codeblocks中plugin的实现

快乐虾

http://blog.csdn.net/lights_joy/

lights@hb165.com

本文适用于

codeblocks-8.02

vs2005

欢迎转载，但请保留作者信息

1.1 Plugin加载

Codeblocks将plugin放在可执行文件目录下的share/CodeBlocks/plugins子目录中，全部以DLL的形式存在。在codeblock启动时会调用如下函数：

int PluginManager::ScanForPlugins(const wxString& path)

{

…………………………………..

wxDir dir(path);

wxString filename;

wxString failed;

bool ok = dir.GetFirst(&filename, PluginsMask, wxDIR_FILES);

while (ok)

{

…………………….

// load manifest

m_pCurrentlyLoadingManifestDoc = 0;

if (ReadManifestFile(filename))

{

if (LoadPlugin(path + _T('/') + filename))

++count;

else

failed << _T('/n') << filename;

}

delete m_pCurrentlyLoadingManifestDoc;

m_pCurrentlyLoadingManifestDoc = 0;

ok = dir.GetNext(&filename);

}

…………………………………..

}

在上述代码中，将首先读取与dll同名的manifest，其实它就是一个放在share/codeblocks子目录下的同名zip文件，这个zip文件中两个文件：manifest.xml和configuration.xrc，其实这两个文件都是XML文档，manifest.xml描述了这个插件的功能，作者等信息，而另一个文件则是一些配置信息。

在读取manifest成功后将调用LoadPlugin函数：

bool PluginManager::LoadPlugin(const wxString& pluginName)

{

// clear registration temporary vector

m_RegisteredPlugins.clear();

// load library

m_CurrentlyLoadingFilename = pluginName;

m_pCurrentlyLoadingLib = LibLoader::LoadLibrary(pluginName);

if (!m_pCurrentlyLoadingLib->IsLoaded())

{

Manager::Get()->GetLogManager()->LogError(F(_T("%s: not loaded (missing symbols?)"), pluginName.c_str()));

LibLoader::RemoveLibrary(m_pCurrentlyLoadingLib);

m_pCurrentlyLoadingLib = 0;

m_CurrentlyLoadingFilename.Clear();

return false;

}

// by now, the library has loaded and its global variables are initialized.

// this means it has already called RegisterPlugin()

// now we can actually create the plugin(s) instance(s) :)

// try to load the plugin(s)

std::vector<PluginRegistration>::iterator it;

for (it = m_RegisteredPlugins.begin(); it != m_RegisteredPlugins.end(); ++it)

{

PluginRegistration& pr = *it;

cbPlugin* plug = 0L ;

try

{

plug = pr.createProc();

}

catch (cbException& exception)

{

exception.ShowErrorMessage(false);

continue;

}

// all done; add it to our list

PluginElement* plugElem = new PluginElement;

plugElem->fileName = m_CurrentlyLoadingFilename;

plugElem->info = pr.info;

plugElem->library = m_pCurrentlyLoadingLib;

plugElem->freeProc = pr.freeProc;

plugElem->plugin = plug;

m_Plugins.Add(plugElem);

SetupLocaleDomain(pr.name);

Manager::Get()->GetLogManager()->DebugLog(F(_T("%s: loaded"), pr.name.c_str()));

}

if (m_RegisteredPlugins.empty())

{

// no plugins loaded from this library, but it's not an error

LibLoader::RemoveLibrary(m_pCurrentlyLoadingLib);

}

m_pCurrentlyLoadingLib = 0;

m_CurrentlyLoadingFilename.Clear();

return true;

}

这个函数首先调用LibLoader::LoadLibrary加载DLL，实际上它就是使用LoadLibrary这个API来加载DLL。

在加载完成后，按照注释的说明，这个DLL中应该调用RegisterPlugin函数进行自我注册，这其中当然包括创建实例这样回调函数，然后上述函数很自然地使用这样的回调函数创建Plugin的实例。然后用一个PluginElement来描述它，这个plugElem将用于主界面的菜单等位置。

从上述代码还可以看出，插件至少应该能创建一个cbPlugin的实例。

1.2 插件注册

从调用过程的注释可以知道，在加载DLL时，它应该能够调用RegisterPlugin向codeblock进行注册，下面以astyle这个插件为例看看它的注册过程。

在这个插件中定义了一个全局变量：

namespace

{

PluginRegistrant<AStylePlugin> reg(_T("AStylePlugin"));

}

除此之外没有其它东西可以在DLL加载时执行代码，看看PluginRegistrant这个类：

/** @brief Plugin registration object.

* Use this class to register your new plugin with Code::Blocks.

* All you have to do is instantiate a PluginRegistrant object.

* @par

* Example code to use in one of your plugin's source files (supposedly called "MyPlugin"):

* @code

* namespace

* {

* PluginRegistrant<MyPlugin> registration("MyPlugin");

* }

* @endcode

template<class T> class PluginRegistrant

{

public:

/// @param name The plugin's name.

PluginRegistrant(const wxString& name)

{

Manager::Get()->GetPluginManager()->RegisterPlugin(name, // plugin's name

&CreatePlugin, // creation

&FreePlugin, // destruction

&SDKVersion); // SDK version

}

static cbPlugin* CreatePlugin()

{

return new T;

}

static void FreePlugin(cbPlugin* plugin)

{

delete plugin;

}

static void SDKVersion(int* major, int* minor, int* release)

{

if (major) *major = PLUGIN_SDK_VERSION_MAJOR;

if (minor) *minor = PLUGIN_SDK_VERSION_MINOR;

if (release) *release = PLUGIN_SDK_VERSION_RELEASE;

}

};

由此可见，在主程序加载DLL后还将调用PluginRegistrant ::CreatePlugin这个回调函数，而这个回调函数将创建一个AStylePlugin的实例。

1.3 Plugin功能实现

仍以astyle为例进行分析。Codeblocks将plugin分为几类：

cbCompilerPlugin

cbDebuggerPlugin

cbToolPlugin

cbMimePlugin

cbCodeCompletionPlugin

cbWizardPlugin

astyle要完成代码格式化的功能，因而它选择了cbToolPlugin进行扩展：

class AStylePlugin : public cbToolPlugin

{

public:

AStylePlugin();

~AStylePlugin();

int Configure();

int GetConfigurationGroup() const { return cgEditor; }

cbConfigurationPanel* GetConfigurationPanel(wxWindow* parent);

int Execute();

void OnAttach(); // fires when the plugin is attached to the application

void OnRelease(bool appShutDown); // fires when the plugin is released from the application

};

呵呵，看着好像挺简单的。