NPAPI 插件 编程起步
最近需要写一个Mac平台上的简单的跨浏览器的插件，需要在js中调用本地方法，而npapi满足此要求。
NPAPI就是Netscape Plugin Application Programming Interface的缩写了，虽然Netscape已经去了，但是这个却被沿用下来，在各大浏览器中都得以实现。还是纪念下曾经的浏览器的鼻祖啊。
在网络上搜索了很长时间，一直没有找到合适的满足自己需求的代码例子。且这方面的文档也少的可怜。
还是先提一下，有两个系列的文章还是不错，虽然或许可能也不完全正确，但是帮助理解npapi的编程模型是非常有帮助的：
- http://colonelpanic.net/category/plugindev/npapi-plugindev/
- http://rintarou.dyndns.org/category/browser/plugin
下面是我寻找解决方法的过程
- 一开始找到mozilla的一篇官方文档：Writing a plugin for Mac OS X，这里面提到了了官方的代码库中有demo，于是就跑到公司checkout下mozilla的分支。并看了下里面的一个mac的例子.
不过这个例子没有使用npruntime的东西，加上一开始的时候对npapi不熟悉，就继续搜索. - 在google， stackoverflow，github, google codes 中不停的搜索，结果甚少，最后找到一个npruntime的例子，Call Native API from Google Chrome Extension on Mac OS X只可惜编译后只能在mac的chrome下运行。
- 后来又找到了Firebreath这个跨平台的浏览器NPAPI插件开发框架，可以通过python和cmake的配合，生成适合不同操作系统的浏览器插件的工程，于是就测试了，果真生成xcode项目后，编译，然后测试了下js调用插件的方法，还真能在各个浏览器（测试了三个比较常用的safari，chrome，firefox）下运行。但是无奈由于包含一些高级的程序代码其最小编译后的大小都2m+对于一个功能单一的插件来讲，无疑是让人无法接受的，所以继续找demo.
- 后来找到了npsimple-win32 这个windows下的vs的项目，我将其移植到mac上，编译运行后，唯独在safari下无法运行，悲剧的一塌糊涂，对于一个npapi不同的浏览器在实现的具体细节上竟然有细微的差别，真是太变态鸟。
- 最后无奈之下，将Weikit开源项目中的例子弄出来，然后和npruntime的相关代码进行整合，发现在safari，chrome可以运行在firefox中没法运行，好吧，至少现在两个例子的并集是完整的，我就将两个代码进行查看，最终找出了问题的所在，在safari下需要启动CoreGraphics，而在firefox下scriptable的NPObject的hasProperty和getProperty必须设置，可能在firefox下调用某函数，先去scriptable NPObject中找有没有这个名字的属性，然后在找方法吧。
最后终于写出了一个简单的例子
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#import <WebKit/npapi.h>
#import <WebKit/npfunctions.h>
#import <WebKit/npruntime.h>
// Browser function table，可以通过它来得到浏览器提供的功能
static NPNetscapeFuncs
* browser
;
static
const
char
*plugin_method_name_open
=
"open"
;
////////////////////////////////////
/*******各种接口的声明*********/
//在NPAPI编程的接口中你会发现有NP_打头的，有NPP_打头的，有NPN_打头的
//NP是npapi的插件库提供给浏览器的最上层的接口
//NPP即NP Plugin是插件本身提供给浏览器调用的接口，主要被用来填充NPPluginFuncs的结构体
//NPN即NP Netscape ,是浏览器提供给插件使用的接口，这些接口一般都在NPNetscapeFuncs结构体中
//Mach-o entry points,浏览器和创建交流的最上层的接口
NPError NP_Initialize
(NPNetscapeFuncs
*browserFuncs
)
;
NPError NP_GetEntryPoints
(NPPluginFuncs
*pluginFuncs
)
;
void NP_Shutdown
(
void
)
;
//NPP Functions
NPError NPP_New
(NPMIMEType pluginType
, NPP instance
,
uint16_t mode
,
int16_t argc
,
char
* argn
[
]
,
char
* argv
[
]
, NPSavedData
* saved
)
;
NPError NPP_Destroy
(NPP instance
, NPSavedData
** save
)
;
NPError NPP_SetWindow
(NPP instance
, NPWindow
* window
)
;
NPError NPP_NewStream
(NPP instance
, NPMIMEType type
, NPStream
* stream
, NPBool seekable
,
uint16_t
* stype
)
;
NPError NPP_DestroyStream
(NPP instance
, NPStream
* stream
, NPReason reason
)
;
int32 NPP_WriteReady
(NPP instance
, NPStream
* stream
)
;
int32 NPP_Write
(NPP instance
, NPStream
* stream
,
int32 offset
,
int32 len
,
void
* buffer
)
;
void NPP_StreamAsFile
(NPP instance
, NPStream
* stream
,
const
char
* fname
)
;
void NPP_Print
(NPP instance
, NPPrint
* platformPrint
)
;
int16_t NPP_HandleEvent
(NPP instance
,
void
* event
)
;
void NPP_URLNotify
(NPP instance
,
const
char
* URL
, NPReason reason
,
void
* notifyData
)
;
NPError NPP_GetValue
(NPP instance
, NPPVariable variable
,
void
*value
)
;
NPError NPP_SetValue
(NPP instance
, NPNVariable variable
,
void
*value
)
;
//Functions for scriptablePluginClass
bool plugin_has_method
(NPObject
*obj
, NPIdentifier methodName
)
;
bool plugin_invoke
(NPObject
*obj
, NPIdentifier methodName
,
const NPVariant
*args
,
uint32_t argCount
, NPVariant
*result
)
;
bool hasProperty
(NPObject
*obj
, NPIdentifier propertyName
)
;
bool getProperty
(NPObject
*obj
, NPIdentifier propertyName
, NPVariant
*result
)
;
////////////////////////////////////
static
struct NPClass scriptablePluginClass
=
{
NP_CLASS_STRUCT_VERSION
,
NULL
,
NULL
,
NULL
,
plugin_has_method
,
plugin_invoke
,
NULL
,
hasProperty
,
getProperty
,
NULL
,
NULL
,
}
;
//接口的实现
NPError NP_Initialize
(NPNetscapeFuncs
* browserFuncs
)
{
browser
= browserFuncs
;
return NPERR_NO_ERROR
;
}
NPError NP_GetEntryPoints
(NPPluginFuncs
* pluginFuncs
)
{
pluginFuncs
->version
=
11
;
pluginFuncs
->size
=
sizeof
(pluginFuncs
)
;
pluginFuncs
->newp
= NPP_New
;
pluginFuncs
->destroy
= NPP_Destroy
;
pluginFuncs
->setwindow
= NPP_SetWindow
;
pluginFuncs
->newstream
= NPP_NewStream
;
pluginFuncs
->destroystream
= NPP_DestroyStream
;
pluginFuncs
->asfile
= NPP_StreamAsFile
;
pluginFuncs
->writeready
= NPP_WriteReady
;
pluginFuncs
->write
=
(NPP_WriteProcPtr
)NPP_Write
;
pluginFuncs
->print
= NPP_Print
;
pluginFuncs
->event
= NPP_HandleEvent
;
pluginFuncs
->urlnotify
= NPP_URLNotify
;
pluginFuncs
->getvalue
= NPP_GetValue
;
pluginFuncs
->setvalue
= NPP_SetValue
;
return NPERR_NO_ERROR
;
}
void NP_Shutdown
(
void
)
{
}
bool plugin_has_method
(NPObject
*obj
, NPIdentifier methodName
)
{
// This function will be called when we invoke method on this plugin elements.
NPUTF8
*name
= browser
->utf8fromidentifier
(methodName
)
;
bool result
=
strcmp
(name
, plugin_method_name_open
)
==
0
;
browser
->memfree
(name
)
;
return result
;
}
bool plugin_invoke
(NPObject
*obj
, NPIdentifier methodName
,
const NPVariant
*args
,
uint32_t argCount
, NPVariant
*result
)
{
// Make sure the method called is "open".
NPUTF8
*name
= browser
->utf8fromidentifier
(methodName
)
;
if
(
strcmp
(name
, plugin_method_name_open
)
==
0
)
{
browser
->memfree
(name
)
;
BOOLEAN_TO_NPVARIANT
(
false
,
*result
)
;
// Meke sure the arugment has at least one String parameter.
if
(argCount
>
0
&& NPVARIANT_IS_STRING
(args
[
0
]
)
)
{
// Build CFURL object from the arugment.
NPString str
= NPVARIANT_TO_STRING
(args
[
0
]
)
;
CFURLRef url
= CFURLCreateWithBytes
(NULL
,
(
const UInt8
*
)str.
UTF8Characters
, str.
UTF8Length
, kCFStringEncodingUTF8
, NULL
)
;
if
(url
)
{
// Open URL with the default application by Launch Service.
OSStatus res
= LSOpenCFURLRef
(url
, NULL
)
;
CFRelease
(url
)
;
BOOLEAN_TO_NPVARIANT
(res
== noErr
,
*result
)
;
}
}
return
true
;
}
browser
->memfree
(name
)
;
return
false
;
}
bool hasProperty
(NPObject
*obj
, NPIdentifier propertyName
)
{
return
false
;
}
bool getProperty
(NPObject
*obj
, NPIdentifier propertyName
, NPVariant
*result
)
{
return
false
;
}
//NPP Functions Implements
NPError NPP_New
(NPMIMEType pluginType
, NPP instance
,
uint16_t mode
,
int16_t argc
,
char
* argn
[
]
,
char
* argv
[
]
, NPSavedData
* saved
)
{
// Create per-instance storage
//obj = (PluginObject *)malloc(sizeof(PluginObject));
//bzero(obj, sizeof(PluginObject));
//obj->npp = instance;
//instance->pdata = obj;
if
(
!instance
->pdata
)
{
instance
->pdata
= browser
->createobject
(instance
,
&scriptablePluginClass
)
;
}
// Ask the browser if it supports the CoreGraphics drawing model
NPBool supportsCoreGraphics
;
if
(browser
->getvalue
(instance
, NPNVsupportsCoreGraphicsBool
,
&supportsCoreGraphics
)
!= NPERR_NO_ERROR
)
supportsCoreGraphics
= FALSE
;
if
(
!supportsCoreGraphics
)
return NPERR_INCOMPATIBLE_VERSION_ERROR
;
// If the browser supports the CoreGraphics drawing model, enable it.
browser
->setvalue
(instance
, NPPVpluginDrawingModel
,
(
void
*
)NPDrawingModelCoreGraphics
)
;
return NPERR_NO_ERROR
;
}
NPError NPP_Destroy
(NPP instance
, NPSavedData
** save
)
{
// If we created a plugin instance, we'll destroy and clean it up.
NPObject
*pluginInstance
=instance
->pdata
;
if
(
!pluginInstance
)
{
browser
->releaseobject
(pluginInstance
)
;
pluginInstance
= NULL
;
}
return NPERR_NO_ERROR
;
}
NPError NPP_SetWindow
(NPP instance
, NPWindow
* window
)
{
return NPERR_NO_ERROR
;
}
NPError NPP_NewStream
(NPP instance
, NPMIMEType type
, NPStream
* stream
, NPBool seekable
,
uint16_t
* stype
)
{
*stype
= NP_ASFILEONLY
;
return NPERR_NO_ERROR
;
}
NPError NPP_DestroyStream
(NPP instance
, NPStream
* stream
, NPReason reason
)
{
return NPERR_NO_ERROR
;
}
int32 NPP_WriteReady
(NPP instance
, NPStream
* stream
)
{
return
0
;
}
int32 NPP_Write
(NPP instance
, NPStream
* stream
,
int32 offset
,
int32 len
,
void
* buffer
)
{
return
0
;
}
void NPP_StreamAsFile
(NPP instance
, NPStream
* stream
,
const
char
* fname
)
{
}
void NPP_Print
(NPP instance
, NPPrint
* platformPrint
)
{
}
int16_t NPP_HandleEvent
(NPP instance
,
void
* event
)
{
return
0
;
}
void NPP_URLNotify
(NPP instance
,
const
char
* url
, NPReason reason
,
void
* notifyData
)
{
}
NPError NPP_GetValue
(NPP instance
, NPPVariable variable
,
void
*value
)
{
NPObject
*pluginInstance
=NULL
;
switch
(variable
)
{
case NPPVpluginScriptableNPObject
:
// If we didn't create any plugin instance, we create it.
pluginInstance
=instance
->pdata
;
if
(pluginInstance
)
{
browser
->retainobject
(pluginInstance
)
;
}
*
(NPObject
**
)value
= pluginInstance
;
break
;
default
:
return NPERR_GENERIC_ERROR
;
}
return NPERR_NO_ERROR
;
}
NPError NPP_SetValue
(NPP instance
, NPNVariable variable
,
void
*value
)
{
return NPERR_GENERIC_ERROR
;
}
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#import <WebKit/npapi.h>
#import <WebKit/npfunctions.h> #import <WebKit/npruntime.h> // Browser function table，可以通过它来得到浏览器提供的功能 static NPNetscapeFuncs * browser ; static const char *plugin_method_name_open = "open" ; //////////////////////////////////// /*******各种接口的声明*********/ //在NPAPI编程的接口中你会发现有NP_打头的，有NPP_打头的，有NPN_打头的 //NP是npapi的插件库提供给浏览器的最上层的接口 //NPP即NP Plugin是插件本身提供给浏览器调用的接口，主要被用来填充NPPluginFuncs的结构体 //NPN即NP Netscape ,是浏览器提供给插件使用的接口，这些接口一般都在NPNetscapeFuncs结构体中 //Mach-o entry points,浏览器和创建交流的最上层的接口 NPError NP_Initialize (NPNetscapeFuncs *browserFuncs ) ; NPError NP_GetEntryPoints (NPPluginFuncs *pluginFuncs ) ; void NP_Shutdown ( void ) ; //NPP Functions NPError NPP_New (NPMIMEType pluginType , NPP instance , uint16_t mode , int16_t argc , char * argn [ ] , char * argv [ ] , NPSavedData * saved ) ; NPError NPP_Destroy (NPP instance , NPSavedData ** save ) ; NPError NPP_SetWindow (NPP instance , NPWindow * window ) ; NPError NPP_NewStream (NPP instance , NPMIMEType type , NPStream * stream , NPBool seekable , uint16_t * stype ) ; NPError NPP_DestroyStream (NPP instance , NPStream * stream , NPReason reason ) ; int32 NPP_WriteReady (NPP instance , NPStream * stream ) ; int32 NPP_Write (NPP instance , NPStream * stream , int32 offset , int32 len , void * buffer ) ; void NPP_StreamAsFile (NPP instance , NPStream * stream , const char * fname ) ; void NPP_Print (NPP instance , NPPrint * platformPrint ) ; int16_t NPP_HandleEvent (NPP instance , void * event ) ; void NPP_URLNotify (NPP instance , const char * URL , NPReason reason , void * notifyData ) ; NPError NPP_GetValue (NPP instance , NPPVariable variable , void *value ) ; NPError NPP_SetValue (NPP instance , NPNVariable variable , void *value ) ; //Functions for scriptablePluginClass bool plugin_has_method (NPObject *obj , NPIdentifier methodName ) ; bool plugin_invoke (NPObject *obj , NPIdentifier methodName , const NPVariant *args , uint32_t argCount , NPVariant *result ) ; bool hasProperty (NPObject *obj , NPIdentifier propertyName ) ; bool getProperty (NPObject *obj , NPIdentifier propertyName , NPVariant *result ) ; //////////////////////////////////// static struct NPClass scriptablePluginClass = { NP_CLASS_STRUCT_VERSION , NULL , NULL , NULL , plugin_has_method , plugin_invoke , NULL , hasProperty , getProperty , NULL , NULL , } ; //接口的实现 NPError NP_Initialize (NPNetscapeFuncs * browserFuncs ) { browser = browserFuncs ; return NPERR_NO_ERROR ; } NPError NP_GetEntryPoints (NPPluginFuncs * pluginFuncs ) { pluginFuncs ->version = 11 ; pluginFuncs ->size = sizeof (pluginFuncs ) ; pluginFuncs ->newp = NPP_New ; pluginFuncs ->destroy = NPP_Destroy ; pluginFuncs ->setwindow = NPP_SetWindow ; pluginFuncs ->newstream = NPP_NewStream ; pluginFuncs ->destroystream = NPP_DestroyStream ; pluginFuncs ->asfile = NPP_StreamAsFile ; pluginFuncs ->writeready = NPP_WriteReady ; pluginFuncs ->write = (NPP_WriteProcPtr )NPP_Write ; pluginFuncs ->print = NPP_Print ; pluginFuncs ->event = NPP_HandleEvent ; pluginFuncs ->urlnotify = NPP_URLNotify ; pluginFuncs ->getvalue = NPP_GetValue ; pluginFuncs ->setvalue = NPP_SetValue ; return NPERR_NO_ERROR ; } void NP_Shutdown ( void ) { } bool plugin_has_method (NPObject *obj , NPIdentifier methodName ) { // This function will be called when we invoke method on this plugin elements. NPUTF8 *name = browser ->utf8fromidentifier (methodName ) ; bool result = strcmp (name , plugin_method_name_open ) == 0 ; browser ->memfree (name ) ; return result ; } bool plugin_invoke (NPObject *obj , NPIdentifier methodName , const NPVariant *args , uint32_t argCount , NPVariant *result ) { // Make sure the method called is "open". NPUTF8 *name = browser ->utf8fromidentifier (methodName ) ; if ( strcmp (name , plugin_method_name_open ) == 0 ) { browser ->memfree (name ) ; BOOLEAN_TO_NPVARIANT ( false , *result ) ; // Meke sure the arugment has at least one String parameter. if (argCount > 0 && NPVARIANT_IS_STRING (args [ 0 ] ) ) { // Build CFURL object from the arugment. NPString str = NPVARIANT_TO_STRING (args [ 0 ] ) ; CFURLRef url = CFURLCreateWithBytes (NULL , ( const UInt8 * )str. UTF8Characters , str. UTF8Length , kCFStringEncodingUTF8 , NULL ) ; if (url ) { // Open URL with the default application by Launch Service. OSStatus res = LSOpenCFURLRef (url , NULL ) ; CFRelease (url ) ; BOOLEAN_TO_NPVARIANT (res == noErr , *result ) ; } } return true ; } browser ->memfree (name ) ; return false ; } bool hasProperty (NPObject *obj , NPIdentifier propertyName ) { return false ; } bool getProperty (NPObject *obj , NPIdentifier propertyName , NPVariant *result ) { return false ; } //NPP Functions Implements NPError NPP_New (NPMIMEType pluginType , NPP instance , uint16_t mode , int16_t argc , char * argn [ ] , char * argv [ ] , NPSavedData * saved ) { // Create per-instance storage //obj = (PluginObject *)malloc(sizeof(PluginObject)); //bzero(obj, sizeof(PluginObject)); //obj->npp = instance; //instance->pdata = obj; if ( !instance ->pdata ) { instance ->pdata = browser ->createobject (instance , &scriptablePluginClass ) ; } // Ask the browser if it supports the CoreGraphics drawing model NPBool supportsCoreGraphics ; if (browser ->getvalue (instance , NPNVsupportsCoreGraphicsBool , &supportsCoreGraphics ) != NPERR_NO_ERROR ) supportsCoreGraphics = FALSE ; if ( !supportsCoreGraphics ) return NPERR_INCOMPATIBLE_VERSION_ERROR ; // If the browser supports the CoreGraphics drawing model, enable it. browser ->setvalue (instance , NPPVpluginDrawingModel , ( void * )NPDrawingModelCoreGraphics ) ; return NPERR_NO_ERROR ; } NPError NPP_Destroy (NPP instance , NPSavedData ** save ) { // If we created a plugin instance, we'll destroy and clean it up. NPObject *pluginInstance =instance ->pdata ; if ( !pluginInstance ) { browser ->releaseobject (pluginInstance ) ; pluginInstance = NULL ; } return NPERR_NO_ERROR ; } NPError NPP_SetWindow (NPP instance , NPWindow * window ) { return NPERR_NO_ERROR ; } NPError NPP_NewStream (NPP instance , NPMIMEType type , NPStream * stream , NPBool seekable , uint16_t * stype ) { *stype = NP_ASFILEONLY ; return NPERR_NO_ERROR ; } NPError NPP_DestroyStream (NPP instance , NPStream * stream , NPReason reason ) { return NPERR_NO_ERROR ; } int32 NPP_WriteReady (NPP instance , NPStream * stream ) { return 0 ; } int32 NPP_Write (NPP instance , NPStream * stream , int32 offset , int32 len , void * buffer ) { return 0 ; } void NPP_StreamAsFile (NPP instance , NPStream * stream , const char * fname ) { } void NPP_Print (NPP instance , NPPrint * platformPrint ) { } int16_t NPP_HandleEvent (NPP instance , void * event ) { return 0 ; } void NPP_URLNotify (NPP instance , const char * url , NPReason reason , void * notifyData ) { } NPError NPP_GetValue (NPP instance , NPPVariable variable , void *value ) { NPObject *pluginInstance =NULL ; switch (variable ) { case NPPVpluginScriptableNPObject : // If we didn't create any plugin instance, we create it. pluginInstance =instance ->pdata ; if (pluginInstance ) { browser ->retainobject (pluginInstance ) ; } * (NPObject ** )value = pluginInstance ; break ; default : return NPERR_GENERIC_ERROR ; } return NPERR_NO_ERROR ; } NPError NPP_SetValue (NPP instance , NPNVariable variable , void *value ) { return NPERR_GENERIC_ERROR ; } |
测试代码
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<html>
<head> <script> function run() { var plugin = document.getElementById("pluginId"); plugin.open("http://www.geeklu.com"); } </script> </head> <body > <embed width="0" height="0" type="test/x-open-with-default-plugin" id="pluginId"> <button onclick="run()">run </button> </body> </html> |
Tags: c, Mac, npapi
插件和扩展 区别
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