WebAssembly迁移指南

P）NaCl弃用公告

鉴于跨浏览器WebAssembly支持的势头，我们计划将我们的本机代码工作重点放在WebAssembly上，并计划在2018年第一季度删除对PNaCl的支持（Chrome应用除外）。我们相信围绕WebAssembly的充满活力的生态系统 使其更适合新的和现有的高性能Web应用程序，并且PNaCl的使用率足够低以保证弃用。

我们最近还宣布了 ChromeOS以外的Chrome应用程序 2018年第一季度的弃用 。

工具链迁移

对于大多数（P）NaCl用例，我们建议从NaCl SDK转换到Emscripten。如果您的应用程序可移植到Linux，使用SDL或POSIX API ，则迁移可能相当简单 。虽然没有直接支持NaCl / Pepper API，但我们试图列出Web API等价物。对于更具挑战性的移植案例，请与 本地客户讨论@ googlegroups联系。COM

API迁移

我们在此概述了Web平台替代每个暴露于（P）NaCl的API的状态。此外，该表列出了Emscripten中提供最接近替代品的库或选项。

我们希望在2017年为WebAssembly添加共享内存线程支持，因为线程对匹配（P）NaCl最有趣的用例至关重要。假定即将支持线程的迁移项目标记如下。如果您的应用程序的流控制在很大程度上依赖于阻止API，您可能还会发现需要线程支持才能方便地移植。

虽然我们在此表中试图准确，但毫无疑问会有错误或遗漏。如果您遇到一个，请通过 native-client-discuss @googlegroups联系我们。COM

PPAPI

PPB_Audio

PPAPI方法	假设线程	Emscripten	Web API	限制
Create	X	SDL（部分）	GAP（部分） - AudioWorkletNode相当于ROUGHLY	仍在标准化。
GetCurrentConfig		SDL	AudioContext.*（获取传入的设置）
StartPlayback		SDL	AudioBufferSourceNode.start
StopPlayback		SDL	AudioBufferSourceNode.stop

PPB_AudioBuffer

PPAPI方法	假设线程	Emscripten	Web API	限制
GetTimestamp		SDL	AudioBufferSourceNode.start（parameter）	每次传递而不是附加到缓冲区。
setTimestamp		SDL	AudioBufferSourceNode.start（parameter）
GetSampleRate		SDL	AudioBuffer.sampleRate
GetSampleSize		GAP	GAP - WebAudio仅使用32位浮点数，PPAPI使用16位int。	PPAPI理论上支持多种采样大小。实际上，它只支持16位采样。不幸的是，开发人员已经要求16位样本大小以节省内存使用。
GetNumberOfChannels		SDL	AudioBuffer.numberOfChannels
GetDataBuffer		SDL	AudioBuffer.getChannelData
GetBufferSize		SDL	AudioBuffer.length

PPB_AudioConfig

PPAPI方法	假设线程	Emscripten	Web API	限制
CreateStereo16Bit		GAP	GAP - 仅支持32位浮点样本
GetSampleRate		SDL	AudioContext.sampleRate
GetSampleFrameCount		SDL	AudioBuffer.length
RecommendSampleRate		SDL	AudioContext.sampleRate（来自默认构造）	默认情况下，AudioContext将具有首选采样率。
RecommendSampleFrameCount		GAP	GAP - 没有获得推荐缓冲区大小的机制。

PPB_Console

PPAPI方法	假设线程	Emscripten	Web API	限制
Log		UTIME	console.log/warn/error/...
LogWithSource		GAP	GAP	PPAPI提供了一种覆盖控制台消息中的源文件名和行号的方法。（虽然JS API提供了样式文本的方法）。

PPB_Core

PPAPI方法	假设线程	Emscripten	Web API	限制
getTime		utime	new Date().getTime()
getTimeTicks		utime	new Date().getTime()
IsMainThread		GAP	window.document !== undefined
CallOnMainThread		GAP	Worker.postMessage + Atomics.wait	可以构建等效同步。

PPB_FileIO

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		FS (partial)	FileReader / FileWrite (Entry.createReader / Entry.createWriter)	创建和打开使用的方式不同，但这些部分具有相同的功能。
Open		FS (partial)	FileReader / FileWrite (Entry.createReader / Entry.createWriter)
Query		FS (partial)	Entry.getMetadata
Touch		FS (partial)	GAP (partial) - No direct equivalent, but no access time either.	修改时间可以通过写入来提高。
Read		FS (partial)	Entry.getFile + Blob.slice + FileReader.getBinaryData	请注意，此API需要额外的副本才能读取线性内存，如果Blob切片未使用mmap进行优化，则可能会更糟。
Write		FS (partial)	FileWriter.seek + FileWriter.write 'write*' Events
SetLength		FS (partial)	FileWriter.truncate + 'write*' Events
Flush		GAP	GAP - No equivalent, no way to flush.
Close		FS (partial)	No equivalent, open files and directories are implicitly closed.
ReadToArray		GAP	GAP - No equivalent.	允许并行多个子范围读取。

PPB_FileRef

 

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		FS (partial)	Entry.getFile(..., {create:true})
GetFileSystemType		FS (partial)	FileSystem.type
GetName		FS (partial)	Entry.name
GetPath		FS (partial)	Entry.fullPath
GetParent		FS (partial)	Entry.getParent
MakeDirectory		FS (partial)	Entry.getDirectory(..., {create:true})
Touch		FS (partial)	GAP (partial) - No direct equivalent, but no access time either.	修改时间可以通过写入来提高。
Delete		FS (partial)	Entry.remove
Rename		FS (partial)	Entry.moveTo
Query		GAP	Entry.getMetadata	GAP - JS API具有文件大小和上次修改日期，但没有创建日期和上次访问日期。
ReadDirectoryEntries		FS (partial)	Directory.readEntries

PPB_FileSystem

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		FS (partial)	window.requestFileSystem	JS API只需一步即可完成
Open		GAP	window.requestFileSystem	GAP - Filesystems API仅限chrome。IndexedDB在子范围写入方面具有额外的性能限制。
GetType		GAP	FileSystem.type

PPB_Fullscreen

PPAPI方法	假设线程	Emscripten	Web API	限制
IsFullScreen		html5.h	Document.fullscreenEnabled
SetFullscreen		html5.h	Document.requestFullscreen
GetScreenSize		html5.h	Document.exitFullscreen

PPB_Gamepad

PPAPI方法	假设线程	Emscripten	Web API	限制
Sample		SDL	Gamepad.*	GAP - PPAPI公开了一个时间戳值，但JS API没有提供这个（虽然它是规范的）。

PPB_Graphics2D

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		SDL	Canvas.getContext('2d')
Describe		SDL	Canvas.clientWidth + Canvas.clientHeight
PaintImageData		SDL	CanvasRenderingContext2d.putImageData
Scroll		GAP	CanvasRenderingContext2d.scrollIntoView	GAP（部分） - 不完全匹配（可能必须求助于getImageData + putImageData，这将很慢）。不是跨浏览器标准。
ReplaceContents		SDL	CanvasRenderingContext2d.drawImage
Flush		GAP	GAP - 仅返回事件循环会触发刷新。
SetScale		SDL	CanvasRenderingContext2d.scale
GetScale		SDL	CanvasRenderingContext2d.currentTransform
SetLayerTransform		SDL	CanvasRenderingContext2d.setTransform CanvasRenderingContext2d.scale CanvasRenderingContext2d.translate

PPB_Graphics3D

PPAPI方法	假设线程	Emscripten	Web API	限制
GetAttribMaxValue		GAP	GAP - Canvas.getContext允许您设置请求某些大小的深度/模板缓冲区的布尔值，但无法查询可能的内容（或者获取除了开启或关闭之外的任何内容）
Create		SDL	Canvas.getContext
GetAttribs		SDL	WebGLRenderingContext.getContextAttributes
SetAttribs		SDL	Canvas.getContext(.., OPTIONS)
GetError		SDL	WebGLRenderingContext.getError
ResizeBuffers		SDL	Canvas.width = w; Canvas.height = h;
SwapBuffers		GAP	GAP - 无法显式翻转帧，必须返回事件循环.

PPB_ImageData

PPAPI方法	假设线程	Emscripten	Web API	限制
GetNativeImageDataFormat		SDL	ImageData mandates RGBA order
IsImageDataFormatSupported		SDL	ImageData mandates RGBA order
Create		SDL	CanvasRenderingContext2d.createImageData
Describe		SDL	ImageData never has a stride
Map		SDL	ImageData.data
Unmap		SDL	ImageData.data

PPB_InputEvent

PPAPI方法	假设线程	Emscripten	Web API	限制
RequestInputEvents		SDL	没有直接的等价物	由于JS / Wasm在主线程上运行， 并且可以更便宜地过滤事件而不 会导致跨进程往返，因此缺少此 功能可能不太相关。
RequestFilteringInputEvents		SDL	mouse* key* wheel* touch* composition* Events
		SDL	Element.addEventListener
ClearInputEventRequest		SDL	Element.removeEventListener
GetType		SDL	Event class descendants
GetTimeStamp		SDL	Event.timeStamp
GetModifiers		SDL	*Event.altKey/shiftKey/metaKey/ctrlKey

PPB_MouseInputEvent

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		SDL	MouseEvent
GetButton		SDL	MouseEvent.button
GetPosition		SDL	MouseEvent.client*/page*/offset*
GetClickCount		SDL	dblclick' vs 'mousedown' Events
GetMovement		SDL	MouseEvent.movement*

PPB_WheelInputEvent

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		SDL	WheelEvent
GetDelta		SDL	WheelEvent.delta *
GetTicks		GAP	GAP - deltaMode有点包含此信息，但不完整。
GetScrollByPage		GAP	GAP - deltaMode有点包含此信息，但不完整。

PPB_KeyboardInputEvent

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		SDL	的KeyboardEvent
GetKeyCode		SDL	KeyboardEvent.keyCode
GetCharacterText		SDL	KeyboardEvent.key
GetScrollByPage		SDL	KeyboardEvent.code

PPB_TouchInputEvent

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		SDL	的TouchEvent
AddTouchPoint		SDL	TouchEvent.touches.push
GetTouchCount		SDL	TouchEvent.touches.length
GetTouchByIndex		SDL	TouchEvent.touches [I]
GetTouchById		SDL	Touch.indentifer（自己想出来）

PPB_IMEInputEvent

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		GAP	CompositionEvent
getText		GAP	CompositionEvent.data
GetSegmentNumber		GAP	GAP - 没有直接的等价物
GetSegmentOffset		GAP	GAP - 没有直接的等价物
GetTargetSegment		GAP	GAP - 没有直接的等价物
GetSelection		GAP	GAP - 没有直接的等价物

PPB_Instance

PPAPI方法	假设线程	Emscripten	Web API	限制
BindGraphics		SDL	Canvas.getContext（作为绑定是自动的）。
IsFullFrame		GAP	GAP - 不等同于mime类型处理程序。	可以注册NaCl应用程序来处理特定的mime类型并拥有整个文档。

PPB_MediaStreamAudioTrack

PPAPI方法	假设线程	Emscripten	Web API	限制
配置		GAP	GAP - 没有等价物
GetAttrib		GAP	MediaStreamSettings.channelCount
		GAP	MediaStreamSettings.sampleSize
		GAP	MediaStreamSettings.sampleRate
		GAP	GAP - 不等同于PP_MEDIASTREAMAUDIOTRACK_ATTRIB_BUFFERS
		GAP	GAP - 不等同于PP_MEDIASTREAMAUDIOTRACK_ATTRIB_DURATION
GetId		GAP	MediaStream.id
HasEnded		GAP	MediaStream.ended
GetBuffer		GAP	GAP - 没有等价物
RecycleBuffer		GAP	GAP - 没有等价物
Close			GAP - 没有等价物

PPB_MediaStreamVideoTrack

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		GAP	GAP - 没有等价物	能够创建合成流。
Configure		GAP	GAP - 没有等价物
GetAttrib		GAP	MediaStreamSettings.width
		GAP	MediaStreamSettings.height
		GAP	GAP - 不等同于PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES
		GAP	GAP - 不等同于PP_MEDIASTREAMVIDEOTRACK_ATTRIB_FORMAT
GetId		GAP	MediaStream.id
HasEnded		GAP	MediaStream.ended
getFrame		GAP	GAP - 没有等价物
RecycleFrame		GAP	GAP - 没有等价物
Close		GAP	GAP - 没有等价物
GetEmptyFrame		GAP	GAP - 没有等价物
PutFrame		GAP	GAP - 没有等价物

PPB_MessageLoop

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		N / A	工人得到一个隐含的事件循环。
GetForMainThread		N / A	工人得到一个隐含的事件循环。
GetCurrent		N / A	工人得到一个隐含的事件循环。
AttachToCurrentThread		N / A	工人得到一个隐含的事件循环。
Run		N / A	工人得到一个隐含的事件循环。
PostWork		N / A	工人得到一个隐含的事件循环。
PostQuit		N / A	工人得到一个隐含的事件循环。

PPB_Messaging

PPAPI方法	假设线程	Emscripten	Web API	限制
PostMessage的		N / A	Window.postMessage
RegisterMessageHandler		N / A	Window.addEventListener
UnregisterMessageHandler		N / A	Window.removeEventListener

PPB_MouseCursor

PPAPI方法	假设线程	Emscripten	Web API	限制
setCursor		SDL	Element.style.cursor	支持相同的库存光标集。自定义游标可以使用url（..）完成。动态自定义游标可以使用数据URI完成。CSS3支持指定热点。

PPB_MouseLock

PPAPI方法	假设线程	Emscripten	Web API	限制
LockMouse		SDL	Element.requestPointerLock
UnlockMouse		SDL	Element.exitPointerLock

PPB_OpenGLES2

PPAPI方法	假设线程	Emscripten	Web API	限制
Several Methods		OpenGLES	在功能上接近WebGL 1.0。
	X		GAP - 没有屏幕外画布，渲染必须在主线程上完成。

PPB_TextInputController

PPAPI方法	假设线程	Emscripten	Web API	限制
SetTextInputType		GAP	GAP - 没有关于浏览器包含输入的等效提示。	一些开发人员希望能够以这种方式提示，或者最好能够在画布内嵌入和显示内联的IME事件/输出。
UpdateCaretPosition		GAP	GAP - 没有关于浏览器包含输入的等效提示。
CancelCompositionText		GAP	GAP - 没有关于浏览器包含输入的等效提示。
UpdateSurroundingText		GAP	GAP - 没有关于浏览器包含输入的等效提示。

PPB_URLLoader

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		embind	new XMLHttpRequest（）;
Open		embind	XMLHttpRequest.open
FollowRedirect		embind	Request.redirect
		GAP	GAP - 没有XMLHTTPRequest等价物
GetUploadProgress		embind	XMLHttpRequest'progress'事件
		GAP	GAP - 没有等效的Fetch API
GetDownloadProgress		embind	XMLHttpRequest'progress'事件
		GAP	GAP - 没有等效的Fetch API
GetResponseInfo		embind	XMLHttpRequest.getAllResponseHeaders
		embind	获取响应。*
ReadResponseBody		embind	XMLHttpRequest.response
		embind	身体。*（响应是身体）
FinishStreamingToFile		embind	GAP - 没有直接的等价物	XMLHttpRequest和Fetch都假设流式传输到内存，而不是直接到存储。
Close		embind	XMLHttpRequest.abort
		GAP	GAP - 没有等效的Fetch API

PPB_URLRequestInfo

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		embind	XMLHttpRequest的
		embind	获取请求	无法流式传输到文件。
SetProperty		GAP	GAP - 没有XMLHttpRequest的直接等价物	XMLHttpRequest不提供重定向后的每个请求限制的直接方法，流式传输到文件，设置引用者或凭据策略。
		embind	请求。*
AppendDataToBody		embind	XMLHttpRequest.send	GAP - 两者都必须拥有整个身体，而不是一块。
		embind	fetch（..，options：body）
AppendFileToBody		GAP	GAP - 没有直接的等价物
		N / A	<FORM>	您也可以使用FileReader阅读并上传，但这更像是AppendDataToBody

PPB_URLResponseInfo

PPAPI方法	假设线程	Emscripten	Web API	限制
getProperty		embind	XMLHttpRequest.getAllResponseHeaders + others
		embind	Fetch Response.*
GetBodyAsFileRef		embind	Fetch Response (Body) .blob()	假设存储层优化传输。

PPB_Var

PPAPI方法	假设线程	Emscripten	Web API	限制
VarFromUtf8		embind	TextDecoder.decode
VarToUtf8		embind	TextEncoder.encode
VarFromResource		N / A	N / A
VarToResource		N / A	N / A

PPB_VarArray

PPAPI方法	假设线程	Emscripten	Web API	限制
Get		embind	阵列[I]
Set		embind	数组[i] = x
GetLength		embind	Array.length
SetLength		embind	Array.length = n

PPB_VarArrayBuffer

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		embind	new ArrayBuffer(n)
ByteLength		embind	ArrayBuffer.byteLength
Map		GAP	GAP - 没有直接的等价物	Asm.js / Wasm模块无法映射除单个线性内存堆之外的ArrayBuffer区域。未来的多个记忆或内存映射可能会改善这一点
Unmap		GAP	GAP - 没有直接的等价物

PPB_VarDictionary

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		embind	{}
Get		embind	<Object>[i]
Set		embind	<Object>[i] = x
Delete		embind	delete <Object>[i]
HasKey		embind	x in <Object>
GetKeys		embind	for (k in <Object>) {}	没有字面上的等价物，但它可以构建。

PPB_VideoDecoder

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		GAP	GAP - No equivalent
Initialize		GAP	GAP - No equivalent
Decode		GAP	GAP - No equivalent
GetPicture		GAP	GAP - No equivalent
RecyclePicture		GAP	GAP - No equivalent
Flush		GAP	GAP - No equivalent
Reset		GAP	GAP - No equivalent

PPB_VideoEncoder

PPAPI方法	假设线程	Emscripten	Web API	限制
Create		GAP	GAP - No equivalent	Overlap with MediaRecorder API, but not exact.
GetSupportedProfiles		GAP	GAP - No equivalent
Initialize		GAP	GAP - No equivalent
GetFramesRequired		GAP	GAP - No equivalent
GetFrameCodedSize		GAP	GAP - No equivalent
GetVideoFrame		GAP	GAP - No equivalent
Encode		GAP	GAP - No equivalent
GetBitstreamBuffer		GAP	GAP - No equivalent
RecycleBitstreamBuffer		GAP	GAP - No equivalent
RequestEncodingParametersChange		GAP	GAP - No equivalent
Close		GAP	GAP - No equivalent

PPB_VideoFrame

PPAPI方法	假设线程	Emscripten	Web API	限制
GetTimestamp		间隙	GAP - 没有等价物
setTimestamp		间隙	GAP - 没有等价物
getFormat		间隙	GAP - 没有等价物
getSize		间隙	GAP - 没有等价物
GetDataBuffer		间隙	GAP - 没有等价物
GetDataBufferSize		间隙	GAP - 没有等价物

PPB_View

PPAPI方法	假设线程	Emscripten	Web API	限制
GetRect		embind	Element.getBoundingClientRect
IsFullscreen		embind	Document.fullScreenEnabled	与文档相关而不仅仅是单个元素。
ISVISIBLE		embind	IntersectionObserver
IsPageVisible		embind	document.visibilityState
GetClipRect		embind	IntersectionObserver
GetDeviceScale		embind	window.devicePixelRatio
GetCSSScale		embind	<Element> .getBoundingClientRect（）。width / <Element> .offsetWidth
GetScrollOffset		embind	<Element> .scrollTop / <Element> .scrollLeft

PPB_WebSocket

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		GAP	WebSocket.WebSocket
Connect		GAP	WebSocket.WebSocket(url, ...) WebSocket 'open' Event
Close		GAP	WebSocket.close
ReceiveMessage		GAP	WebSocket 'message' Event WebSocket 'error' Event WebSocket 'close' Event
SendMessage		GAP	WebSocket.send
GetBufferedAmount		GAP	WebSocket.bufferedAmount
GetCloseCode		GAP	CloseEvent.code
GetCloseReason		GAP	CloseEvent.reason
GetCloseWasClean		GAP	CloseEvent.wasClean
GetExtensions		GAP	WebSocket.extensions
GetProtocol		GAP	WebSocket.protocol
GetReadyState		GAP	WebSocket.readyState
GetURL		GAP	WebSocket.url

PPP_Graphics3D

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Graphics3DContextLost		SDL	Canvas 'webglcontextlost' Event

PPP_InputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
HandleInputEvent		SDL	Element.addEventListener

PPP_Instance

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
DidCreate		N/A	<Element>[key]	General DOM access lets you fish out tag attributes
DidDestroy		N/A	N/A	Not triggered for NaCl
DidChangeView		N/A	Element 'resize' Event
DidChangeFocus		N/A	Element 'focus', 'focusin', 'focusout' Events
HandleDocumentLoad		N/A	GAP - No way to register as a mime type handler	NaCl modules via apps + a manifest entry can be set up to handle particular mime types.

PPP_MessageHandler

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
HandleMessage		embind	MessagePort 'message' Event Window 'message' Event
HandleBlockingMessage		N/A	GAP - No direct equivalent	Similar synchronization can be done off main thread with Atomics.wait. This was added to support emulation of synchronous plugin APIs.

PPP_Messaging

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
HandleMessage		embind	MessagePort 'message' Event Window 'message' Event

PPP_MouseLock

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
MouseLockLost		SDL	Element 'pointerlockchange', 'pointerlockerror' Events

IRT

PPB_Audio

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create	x	SDL (partial)	GAP (partial) - AudioWorkletNode ROUGHLY equivalent	Still being standardized.
GetCurrentConfig		SDL	AudioContext.* (gets back settings passed in)
StartPlayback		SDL	AudioBufferSourceNode.start
StopPlayback		SDL	AudioBufferSourceNode.stop

PPB_AudioBuffer

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetTimestamp		SDL	AudioBufferSourceNode.start (parameter)	Passed in each time instead of attached to the buffer.
SetTimestamp		SDL	AudioBufferSourceNode.start (parameter)
GetSampleRate		SDL	AudioBuffer.sampleRate
GetSampleSize		GAP	GAP - WebAudio only uses 32-bit float, PPAPI does 16-bit int.	PPAPI theoretically supports multiple sampling sizes. In practice, it only supports 16-bit samples. Unfortunately, developers have requested 16-bit sample sizes to save on memory use.
GetNumberOfChannels		SDL	AudioBuffer.numberOfChannels
GetDataBuffer		SDL	AudioBuffer.getChannelData
GetBufferSize		SDL	AudioBuffer.length

PPB_AudioConfig

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
CreateStereo16Bit		GAP	GAP - Only 32-bit float samples supported
GetSampleRate		SDL	AudioContext.sampleRate
GetSampleFrameCount		SDL	AudioBuffer.length
RecommendSampleRate		SDL	AudioContext.sampleRate (from default construct)	An AudioContext will have the preferred sampling rate by default.
RecommendSampleFrameCount		GAP	GAP - No mechanism to get a recommended buffer size.

PPB_Console

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Log		utime	console.log/warn/error/...
LogWithSource		GAP	GAP	PPAPI provides a way to override the source filename and line number in a console message. (Though JS API provides way to style text).

PPB_Core

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
getTime		utime	new Date().getTime()
getTimeTicks		utime	new Date().getTime()
IsMainThread		GAP	window.document !== undefined
CallOnMainThread		GAP	Worker.postMessage + Atomics.wait	Equivalent synchronization can be built.

PPB_FileIO

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		FS (partial)	FileReader / FileWrite (Entry.createReader / Entry.createWriter)	Create and open are used differently, but the pieces are of equal power.
Open		FS (partial)	FileReader / FileWrite (Entry.createReader / Entry.createWriter)
Query		FS (partial)	Entry.getMetadata
Touch		FS (partial)	GAP (partial) - No direct equivalent, but no access time either.	Modify time can be bumped by writing.
Read		FS (partial)	Entry.getFile + Blob.slice + FileReader.getBinaryData	Note, this API requires an extra copy to get a read into linear memory, and may be worse than that if Blob slices are not optimizes to use mmap.
Write		FS (partial)	FileWriter.seek + FileWriter.write 'write*' Events
SetLength		FS (partial)	FileWriter.truncate + 'write*' Events
Flush		GAP	GAP - No equivalent, no way to flush.
Close		FS (partial)	No equivalent, open files and directories are implicitly closed.
ReadToArray		GAP	GAP - No equivalent.	Allows multiple subrange reads in parallel.

PPB_FileRef

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		FS (partial)	Entry.getFile(..., {create:true})
GetFileSystemType		FS (partial)	FileSystem.type
GetName		FS (partial)	Entry.name
GetPath		FS (partial)	Entry.fullPath
GetParent		FS (partial)	Entry.getParent
MakeDirectory		FS (partial)	Entry.getDirectory(..., {create:true})
Touch		FS (partial)	GAP (partial) - No direct equivalent, but no access time either.	Modify time can be bumped by writing.
Delete		FS (partial)	Entry.remove
Rename		FS (partial)	Entry.moveTo
Query		GAP	Entry.getMetadata	GAP - JS API has file size and last modified date, but doesn't have creation date and last accessed date.
ReadDirectoryEntries		FS (partial)	Directory.readEntries

PPB_FileSystem

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		FS (partial)	window.requestFileSystem	JS API does both in one step
Open		GAP	window.requestFileSystem	GAP - Filesystems API is chrome only. IndexedDB has additional performance limitations around subrange writes.
GetType		GAP	FileSystem.type

PPB_Fullscreen

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
IsFullScreen		html5.h	Document.fullscreenEnabled
SetFullscreen		html5.h	Document.requestFullscreen
GetScreenSize		html5.h	Document.exitFullscreen

PPB_Gamepad

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Sample		SDL	Gamepad.*	GAP - PPAPI exposes a timestamp value, but the JS API doesn't provide this (though it is spec'd).

PPB_Graphics2D

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		SDL	Canvas.getContext('2d')
Describe		SDL	Canvas.clientWidth + Canvas.clientHeight
PaintImageData		SDL	CanvasRenderingContext2d.putImageData
Scroll		GAP	CanvasRenderingContext2d.scrollIntoView	GAP (partial) - Not an exact match (might have to resort to getImageData + putImageData which will be slow). Not a cross-browser standard.
ReplaceContents		SDL	CanvasRenderingContext2d.drawImage
Flush		GAP	GAP - Only returning to the event loop triggers the flush.
SetScale		SDL	CanvasRenderingContext2d.scale
GetScale		SDL	CanvasRenderingContext2d.currentTransform
SetLayerTransform		SDL	CanvasRenderingContext2d.setTransform CanvasRenderingContext2d.scale CanvasRenderingContext2d.translate

PPB_Graphics3D

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetAttribMaxValue		GAP	GAP - Canvas.getContext lets you set booleans requesting depth / stencil buffers of certain sizes, but does not have a way to query what's possible (or get anything other than on or off for each)
Create		SDL	Canvas.getContext
GetAttribs		SDL	WebGLRenderingContext.getContextAttributes
SetAttribs		SDL	Canvas.getContext(.., OPTIONS)
GetError		SDL	WebGLRenderingContext.getError
ResizeBuffers		SDL	Canvas.width = w; Canvas.height = h;
SwapBuffers		GAP	GAP - No way to explicitly flip a frame, must return to the event loop.

PPB_ImageData

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetNativeImageDataFormat		SDL	ImageData mandates RGBA order
IsImageDataFormatSupported		SDL	ImageData mandates RGBA order
Create		SDL	CanvasRenderingContext2d.createImageData
Describe		SDL	ImageData never has a stride
Map		SDL	ImageData.data
Unmap		SDL	ImageData.data

PPB_InputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
RequestInputEvents		SDL	No direct equivalent	The lack of this feature is probably less relevant as JS / Wasm runs on the main thread and can more cheaply filter events without incurring a cross process round-trip.
RequestFilteringInputEvents		SDL	mouse* key* wheel* touch* composition* Events
		SDL	Element.addEventListener
ClearInputEventRequest		SDL	Element.removeEventListener
GetType		SDL	Event class descendants
GetTimeStamp		SDL	Event.timeStamp
GetModifiers		SDL	*Event.altKey/shiftKey/metaKey/ctrlKey

PPB_MouseInputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		SDL	MouseEvent
GetButton		SDL	MouseEvent.button
GetPosition		SDL	MouseEvent.client*/page*/offset*
GetClickCount		SDL	dblclick' vs 'mousedown' Events
GetMovement		SDL	MouseEvent.movement*

PPB_WheelInputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		SDL	WheelEvent
GetDelta		SDL	WheelEvent.delta*
GetTicks		GAP	GAP - deltaMode kinda of contains this info, but incompletely.
GetScrollByPage		GAP	GAP - deltaMode kinda of contains this info, but incompletely.

PPB_KeyboardInputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		SDL	KeyboardEvent
GetKeyCode		SDL	KeyboardEvent.keyCode
GetCharacterText		SDL	KeyboardEvent.key
GetCode		SDL	KeyboardEvent.code

PPB_TouchInputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		SDL	TouchEvent
AddTouchPoint		SDL	TouchEvent.touches.push
GetTouchCount		SDL	TouchEvent.touches.length
GetTouchByIndex		SDL	TouchEvent.touches[i]
GetTouchById		SDL	Touch.indentifer (to figure this out yourself)

PPB_IMEInputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		GAP	CompositionEvent
GetText		GAP	CompositionEvent.data
GetSegmentNumber		GAP	GAP - No direct equivalent
GetSegmentOffset		GAP	GAP - No direct equivalent
GetTargetSegment		GAP	GAP - No direct equivalent
GetSelection		GAP	GAP - No direct equivalent

PPB_Instance

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
BindGraphics		SDL	Canvas.getContext (moot as binding is automatic).
IsFullFrame		GAP	GAP - No equivalent to mime type handlers.	NaCl apps can be registered to handle a particular mime type and own the whole document.

PPB_MediaStreamAudioTrack

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Configure		GAP	GAP - No equivalent
GetAttrib		GAP	MediaStreamSettings.channelCount
		GAP	MediaStreamSettings.sampleSize
		GAP	MediaStreamSettings.sampleRate
		GAP	GAP - no equivalent to PP_MEDIASTREAMAUDIOTRACK_ATTRIB_BUFFERS
		GAP	GAP - no equivalent to PP_MEDIASTREAMAUDIOTRACK_ATTRIB_DURATION
GetId		GAP	MediaStream.id
HasEnded		GAP	MediaStream.ended
GetBuffer		GAP	GAP - No equivalent
RecycleBuffer		GAP	GAP - No equivalent
Close		GAP	GAP - No equivalent

PPB_MediaStreamVideoTrack

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		GAP	GAP - No equivalent	Ability to create synthetic stream.
Configure		GAP	GAP - No equivalent
GetAttrib		GAP	MediaStreamSettings.width
		GAP	MediaStreamSettings.height
		GAP	GAP - no equivalent to PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES
		GAP	GAP - no equivalent to PP_MEDIASTREAMVIDEOTRACK_ATTRIB_FORMAT
GetId		GAP	MediaStream.id
HasEnded		GAP	MediaStream.ended
GetFrame		GAP	GAP - No equivalent
RecycleFrame		GAP	GAP - No equivalent
Close		GAP	GAP - No equivalent
GetEmptyFrame		GAP	GAP - No equivalent
PutFrame		GAP	GAP - No equivalent

PPB_MessageLoop

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		N/A	Mostly moot, workers get an implicit event loop.
GetForMainThread		N/A	Mostly moot, workers get an implicit event loop.
GetCurrent		N/A	Mostly moot, workers get an implicit event loop.
AttachToCurrentThread		N/A	Mostly moot, workers get an implicit event loop.
Run		N/A	Mostly moot, workers get an implicit event loop.
PostWork		N/A	Mostly moot, workers get an implicit event loop.
PostQuit		N/A	Mostly moot, workers get an implicit event loop.

PPB_Messaging

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
PostMessage		N/A	Window.postMessage
RegisterMessageHandler		N/A	Window.addEventListener
UnregisterMessageHandler		N/A	Window.removeEventListener

PPB_MouseCursor

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
SetCursor		SDL	Element.style.cursor	Same set of stock cursors are supported. Custom cursors can be done with url(..). Dynamic custom cursors can be done with data URIs. CSS3 supports specifying the hotspot.

PPB_MouseLock

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
LockMouse		SDL	Element.requestPointerLock
UnlockMouse		SDL	Element.exitPointerLock

PPB_OpenGLES2

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Several Methods		OpenGLES	Close to WebGL 1.0 in functionality.
	x		GAP - Without offscreen canvas, rendering must be done on the main thread.

PPB_TextInputController

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
SetTextInputType		GAP	GAP - No equivalent hints to browser about canvas containing input.	Some developers would like to either be able to hint in this fashion, or preferably the ability to intercept and display IME events / output inline inside a canvas.
UpdateCaretPosition		GAP	GAP - No equivalent hints to browser about canvas containing input.
CancelCompositionText		GAP	GAP - No equivalent hints to browser about canvas containing input.
UpdateSurroundingText		GAP	GAP - No equivalent hints to browser about canvas containing input.

PPB_URLLoader

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		embind	new XMLHttpRequest();
Open		embind	XMLHttpRequest.open
FollowRedirect		embind	Request.redirect
		GAP	GAP - No XMLHTTPRequest equivalent
GetUploadProgress		embind	XMLHttpRequest 'progress' Event
		GAP	GAP - No Fetch API equivalent
GetDownloadProgress		embind	XMLHttpRequest 'progress' Event
		GAP	GAP - No Fetch API equivalent
GetResponseInfo		embind	XMLHttpRequest.getAllResponseHeaders
		embind	Fetch Response.*
ReadResponseBody		embind	XMLHttpRequest.response
		embind	Body.* (Response is a Body)
FinishStreamingToFile		embind	GAP - No direct equivalent	XMLHttpRequest and Fetch both assume streaming to memory, rather than directly to a storage.
Close		embind	XMLHttpRequest.abort
		GAP	GAP - No Fetch API equivalent

PPB_URLRequestInfo

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		embind	XMLHttpRequest
		embind	Fetch Request	No way to stream to a file.
SetProperty		GAP	GAP - No direct equivalent for XMLHttpRequest	XMLHttpRequest doesn't provide direct ways to per-request limit following redirects, stream to a file, set referrer or credentials policy.
		embind	Request.*
AppendDataToBody		embind	XMLHttpRequest.send	GAP - Both must have the whole body, rather than a chunk.
		embind	fetch(.., options:body)
AppendFileToBody		GAP	GAP - No direct equivalent
		N/A	<form>	You can also read with FileReader and upload, but that's more like AppendDataToBody

PPB_URLResponseInfo

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetProperty		embind	XMLHttpRequest.getAllResponseHeaders + others
		embind	Fetch Response.*
GetBodyAsFileRef		embind	Fetch Response (Body) .blob()	Assumes storage layer optimizes transfer.

PPB_Var

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
VarFromUtf8		embind	TextDecoder.decode
VarToUtf8		embind	TextEncoder.encode
VarFromResource		N/A	N/A
VarToResource		N/A	N/A

PPB_VarArray

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Get		embind	Array[i]
Set		embind	Array[i] = x
GetLength		embind	Array.length
SetLength		embind	Array.length = n

PPB_VarArrayBuffer

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		embind	new ArrayBuffer(n)
ByteLength		embind	ArrayBuffer.byteLength
Map		GAP	GAP - No direct equivalent	Asm.js / Wasm modules are unable to map regions of an ArrayBuffer other than their single linear memory heap. Future multiple memories or memory mapping might improve this.
Unmap		GAP	GAP - No direct equivalent

PPB_VarDictionary

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		embind	{}
Get		embind	<Object>[i]
Set		embind	<Object>[i] = x
Delete		embind	delete <Object>[i]
HasKey		embind	x in <Object>
GetKeys		embind	for (k in <Object>) {}	No literal equivalent, but it can be built.

PPB_VideoDecoder

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		GAP	GAP - No equivalent
Initialize		GAP	GAP - No equivalent
Decode		GAP	GAP - No equivalent
GetPicture		GAP	GAP - No equivalent
RecyclePicture		GAP	GAP - No equivalent
Flush		GAP	GAP - No equivalent
Reset		GAP	GAP - No equivalent

PPB_VideoEncoder

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		GAP	GAP - No equivalent	Overlap with MediaRecorder API, but not exact.
GetSupportedProfiles		GAP	GAP - No equivalent
Initialize		GAP	GAP - No equivalent
GetFramesRequired		GAP	GAP - No equivalent
GetFrameCodedSize		GAP	GAP - No equivalent
GetVideoFrame		GAP	GAP - No equivalent
Encode		GAP	GAP - No equivalent
GetBitstreamBuffer		GAP	GAP - No equivalent
RecycleBitstreamBuffer		GAP	GAP - No equivalent
RequestEncodingParametersChange		GAP	GAP - No equivalent
Close		GAP	GAP - No equivalent

PPB_VideoFrame

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetTimestamp		GAP	GAP - No equivalent
SetTimestamp		GAP	GAP - No equivalent
GetFormat		GAP	GAP - No equivalent
GetSize		GAP	GAP - No equivalent
GetDataBuffer		GAP	GAP - No equivalent
GetDataBufferSize		GAP	GAP - No equivalent

PPB_View

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetRect		embind	Element.getBoundingClientRect
IsFullscreen		embind	Document.fullScreenEnabled	Pertains to document instead of just single element.
IsVisible		embind	IntersectionObserver
IsPageVisible		embind	document.visibilityState
GetClipRect		embind	IntersectionObserver
GetDeviceScale		embind	window.devicePixelRatio
GetCSSScale		embind	<Element>.getBoundingClientRect().width / <Element>.offsetWidth
GetScrollOffset		embind	<Element>.scrollTop / <Element>.scrollLeft

PPB_WebSocket

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create		GAP	WebSocket.WebSocket
Connect		GAP	WebSocket.WebSocket(url, ...) WebSocket 'open' Event
Close		GAP	WebSocket.close
ReceiveMessage		GAP	WebSocket 'message' Event WebSocket 'error' Event WebSocket 'close' Event
SendMessage		GAP	WebSocket.send
GetBufferedAmount		GAP	WebSocket.bufferedAmount
GetCloseCode		GAP	CloseEvent.code
GetCloseReason		GAP	CloseEvent.reason
GetCloseWasClean		GAP	CloseEvent.wasClean
GetExtensions		GAP	WebSocket.extensions
GetProtocol		GAP	WebSocket.protocol
GetReadyState		GAP	WebSocket.readyState
GetURL		GAP	WebSocket.url

PPP_Graphics3D

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Graphics3DContextLost		SDL	Canvas 'webglcontextlost' Event

PPP_InputEvent

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
HandleInputEvent		SDL	Element.addEventListener

PPP_Instance

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
DidCreate		N/A	<Element>[key]	General DOM access lets you fish out tag attributes
DidDestroy		N/A	N/A	Not triggered for NaCl
DidChangeView		N/A	Element 'resize' Event
DidChangeFocus		N/A	Element 'focus', 'focusin', 'focusout' Events
HandleDocumentLoad		N/A	GAP - No way to register as a mime type handler	NaCl modules via apps + a manifest entry can be set up to handle particular mime types.

PPP_MessageHandler

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
HandleMessage		embind	MessagePort 'message' Event Window 'message' Event
HandleBlockingMessage		N/A	GAP - No direct equivalent	Similar synchronization can be done off main thread with Atomics.wait. This was added to support emulation of synchronous plugin APIs.

PPP_Messaging

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
HandleMessage		embind	MessagePort 'message' Event Window 'message' Event

PPP_MouseLock

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
MouseLockLost		SDL	Element 'pointerlockchange', 'pointerlockerror' Events

PPAPI (Apps)

PPB_HostResolver

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create	x	GAP	GAP (partial) - No direct equivalent
Resolve	x	GAP	GAP (partial) - No direct equivalent
GetCanonicalName	x	GAP	GAP (partial) - No direct equivalent
GetNetAddressCount	x	GAP	GAP (partial) - No direct equivalent
GetNetAddress	x	GAP	GAP (partial) - No direct equivalent

PPB_NetAddress

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
CreateFromIPv4Address	x	GAP	GAP (partial) - No direct equivalent
CreateFromIPv6Address	x	GAP	GAP (partial) - No direct equivalent
GetFamily	x	GAP	GAP (partial) - No direct equivalent
DescribeAsString	x	GAP	GAP (partial) - No direct equivalent
DescribeAsIPv4Address	x	GAP	GAP (partial) - No direct equivalent
DescribeAsIPv6Address	x	GAP	GAP (partial) - No direct equivalent

PPB_NetworkList

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetCount	x	GAP	GAP - No direct equivalent
GetName	x	GAP	GAP - No direct equivalent
GetType	x	GAP	GAP - No direct equivalent
GetState	x	GAP	GAP - No direct equivalent
GetIpAddress	x	GAP	GAP - No direct equivalent
GetDisplayName	x	GAP	GAP - No direct equivalent
GetMTU	x	GAP	GAP - No direct equivalent

PPB_NetworkMonitor

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create	x	GAP	GAP - No direct equivalent
UpdateNetworkList	x	GAP	GAP - No direct equivalent

PPB_NetworkProxy

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
GetProxyForURL	x	GAP	GAP - No direct equivalent

PPB_TCPSocket

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create	x	GAP	chrome.sockets.tcp.create	WebSockets / WebRTC closest practical equivalent on open Web.
	x	GAP	chrome.sockets.tcpServer.create
Bind	x	GAP	chrome.sockets.tcpServer.create
Connect	x	GAP	chrome.sockets.tcp.connect
GetLocalAddress	x	GAP	chrome.sockets.udp.SocketInfo
GetRemoteAddress	x	GAP	chrome.sockets.udp.SocketInfo
Read	x	GAP	onReceive* Events
Write	x	GAP	chrome.sockets.tcp.send
Listen	x	GAP	chrome.sockets.tcpServer.listen
Accept	x	GAP	onAccept* Events
Close	x	GAP	chrome.sockets.tcp.close
	x	GAP	chrome.sockets.tcpServer.close
SetOption	x	GAP	chrome.sockets.tcp.update
	x	GAP	chrome.sockets.tcpServer.update

PPB_UDPSocket

PPAPI Method	Assumes Threads	Emscripten	Web API	Limitations
Create	x	GAP	chrome.sockets.udp.create	GAP (partial) - WebRTC closest practical open Web equivalent
Bind	x	GAP	chrome.sockets.udp.bind
GetBoundAddress	x	GAP	chrome.sockets.udp.SocketInfo
RecvFrom	x	GAP	onReceive* Events
SendTo	x	GAP	chrome.sockets.udp.send
Close	x	GAP	chrome.sockets.udp.close
SetOption	x	GAP	chrome.sockets.udp.update
JoinGroup	x	GAP	chrome.sockets.udp.joinGroup
LeaveGroup	x	GAP	chrome.sockets.udp.leaveGroup

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