 ccConsole::Warning("\tUnsupported or invalid plugin type");
52 }
53 }
54 else
55 {
56 delete plugin;
57 plugin = 0;
58 ccConsole::Warning(QString("[Plugin] %1")/.arg(pluginsDir.absoluteFilePath(filename))/.arg(loader.errorString()));
59 }
60 }
61
62 if (menuPlugins)
63 {
64 menuPlugins->setEnabled(!m_stdPlugins.empty());
65 }
66
67 if (toolBarPluginTools->isEnabled())
68 {
69 actionDisplayPluginTools->setEnabled(true);
70 actionDisplayPluginTools->setChecked(true);
71 }
72 else
73 {
74 //DGM: doesn’t work ?
75 //actionDisplayPluginTools->setChecked(false);
76 }
77
78 if (toolBarGLFilters->isEnabled())
79 {
80 actionDisplayGLFiltersTools->setEnabled(true);
81 actionDisplayGLFiltersTools->setChecked(true);
82 }
83 else
84 {
85 //DGM: doesn’t work ?
86 //actionDisplayGLFiltersTools->setChecked(false);
87 }
88 }
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主程序在加载插件时会调用插件的setMainAppInterface方法，将主程序参数传入，这样插件就可以获取主程序的内容了。
1 //! Sets application entry point
2 /** Called just after plugin creation by qCC
3 */
4 virtual void setMainAppInterface(ccMainAppInterface app);
3、获取主窗体中的点云图层
在doAction中的代码：
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1 const ccHObject::Container& selectedEntities = m_app->getSelectedEntities();
2 size_t selNum = selectedEntities.size();
3 if (selNum!=1)
4 {
5 m_app->dispToConsole(“Select only one cloud!”,ccMainAppInterface::ERR_CONSOLE_MESSAGE);
6 return;
7 }
8
9 ccHObject* ent = selectedEntities[0];
10 assert(ent);
11 if (!ent || !ent->isA(CC_TYPES::POINT_CLOUD))
12 {
13 m_app->dispToConsole(“Select a real point cloud!”,ccMainAppInterface::ERR_CONSOLE_MESSAGE);
14 return;
15 }
16
17 ccPointCloud* pc = static_cast<ccPointCloud*>(ent);
18
19 //input cloud
20 unsigned count = pc->size();
21 bool hasNorms = pc->hasNormals();
22 CCVector3 bbMin, bbMax;
23 pc->getBoundingBox(bbMin,bbMax);
24 const CCVector3d& globalShift = pc->getGlobalShift();
25 double globalScale = pc->getGlobalScale();
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